Chapter IV. — Tendril-Bearers —(continued)

CUCURBITACEAE. — Homologous nature of the tendrils — Echinocystis lobata, remarkable¹ movements of the tendrils to avoid seizing the terminal shoot — Tendrils not excited by contact with another tendril or by drops of water — Undulatory movement of the extremity² of the tendril — Hanburya, adherent³ discs — VITACAE— Gradation between the flower-peduncles and tendrils of the vine — Tendrils of the Virginian Creeper turn from the light, and, after contact, develop adhesive⁴ discs — SAPINDACEAE— PASSIFLORACEAE— Passiflora gracilis — Rapid revolving⁵ movement and sensitiveness of the tendrils — Not sensitive to the contact of other tendrils or of drops of water — Spiral contraction⁶ of tendrils — Summary on the nature and action of tendrils.

CUCURBITACEAE. — The tendrils in this family have been ranked by competent judges as modified leaves, stipules, or branches; or as partly a leaf and partly a branch. De Candolle believes that the tendrils differ in their homological nature in two of the tribes.29 From facts recently adduced, Mr. Berkeley thinks that Payer’s view is the most probable, namely, that the tendril is “a separate portion of the leaf itself;” but much may be said in favour of the belief that it is a modified flower-peduncle. 30

Echinocystis lobata. — Numerous observations were made on this plant (raised from seed sent me by Prof. Asa Gray), for the spontaneous revolving movements of the internodes and tendrils were first observed by me in this case, and greatly perplexed⁷ me. My observations may now be much condensed. I observed thirty-five revolutions of the internodes and tendrils; the slowest rate was 2 hrs. and the average rate, with no great fluctuations⁸, 1 hr. 40 m. Sometimes I tied the internodes, so that the tendrils alone moved; at other times I cut off the tendrils whilst very young, so that the internodes revolved¹⁰ by themselves; but the rate was not thus affected¹¹. The course generally pursued was with the sun, but often in an opposite direction. Sometimes the movement during a short time would either stop or be reversed; and this apparently¹² was due to interference from the light, as, for instance, when I placed a plant close to a window. In one instance, an old tendril, which had nearly ceased revolving, moved in one direction, whilst a young tendril above moved in an opposite course. The two uppermost internodes alone revolve⁹; and as soon as the lower one grows old, only its upper part continues to move. The ellipses¹³ or circles swept by the summits of the internodes are about three inches in diameter; whilst those swept by the tips of the tendrils, are from 15 to 16 inches in diameter. During the revolving movement, the internodes become successively curved to all points of the compass; in one part of their course they are often inclined, together with the tendrils, at about 45 degrees to the horizon, and in another part stand vertically¹⁴ up. There was something in the appearance of the revolving internodes which continually gave the false impression that their movement was due to the weight of the long and spontaneously revolving tendril; but, on cutting off the latter with sharp scissors, the top of the shoot rose only a little, and went on revolving. This false appearance is apparently due to the internodes and tendrils all curving and moving harmoniously¹⁶ together.

A revolving tendril, though inclined during the greater part of its course at an angle of about 45 degrees (in one case of only 37 degrees) above the horizon, stiffened¹⁷ and straightened itself from tip to base in a certain part of its course, thus becoming nearly or quite vertical¹⁵. I witnessed this repeatedly; and it occurred both when the supporting internodes were free and when they were tied up; but was perhaps most conspicuous¹⁹ in the latter case, or when the whole shoot happened to be much inclined. The tendril forms a very acute angle with the projecting extremity of the stem or shoot; and the stiffening²⁰ always occurred as the tendril approached, and had to pass over the shoot in its circular course. If it had not possessed²¹ and exercised this curious power, it would infallibly have struck against the extremity of the shoot and been arrested. As soon as the tendril with its three branches begins to stiffen¹⁸ itself in this manner and to rise from an inclined into a vertical position, the revolving motion becomes more rapid; and as soon as the tendril has succeeded in passing over the extremity of the shoot or point of difficulty, its motion, coinciding with that from its weight, often causes it to fall into its previously²² inclined position so quickly, that the apex²³ could be seen travelling like the minute hand of a gigantic clock.

The tendrils are thin, from 7 to 9 inches in length, with a pair of short lateral²⁴ branches rising not far from the base. The tip is slightly and permanently²⁵ curved, so as to act to a limited extent as a hook. The concave side of the tip is highly sensitive to a touch; but not so the convex side, as was likewise observed to be the case with other species of the family by Mohl (p. 65). I repeatedly proved this difference by lightly rubbing four or five times the convex side of one tendril, and only once or twice the concave side of another tendril, and the latter alone curled inwards. In a few hours afterwards, when the tendrils which had been rubbed on the concave side had straightened themselves, I reversed the process of rubbing, and always with the same result. After touching²⁶ the concave side, the tip becomes sensibly curved in one or two minutes; and subsequently, if the touch has been at all rough, it coils itself into a helix. But the helix will, after a time, straighten itself, and be again ready to act. A loop of thin thread only one-sixteenth of a grain in weight caused a temporary flexure. The lower part was repeatedly rubbed rather roughly, but no curvature ensued; yet this part is sensitive to prolonged pressure, for when it came into contact with a stick, it would slowly wind round it.

One of my plants bore two shoots near together, and the tendrils were repeatedly drawn²⁷ across one another, but it is a singular fact that they did not once catch each other. It would appear as if they had become habituated to contact of this kind, for the pressure thus caused must have been much greater than that caused by a loop of soft thread weighing only the one-sixteenth of a grain. I have, however, seen several tendrils of Bryonia dioica interlocked, but they subsequently released one another. The tendrils of the Echinocystis are also habituated to drops of water or to rain; for artificial rain made by violently flirting²⁸ a wet brush over them produced not the least effect.

The revolving movement of a tendril is not stopped by the curving of its extremity after it has been touched. When one of the lateral branches has firmly clasped an object, the middle branch continues to revolve. When a stem is bent²⁹ down and secured, so that the tendril depends but is left free to move, its previous revolving movement is nearly or quite stopped; but it soon begins to bend upwards³⁰, and as soon as it has become horizontal the revolving movement recommences. I tried this four times; the tendril generally rose to a horizontal position in an hour or an hour and a half; but in one case, in which a tendril depended at an angle of 45 degrees beneath the horizon, the uprising took two hours; in half an hour afterwards it rose to 23 degrees above the horizon and then recommenced revolving. This upward movement is independent of the action of light, for it occurred twice in the dark, and on another occasion the light came in on one side alone. The movement no doubt is guided by opposition³¹ to the force of gravity, as in the case of the ascent³² of the plumules of germinating³³ seeds.

A tendril does not long retain its revolving power; and as soon as this is lost, it bends downwards³⁴ and contracts spirally. After the revolving movement has ceased, the tip still retains for a short time its sensitiveness to contact, but this can be of little or no use to the plant.

Though the tendril is highly flexible, and though the extremity travels, under favourable³⁵ circumstances, at about the rate of an inch in two minutes and a quarter, yet its sensitiveness to contact is so great that it hardly ever fails to seize a thin stick placed in its path. The following case surprised me much: I placed a thin, smooth, cylindrical³⁶ stick (and I repeated the experiment seven times) so far from a tendril, that its extremity could only curl half or three-quarters round the stick; but I always found that the tip managed in the course of a few hours to curl twice or even thrice round the stick. I at first thought that this was due to rapid growth on the outside; but by coloured points and measurements I proved that there had been no sensible increase of length within the time. When a stick, flat on one side, was similarly placed, the tip of the tendril could not curl beyond the flat surface, but coiled itself into a helix, which, turning to one side, lay flat on the little flat surface of wood. In one instance a portion of tendril three-quarters of an inch in length was thus dragged on to the flat surface by the coiling in of the helix. But the tendril thus acquires a very insecure hold, and generally after a time slips off. In one case alone the helix subsequently uncoiled itself, and the tip then passed round and clasped the stick. The formation of the helix on the flat side of the stick apparently shows us that the continued striving of the tip to curl itself closely inwards gives the force which drags the tendril round a smooth cylindrical stick. In this latter case, whilst the tendril was slowly and quite insensibly crawling onwards, I observed several times through a lens that the whole surface was not in close contact with the stick; and I can understand the onward³⁸ progress only by supposing that the movement is slightly undulatory or vermicular, and that the tip alternately straightens itself a little and then again curls inwards. It thus drags itself onwards by an insensibly slow, alternate movement, which may be compared to that of a strong man suspended by the ends of his fingers to a horizontal pole, who works his fingers onwards until he can grasp the pole with the palm of his hand. However this may be, the fact is certain that a tendril which has caught a round stick with its extreme point, can work itself onwards until it has passed twice or even thrice round the stick, and has permanently grasped it.

Hanburya Mexicana. — The young internodes and tendrils of this anomalous³⁹ member of the family, revolve in the same manner and at about the same rate as those of the Echinocystis. The stem does not twine⁴⁰, but can ascend⁴¹ an upright stick by the aid of its tendrils. The concave tip of the tendril is very sensitive; after it had become rapidly coiled into a ring owing to a single touch, it straightened itself in 50 m. The tendril, when in full action, stands vertically up, with the projecting extremity of the young stem thrown a little on one side, so as to be out of the way; but the tendril bears on the inner side, near its base, a short rigid⁴² branch, which projects out at right angles like a spur, with the terminal half bowed a little downwards. Hence, as the main vertical branch revolves⁴³, the spur, from its position and rigidity⁴⁴, cannot pass over the extremity of the shoot, in the same curious manner as do the three branches of the tendril of the Echinocystis, namely, by stiffening themselves at the proper point. The spur is therefore pressed laterally⁴⁵ against the young stem in one part of the revolving course, and thus the sweep of the lower part of the main branch is much restricted. A nice case of coadaptation here comes into play: in all the other tendrils observed by me, the several branches become sensitive at the same period: had this been the case with the Hanburya, the inwardly directed, spur-like branch, from being pressed, during the revolving movement, against the projecting end of the shoot, would infallibly have seized it in a useless or injurious manner. But the main branch of the tendril, after revolving for a time in a vertical position, spontaneously bends downwards; and in doing so, raises the spur-like branch, which itself also curves upwards; so that by these combined movements it rises above the projecting end of the shoot, and can now move freely without touching the shoot; and now it first becomes sensitive.

The tips of both branches, when they come into contact with a stick, grasp it like any ordinary tendril. But in the course of a few days, the lower surface swells⁴⁷ and becomes developed into a cellular⁴⁸ layer, which adapts itself closely to the wood, and firmly adheres to it. This layer is analogous⁴⁹ to the adhesive discs formed by the extremities⁵⁰ of the tendrils of some species of Bignonia and of Ampelopsis; but in the Hanburya the layer is developed along the terminal inner surface, sometimes for a length of 1.75 inches, and not at the extreme tip. The layer is white, whilst the tendril is green, and near the tip it is sometimes thicker than the tendril itself; it generally spreads a little beyond the sides of the tendril, and is fringed with free elongated⁵¹ cells, which have enlarged globular or retort-shaped heads. This cellular layer apparently secretes⁵² some resinous⁵³ cement; for its adhesion to the wood was not lessened⁵⁴ by an immersion⁵⁵ of 24 hrs. in alcohol or water, but was quite loosened by a similar immersion in ether or turpentine. After a tendril has once firmly coiled itself round a stick, it is difficult to imagine of what use the adhesive cellular layer can be. Owing to the spiral contraction which soon ensues, the tendrils were never able to remain, excepting in one instance, in contact with a thick post or a nearly flat surface; if they had quickly become attached by means of the adhesive layer, this would evidently have been of service to the plant.

The tendrils of Bryonia dioica, Cucurbita ovifera, and Cucumis sativa are sensitive and revolve. Whether the internodes likewise revolve I did not observe. In Anguria Warscewiczii, the internodes, though thick and stiff, revolve: in this plant the lower surface of the tendril, some time after clasping a stick, produces a coarsely cellular layer or cushion, which adapts itself closely to the wood, like that formed by the tendril of the Hanburya; but it is not in the least adhesive. In Zanonia Indica, which belongs to a different tribe of the family, the forked tendrils and the internodes revolve in periods between 2 hrs. 8 m. and 3 hrs. 35 m., moving against the sun.

VITACEAE. — In this family and in the two following, namely, the Sapindaceae and Passifloraceae, the tendrils are modified flower-peduncles; and are therefore axial in their nature. In this respect they differ from all those previously described, with the exception, perhaps, of the Cucurbitaceae. The homological nature, however, of a tendril seems to make no difference in its action.

Vitis vinifera. — The tendril is thick and of great length; one from a vine growing out of doors and not vigorously, was 16 inches long. It consists of a peduncle (A), bearing two branches which diverge⁵⁶ equally from it. One of the branches (B) has a scale at its base; it is always, as far as I have seen, longer than the other and often bifurcates⁵⁸. The branches when rubbed become curved, and subsequently straighten themselves. After a tendril has clasped any object with its extremity, it contracts spirally; but this does not occur (Palm, p. 56) when no object has been seized. The tendrils move spontaneously from side to side; and on a very hot day, one made two elliptical revolutions, at an average rate of 2 hrs. 15 m. During these movements a coloured line, painted along the convex surface, appeared after a time on one side, then on the concave side, then on the opposite side, and lastly again on the convex side. The two branches of the same tendril have independent movements. After a tendril has spontaneously revolved for a time, it bends from the light towards the dark: I do not state this on my own authority, but on that of Mohl and Dutrochet. Mohl (p. 77) says that in a vine planted against a wall the tendrils point towards it, and in a vineyard generally more or less to the north.

The young internodes revolve spontaneously; but the movement is unusually slight. A shoot faced a window, and I traced its course on the glass during two perfectly⁵⁹ calm and hot days. On one of these days it described, in the course of ten hours, a spire⁶⁰, representing two and a half ellipses. I also placed a bell-glass over a young Muscat grape in the hot-house, and it made each day three or four very small oval revolutions; the shoot moving less than half an inch from side to side. Had it not made at least three revolutions whilst the sky was uniformly overcast⁶¹, I should have attributed this slight degree of movement to the varying action of the light. The extremity of the stem is more or less bent downwards, but it never reverses its curvature, as so generally occurs with twining plants.

Various authors (Palm, p. 55; Mohl, p. 45; Lindley, &c.) believe that the tendrils of the vine are modified flower-peduncles. I here give a drawing (fig⁶². 10) of the ordinary state of a young flower-stalk: it consists of the “common peduncle” (A); of the “flower-tendril” (B), which is represented as having caught a twig⁶³; and of the “sub-peduncle” (C) bearing the flower-buds. The whole moves spontaneously, like a true tendril, but in a less degree; the movement, however, is greater when the sub-peduncle (C) does not bear many flower-buds. The common peduncle (A) has not the power of clasping a support, nor has the corresponding part of a true tendril. The flower-tendril (B) is always longer than the sub-peduncle (C) and has a scale at its base; it sometimes bifurcates, and therefore corresponds in every detail with the longer scale-bearing branch (B, fig. 9) of the true tendril. It is, however, inclined backwards⁶⁴ from the sub-peduncle (C), or stands at right angles with it, and is thus adapted to aid in carrying the future bunch of grapes. When rubbed, it curves and subsequently straightens itself; and it can, as is shown in the drawing, securely clasp a support. I have seen an object as soft as a young vine-leaf caught by one.

The lower and naked part of the sub-peduncle (C) is likewise slightly sensitive to a rub, and I have seen it bent round a stick and even partly round a leaf with which it had come into contact. That the sub-peduncle has the same nature as the corresponding branch of an ordinary tendril, is well shown when it bears only a few flowers; for in this case it becomes less branched, increases in length, and gains both in sensitiveness and in the power of spontaneous movement. I have twice seen sub-peduncles which bore from thirty to forty flower-buds, and which had become considerably⁶⁵ elongated and were completely wound round sticks, exactly like true tendrils. The whole length of another sub-peduncle, bearing only eleven flower-buds, quickly became curved when slightly rubbed; but even this scanty⁶⁶ number of flowers rendered the stalk less sensitive than the other branch, that is, the flower-tendril; for the latter after a lighter⁶⁷ rub became curved more quickly and in a greater degree. I have seen a sub-peduncle thickly covered with flower-buds, with one of its higher lateral branchlets bearing from some cause only two buds; and this one branchlet had become much elongated and had spontaneously caught hold of an adjoining twig; in fact, it formed a little sub-tendril. The increasing length of the sub-peduncle (C) with the decreasing number of the flower-buds is a good instance of the law of compensation. In accordance with this same principle, the true tendril as a whole is always longer than the flower-stalk; for instance, on the same plant, the longest flower-stalk (measured from the base of the common peduncle to the tip of the flower-tendril) was 8.5 inches in length, whilst the longest tendril was nearly double this length, namely 16 inches.

The gradations from the ordinary state of a flower-stalk, as represented in the drawing (fig. 10), to that of a true tendril (fig. 9) are complete. We have seen that the sub-peduncle (C), whilst still bearing from thirty to forty flower-buds, sometimes becomes a little elongated and partially⁶⁸ assumes all the characters of the corresponding branch of a true tendril. From this state we can trace every stage till we come to a full-sized perfect tendril, bearing on the branch which corresponds with the sub-peduncle one single flower-bud! Hence there can be no doubt that the tendril is a modified flower-peduncle.

Another kind of gradation well deserves notice. Flower-tendrils (B, fig. 10) sometimes produce a few flower-buds. For instance, on a vine growing against my house, there were thirteen and twenty-two flower-buds respectively on two flower-tendrils, which still retained their characteristic qualities of sensitiveness and spontaneous movement, but in a somewhat lessened degree. On vines in hothouses, so many flowers are occasionally produced on the flower-tendrils that a double bunch of grapes is the result; and this is technically⁶⁹ called by gardeners a “cluster.” In this state the whole bunch of flowers presents scarcely any resemblance to a tendril; and, judging from the facts already given, it would probably possess little power of clasping a support, or of spontaneous movement. Such flower-stalks closely resemble in structure those borne by Cissus. This genus, belonging to the same family of the Vitaceae, produces well-developed tendrils and ordinary bunches of flowers; but there are no gradations between the two states. If the genus Vitis had been unknown, the boldest believer in the modification⁷⁰ of species would never have surmised⁷¹ that the same individual plant, at the same period of growth, would have yielded every possible gradation between ordinary flower-stalks for the support of the flowers and fruit, and tendrils used exclusively for climbing. But the vine clearly gives us such a case; and it seems to me as striking and curious an instance of transition as can well be conceived.

Cissus discolor. — The young shoots show no more movement than can be accounted for by daily variations in the action of the light. The tendrils, however, revolve with much regularity⁷², following the sun; and, in the plants observed by me, swept circles of about 5 inches in diameter. Five circles were completed in the following times:— 4 hrs. 45 m., 4 hrs. 50 m., 4 hrs. 45 m., 4 hrs. 30 m., and 5 hrs. The same tendril continues to revolve during three or four days. The tendrils are from 3.5 to 5 inches in length. They are formed of a long foot-stalk, bearing two short branches, which in old plants again bifurcate⁵⁷. The two branches are not of quite equal length; and as with the vine, the longer one has a scale at its base. The tendril stands vertically upwards; the extremity of the shoot being bent abruptly⁷³ downwards, and this position is probably of service to the plant by allowing the tendril to revolve freely and vertically.

Both branches of the tendril, whilst young, are highly sensitive. A touch with a pencil, so gentle as only just to move a tendril borne at the end of a long flexible shoot, sufficed to cause it to become perceptibly curved in four or five minutes. It became straight again in rather above one hour. A loop of soft thread weighing one-seventh of a grain (9.25 mg.) was thrice tried, and each time caused the tendril to become curved in 30 or 40 m. Half this weight produced no effect. The long foot-stalk is much less sensitive, for a slight rubbing produced no effect, although prolonged contact with a stick caused it to bend. The two branches are sensitive on all sides, so that they converge⁷⁴ if touched on their inner sides, and diverge if touched on their outer sides. If a branch be touched at the same time with equal force on opposite sides, both sides are equally stimulated⁷⁵ and there is no movement. Before examining this plant, I had observed only tendrils which are sensitive on one side alone, and these when lightly pressed between the finger and thumb become curved; but on thus pinching many times the tendrils of the Cissus no curvature ensued, and I falsely inferred at first that they were not at all sensitive.

Cissus antarcticus. — The tendrils on a young plant were thick and straight, with the tips a little curved. When their concave surfaces were rubbed, and it was necessary to do this with some force, they very slowly became curved, and subsequently straight again. They are therefore much less sensitive than those of the last species; but they made two revolutions, following the sun, rather more rapidly, viz., in 3 hrs. 30 m. and 4 hrs. The internodes do not revolve.

Ampelopsis hederacea (Virginian Creeper). — The internodes apparently do not move more than can be accounted for by the varying action of the light. The tendrils are from 4 to 5 inches in length, with the main stem sending off several lateral branches, which have their tips curved, as may be seen in the upper figure (fig. 11). They exhibit no true spontaneous revolving movement, but turn, as was long ago observed by Andrew Knight⁷⁶, 31 from the light to the dark. I have seen several tendrils move in less than 24 hours, through an angle of 180 degrees to the dark side of a case in which a plant was placed, but the movement is sometimes much slower. The several lateral branches often move independently of one another, and sometimes irregularly, without any apparent cause. These tendrils are less sensitive to a touch than any others observed by me. By gentle but repeated rubbing with a twig, the lateral branches, but not the main stem, became in the course of three or four hours slightly curved; but they seemed to have hardly any power of again straightening themselves. The tendrils of a plant which had crawled over a large box-tree clasped several of the branches; but I have repeatedly seen that they will withdraw themselves after seizing a stick. When they meet with a flat surface of wood or a wall (and this is evidently what they are adapted for), they turn all their branches towards it, and, spreading them widely apart, bring their hooked tips laterally into contact with it. In effecting this, the several branches, after touching the surface, often rise up, place themselves in a new position, and again come down into contact with it.

In the course of about two days after a tendril has arranged its branches so as to press on any surface, the curved tips swell⁴⁶, become bright red, and form on their under-sides the well-known little discs or cushions with which they adhere firmly. In one case the tips were slightly swollen⁷⁷ in 38 hrs. after coming into contact with a brick; in another case they were considerably swollen in 48 hrs., and in an additional 24 hrs. were firmly attached to a smooth board; and lastly, the tips of a younger tendril not only swelled⁷⁸ but became attached to a stuccoed wall in 42 hrs. These adhesive discs resemble, except in colour and in being larger, those of Bignonia capreolata. When they were developed in contact with a ball of tow, the fibres were separately enveloped⁷⁹, but not in so effective a manner as by B. capreolata. Discs are never developed, as far as I have seen, without the stimulus⁸⁰ of at least temporary contact with some object. 32 They are generally first formed on one side of the curved tip, the whole of which often becomes so much changed in appearance, that a line of the original green tissue can be traced only along the concave surface. When, however, a tendril has clasped a cylindrical stick, an irregular rim³⁷ or disc is sometimes formed along the inner surface at some little distance from the curved tip; this was also observed (p. 71) by Mohl. The discs consist of enlarged cells, with smooth projecting hemispherical surfaces, coloured red; they are at first gorged⁸¹ with fluid (see section given by Mohl, p. 70), but ultimately become woody.

As the discs soon adhere firmly to such smooth surfaces as planed or painted wood, or to the polished leaf of the ivy⁸², this alone renders it probable that some cement is secreted⁸³, as has been asserted to be the case (quoted by Mohl, p. 71) by Malpighi. I removed a number of discs formed during the previous year from a stuccoed wall, and left them during many hours, in warm water, diluted⁸⁴ acetic⁸⁵ acid and alcohol; but the attached grains of silex were not loosened. Immersion in sulphuric ether for 24 hrs. loosened them much, but warmed essential oils (I tried oil of thyme and peppermint) completely released every particle of stone in the course of a few hours. This seems to prove that some resinous cement is secreted. The quantity, however, must be small; for when a plant ascended⁸⁶ a thinly whitewashed⁸⁷ wall, the discs adhered firmly to the whitewash⁸⁸; but as the cement never penetrated⁸⁹ the thin layer, they were easily withdrawn⁹⁰, together with little scales of the whitewash. It must not be supposed that the attachment⁹¹ is effected exclusively by the cement; for the cellular outgrowth completely envelopes every minute and irregular projection⁹², and insinuates⁹³ itself into every crevice⁹⁴.

A tendril which has not become attached to any body, does not contract spirally; and in course of a week or two shrinks into the finest thread, withers⁹⁶ and drops off. An attached tendril, on the other hand, contracts spirally, and thus becomes highly elastic⁹⁷, so that when the main foot-stalk is pulled the strain is distributed equally between all the attached discs. For a few days after the attachment of the discs, the tendril remains⁹⁸ weak and brittle⁹⁹, but it rapidly increases in thickness and acquires great strength. During the following winter it ceases to live, but adheres firmly in a dead state both to its own stem and to the surface of attachment. In the accompanying diagram (fig. 11.) we see the difference between a tendril (B) some weeks after its attachment to a wall, with one (A) from the same plant fully¹⁰⁰ grown but unattached. That the change in the nature of the tissues, as well as the spiral contraction, are consequent on the formation of the discs, is well shown by any lateral branches which have not become attached; for these in a week or two wither⁹⁵ and drop off, in the same manner as does the whole tendril if unattached. The gain in strength and durability¹⁰¹ in a tendril after its attachment is something wonderful. There are tendrils now adhering to my house which are still strong, and have been exposed to the weather in a dead state for fourteen or fifteen years. One single lateral branchlet of a tendril, estimated to be at least ten years old, was still elastic and supported a weight of exactly two pounds. The whole tendril had five disc-bearing branches of equal thickness and apparently of equal strength; so that after having been exposed during ten years to the weather, it would probably have resisted a strain of ten pounds!

SAPINDACEAE. — Cardiospermum halicacabum. — In this family, as in the last, the tendrils are modified flower-peduncles. In the present plant the two lateral branches of the main flower-peduncle have been converted into a pair of tendrils, corresponding with the single “flower-tendril” of the common vine. The main peduncle is thin, stiff, and from 3 to 4.5 inches in length. Near the summit, above two little bracts, it divides into three branches. The middle one divides and re-divides, and bears the flowers; ultimately it grows half as long again as the two other modified branches. These latter are the tendrils; they are at first thicker and longer than the middle branch, but never become more than an inch in length. They taper¹⁰² to a point and are flattened¹⁰³, with the lower clasping surface destitute¹⁰⁴ of hairs. At first they project straight up; but soon diverging¹⁰⁵, spontaneously curl downwards so as to become symmetrically and elegantly hooked, as represented in the diagram. They are now, whilst the flower-buds are still small, ready for action.

The two or three upper internodes, whilst young, steadily¹⁰⁶ revolve; those on one plant made two circles, against the course of the sun, in 3 hrs. 12 m.; in a second plant the same course was followed, and the two circles were completed in 3 hrs. 41 m.; in a third plant, the internodes followed the sun and made two circles in 3 hrs. 47 m. The average rate of these six revolutions was 1 hr. 46 m. The stem shows no tendency to twine spirally round a support; but the allied¹⁰⁷ tendril-bearing genus Paullinia is said (Mohl, p. 4) to be a twiner¹⁰⁸. The flower-peduncles, which stand up above the end of the shoot, are carried round and round by the revolving movement of the internodes; and when the stem is securely tied, the long and thin flower-peduncles themselves are seen to be in continued and sometimes rapid movement from side to side. They sweep a wide space, but only occasionally revolve in a regular elliptical course. By the combined movements of the internodes and peduncles, one of the two short hooked tendrils, sooner or later, catches hold of some twig or branch, and then it curls round and securely grasps it. These tendrils are, however, but slightly sensitive; for by rubbing their under surface only a slight movement is slowly produced. I hooked a tendril on to a twig; and in 1 hr. 45 m. it was curved considerably inwards; in 2 hrs. 30 m. it formed a ring; and in from 5 to 6 hours from being first hooked, it closely grasped the stick. A second tendril acted at nearly the same rate; but I observed one that took 24 hours before it curled twice round a thin twig. Tendrils which have caught nothing, spontaneously curl up to a close helix after the interval¹⁰⁹ of several days. Those which have curled round some object, soon become a little thicker and tougher. The long and thin main peduncle, though spontaneously moving, is not sensitive and never clasps a support. Nor does it ever contract spirally, 33 although a contraction of this kind apparently would have been of service to the plant in climbing. Nevertheless it climbs pretty well without this aid. The seed-capsules though light, are of enormous size (hence its English name of balloon-vine), and as two or three are carried on the same peduncle, the tendrils rising close to them may be of service in preventing their being dashed to pieces by the wind. In the hothouse the tendrils served simply for climbing.

The position of the tendrils alone suffices to show their homological nature. In two instances one of two tendrils produced a flower at its tip; this, however, did not prevent its acting¹¹⁰ properly and curling round a twig. In a third case both lateral branches which ought to have been modified into tendrils, produced flowers like the central branch, and had quite lost their tendril-structure.

I have seen, but was not enabled carefully to observe, only one other climbing Sapindaceous plant, namely, Paullinia. It was not in flower, yet bore long forked tendrils. So that, Paullinia, with respect to its tendrils, appears to bear the same relation to Cardiospermum that Cissus does to Vitis.

PASSIFLORACEAE. — After reading the discussion and facts given by Mohl (p. 47) on the nature of the tendrils in this family, no one can doubt that they are modified flower-peduncles. The tendrils and the flower-peduncles rise close side by side; and my son, William E. Darwin, made sketches¹¹¹ for me of their earliest state of development in the hybrid¹¹² P. floribunda. The two organs appear at first as a single papilla which gradually divides; so that the tendril appears to be a modified branch of the flower-peduncle. My son found one very young tendril surmounted¹¹³ by traces of floral organs, exactly like those on the summit of the true flower-peduncle at the same early age.

Passiflora gracilis. — This well-named, elegant, annual species differs from the other members of the group observed by me, in the young internodes having the power of revolving. It exceeds all the other climbing plants which I have examined, in the rapidity of its movements, and all tendril-bearers in the sensitiveness of the tendrils. The internode which carries the upper active tendril and which likewise carries one or two younger immature¹¹⁴ internodes, made three revolutions, following the sun, at an average rate of 1 hr. 4 m.; it then made, the day becoming very hot, three other revolutions at an average rate of between 57 and 58 m.; so that the average of all six revolutions was 1 hr. 1 m. The apex of the tendril describes elongated ellipses, sometimes narrow and sometimes broad, with their longer axes inclined in slightly different directions. The plant can ascend a thin upright stick by the aid of its tendrils; but the stem is too stiff for it to twine spirally round it, even when not interfered¹¹⁵ with by the tendrils, these having been successively pinched off at an early age.

When the stem is secured, the tendrils are seen to revolve in nearly the same manner and at the same rate as the internodes. 34 The tendrils are very thin, delicate, and straight, with the exception of the tips, which are a little curved; they are from 7 to 9 inches in length. A half-grown tendril is not sensitive; but when nearly full-grown they are extremely sensitive. A single delicate touch on the concave surface of the tip soon caused one to curve; and in 2 minutes it formed an open helix. A loop of soft thread weighing one thirty-second of a grain (2.02 mg.) placed most gently on the tip, thrice caused distinct curvature. A bent bit of thin platina wire weighing only fiftieth of a grain (1.23 mg.) twice produced the same effect; but this latter weight, when left suspended, did not suffice to cause a permanent curvature. These trials were made under a bell-glass, so that the loops of thread and wire were not agitated¹¹⁶ by the wind. The movement after a touch is very rapid: I took hold of the lower part of several tendrils, and then touched their concave tips with a thin twig and watched them carefully through a lens; the tips evidently began to bend after the following intervals¹¹⁷ — 31, 25, 32, 31, 28, 39, 31, and 30 seconds; so that the movement was generally perceptible in half a minute after a touch; but on one occasion it was distinctly visible in 25 seconds. One of the tendrils which thus became bent in 31 seconds, had been touched two hours previously and had coiled into a helix; so that in this interval it had straightened itself and had perfectly recovered its irritability¹¹⁸.

To ascertain¹¹⁹ how often the same tendril would become curved when touched, I kept a plant in my study, which from being cooler than the hot-house was not very favourable for the experiment. The extremity was gently rubbed four or five times with a thin stick, and this was done as often as it was observed to have become nearly straight again after having been in action; and in the course of 54 hrs. it answered to the stimulus 21 times, becoming each time hooked or spiral. On the last occasion, however, the movement was very slight, and soon afterwards permanent spiral contraction commenced. No trials were made during the night, so that the tendril would perhaps have answered a greater number of times to the stimulus; though, on the other hand, from having no rest it might have become exhausted¹²⁰ from so many quickly repeated efforts.

I repeated the experiment made on the Echinocystis, and placed several plants of this Passiflora so close together, that their tendrils were repeatedly dragged over each other; but no curvature ensued. I likewise repeatedly flirted¹²¹ small drops of water from a brush on many tendrils, and syringed others so violently that the whole tendril was dashed about, but they never became curved. The impact from the drops of water was felt far more distinctly on my hand than that from the loops of thread (weighing one thirty-second of a grain) when allowed to fall on it from a height, and these loops, which caused the tendrils to become curved, had been placed most gently on them. Hence it is clear, that the tendrils either have become habituated to the touch of other tendrils and drops of rain, or that they were from the first rendered sensitive only to prolonged though excessively slight pressure of solid objects, with the exclusion¹²² of that from other tendrils. To show the difference in the kind of sensitiveness in different plants and likewise to show the force of the syringe used, I may add that the lightest jet from it instantly caused the leaves of a Mimosa to close; whereas the loop of thread weighing one thirty-second of a grain, when rolled into a ball and placed gently on the glands¹²³ at the bases of the leaflets of the Mimosa, caused no action.

Passiflora punctata. — The internodes do not move, but the tendrils revolve regularly. A half-grown and very sensitive tendril made three revolutions, opposed to the course of the sun, in 3 hrs. 5 m., 2 hrs. 40 m. and 2 hrs. 50 m.; perhaps it might have travelled more quickly when nearly full-grown. A plant was placed in front of a window, and, as with twining stems, the light accelerated the movement of the tendril in one direction and retarded¹²⁴ it in the other; the semicircle towards the light being performed in one instance in 15 m. less time and in a second instance in 20 m. less time than that required by the semicircle towards the dark end of the room. Considering the extreme tenuity of these tendrils, the action of the light on them is remarkable. The tendrils are long, and, as just stated, very thin, with the tip slightly curved or hooked. The concave side is extremely sensitive to a touch — even a single touch causing it to curl inwards; it subsequently straightened itself, and was again ready to act. A loop of soft thread weighing one fourteenth of a grain (4.625 mg.) caused the extreme tip to bend; another time I tried to hang the same little loop on an inclined tendril, but three times it slid off; yet this extraordinarily¹²⁵ slight degree of friction¹²⁶ sufficed to make the tip curl. The tendril, though so sensitive, does not move very quickly after a touch, no conspicuous movement being observable until 5 or 10 m. had elapsed. The convex side of the tip is not sensitive to a touch or to a suspended loop of thread. On one occasion I observed a tendril revolving with the convex side of the tip forwards, and in consequence it was not able to clasp a stick, against which it scraped; whereas tendrils revolving with the concave side forward, promptly¹²⁷ seize any object in their path.

Passiflora quadrangularis. — This is a very distinct species. The tendrils are thick, long, and stiff; they are sensitive to a touch only on the concave surface towards the extremity. When a stick was placed so that the middle of the tendril came into contact with it, no curvature ensued. In the hothouse a tendril made two revolutions, each in 2 hrs. 22 m.; in a cool room one was completed in 3 hrs., and a second in 4 hrs. The internodes do not revolve; nor do those of the hybrid P. floribunda.

Tacsonia manicata. — Here again the internodes do not revolve. The tendrils are moderately thin and long; one made a narrow ellipse in 5 hrs. 20 m., and the next day a broad ellipse in 5 hrs. 7 m. The extremity being lightly rubbed on the concave surface, became just perceptibly curved in 7 m., distinctly in 10 m., and hooked in 20 m.

We have seen that the tendrils in the last three families, namely, the Vitaceae, Sapindaceae and Passifloraceae, are modified flower-peduncles. This is likewise the case, according to De Candolle (as quoted by Mohl), with the tendrils of Brunnichia, one of the Polygonaceae. In two or three species of Modecca, one of the Papayaceae, the tendrils, as I hear from Prof. Oliver, occasionally bear flowers and fruit; so that they are axial in their nature.

The Spiral Contraction of Tendrils.

This movement, which shortens the tendrils and renders them elastic, commences in half a day, or in a day or two after their extremities have caught some object. There is no such movement in any leaf-climber, with the exception of an occasional trace of it in the petioles of Tropaeolum tricolorum. On the other hand, the tendrils of all tendril-bearing plants, contract spirally after they have caught an object with the following exceptions. Firstly, Corydalis claviculata, but then this plant might be called a leaf-climber. Secondly¹²⁸ and thirdly, Bignonia unguis with its close allies, and Cardiospermum; but their tendrils are so short that their contraction could hardly occur, and would be quite superfluous¹²⁹. Fourthly, Smilax aspera offers a more marked exception, as its tendrils are moderately long. The tendrils of Dicentra, whilst the plant is young, are short and after attachment only become slightly flexuous; in older plants they are longer and then they contract spirally. I have seen no other exceptions to the rule that tendrils, after clasping with their extremities a support, undergo spiral contraction. When, however, the tendril of a plant of which the stem is immovably fixed¹³⁰, catches some fixed object, it does not contract, simply because it cannot; this, however, rarely occurs. In the common Pea the lateral branches alone contract, and not the central stem; and with most plants, such as the Vine, Passiflora, Bryony, the basal portion never forms a spire.

I have said that in Corydalis claviculata the end of the leaf or tendril (for this part may be indifferently so called) does not contract into a spire. The branchlets, however, after they have wound round thin twigs¹³¹, become deeply sinuous¹³² or zigzag¹³³. Moreover the whole end of the petiole or tendril, if it seizes nothing, bends after a time abruptly downwards and inwards, showing that its outer surface has gone on growing after the inner surface has ceased to grow. That growth is the chief cause of the spiral contraction of tendrils may be safely admitted, as shown by the recent researches of H. de Vries. I will, however, add one little fact in support of this conclusion.

If the short, nearly straight portion of an attached tendril of Passiflora gracilis, (and, as I believe, of other tendrils,) between the opposed spires¹³⁴, be examined, it will be found to be transversely wrinkled in a conspicuous manner on the outside; and this would naturally follow if the outer side had grown more than the inner side, this part being at the same time forcibly prevented from becoming curved. So again the whole outer surface of a spirally wound tendril becomes wrinkled if it be pulled straight. Nevertheless, as the contraction travels from the extremity of a tendril, after it has been stimulated by contact with a support, down to the base, I cannot avoid doubting, from reasons presently to be given, whether the whole effect ought to be attributed to growth. An unattached tendril rolls itself up into a flat helix, as in the case of Cardiospermum, if the contraction commences at the extremity and is quite regular; but if the continued growth of the outer surface is a little lateral, or if the process begins near the base, the terminal portion cannot be rolled up within the basal portion, and the tendril then forms a more or less open spire. A similar result follows if the extremity has caught some object, and is thus held fast.

The tendrils of many kinds of plants, if they catch nothing, contract after an interval of several days or weeks into a spire; but in these cases the movement takes place after the tendril has lost its revolving power and hangs down; it has also then partly or wholly lost its sensibility; so that this movement can be of no use. The spiral contraction of unattached tendrils is a much slower process than that of attached ones. Young tendrils which have caught a support and are spirally contracted, may constantly be seen on the same stem with the much older unattached and uncontracted tendrils. In the Echinocystis I have seen a tendril with the two lateral branches encircling twigs and contracted into beautiful spires, whilst the main branch which had caught nothing remained for many days straight. In this plant I once observed a main branch after it had caught a stick become spirally flexuous in 7 hrs., and spirally contracted in 18 hrs. Generally the tendrils of the Echinocystis begin to contract in from 12 hrs. to 24 hrs. after catching¹³⁵ some object; whilst unattached tendrils do not begin to contract until two or three or even more days after all revolving movement has ceased. A full-grown tendril of Passiflora quadrangularis which had caught a stick began in 8 hrs. to contract, and in 24 hrs. formed several spires; a younger tendril, only two-thirds grown, showed the first trace of contraction in two days after clasping a stick, and in two more days formed several spires. It appears, therefore, that the contraction does not begin until the tendril is grown to nearly its full length. Another young tendril of about the same age and length as the last did not catch any object; it acquired its full length in four days; in six additional days it first became flexuous, and in two more days formed one complete spire. This first spire was formed towards the basal end, and the contraction steadily but slowly progressed towards the apex; but the whole was not closely wound up into a spire until 21 days had elapsed from the first observation, that is, until 17 days after the tendril had grown to its full length.

The spiral contraction of tendrils is quite independent of their power of spontaneously revolving, for it occurs in tendrils, such as those of Lathyrus grandiflorus and Ampelopsis hederacea, which do not revolve. It is not necessarily related to the curling of the tips round a support, as we see with the Ampelopsis and Bignonia capreolata, in which the development of adherent discs suffices to cause spiral contraction. Yet in some cases this contraction seems connected with the curling or clasping movement, due to contact with a support; for not only does it soon follow this act, but the contraction generally begins close to the curled extremity, and travels downwards to the base. If, however, a tendril be very slack, the whole length almost simultaneously¹³⁶ becomes at first flexuous and then spiral. Again, the tendrils of some few plants never contract spirally unless they have first seized hold of some object; if they catch nothing they hang down, remaining straight, until they wither and drop off: this is the case with the tendrils of Bignonia, which consist of modified leaves, and with those of three genera of the Vitaceae, which are modified flower-peduncles. But in the great majority of cases, tendrils which have never come in contact with any object, after a time contract spirally. All these facts taken together, show that the act of clasping a support and the spiral contraction of the whole length of the tendril, are phenomena¹³⁷ not necessarily connected.

The spiral contraction which ensues after a tendril has caught a support is of high service to the plant; hence its almost universal occurrence with species belonging to widely different orders. When a shoot is inclined and its tendril has caught an object above, the spiral contraction drags up the shoot. When the shoot is upright, the growth of the stem, after the tendrils have seized some object above, would leave it slack, were it not for the spiral contraction which draws up the stem as it increases in length. Thus there is no waste of growth, and the stretched stem ascends¹³⁸ by the shortest course. When a terminal branchlet of the tendril of Cobaea catches a stick, we have seen how well the spiral contraction successively brings the other branchlets, one after the other, into contact with the stick, until the whole tendril grasps it in an inextricable knot. When a tendril has caught a yielding object, this is sometimes enveloped and still further secured by the spiral folds, as I have seen with Passiflora quadrangularis; but this action is of little importance.

A far more important service rendered by the spiral contraction of the tendrils is that they are thus made highly elastic. As before remarked under Ampelopsis, the strain is thus distributed equally between the several attached branches; and this renders the whole far stronger than it otherwise would be, as the branches cannot break separately. It is this elasticity¹³⁹ which protects both branched and simple tendrils from being torn away from their supports during stormy weather. I have more than once gone on purpose during a gale¹⁴⁰ to watch a Bryony growing in an exposed hedge, with its tendrils attached to the surrounding bushes; and as the thick and thin branches were tossed to and fro by the wind, the tendrils, had they not been excessively elastic, would instantly have been torn off and the plant thrown prostrate¹⁴¹. But as it was, the Bryony safely rode out the gale, like a ship with two anchors down, and with a long range of cable ahead to serve as a spring as she surges to the storm.

When an unattached tendril contracts spirally, the spire always runs in the same direction from tip to base. A tendril, on the other hand, which has caught a support by its extremity, although the same side is concave from end to end, invariably becomes twisted in one part in one direction, and in another part in the opposite direction; the oppositely turned spires being separated by a short straight portion. This curious and symmetrical structure has been noticed by several botanists¹⁴², but has not been sufficiently¹⁴³ explained. 35 It occurs without exception with all tendrils which after catching an object contract spirally, but is of course most conspicuous in the longer tendrils. It never occurs with uncaught tendrils; and when this appears to have occurred, it will be found that the tendril had originally seized some object and had afterwards been torn free. Commonly, all the spires at one end of an attached tendril run in one direction, and all those at the other end in the opposite direction, with a single short straight portion in the middle; but I have seen a tendril with the spires alternately turning five times in opposite directions, with straight pieces between them; and M. Leon has seen seven or eight such alternations. Whether the spires turn once or more than once in opposite directions, there are as many turns in the one direction as in the other. For instance, I gathered ten attached tendrils of the Bryony, the longest with 33, and the shortest with only 8 spiral turns; and the number of turns in the one direction was in every case the same (within one) as in the opposite direction.

The explanation of this curious little fact is not difficult. I will not attempt any geometrical reasoning, but will give only a practical illustration. In doing this, I shall first have to allude¹⁴⁴ to a point which was almost passed over when treating of Twining-plants. If we hold in our left hand a bundle of parallel strings¹⁴⁵, we can with our right hand turn these round and round, thus imitating the revolving movement of a twining plant, and the strings do not become twisted. But if we hold at the same time a stick in our left hand, in such a position that the strings become spirally turned round it, they will inevitably¹⁴⁶ become twisted. Hence a straight coloured line, painted along the internodes of a twining plant before it has wound round a support, becomes twisted or spiral after it has wound round. I painted a red line on the straight internodes of a Humulus, Mikania, Ceropegia, Convolvulus, and Phaseolus, and saw it become twisted as the plant wound round a stick. It is possible that the stems of some plants by spontaneously turning on their own axes, at the proper rate and in the proper direction, might avoid becoming twisted; but I have seen no such case.

In the above illustration, the parallel strings were wound round a stick; but this is by no means necessary, for if wound into a hollow coil (as can be done with a narrow slip of elastic paper) there is the same inevitable¹⁴⁷ twisting of the axis¹⁴⁸. When, therefore, a free tendril coils itself into a spire, it must either become twisted along its whole length (and this never occurs), or the free extremity must turn round as many times as there are spires formed. It was hardly necessary to observe this fact; but I did so by affixing¹⁴⁹ little paper vanes to the extreme points of the tendrils of Echinocystis and Passiflora quadrangularis; and as the tendril contracted itself into successive spires, the vane slowly revolved.

We can now understand the meaning of the spires being invariably turned in opposite directions, in tendrils which from having caught some object are fixed at both ends. Let us suppose a caught tendril to make thirty spiral turns all in the same direction; the inevitable result would be that it would become twisted thirty times on its own axis. This twisting would not only require considerable force, but, as I know by trial, would burst the tendril before the thirty turns were completed. Such cases never really occur; for, as already stated, when a tendril has caught a support and is spirally contracted, there are always as many turns in one direction as in the other; so that the twisting of the axis in the one direction is exactly compensated¹⁵⁰ by the twisting in the opposite direction. We can further see how the tendency is given to make the later formed coils opposite to those, whether turned to the right or to the left, which are first made. Take a piece of string, and let it hang down with the lower end fixed to the floor; then wind the upper end (holding the string quite loosely) spirally round a perpendicular¹⁵¹ pencil, and this will twist the lower part of the string; and after it has been sufficiently twisted, it will be seen to curve itself into an open spire, with the curves running in an opposite direction to those round the pencil, and consequently with a straight piece of string between the opposed spires. In short, we have given to the string the regular spiral arrangement of a tendril caught at both ends. The spiral contraction generally begins at the extremity which has clasped a support; and these first-formed spires give a twist to the axis of the tendril, which necessarily inclines the basal part into an opposite spiral curvature. I cannot resist giving one other illustration, though superfluous: when a haberdasher winds up ribbon for a customer, he does not wind it into a single coil; for, if he did, the ribbon would twist itself as many times as there were coils; but he winds it into a figure of eight on his thumb and little finger, so that he alternately takes turns in opposite directions, and thus the ribbon is not twisted. So it is with tendrils, with this sole difference, that they take several consecutive¹⁵² turns in one direction and then the same number in an opposite direction; but in both cases the self-twisting is avoided.

Summary on the Nature and Action of Tendrils.

With the majority of tendril-bearing plants the young internodes revolve in more or less broad ellipses, like those made by twining plants; but the figures described, when carefully traced, generally form irregular ellipsoidal spires. The rate of revolution varies from one to five hours in different species, and consequently is in some cases more rapid than with any twining plant, and is never so slow as with those many twiners which take more than five hours for each revolution. The direction is variable even in the same individual plant. In Passiflora, the internodes of only one species have the power of revolving. The Vine is the weakest revolver observed by me, apparently exhibiting only a trace of a former power. In the Eccremocarpus the movement is interrupted by many long pauses. Very few tendril-bearing plants can spirally twine up an upright stick. Although the power of twining has generally been lost, either from the stiffness or shortness of the internodes, from the size of the leaves, or from some other unknown cause, the revolving movement of the stem serves to bring the tendrils into contact with surrounding objects.

The tendrils themselves also spontaneously revolve. The movement begins whilst the tendril is young, and is at first slow. The mature tendrils of Bignonia littoralis move much slower than the internodes. Generally, the internodes and tendrils revolve together at the same rate; in Cissus, Cobaea, and most Passiflorae, the tendrils alone revolve; in other cases, as with Lathyrus aphaca, only the internodes move, carrying with them the motionless tendrils; and, lastly (and this is the fourth possible case), neither internodes nor tendrils spontaneously revolve, as with Lathyrus grandiflorus and Ampelopsis. In most Bignonias, Eccremocarpus Mutisia, and the Fumariaceae, the internodes, petioles and tendrils all move harmoniously together. In every case the conditions of life must be favourable in order that the different parts should act in a perfect manner.

Tendrils revolve by the curvature of their whole length, excepting the sensitive extremity and the base, which parts do not move, or move but little. The movement is of the same nature as that of the revolving internodes, and, from the observations of Sachs and H. de Vries, no doubt is due to the same cause, namely, the rapid growth of a longitudinal band, which travels round the tendril and successively bows each part to the opposite side. Hence, if a line be painted along that surface which happens at the time to be convex, the line becomes first lateral, then concave, then lateral, and ultimately again convex. This experiment can be tried only on the thicker tendrils, which are not affected by a thin crust of dried paint. The extremities are often slightly curved or hooked, and the curvature of this part is never reversed; in this respect they differ from the extremities of twining shoots, which not only reverse their curvature, or at least become periodically straight, but curve themselves in a greater degree than the lower part. In most other respects a tendril acts as if it were one of several revolving internodes, which all move together by successively bending to each point of the compass. There is, however, in many cases this unimportant difference, that the curving tendril is separated from the curving internode by a rigid petiole. With most tendril-bearers the summit of the stem or shoot projects above the point from which the tendril arises; and it is generally bent to one side, so as to be out of the way of the revolutions swept by the tendril. In those plants in which the terminal shoot is not sufficiently out of the way, as we have seen with the Echinocystis, as soon as the tendril comes in its revolving course to this point, it stiffens¹⁵³ and straightens itself, and thus rising vertically up passes over the obstacle in an admirable manner.

All tendrils are sensitive, but in various degrees, to contact with an object, and curve towards the touched side. With several plants a single touch, so slight as only just to move the highly flexible tendril, is enough to induce curvature. Passiflora gracilis possesses the most sensitive tendrils which I have observed: a bit of platina wire 0.02 of a grain (1.23 mg.) in weight, gently placed on the concave point, caused a tendril to become hooked, as did a loop of soft, thin cotton thread weighing one thirty-second of a grain (2.02 mg.) With the tendrils of several other plants, loops weighing one sixteenth of a grain (4.05 mg.) sufficed. The point of a tendril of Passiflora gracilis began to move distinctly in 25 seconds after a touch, and in many cases after 30 seconds. Asa Gray also saw movement in the tendrils of the Cucurbitaceous genus, Sicyos, in 30 seconds. The tendrils of some other plants, when lightly rubbed, moved in a few minutes; with Dicentra in half-an-hour; with Smilax in an hour and a quarter or half; and with Ampelopsis still more slowly. The curling movement consequent on a single touch continues to increase for a considerable time, then ceases; after a few hours the tendril uncurls itself, and is again ready to act. When the tendrils of several kinds of plants were caused to bend by extremely light weights suspended on them, they seemed to grow accustomed to so slight a stimulus, and straightened themselves, as if the loops had been removed. It makes no difference what sort of object a tendril touches, with the remarkable exception of other tendrils and drops of water, as was observed with the extremely sensitive-tendrils of Passiflora gracilis and of the Echinocystis. I have, however, seen tendrils of the Bryony which had temporarily caught other tendrils, and often in the case of the vine.

Tendrils of which the extremities are permanently and slightly curved, are sensitive only on the concave surface; other tendrils, such as those of the Cobaea (though furnished with horny hooks directed to one side) and those of Cissus discolor, are sensitive on all sides. Hence the tendrils of this latter plant, when stimulated by a touch of equal force on opposite sides, did not bend. The inferior and lateral surfaces of the tendrils of Mutisia are sensitive, but not the upper surface. With branched tendrils, the several branches act alike; but in the Hanburya the lateral spur-like branch does not acquire (for excellent reasons which have been explained) its sensitiveness nearly so soon as the main branch. With most tendrils the lower or basal part is either not at all sensitive, or sensitive only to prolonged contact. We thus see that the sensitiveness of tendrils is a special and localized capacity. It is quite independent of the power of spontaneously revolving; for the curling of the terminal portion from touch does not in the least interrupt the former movement. In Bignonia unguis and its close allies, the petioles of the leaves, as well as the tendrils, are sensitive to a touch.

Twining plants when they come into contact with a stick, curl round it invariably in the direction of their revolving movement; but tendrils curl indifferently to either side, in accordance with the position of the stick and the side which is first touched. The clasping movement of the extremity is apparently not steady, but undulatory or vermicular in its nature, as may be inferred from the curious manner in which the tendrils of the Echinocystis slowly crawled round a smooth stick.

As with a few exceptions tendrils spontaneously revolve, it may be asked — why have they been endowed with sensitiveness? — why, when they come into contact with a stick, do they not, like twining plants, spirally wind round it? One reason may be that they are in most cases so flexible and thin, that when brought into contact with any object, they would almost certainly yield and be dragged onwards by the revolving movement. Moreover, the sensitive extremities have no revolving power as far as I have observed, and could not by this means curl round a support. With twining plants, on the other hand, the extremity spontaneously bends more than any other part; and this is of high importance for the ascent of the plant, as may be seen on a windy day. It is, however, possible that the slow movement of the basal and stiffer parts of certain tendrils, which wind round sticks placed in their path, may be analogous to that of twining plants. But I hardly attended sufficiently to this point, and it would have been difficult to distinguish between a movement due to extremely dull irritability, from the arrestment of the lower part, whilst the upper part continued to move onwards.

Tendrils which are only three-fourths grown, and perhaps even at an earlier age, but not whilst extremely young, have the power of revolving and of grasping any object which they touch. These two capacities are generally acquired at about the same period, and both fail when the tendril is full grown. But in Cobaea and Passiflora punctata the tendrils begin to revolve in a useless manner, before they have become sensitive. In the Echinocystis they retain their sensitiveness for some time after they have ceased to revolve and after they have sunk downwards; in this position, even if they were able to seize an object, such power would be of no service in supporting the stem. It is a rare circumstance thus to detect any superfluity or imperfection in the action of tendrils — organs which are so excellently adapted for the functions which they have to perform; but we see that they are not always perfect, and it would be rash to assume that any existing tendril has reached the utmost limit of perfection.

Some tendrils have their revolving motion accelerated or retarded, in moving to or from the light; others, as with the Pea, seem indifferent to its action; others move steadily from the light to the dark, and this aids them in an important manner in finding a support. For instance, the tendrils of Bignonia capreolata bend from the light to the dark as truly as a wind-vane from the wind. In the Eccremocarpus the extremities alone twist and turn about so as to bring their finer branches and hooks into close contact with any dark surface, or into crevices¹⁵⁴ and holes.

A short time after a tendril has caught a support, it contracts with some rare exceptions into a spire; but the manner of contraction and the several important advantages thus gained have been discussed so lately, that nothing need here be repeated on the subject. Tendrils soon after catching a support grow much stronger and thicker, and sometimes more durable¹⁵⁵ to a wonderful degree; and this shows how much their internal tissues must be changed. Occasionally it is the part which is wound round a support which chiefly becomes thicker and stronger; I have seen, for instance, this part of a tendril of Bignonia aequinoctialis twice as thick and rigid as the free basal part. Tendrils which have caught nothing soon shrink and wither; but in some species of Bignonia they disarticulate and fall off like leaves in autumn.

Any one who had not closely observed tendrils of many kinds would probably infer that their action was uniform. This is the case with the simpler kinds, which simply curl round an object of moderate thickness, whatever its nature may be. 36 But the genus Bignonia shows us what diversity of action there may be between the tendrils of closely allied species. In all the nine species observed by me, the young internodes revolve vigorously; the tendrils also revolve, but in some of the species in a very feeble manner; and lastly the petioles of nearly all revolve, though with unequal power. The petioles of three of the species, and the tendrils of all are sensitive to contact. In the first-described species, the tendrils resemble in shape a bird’s foot, and they are of no service to the stem in spirally ascending¹⁵⁶ a thin upright stick, but they can seize firm hold of a twig or branch. When the stem twines¹⁵⁷ round a somewhat thick stick, a slight degree of sensitiveness possessed by the petioles is brought into play, and the whole leaf together with the tendril winds round it. In B. unguis the petioles are more sensitive, and have greater power of movement than those of the last species; they are able, together with the tendrils, to wind inextricably round a thin upright stick; but the stem does not twine so well. B. Tweedyana has similar powers, but in addition, emits aerial roots which adhere to the wood. In B. venusta the tendrils are converted into elongated three-pronged grapnels, which move spontaneously in a conspicuous manner; the petioles, however, have lost their sensitiveness. The stem of this species can twine round an upright stick, and is aided in its ascent by the tendrils seizing the stick alternately some way above and then contracting spirally. In B. littoralis the tendrils, petioles, and internodes, all revolve spontaneously. The stem, however, cannot twine, but ascends an upright stick by seizing it above with both tendrils together, which then contract into a spire. The tips of these tendrils become developed into adhesive discs. B. speciosa possesses similar powers of movement as the last species, but it cannot twine round a stick, though it can ascend by clasping the stick horizontally with one or both of its unbranched tendrils. These tendrils continually insert their pointed¹⁵⁸ ends into minute crevices or holes, but as they are always withdrawn by the subsequent spiral contraction, the habit seems to us in our ignorance useless. Lastly, the stem of B. capreolata twines imperfectly; the much-branched tendrils revolve in a capricious manner, and bend from the light to the dark; their hooked extremities, even whilst immature, crawl into crevices, and, when mature, seize any thin projecting point; in either case they develop adhesive discs, and these have the power of enveloping¹⁵⁹ the finest fibres.

In the allied Eccremocarpus the internodes, petioles, and much-branched tendrils all spontaneously revolve together. The tendrils do not as a whole turn from the light; but their bluntly-hooked extremities arrange themselves neatly¹⁶⁰ on any surface with which they come into contact, apparently so as to avoid the light. They act best when each branch seizes a few thin stems, like the culms of a grass, which they afterwards draw together into a solid bundle by the spiral contraction of all the branches. In Cobaea the finely-branched tendrils alone revolve; the branches terminate in sharp, hard, double, little hooks, with both points directed to the same side; and these turn by well-adapted movements to any object with which they come into contact. The tips of the branches also crawl into dark crevices or holes. The tendrils and internodes of Ampelopsis have little or no power of revolving; the tendrils are but little sensitive to contact; their hooked extremities cannot seize thin objects; they will not even clasp a stick, unless in extreme need of a support; but they turn from the light to the dark, and, spreading out their branches in contact with any nearly flat surface, develop discs. These adhere by the secretion¹⁶¹ of some cement to a wall, or even to a polished surface; and this is more than the discs of the Bignonia capreolata can effect.

The rapid development of these adherent discs is one of the most remarkable peculiarities¹⁶² possessed by any tendrils. We have seen that such discs are formed by two species of Bignonia, by Ampelopsis, and, according to Naudin, 37 by the Cucurbitaceous genus Peponopsis adhaerens. In Anguria the lower surface of the tendril, after it has wound round a stick, forms a coarsely cellular layer, which closely fits the wood, but is not adherent; whilst in Hanburya a similar layer is adherent. The growth of these cellular out-growths depends, (except in the case of the Haplolophium and of one species of Ampelopsis,) on the stimulus from contact. It is a singular fact that three families, so widely distinct as the Bignoniaceae, Vitaceae, and Cucurbitaceae, should possess species with tendrils having this remarkable power.

Sachs attributes all the movements of tendrils to rapid growth on the side opposite to that which becomes concave. These movements consist of revolving nutation, the bending to and from the light, and in opposition to gravity, those caused by a touch, and spiral contraction. It is rash to differ from so great an authority, but I cannot believe that one at least of these movements — curvature from a touch — is thus caused. 38 In the first place it may be remarked that the movement of nutation differs from that due to a touch, in so far that in some cases the two powers are acquired by the same tendril at different periods of growth; and the sensitive part of the tendril does not seem capable of nutation. One of my chief reasons for doubting whether the curvature from a touch is the result of growth, is the extraordinary rapidity of the movement. I have seen the extremity of a tendril of Passiflora gracilis, after being touched, distinctly bent in 25 seconds, and often in 30 seconds; and so it is with the thicker tendril of Sicyos. It appears hardly credible¹⁶³ that their outer surfaces could have actually grown in length, which implies a permanent modification of structure, in so short a time. The growth, moreover, on this view must be considerable, for if the touch has been at all rough the extremity is coiled in two or three minutes into a spire of several turns.

When the extreme tip of the tendril of Echinocystis caught hold of a smooth stick, it coiled itself in a few hours (as described at p. 132) twice or thrice round the stick, apparently by an undulatory movement. At first I attributed this movement to the growth of the outside; black marks were therefore made, and the interspaces measured, but I could not thus detect any increase in length. Hence it seems probable in this case and in others, that the curvature of the tendril from a touch depends on the contraction of the cells along the concave side. Sachs himself admits 39 that “if the growth which takes place in the entire tendril at the time of contact with a support is small, a considerable acceleration¹⁶⁴ occurs on the convex surface, but in general there is no elongation on the concave surface, or there may even be a contraction; in the case of a tendril of Cucurbita this contraction amounted to nearly one-third of the original length.” In a subsequent passage Sachs seems to feel some difficulty in accounting¹⁶⁵ for this kind of contraction. It must not however be supposed from the foregoing remarks that I entertain any doubt, after reading De Vries’ observations, about the outer and stretched surfaces of attached tendrils afterwards increasing in length by growth. Such increase seems to me quite compatible with the first movement being independent of growth. Why a delicate touch should cause one side of a tendril to contract we know as little as why, on the view held by Sachs, it should lead to extraordinarily rapid growth of the opposite side. The chief or sole reason for the belief that the curvature of a tendril when touched is due to rapid growth, seems to be that tendrils lose their sensitiveness and power of movement after they have grown to their full length; but this fact is intelligible¹⁶⁶, if we bear in mind that all the functions of a tendril are adapted to drag up the terminal growing shoot towards the light. Of what use would it be, if an old and full-grown tendril, arising from the lower part of a shoot, were to retain its power of clasping a support? This would be of no use; and we have seen with tendrils so many instances of close adaptation and of the economy of means, that we may feel assured that they would acquire irritability and the power of clasping a support at the proper age — namely, youth — and would not uselessly retain such power beyond the proper age.

1 remarkable   

adj.显著的，异常的，非凡的，值得注意的

参考例句：

• She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
• These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。

2 extremity   

n.末端，尽头；尽力；终极；极度

参考例句：

• I hope you will help them in their extremity.我希望你能帮助在穷途末路的他们。
• What shall we do in this extremity?在这种极其困难的情况下我们该怎么办呢？

3 adherent   

n.信徒，追随者，拥护者

参考例句：

• He was most liberal where money would bring him a powerful or necessary political adherent.在金钱能够收买一个干练的或者必需的政治拥护者的地方，他是最不惜花钱的。
• He's a pious adherent of Buddhism.他是一位虔诚的佛教徒。

4 adhesive   

n.粘合剂；adj.可粘着的，粘性的

参考例句：

• You'll need a strong adhesive to mend that chair. 你需要一种粘性很强的东西来修理那把椅子。
• Would you give me an adhesive stamp?请给我一枚带胶邮票好吗？

5 revolving   

adj.旋转的，轮转式的；循环的v.（使）旋转( revolve的现在分词 )；细想

参考例句：

• The theatre has a revolving stage. 剧院有一个旋转舞台。
• The company became a revolving-door workplace. 这家公司成了工作的中转站。

6 contraction   

n.缩略词，缩写式，害病

参考例句：

• The contraction of this muscle raises the lower arm.肌肉的收缩使前臂抬起。
• The forces of expansion are balanced by forces of contraction.扩张力和收缩力相互平衡。

7 perplexed   

adj.不知所措的

参考例句：

• The farmer felt the cow,went away,returned,sorely perplexed,always afraid of being cheated.那农民摸摸那头牛，走了又回来，犹豫不决，总怕上当受骗。
• The child was perplexed by the intricate plot of the story.这孩子被那头绪纷繁的故事弄得迷惑不解。

8 fluctuations   

波动，涨落，起伏( fluctuation的名词复数 )

参考例句：

• He showed the price fluctuations in a statistical table. 他用统计表显示价格的波动。
• There were so many unpredictable fluctuations on the Stock Exchange. 股票市场瞬息万变。

9 revolve   

vi.(使)旋转；循环出现

参考例句：

• The planets revolve around the sun.行星绕着太阳运转。
• The wheels began to revolve slowly.车轮开始慢慢转动。

10 revolved   

v.（使）旋转( revolve的过去式和过去分词 )；细想

参考例句：

• The fan revolved slowly. 电扇缓慢地转动着。
• The wheel revolved on its centre. 轮子绕中心转动。 来自《简明英汉词典》

11 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

12 apparently   

adv.显然地；表面上，似乎

参考例句：

• An apparently blind alley leads suddenly into an open space.山穷水尽，豁然开朗。
• He was apparently much surprised at the news.他对那个消息显然感到十分惊异。

13 ellipses   

n.椭园，省略号；椭圆( ellipse的名词复数 )；（语法结构上的）省略( ellipsis的名词复数 )

参考例句：

• The planets move around the sun in ellipses. 各行星围绕太阳按椭圆形运转。 来自《简明英汉词典》
• Summations are almost invariably indicated ellipses instead of the more prevalent sigma notation. 在表示“连加”的式子中，几乎一成不变地使用省略号来代替更为流行的“∑”符号。 来自辞典例句

14 vertically   

adv.垂直地

参考例句：

• Line the pages for the graph both horizontally and vertically.在这几页上同时画上横线和竖线，以便制作图表。
• The human brain is divided vertically down the middle into two hemispheres.人脑从中央垂直地分为两半球。

15 vertical   

adj.垂直的，顶点的，纵向的；n.垂直物，垂直的位置

参考例句：

• The northern side of the mountain is almost vertical.这座山的北坡几乎是垂直的。
• Vertical air motions are not measured by this system.垂直气流的运动不用这种系统来测量。

16 harmoniously   

和谐地，调和地

参考例句：

• The president and Stevenson had worked harmoniously over the last eighteen months. 在过去一年半里，总统和史蒂文森一起工作是融洽的。
• China and India cannot really deal with each other harmoniously. 中国和印度这两只猛兽不可能真心实意地和谐相处。

17 stiffened   

加强的

参考例句：

• He leaned towards her and she stiffened at this invasion of her personal space. 他向她俯过身去，这种侵犯她个人空间的举动让她绷紧了身子。
• She stiffened with fear. 她吓呆了。

18 stiffen   

v.(使)硬，(使)变挺，(使)变僵硬

参考例句：

• The blood supply to the skin is reduced when muscles stiffen.当肌肉变得僵硬时，皮肤的供血量就减少了。
• I was breathing hard,and my legs were beginning to stiffen.这时我却气吁喘喘地开始感到脚有点僵硬。

19 conspicuous   

adj.明眼的，惹人注目的；炫耀的，摆阔气的

参考例句：

• It is conspicuous that smoking is harmful to health.很明显，抽烟对健康有害。
• Its colouring makes it highly conspicuous.它的色彩使它非常惹人注目。

20 stiffening   

n. (使衣服等)变硬的材料, 硬化 动词stiffen的现在分词形式

参考例句：

• Her mouth stiffening, she could not elaborate. 她嘴巴僵直，无法细说下去。
• No genius, not a bad guy, but the attacks are hurting and stiffening him. 不是天才，人也不坏，但是四面八方的攻击伤了他的感情，使他横下了心。

21 possessed   

adj.疯狂的；拥有的，占有的

参考例句：

• He flew out of the room like a man possessed.他像着了魔似地猛然冲出房门。
• He behaved like someone possessed.他行为举止像是魔怔了。

22 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

23 apex   

n.顶点，最高点

参考例句：

• He reached the apex of power in the early 1930s.他在三十年代初达到了权力的顶峰。
• His election to the presidency was the apex of his career.当选总统是他一生事业的顶峰。

24 lateral   

adj.侧面的，旁边的

参考例句：

• An airfoil that controls lateral motion.能够控制横向飞行的机翼。
• Mr.Dawson walked into the court from a lateral door.道森先生从一个侧面的门走进法庭。

25 permanently   

adv.永恒地，永久地，固定不变地

参考例句：

• The accident left him permanently scarred.那次事故给他留下了永久的伤疤。
• The ship is now permanently moored on the Thames in London.该船现在永久地停泊在伦敦泰晤士河边。

26 touching   

adj.动人的，使人感伤的

参考例句：

• It was a touching sight.这是一幅动人的景象。
• His letter was touching.他的信很感人。

27 drawn   

v.拖，拉，拔出；adj.憔悴的，紧张的

参考例句：

• All the characters in the story are drawn from life.故事中的所有人物都取材于生活。
• Her gaze was drawn irresistibly to the scene outside.她的目光禁不住被外面的风景所吸引。

28 flirting   

v.调情，打情骂俏( flirt的现在分词 )

参考例句：

• Don't take her too seriously; she's only flirting with you. 别把她太当真，她只不过是在和你调情罢了。 来自《现代汉英综合大词典》
• 'she's always flirting with that new fellow Tseng!" “她还同新来厂里那个姓曾的吊膀子！ 来自子夜部分

29 bent   

n.爱好，癖好；adj.弯的；决心的，一心的

参考例句：

• He was fully bent upon the project.他一心扑在这项计划上。
• We bent over backward to help them.我们尽了最大努力帮助他们。

30 upwards   

adv.向上，在更高处...以上

参考例句：

• The trend of prices is still upwards.物价的趋向是仍在上涨。
• The smoke rose straight upwards.烟一直向上升。

31 opposition   

n.反对，敌对

参考例句：

• The party leader is facing opposition in his own backyard.该党领袖在自己的党內遇到了反对。
• The police tried to break down the prisoner's opposition.警察设法制住了那个囚犯的反抗。

32 ascent   

n.(声望或地位)提高；上升，升高；登高

参考例句：

• His rapid ascent in the social scale was surprising.他的社会地位提高之迅速令人吃惊。
• Burke pushed the button and the elevator began its slow ascent.伯克按动电钮，电梯开始缓慢上升。

33 germinating   

n.& adj.发芽（的）v.（使）发芽( germinate的现在分词 )

参考例句：

• Glyoxysomes are particularly well known in germinating fatly seeds. 人们已经知道，萌发的含油种子中有乙醛酸循环体。 来自辞典例句
• Modern, industrial society, slowly germinating in the shadow of medievalism, burst the bonds of feudalism. 现代工业社会缓慢地在中世纪精神的阴影下孕育成长着，终于挣脱了封建制度的枷锁。 来自辞典例句

34 downwards   

adj./adv.向下的（地），下行的（地）

参考例句：

• He lay face downwards on his bed.他脸向下伏在床上。
• As the river flows downwards,it widens.这条河愈到下游愈宽。

35 favourable   

adj.赞成的，称赞的，有利的，良好的，顺利的

参考例句：

• The company will lend you money on very favourable terms.这家公司将以非常优惠的条件借钱给你。
• We found that most people are favourable to the idea.我们发现大多数人同意这个意见。

36 cylindrical   

adj.圆筒形的

参考例句：

• huge cylindrical gas tanks 巨大的圆柱形贮气罐
• Beer cans are cylindrical. 啤酒罐子是圆筒形的。

37 rim   

n.(圆物的)边，轮缘；边界

参考例句：

• The water was even with the rim of the basin.盆里的水与盆边平齐了。
• She looked at him over the rim of her glass.她的目光越过玻璃杯的边沿看着他。

38 onward   

adj.向前的，前进的；adv.向前，前进，在先

参考例句：

• The Yellow River surges onward like ten thousand horses galloping.黄河以万马奔腾之势滚滚向前。
• He followed in the steps of forerunners and marched onward.他跟随着先辈的足迹前进。

39 anomalous   

adj.反常的；不规则的

参考例句：

• For years this anomalous behaviour has baffled scientists.几年来这种反常行为让科学家们很困惑。
• The mechanism of this anomalous vascular response is unknown.此种不规则的血管反应的机制尚不清楚。

40 twine   

v.搓，织，编饰；（使）缠绕

参考例句：

• He tied the parcel with twine.他用细绳捆包裹。
• Their cardboard boxes were wrapped and tied neatly with waxed twine.他们的纸板盒用蜡线扎得整整齐齐。

41 ascend   

vi.渐渐上升，升高；vt.攀登，登上

参考例句：

• We watched the airplane ascend higher and higher.我们看着飞机逐渐升高。
• We ascend in the order of time and of development.我们按时间和发展顺序向上溯。

42 rigid   

adj.严格的，死板的；刚硬的，僵硬的

参考例句：

• She became as rigid as adamant.她变得如顽石般的固执。
• The examination was so rigid that nearly all aspirants were ruled out.考试很严，几乎所有的考生都被淘汰了。

43 revolves   

v.（使）旋转( revolve的第三人称单数 )；细想

参考例句：

• The earth revolves both round the sun and on its own axis. 地球既公转又自转。 来自《现代汉英综合大词典》
• Thus a wheel revolves on its axle. 于是，轮子在轴上旋转。 来自《简明英汉词典》

44 rigidity   

adj.钢性，坚硬

参考例句：

• The rigidity of the metal caused it to crack.这金属因刚度强而产生裂纹。
• He deplored the rigidity of her views.他痛感她的观点僵化。

45 laterally   

ad.横向地；侧面地；旁边地

参考例句：

• Shafts were sunk, with tunnels dug laterally. 竖井已经打下，并且挖有横向矿道。
• When the plate becomes unstable, it buckles laterally. 当板失去稳定时，就发生横向屈曲。

46 swell   

vi.膨胀，肿胀；增长，增强

参考例句：

• The waves had taken on a deep swell.海浪汹涌。
• His injured wrist began to swell.他那受伤的手腕开始肿了。

47 swells   

增强( swell的第三人称单数 )； 肿胀； （使）凸出； 充满（激情）

参考例句：

• The waters were heaving up in great swells. 河水正在急剧上升。
• A barrel swells in the middle. 水桶中部隆起。

48 cellular   

adj.移动的；细胞的，由细胞组成的

参考例句：

• She has a cellular telephone in her car.她的汽车里有一部无线通讯电话机。
• Many people use cellular materials as sensitive elements in hygrometers.很多人用蜂窝状的材料作为测量温度的传感元件。

49 analogous   

adj.相似的；类似的

参考例句：

• The two situations are roughly analogous.两种情況大致相似。
• The company is in a position closely analogous to that of its main rival.该公司与主要竞争对手的处境极为相似。

50 extremities   

n.端点( extremity的名词复数 )；尽头；手和足；极窘迫的境地

参考例句：

• She was most noticeable, I thought, in respect of her extremities. 我觉得她那副穷极可怜的样子实在太惹人注目。 来自辞典例句
• Winters may be quite cool at the northwestern extremities. 西北边区的冬天也可能会相当凉。 来自辞典例句

51 elongated   

v.延长，加长( elongate的过去式和过去分词 )

参考例句：

• Modigliani's women have strangely elongated faces. 莫迪里阿尼画中的妇女都长着奇长无比的脸。
• A piece of rubber can be elongated by streching. 一块橡皮可以拉长。 来自《用法词典》

52 secretes   

v.（尤指动物或植物器官）分泌( secrete的第三人称单数 )；隐匿，隐藏

参考例句：

• The pineal gland secretes melanin during times of relaxation and visualization. 松果体在放松时分泌黑色素是明白无误的。 来自互联网
• For example, the archegonium (female organ) of the moss Funaria secretes sucrose. 例如藓类颈卵器（雌性器官）分泌蔗糖。 来自互联网

53 resinous   

adj.树脂的，树脂质的，树脂制的

参考例句：

• Alcohol is a solvent of resinous substances.酒精是树脂性物质的溶媒。
• He observed that the more resinous the wood, the more resistant it was to decay.他观察到木材含树脂越多，其抗腐力越强。

54 lessened   

减少的，减弱的

参考例句：

• Listening to the speech through an interpreter lessened its impact somewhat. 演讲辞通过翻译的嘴说出来，多少削弱了演讲的力量。
• The flight to suburbia lessened the number of middle-class families living within the city. 随着迁往郊外的风行，住在城内的中产家庭减少了。

55 immersion   

n.沉浸；专心

参考例句：

• The dirt on the bottom of the bath didn't encourage total immersion.浴缸底有污垢，不宜全身浸泡于其中。
• The wood had become swollen from prolonged immersion.因长时间浸泡，木头发胀了。

56 diverge   

v.分叉，分歧，离题，使...岔开，使转向

参考例句：

• This is where our opinions diverge from each other.这就是我们意见产生分歧之处。
• Don't diverge in your speech.发言不要离题。

57 bifurcate   

adj.二叉的，双峰的

参考例句：

• Drainage was to the north and individual channels bifurcate in that direction.整个水系向北排水,各个河道朝该方向分叉。
• Communicative and semantive translation bifurcate at a later stage of analytical or cognitive translation.交际翻译和语义翻译在认知翻译的后阶段分道扬镳。

58 bifurcates   

n.（指道路、河流、树枝等）分岔，分成两支( bifurcate的名词复数 )；使分枝，使分叉；分叉的v.（指道路、河流、树枝等）分岔，分成两支( bifurcate的第三人称单数 )；使分枝，使分叉

参考例句：

• The stream bifurcates into two narrow winding channels. 那条小溪分成两股窄而弯曲的支流。 来自《简明英汉词典》
• The blood supply bifurcates between eight and thirty times before reaching each particular location in the body. 血液要分流8到30次才能到达身体的各个部位。 来自辞典例句

59 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。

60 spire   

n.(教堂)尖顶，尖塔，高点

参考例句：

• The church spire was struck by lightning.教堂的尖顶遭到了雷击。
• They could just make out the spire of the church in the distance.他们只能辨认出远处教堂的尖塔。

61 overcast   

adj.阴天的，阴暗的，愁闷的；v.遮盖，（使）变暗，包边缝；n.覆盖，阴天

参考例句：

• The overcast and rainy weather found out his arthritis.阴雨天使他的关节炎发作了。
• The sky is overcast with dark clouds.乌云满天。

62 fig   

n.无花果(树)

参考例句：

• The doctor finished the fig he had been eating and selected another.这位医生吃完了嘴里的无花果，又挑了一个。
• You can't find a person who doesn't know fig in the United States.你找不到任何一个在美国的人不知道无花果的。

63 twig   

n.小树枝，嫩枝；v.理解

参考例句：

• He heard the sharp crack of a twig.他听到树枝清脆的断裂声。
• The sharp sound of a twig snapping scared the badger away.细枝突然折断的刺耳声把獾惊跑了。

64 backwards   

adv.往回地，向原处，倒，相反，前后倒置地

参考例句：

• He turned on the light and began to pace backwards and forwards.他打开电灯并开始走来走去。
• All the girls fell over backwards to get the party ready.姑娘们迫不及待地为聚会做准备。

65 considerably   

adv.极大地；相当大地；在很大程度上

参考例句：

• The economic situation has changed considerably.经济形势已发生了相当大的变化。
• The gap has narrowed considerably.分歧大大缩小了。

66 scanty   

adj.缺乏的，仅有的，节省的，狭小的，不够的

参考例句：

• There is scanty evidence to support their accusations.他们的指控证据不足。
• The rainfall was rather scanty this month.这个月的雨量不足。

67 lighter   

n.打火机，点火器；驳船；v.用驳船运送；light的比较级

参考例句：

• The portrait was touched up so as to make it lighter.这张画经过润色，色调明朗了一些。
• The lighter works off the car battery.引燃器利用汽车蓄电池打火。

68 partially   

adv.部分地，从某些方面讲

参考例句：

• The door was partially concealed by the drapes.门有一部分被门帘遮住了。
• The police managed to restore calm and the curfew was partially lifted.警方设法恢复了平静，宵禁部分解除。

69 technically   

adv.专门地，技术上地

参考例句：

• Technically it is the most advanced equipment ever.从技术上说，这是最先进的设备。
• The tomato is technically a fruit,although it is eaten as a vegetable.严格地说，西红柿是一种水果，尽管它是当作蔬菜吃的。

70 modification   

n.修改，改进，缓和，减轻

参考例句：

• The law,in its present form,is unjust;it needs modification.现行的法律是不公正的，它需要修改。
• The design requires considerable modification.这个设计需要作大的修改。

71 surmised   

v.臆测，推断( surmise的过去式和过去分词 )；揣测；猜想

参考例句：

• From the looks on their faces, I surmised that they had had an argument. 看他们的脸色，我猜想他们之间发生了争执。
• From his letter I surmised that he was unhappy. 我从他的信中推测他并不快乐。 来自《简明英汉词典》

72 regularity   

n.规律性，规则性；匀称，整齐

参考例句：

• The idea is to maintain the regularity of the heartbeat.问题就是要维持心跳的规律性。
• He exercised with a regularity that amazed us.他锻炼的规律程度令我们非常惊讶。

73 abruptly   

adv.突然地，出其不意地

参考例句：

• He gestured abruptly for Virginia to get in the car.他粗鲁地示意弗吉尼亚上车。
• I was abruptly notified that a half-hour speech was expected of me.我突然被通知要讲半个小时的话。

74 converge   

vi.会合；聚集，集中；(思想、观点等)趋近

参考例句：

• The results converge towards this truth.其结果趋近于这个真理。
• Parallel lines converge at infinity.平行线永不相交。

75 stimulated   

a.刺激的

参考例句：

• The exhibition has stimulated interest in her work. 展览增进了人们对她作品的兴趣。
• The award has stimulated her into working still harder. 奖金促使她更加努力地工作。

76 knight   

n.骑士，武士；爵士

参考例句：

• He was made an honourary knight.他被授予荣誉爵士称号。
• A knight rode on his richly caparisoned steed.一个骑士骑在装饰华丽的马上。

77 swollen   

adj.肿大的，水涨的；v.使变大，肿胀

参考例句：

• Her legs had got swollen from standing up all day.因为整天站着，她的双腿已经肿了。
• A mosquito had bitten her and her arm had swollen up.蚊子叮了她，她的手臂肿起来了。

78 swelled   

增强( swell的过去式和过去分词 )； 肿胀； （使）凸出； 充满（激情）

参考例句：

• The infection swelled his hand. 由于感染，他的手肿了起来。
• After the heavy rain the river swelled. 大雨过后，河水猛涨。

79 enveloped   

v.包围，笼罩，包住( envelop的过去式和过去分词 )

参考例句：

• She was enveloped in a huge white towel. 她裹在一条白色大毛巾里。
• Smoke from the burning house enveloped the whole street. 燃烧着的房子冒出的浓烟笼罩了整条街。 来自《简明英汉词典》

80 stimulus   

n.刺激，刺激物，促进因素，引起兴奋的事物

参考例句：

• Regard each failure as a stimulus to further efforts.把每次失利看成对进一步努力的激励。
• Light is a stimulus to growth in plants.光是促进植物生长的一个因素。

81 gorged   

v.（用食物把自己）塞饱，填饱( gorge的过去式和过去分词 )；作呕

参考例句：

• He gorged himself at the party. 在宴会上他狼吞虎咽地把自己塞饱。 来自《简明英汉词典》
• The men, gorged with food, had unbuttoned their vests. 那些男人，吃得直打饱嗝，解开了背心的钮扣。 来自辞典例句

82 ivy   

n.常青藤，常春藤

参考例句：

• Her wedding bouquet consisted of roses and ivy.她的婚礼花篮包括玫瑰和长春藤。
• The wall is covered all over with ivy.墙上爬满了常春藤。

83 secreted   

v.（尤指动物或植物器官）分泌( secrete的过去式和过去分词 )；隐匿，隐藏

参考例句：

• Insulin is secreted by the pancreas. 胰岛素是胰腺分泌的。
• He secreted his winnings in a drawer. 他把赢来的钱藏在抽届里。 来自《简明英汉词典》

84 diluted   

无力的，冲淡的

参考例句：

• The paint can be diluted with water to make a lighter shade. 这颜料可用水稀释以使色度淡一些。
• This pesticide is diluted with water and applied directly to the fields. 这种杀虫剂用水稀释后直接施用在田里。

85 acetic   

adj.酸的

参考例句：

• Acetic acid is one of the organic acids which have many uses.醋酸是用途最广泛的有机酸之一。
• The wine in him has almost melted acetic acid.他一肚皮的酒几乎全化为了醋酸。

86 ascended   

v.上升，攀登( ascend的过去式和过去分词 )

参考例句：

• He has ascended into heaven. 他已经升入了天堂。 来自《简明英汉词典》
• The climbers slowly ascended the mountain. 爬山运动员慢慢地登上了这座山。 来自《简明英汉词典》

87 whitewashed   

粉饰，美化，掩饰( whitewash的过去式和过去分词 )

参考例句：

• The wall had been whitewashed. 墙已粉过。
• The towers are in the shape of bottle gourds and whitewashed. 塔呈圆形，状近葫芦，外敷白色。 来自汉英文学 - 现代散文

88 whitewash   

v.粉刷，掩饰；n.石灰水，粉刷，掩饰

参考例句：

• They tried hard to whitewash themselves.他们力图粉饰自己。
• What he said was a load of whitewash.他所说的是一大堆粉饰之词。

89 penetrated   

adj. 击穿的，鞭辟入里的 动词penetrate的过去式和过去分词形式

参考例句：

• The knife had penetrated his chest. 刀子刺入了他的胸膛。
• They penetrated into territory where no man had ever gone before. 他们已进入先前没人去过的地区。

90 withdrawn   

vt.收回；使退出；vi.撤退，退出

参考例句：

• Our force has been withdrawn from the danger area.我们的军队已从危险地区撤出。
• All foreign troops should be withdrawn to their own countries.一切外国军队都应撤回本国去。

91 attachment   

n.附属物，附件；依恋；依附

参考例句：

• She has a great attachment to her sister.她十分依恋她的姐姐。
• She's on attachment to the Ministry of Defense.她现在隶属于国防部。

92 projection   

n.发射，计划，突出部分

参考例句：

• Projection takes place with a minimum of awareness or conscious control.投射在最少的知觉或意识控制下发生。
• The projection of increases in number of house-holds is correct.对户数增加的推算是正确的。

93 insinuates   

n.暗示( insinuate的名词复数 )；巧妙或迂回地潜入；（使）缓慢进入；慢慢伸入v.暗示( insinuate的第三人称单数 )；巧妙或迂回地潜入；（使）缓慢进入；慢慢伸入

参考例句：

• Slang insinuates itself into the language. 俚语慢慢地渗入语言中。 来自辞典例句
• But the division of labor slowly insinuates itself into this process of production. 但是，分工慢慢地侵入了这种生产过程。 来自英汉非文学 - 家庭、私有制和国家的起源

94 crevice   

n.(岩石、墙等)裂缝；缺口

参考例句：

• I saw a plant growing out of a crevice in the wall.我看到墙缝里长出一棵草来。
• He edged the tool into the crevice.他把刀具插进裂缝里。

95 wither   

vt.使凋谢，使衰退，(用眼神气势等)使畏缩；vi.枯萎，衰退，消亡

参考例句：

• She grows as a flower does-she will wither without sun.她象鲜花一样成长--没有太阳就会凋谢。
• In autumn the leaves wither and fall off the trees.秋天，树叶枯萎并从树上落下来。

96 withers   

马肩隆

参考例句：

• The girl's pitiful history would wring one's withers. 这女孩子的经历令人心碎。
• "I will be there to show you," and so Mr. Withers withdrew. “我会等在那里，领你去看房间的，"威瑟斯先生这样说着，退了出去。 来自英汉文学 - 嘉莉妹妹

97 elastic   

n.橡皮圈，松紧带；adj.有弹性的；灵活的

参考例句：

• Rubber is an elastic material.橡胶是一种弹性材料。
• These regulations are elastic.这些规定是有弹性的。

98 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

99 brittle   

adj.易碎的；脆弱的；冷淡的；(声音)尖利的

参考例句：

• The pond was covered in a brittle layer of ice.池塘覆盖了一层易碎的冰。
• She gave a brittle laugh.她冷淡地笑了笑。

100 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

101 durability   

n.经久性，耐用性

参考例句：

• Nylons have the virtue of durability.尼龙丝袜有耐穿的优点。

102 taper   

n.小蜡烛，尖细，渐弱；adj.尖细的；v.逐渐变小

参考例句：

• You'd better taper off the amount of time given to rest.你最好逐渐地减少休息时间。
• Pulmonary arteries taper towards periphery.肺动脉向周围逐渐变细。

103 flattened   

[医]（水）平扁的，弄平的

参考例句：

• She flattened her nose and lips against the window. 她把鼻子和嘴唇紧贴着窗户。
• I flattened myself against the wall to let them pass. 我身体紧靠着墙让他们通过。

104 destitute   

adj.缺乏的；穷困的

参考例句：

• They were destitute of necessaries of life.他们缺少生活必需品。
• They are destitute of common sense.他们缺乏常识。

105 diverging   

分开( diverge的现在分词 )； 偏离； 分歧； 分道扬镳

参考例句：

• Plants had gradually evolved along diverging and converging pathways. 植物是沿着趋异和趋同两种途径逐渐演化的。
• With member-country bond yields now diverging, 'it's a fragmented set of markets. 但随着成员国债券收益率之差扩大，市场已经分割开来。

106 steadily   

adv.稳定地；不变地；持续地

参考例句：

• The scope of man's use of natural resources will steadily grow.人类利用自然资源的广度将日益扩大。
• Our educational reform was steadily led onto the correct path.我们的教学改革慢慢上轨道了。

107 allied   

adj.协约国的；同盟国的

参考例句：

• Britain was allied with the United States many times in history.历史上英国曾多次与美国结盟。
• Allied forces sustained heavy losses in the first few weeks of the campaign.同盟国在最初几周内遭受了巨大的损失。

108 twiner   

n.缠绕植物；搓绳机

参考例句：

109 interval   

n.间隔，间距；幕间休息，中场休息

参考例句：

• The interval between the two trees measures 40 feet.这两棵树的间隔是40英尺。
• There was a long interval before he anwsered the telephone.隔了好久他才回了电话。

110 acting   

n.演戏，行为，假装；adj.代理的，临时的，演出用的

参考例句：

• Ignore her,she's just acting.别理她，她只是假装的。
• During the seventies,her acting career was in eclipse.在七十年代，她的表演生涯黯然失色。

111 sketches   

n.草图( sketch的名词复数 )；素描；速写；梗概

参考例句：

• The artist is making sketches for his next painting. 画家正为他的下一幅作品画素描。
• You have to admit that these sketches are true to life. 你得承认这些素描很逼真。 来自《简明英汉词典》

112 hybrid   

n.(动，植）杂种，混合物

参考例句：

• That is a hybrid perpetual rose.那是一株杂交的四季开花的蔷薇。
• The hybrid was tall,handsome,and intelligent.那混血儿高大、英俊、又聪明。

113 surmounted   

战胜( surmount的过去式和过去分词 )； 克服（困难）； 居于…之上； 在…顶上

参考例句：

• She was well aware of the difficulties that had to be surmounted. 她很清楚必须克服哪些困难。
• I think most of these obstacles can be surmounted. 我认为这些障碍大多数都是可以克服的。

114 immature   

adj.未成熟的，发育未全的，未充分发展的

参考例句：

• Tony seemed very shallow and immature.托尼看起来好像很肤浅，不夠成熟。
• The birds were in immature plumage.这些鸟儿羽翅未全。

115 interfered   

v.干预( interfere的过去式和过去分词 )；调停；妨碍；干涉

参考例句：

• Complete absorption in sports interfered with his studies. 专注于运动妨碍了他的学业。 来自《简明英汉词典》
• I am not going to be interfered with. 我不想别人干扰我的事情。 来自《简明英汉词典》

116 agitated   

adj.被鼓动的，不安的

参考例句：

• His answers were all mixed up,so agitated was he.他是那样心神不定，回答全乱了。
• She was agitated because her train was an hour late.她乘坐的火车晚点一个小时，她十分焦虑。

117 intervals   

n.[军事]间隔( interval的名词复数 )；间隔时间；[数学]区间；（戏剧、电影或音乐会的）幕间休息

参考例句：

• The forecast said there would be sunny intervals and showers. 预报间晴，有阵雨。
• Meetings take place at fortnightly intervals. 每两周开一次会。

118 irritability   

n.易怒

参考例句：

• It was the almost furtive restlessness and irritability that had possessed him. 那是一种一直纠缠着他的隐秘的不安和烦恼。
• All organisms have irritability while alive. 所有生物体活着时都有应激性。

119 ascertain   

vt.发现，确定，查明，弄清

参考例句：

• It's difficult to ascertain the coal deposits.煤储量很难探明。
• We must ascertain the responsibility in light of different situtations.我们必须根据不同情况判定责任。

120 exhausted   

adj.极其疲惫的，精疲力尽的

参考例句：

• It was a long haul home and we arrived exhausted.搬运回家的这段路程特别长，到家时我们已筋疲力尽。
• Jenny was exhausted by the hustle of city life.珍妮被城市生活的忙乱弄得筋疲力尽。

121 flirted   

v.调情，打情骂俏( flirt的过去式和过去分词 )

参考例句：

• She flirted her fan. 她急速挥动着扇子。 来自《现代英汉综合大词典》
• During his four months in Egypt he flirted with religious emotions. 在埃及逗留的这四个月期间，他又玩弄起宗教情绪来了。 来自辞典例句

122 exclusion   

n.拒绝，排除，排斥，远足，远途旅行

参考例句：

• Don't revise a few topics to the exclusion of all others.不要修改少数论题以致排除所有其他的。
• He plays golf to the exclusion of all other sports.他专打高尔夫球，其他运动一概不参加。

123 glands   

n.腺( gland的名词复数 )

参考例句：

• a snake's poison glands 蛇的毒腺
• the sebaceous glands in the skin 皮脂腺

124 retarded   

a.智力迟钝的，智力发育迟缓的

参考例句：

• The progression of the disease can be retarded by early surgery. 早期手术可以抑制病情的发展。
• He was so slow that many thought him mentally retarded. 他迟钝得很，许多人以为他智力低下。

125 extraordinarily   

adv.格外地；极端地

参考例句：

• She is an extraordinarily beautiful girl.她是个美丽非凡的姑娘。
• The sea was extraordinarily calm that morning.那天清晨，大海出奇地宁静。

126 friction   

n.摩擦，摩擦力

参考例句：

• When Joan returned to work,the friction between them increased.琼回来工作后，他们之间的摩擦加剧了。
• Friction acts on moving bodies and brings them to a stop.摩擦力作用于运动着的物体，并使其停止。

127 promptly   

adv.及时地，敏捷地

参考例句：

• He paid the money back promptly.他立即还了钱。
• She promptly seized the opportunity his absence gave her.她立即抓住了因他不在场给她创造的机会。

128 secondly   

adv.第二，其次

参考例句：

• Secondly,use your own head and present your point of view.第二，动脑筋提出自己的见解。
• Secondly it is necessary to define the applied load.其次，需要确定所作用的载荷。

129 superfluous   

adj.过多的，过剩的，多余的

参考例句：

• She fined away superfluous matter in the design. 她删去了这图案中多余的东西。
• That request seemed superfluous when I wrote it.我这样写的时候觉得这个请求似乎是多此一举。

130 fixed   

adj.固定的，不变的，准备好的；(计算机)固定的

参考例句：

• Have you two fixed on a date for the wedding yet?你们俩选定婚期了吗？
• Once the aim is fixed,we should not change it arbitrarily.目标一旦确定，我们就不应该随意改变。

131 twigs   

细枝，嫩枝( twig的名词复数 )

参考例句：

• Some birds build nests of twigs. 一些鸟用树枝筑巢。
• Willow twigs are pliable. 柳条很软。

132 sinuous   

adj.蜿蜒的，迂回的

参考例句：

• The river wound its sinuous way across the plain.这条河蜿蜒曲折地流过平原。
• We moved along the sinuous gravel walks,with the great concourse of girls and boys.我们沿着曲折的石径,随着男孩女孩汇成的巨流一路走去。

133 zigzag   

n.曲折，之字形；adj.曲折的，锯齿形的；adv.曲折地，成锯齿形地；vt.使曲折；vi.曲折前行

参考例句：

• The lightning made a zigzag in the sky.闪电在天空划出一道Z字形。
• The path runs zigzag up the hill.小径向山顶蜿蜒盘旋。

134 spires   

n.（教堂的） 塔尖，尖顶( spire的名词复数 )

参考例句：

• Her masts leveled with the spires of churches. 船的桅杆和教堂的塔尖一样高。 来自《简明英汉词典》
• White church spires lift above green valleys. 教堂的白色尖顶耸立在绿色山谷中。 来自《简明英汉词典》

135 catching   

adj.易传染的，有魅力的，迷人的，接住

参考例句：

• There are those who think eczema is catching.有人就是认为湿疹会传染。
• Enthusiasm is very catching.热情非常富有感染力。

136 simultaneously   

adv.同时发生地，同时进行地

参考例句：

• The radar beam can track a number of targets almost simultaneously.雷达波几乎可以同时追着多个目标。
• The Windows allow a computer user to execute multiple programs simultaneously.Windows允许计算机用户同时运行多个程序。

137 phenomena   

n.现象

参考例句：

• Ade couldn't relate the phenomena with any theory he knew.艾德无法用他所知道的任何理论来解释这种现象。
• The object of these experiments was to find the connection,if any,between the two phenomena.这些实验的目的就是探索这两种现象之间的联系，如果存在着任何联系的话。

138 ascends   

v.上升，攀登( ascend的第三人称单数 )

参考例句：

• The azygos vein ascends in the right paravertebral gutter. 奇静脉在右侧脊柱旁沟内上升。 来自辞典例句
• The mortality curve ascends gradually to a plateau at age 65. 死亡曲线逐渐上升，到65岁时成平稳状态。 来自辞典例句

139 elasticity   

n.弹性，伸缩力

参考例句：

• The skin eventually loses its elasticity.皮肤最终会失去弹性。
• Every sort of spring has a definite elasticity.每一种弹簧都有一定的弹性。

140 gale   

n.大风，强风，一阵闹声（尤指笑声等）

参考例句：

• We got our roof blown off in the gale last night.昨夜的大风把我们的房顶给掀掉了。
• According to the weather forecast,there will be a gale tomorrow.据气象台预报，明天有大风。

141 prostrate   

v.拜倒，平卧，衰竭；adj.拜倒的，平卧的，衰竭的

参考例句：

• She was prostrate on the floor.她俯卧在地板上。
• The Yankees had the South prostrate and they intended to keep It'so.北方佬已经使南方屈服了,他们还打算继续下去。

142 botanists   

n.植物学家，研究植物的人( botanist的名词复数 )

参考例句：

• Botanists had some difficulty categorizing the newly found plant. 植物学家们不大容易确定这种新发现的植物的种类。 来自辞典例句
• Botanists refer this flower to the rose family. 植物学家将这花归入蔷薇科。 来自辞典例句

143 sufficiently   

adv.足够地，充分地

参考例句：

• It turned out he had not insured the house sufficiently.原来他没有给房屋投足保险。
• The new policy was sufficiently elastic to accommodate both views.新政策充分灵活地适用两种观点。

144 allude   

v.提及，暗指

参考例句：

• Many passages in Scripture allude to this concept.圣经中有许多经文间接地提到这样的概念。
• She also alluded to her rival's past marital troubles.她还影射了对手过去的婚姻问题。

145 strings   

n.弦

参考例句：

• He sat on the bed,idly plucking the strings of his guitar.他坐在床上，随意地拨着吉他的弦。
• She swept her fingers over the strings of the harp.她用手指划过竖琴的琴弦。

146 inevitably   

adv.不可避免地；必然发生地

参考例句：

• In the way you go on,you are inevitably coming apart.照你们这样下去，毫无疑问是会散伙的。
• Technological changes will inevitably lead to unemployment.技术变革必然会导致失业。

147 inevitable   

adj.不可避免的，必然发生的

参考例句：

• Mary was wearing her inevitable large hat.玛丽戴着她总是戴的那顶大帽子。
• The defeat had inevitable consequences for British policy.战败对英国政策不可避免地产生了影响。

148 axis   

n.轴，轴线，中心线；坐标轴，基准线

参考例句：

• The earth's axis is the line between the North and South Poles.地轴是南北极之间的线。
• The axis of a circle is its diameter.圆的轴线是其直径。

149 affixing   

v.附加( affix的现在分词 )；粘贴；加以；盖（印章）

参考例句：

• Formally approves a document by affixing a signature. 以签名的形式正式批准文件。 来自互联网
• Forfixing, insulating, shock affixing parts or screws of many items such as appliances, stereos, and eyeglasses. 电器、音响响、光学学、电脑等的零件、螺丝固定绝缘、防震与接著。 来自互联网

150 compensated   

补偿，报酬( compensate的过去式和过去分词 )； 给（某人）赔偿（或赔款）

参考例句：

• The marvelous acting compensated for the play's weak script. 本剧的精彩表演弥补了剧本的不足。
• I compensated his loss with money. 我赔偿他经济损失。

151 perpendicular   

adj.垂直的，直立的；n.垂直线，垂直的位置

参考例句：

• The two lines of bones are set perpendicular to one another.这两排骨头相互垂直。
• The wall is out of the perpendicular.这墙有些倾斜。

152 consecutive   

adj.连续的，联贯的，始终一贯的

参考例句：

• It has rained for four consecutive days.已连续下了四天雨。
• The policy of our Party is consecutive.我党的政策始终如一。

153 stiffens   

（使）变硬，（使）强硬( stiffen的第三人称单数 )

参考例句：

• Heating the foam stiffens it and forms it. 暖气泡沫stiffens它和形式。
• He stiffens in momentary panic. 他心里一阵惊慌，浑身不自在起来。

154 crevices   

n.（尤指岩石的）裂缝，缺口( crevice的名词复数 )

参考例句：

• It has bedded into the deepest crevices of the store. 它已钻进了店里最隐避的隙缝。 来自辞典例句
• The wind whistled through the crevices in the rock. 风呼啸着吹过岩石的缝隙。 来自辞典例句

155 durable   

adj.持久的，耐久的

参考例句：

• This raincoat is made of very durable material.这件雨衣是用非常耐用的料子做的。
• They frequently require more major durable purchases.他们经常需要购买耐用消费品。

156 ascending   

adj.上升的，向上的

参考例句：

• Now draw or trace ten dinosaurs in ascending order of size.现在按照体型由小到大的顺序画出或是临摹出10只恐龙。

157 twines   

n.盘绕( twine的名词复数 )；麻线；捻；缠绕在一起的东西

参考例句：

• The vine twines round the tree. 这藤盘绕在树干上。 来自《简明英汉词典》
• A stream twines across the valley. 一条小溪蜿蜒流过山谷。 来自《简明英汉词典》

158 pointed   

adj.尖的，直截了当的

参考例句：

• He gave me a very sharp pointed pencil.他给我一支削得非常尖的铅笔。
• She wished to show Mrs.John Dashwood by this pointed invitation to her brother.她想通过对达茨伍德夫人提出直截了当的邀请向她的哥哥表示出来。

159 enveloping   

v.包围，笼罩，包住( envelop的现在分词 )

参考例句：

• Always the eyes watching you and the voice enveloping you. 那眼睛总是死死盯着你，那声音总是紧紧围着你。 来自英汉文学
• The only barrier was a mosquito net, enveloping the entire bed. 唯一的障碍是那顶蚊帐罩住整个床。 来自辞典例句

160 neatly   

adv.整洁地，干净地，灵巧地，熟练地

参考例句：

• Sailors know how to wind up a long rope neatly.水手们知道怎样把一条大绳利落地缠好。
• The child's dress is neatly gathered at the neck.那孩子的衣服在领口处打着整齐的皱褶。

161 secretion   

n.分泌

参考例句：

• Is there much secretion from your eyes?你眼里的分泌物多吗？
• In addition,excessive secretion of oil,water scarcity are also major factors.除此之外，油脂分泌过盛、缺水也都是主要因素。

162 peculiarities   

n. 特质, 特性, 怪癖, 古怪

参考例句：

• the cultural peculiarities of the English 英国人的文化特点
• He used to mimic speech peculiarities of another. 他过去总是模仿别人讲话的特点。

163 credible   

adj.可信任的，可靠的

参考例句：

• The news report is hardly credible.这则新闻报道令人难以置信。
• Is there a credible alternative to the nuclear deterrent?是否有可以取代核威慑力量的可靠办法？

164 acceleration   

n.加速，加速度

参考例句：

• All spacemen must be able to bear acceleration.所有太空人都应能承受加速度。
• He has also called for an acceleration of political reforms.他同时呼吁加快政治改革的步伐。

165 accounting   

n.会计，会计学，借贷对照表

参考例句：

• A job fell vacant in the accounting department.财会部出现了一个空缺。
• There's an accounting error in this entry.这笔账目里有差错。

166 intelligible   

adj.可理解的，明白易懂的，清楚的

参考例句：

• This report would be intelligible only to an expert in computing.只有计算机运算专家才能看懂这份报告。
• His argument was barely intelligible.他的论点不易理解。