Hook–Climbers. — In my introductory remarks, I stated that, besides the two first great classes of climbing plants, namely, those which twine6 round a support, and those endowed with irritability7 enabling them to seize hold of objects by means of their petioles or tendrils, there are two other classes, hook-climbers and root-climbers. Many plants, moreover, as Fritz Muller has remarked, 40 climb or scramble8 up thickets10 in a still more simple fashion, without any special aid, excepting that their leading shoots are generally long and flexible. It may, however, be suspected from what follows, that these shoots in some cases tend to avoid the light. The few hook-climbers which I have observed, namely, Galium aparine, Rubus australis, and some climbing Roses, exhibit no spontaneous revolving11 movement. If they had possessed12 this power, and had been capable of twining, they would have been placed in the class of Twiners; for some twiners are furnished with spines14 or hooks, which aid them in their ascent15. For instance, the Hop16, which is a twiner13, has reflexed hooks as large as those of the Galium; some other twiners have stiff reflexed hairs; and Dipladenia has a circle of blunt spines at the bases of its leaves. I have seen only one tendril-bearing plant, namely, Smilax aspera, which is furnished with reflexed spines; but this is the case with several branch-climbers in South Brazil and Ceylon; and their branches graduate into true tendrils. Some few plants apparently17 depend solely18 on their hooks for climbing, and yet do so efficiently19, as certain palms in the New and Old Worlds. Even some climbing Roses will ascend20 the walls of a tall house, if covered with a trellis. How this is effected I know not; for the young shoots of one such Rose, when placed in a pot in a window, bent21 irregularly towards the light during the day and from the light during the night, like the shoots of any common plant; so that it is not easy to understand how they could have got under a trellis close to the wall. 41
Root-climbers. — A good many plants come under this class, and are excellent climbers. One of the most remarkable22 is the Marcgravia umbellata, the stem of which in the tropical forests of South America, as I hear from Mr. Spruce, grows in a curiously23 flattened24 manner against the trunks of trees; here and there it puts forth25 claspers (roots), which adhere to the trunk, and, if the latter be slender, completely embrace it. When this plant has climbed to the light, it produces free branches with rounded stems, clad with sharp-pointed26 leaves, wonderfully different in appearance from those borne by the stem as long as it remains28 adherent29. This surprising difference in the leaves, I have also observed in a plant of Marcgravia dubia in my hothouse. Root-climbers, as far as I have seen, namely, the Ivy30 (Hedera helix), Ficus repens, and F. barbatus, have no power of movement, not even from the light to the dark. As previously31 stated, the Hoya carnosa (Asclepiadaceae) is a spiral twiner, and likewise adheres by rootlets even to a flat wall. The tendril-bearing Bignonia Tweedyana emits roots, which curve half round and adhere to thin sticks. The Tecoma radicans (Bignoniaceae), which is closely allied32 to many spontaneously revolving species, climbs by rootlets; nevertheless, its young shoots apparently move about more than can be accounted for by the varying action of the light.
I have not closely observed many root-climbers, but can give one curious fact. Ficus repens climbs up a wall just like Ivy; and when the young rootlets are made to press lightly on slips of glass, they emit after about a week’s interval33, as I observed several times, minute drops of clear fluid, not in the least milky34 like that exuded35 from a wound. This fluid is slightly viscid, but cannot be drawn36 out into threads. It has the remarkable property of not soon drying; a drop, about the size of half a pin’s head, was slightly spread out on glass, and I scattered37 on it some minute grains of sand. The glass was left exposed in a drawer during hot and dry weather, and if the fluid had been water, it would certainly have dried in a few minutes; but it remained fluid, closely surrounding each grain of sand, during 128 days: how much longer it would have remained I cannot say. Some other rootlets were left in contact with the glass for about ten days or a fortnight, and the drops of secreted fluid were now rather larger, and so viscid that they could be drawn out into threads. Some other rootlets were left in contact during twenty-three days, and these were firmly cemented to the glass. Hence we may conclude that the rootlets first secrete4 a slightly viscid fluid, subsequently absorb the watery38 parts, (for we have seen that the fluid will not dry by itself,) and ultimately leave a cement. When the rootlets were torn from the glass, atoms of yellowish matter were left on it, which were partly dissolved by a drop of bisulphide of carbon; and this extremely volatile39 fluid was rendered very much less volatile by what it had dissolved.
As the bisulphide of carbon has a strong power of softening40 indurated caoutchouc, I soaked in it during a short time several rootlets of a plant which had grown up a plaistered wall; and I then found many extremely thin threads of transparent41, not viscid, excessively elastic42 matter, precisely43 like caoutchouc, attached to two sets of rootlets on the same branch. These threads proceeded from the bark of the rootlet at one end, and at the other end were firmly attached to particles of silex or mortar44 from the wall. There could be no mistake in this observation, as I played with the threads for a long time under the microscope, drawing them out with my dissecting-needles and letting them spring back again. Yet I looked repeatedly at other rootlets similarly treated, and could never again discover these elastic threads. I therefore infer that the branch in question must have been slightly moved from the wall at some critical period, whilst the secretion45 was in the act of drying, through the absorption of its watery parts. The genus Ficus abounds46 with caoutchouc, and we may conclude from the facts just given that this substance, at first in solution and ultimately modified into an unelastic cement, 42 is used by the Ficus repens to cement its rootlets to any surface which it ascends47. Whether other plants, which climb by their rootlets, emit any cement I do not know; but the rootlets of the Ivy, placed against glass, barely adhered to it, yet secreted a little yellowish matter. I may add, that the rootlets of the Marcgravia dubia can adhere firmly to smooth painted wood.
Vanilla48 aromatica emits aerial roots a foot in length, which point straight down to the ground. According to Mohl (p. 49), these crawl into crevices49, and when they meet with a thin support, wind round it, as do tendrils. A plant which I kept was young, and did not form long roots; but on placing thin sticks in contact with them, they certainly bent a little to that side, in the course of about a day, and adhered by their rootlets to the wood; but they did not bend quite round the sticks, and afterwards they re-pursued their downward course. It is probable that these slight movements of the roots are due to the quicker growth of the side exposed to the light, in comparison with the other side, and not because the roots are sensitive to contact in the same manner as true tendrils. According to Mohl, the rootlets of certain species of Lycopodium act as tendrils. 43
Concluding Remarks on Climbing Plants.
Plants become climbers, in order, as it may be presumed, to reach the light, and to expose a large surface of their leaves to its action and to that of the free air. This is effected by climbers with wonderfully little expenditure50 of organized matter, in comparison with trees, which have to support a load of heavy branches by a massive trunk. Hence, no doubt, it arises that there are so many climbing plants in all quarters of the world, belonging to so many different orders. These plants have been arranged under four classes, disregarding those which merely scramble over bushes without any special aid. Hook-climbers are the least efficient of all, at least in our temperate51 countries, and can climb only in the midst of an entangled52 mass of vegetation. Root-climbers are excellently adapted to ascend naked faces of rock or trunks of trees; when, however, they climb trunks they are compelled to keep much in the shade; they cannot pass from branch to branch and thus cover the whole summit of a tree, for their rootlets require long-continued and close contact with a steady surface in order to adhere. The two great classes of twiners and of plants with sensitive organs, namely, leaf-climbers and tendril-bearers taken together, far exceed in number and in the perfection of their mechanism53 the climbers of the two first classes. Those which have the power of spontaneously revolving and of grasping objects with which they come in contact, easily pass from branch to branch, and securely ramble9 over a wide, sun-lit surface.
The divisions containing twining plants, leaf-climbers, and tendril-bearers graduate to a certain extent into one another, and nearly all have the same remarkable power of spontaneously revolving. Does this gradation, it may be asked, indicate that plants belonging to one subdivision have actually passed during the lapse54 of ages, or can pass, from one state to the other? Has, for instance, any tendril-bearing plant assumed its present structure without having previously existed as a leaf-climber or a twiner? If we consider leaf-climbers alone, the idea that they were primordially56 twiners is forcibly suggested. The internodes of all, without exception, revolve57 in exactly the same manner as twiners; some few can still twine well, and many others in an imperfect manner. Several leaf-climbing genera are closely allied to other genera which are simple twiners. It should also be observed, that the possession of leaves with sensitive petioles, and with the consequent power of clasping an object, would be of comparatively little use to a plant, unless associated with revolving internodes, by which the leaves are brought into contact with a support; although no doubt a scrambling plant would be apt, as Professor Jaeger has remarked, to rest on other plants by its leaves. On the other hand, revolving internodes, without any other aid, suffice to give the power of climbing; so that it seems probable that leaf-climbers were in most cases at first twiners, and subsequently became capable of grasping a support; and this, as we shall presently see, is a great additional advantage.
From analogous58 reasons, it is probable that all tendril-bearers were primordially twiners, that is, are the descendants of plants having this power and habit. For the internodes of the majority revolve; and, in a few species, the flexible stem still retains the capacity of spirally twining round an upright stick. Tendril-bearers have undergone much more modification59 than leaf-climbers; hence it is not surprising that their supposed primordial55 habits of revolving and twining have been more frequently lost or modified than in the case of leaf-climbers. The three great tendril-bearing families in which this loss has occurred in the most marked manner, are the Cucurbitaceae, Passifloraceae, and Vitaceae. In the first, the internodes revolve; but I have heard of no twining form, with the exception (according to Palm, p. 29. 52) of Momordica balsamina, and this is only an imperfect twiner. In the two other families I can hear of no twiners; and the internodes rarely have the power of revolving, this power being confined to the tendrils. The internodes, however, of Passiflora gracilis have the power in a perfect manner, and those of the common Vine in an imperfect degree: so that at least a trace of the supposed primordial habit has been retained by some members of all the larger tendril-bearing groups.
On the view here given, it may be asked, Why have the species which were aboriginally twiners been converted in so many groups into leaf-climbers or tendril-bearers? Of what advantage has this been to them? Why did they not remain simple twiners? We can see several reasons. It might be an advantage to a plant to acquire a thicker stem, with short internodes bearing many or large leaves; and such stems are ill fitted for twining. Any one who will look during windy weather at twining plants will see that they are easily blown from their support; not so with tendril-bearers or leaf-climbers, for they quickly and firmly grasp their support by a much more efficient kind of movement. In those plants which still twine, but at the same time possess tendrils or sensitive petioles, as some species of Bignonia, Clematis, and Tropaeolum, it can readily be observed how incomparably better they grasp an upright stick than do simple twiners. Tendrils, from possessing this power of grasping an object, can be made long and thin; so that little organic matter is expended60 in their development, and yet they sweep a wide circle in search of a support. Tendril-bearers can, from their first growth, ascend along the outer branches of any neighbouring bush, and they are thus always fully27 exposed to the light; twiners, on the contrary, are best fitted to ascend bare stems, and generally have to start in the shade. Within tall and dense61 tropical forests, twining plants would probably succeed better than most kinds of tendril-bearers; but the majority of twiners, at least in our temperate regions, from the nature of their revolving movement, cannot ascend thick trunks, whereas this can be affected62 by tendril-bearers if the trunks are branched or bear twigs63, and by some species if the bark is rugged64.
The advantage gained by climbing is to reach the light and free air with as little expenditure of organic matter as possible; now, with twining plants, the stem is much longer than is absolutely necessary; for instance, I measured the stem of a kidney-bean, which had ascended65 exactly two feet in height, and it was three feet in length: the stem of a pea, on the other hand, which had ascended to the same height by the aid of its tendrils, was but little longer than the height reached. That this saving of the stem is really an advantage to climbing plants, I infer from the species that still twine but are aided by clasping petioles or tendrils, generally making more open spires66 than those made by simple twiners. Moreover, the plants thus aided, after taking one or two turns in one direction, generally ascend for a space straight, and then reverse the direction of their spire67. By this means they ascend to a considerably68 greater height, with the same length of stem, than would otherwise have been possible; and they do this with safety, as they secure themselves at intervals69 by their clasping petioles or tendrils.
We have seen that tendrils consist of various organs in a modified state, namely, leaves, flower-peduncles, branches, and perhaps stipules. With respect to leaves, the evidence of their modification is ample. In young plants of Bignonia the lower leaves often remain quite unchanged, whilst the upper ones have their terminal leaflets converted into perfect tendrils; in Eccremocarpus I have seen a single lateral70 branch of a tendril replaced by a perfect leaflet; in Vicia sativa, on the other hand, leaflets are sometimes replaced by tendril-branches; and many other such cases could be given. But he who believes in the slow modification of species will not be content simply to ascertain71 the homological nature of different kinds of tendrils; he will wish to learn, as far as is possible, by what actual steps leaves, flower-peduncles, &c., have had their functions wholly changed, and have come to serve merely as prehensile72 organs.
In the whole group of leaf-climbers abundant evidence has been given that an organ, still subserving the functions of a leaf, may become sensitive to a touch, and thus grasp an adjoining object. With several leaf-climbers the true leaves spontaneously revolve; and their petioles, after clasping a support grow thicker and stronger. We thus see that leaves may acquire all the leading and characteristic qualities of tendrils, namely, sensitiveness, spontaneous movement, and subsequently increased strength. If their blades or laminae were to abort73, they would form true tendrils. And of this process of abortion74 we can follow every step, until no trace of the original nature of the tendril is left. In Mutisia clematis, the tendril, in shape and colour, closely resembles the petiole of one of the ordinary leaves, together with the midribs of the leaflets, but vestiges75 of the laminae are still occasionally retained. In four genera of the Fumariaceae we can follow the whole process of transformation77. The terminal leaflets of the leaf-climbing Fumaria officinalis are not smaller than the other leaflets; those of the leaf-climbing Adlumia cirrhosa are greatly reduced; those of Corydalis claviculata (a plant which may indifferently be called a leaf-climber or a tendril-bearer) are either reduced to microscopical78 dimensions or have their blades wholly aborted79, so that this plant is actually in a state of transition; and, finally, in the Dicentra the tendrils are perfectly80 characterized. If, therefore, we could behold81 at the same time all the progenitors82 of Dicentra, we should almost certainly see a series like that now exhibited by the above-named three genera. In Tropaeolum tricolorum we have another kind of passage; for the leaves which are first formed on the young stems are entirely83 destitute84 of laminae, and must be called tendrils, whilst the later formed leaves have well-developed laminae. In all cases the acquirement of sensitiveness by the mid-ribs of the leaves appears to stand in some close relation with the abortion of their laminae or blades.
On the view here given, leaf-climbers were primordially twiners, and tendril-bearers (when formed of modified leaves) were primordially leaf-climbers. The latter, therefore, are intermediate in nature between twiners and tendril-bearers, and ought to be related to both. This is the case: thus the several leaf-climbing species of the Antirrhineae, of Solanum, Cocculus, and Gloriosa, have within the same family and even within the same genus, relatives which are twiners. In the genus Mikania, there are leaf-climbing and twining species. The leaf-climbing species of Clematis are very closely allied to the tendril-bearing Naravelia. The Fumariaceae include closely allied genera which are leaf-climbers and tendril-bearers. Lastly, a species of Bignonia is at the same time both a leaf-climber and a tendril-bearer; and other closely allied species are twiners.
Tendrils of another kind consist of modified flower-peduncles. In this case we likewise have many interesting transitional states. The common Vine (not to mention the Cardiospermum) gives us every possible gradation between a perfectly developed tendril and a flower-peduncle covered with flowers, yet furnished with a branch, forming the flower-tendril. When the latter itself bears a few flowers, as we know sometimes is the case, and still retains the power of clasping a support, we see an early condition of all those tendrils which have been formed by the modification of flower-peduncles.
According to Mohl and others, some tendrils consist of modified branches: I have not observed any such cases, and know nothing of their transitional states, but these have been fully described by Fritz Muller. The genus Lophospermum also shows us how such a transition is possible; for its branches spontaneously revolve and are sensitive to contact. Hence, if the leaves on some of the branches of the Lophospermum were to abort, these branches would be converted into true tendrils. Nor is there anything improbable in certain branches alone being thus modified, whilst others remained unaltered; for we have seen with certain varieties of Phaseolus, that some of the branches are thin, flexible, and twine, whilst other branches on the same plant are stiff and have no such power.
If we inquire how a petiole, a branch or flower-peduncle first became sensitive to a touch, and acquired the power of bending towards the touched side, we get no certain answer. Nevertheless an observation by Hofmeister 44 well deserves attention, namely, that the shoots and leaves of all plants, whilst young, move after being shaken. Kerner also finds, as we have seen, that the flower-peduncles of a large number of plants, if shaken or gently rubbed bend to this side. And it is young petioles and tendrils, whatever their homological nature may be, which move on being touched. It thus appears that climbing plants have utilized85 and perfected a widely distributed and incipient86 capacity, which capacity, as far as we can see, is of no service to ordinary plants. If we further inquire how the stems, petioles, tendrils, and flower-peduncles of climbing plants first acquired their power of spontaneously revolving, or, to speak more accurately87, of successively bending to all points of the compass, we are again silenced, or at most can only remark that the power of moving, both spontaneously and from various stimulants88, is far more common with plants, than is generally supposed to be the case by those who have not attended to the subject. I have given one remarkable instance, namely that of the Maurandia semperflorens, the young flower-peduncles of which spontaneously revolve in very small circles, and bend when gently rubbed to the touched side; yet this plant certainly does not profit by these two feebly developed powers. A rigorous examination of other young plants would probably show slight spontaneous movements in their stems, petioles or peduncles, as well as sensitiveness to a touch. 45 We see at least that the Maurandia might, by a little augmentation of the powers which it already possesses, come first to grasp a support by its flower-peduncles, and then, by the abortion of some of its flowers (as with Vitis or Cardiospermum), acquire perfect tendrils.
There is one other interesting point which deserves notice. We have seen that some tendrils owe their origin to modified leaves, and others to modified flower-peduncles; so that some are foliar and others axial in their nature. It might therefore have been expected that they would have presented some difference in function. This is not the case. On the contrary, they present the most complete identity in their several characteristic powers. Tendrils of both kinds spontaneously revolve at about the same rate. Both, when touched, bend quickly to the touched side, and afterwards recover themselves and are able to act again. In both the sensitiveness is either confined to one side or extends all round the tendril. Both are either attracted or repelled89 by the light. The latter property is seen in the foliar tendrils of Bignonia capreolata and in the axial tendrils of Ampelopsis. The tips of the tendrils in these two plants become, after contact, enlarged into discs, which are at first adhesive by the secretion of some cement. Tendrils of both kinds, soon after grasping a support, contract spirally; they then increase greatly in thickness and strength. When we add to these several points of identity the fact that the petiole of Solanum jasminoides, after it has clasped a support, assumes one of the most characteristic features of the axis90, namely, a closed ring of woody vessels91, we can hardly avoid asking, whether the difference between foliar and axial organs can be of so fundamental a nature as is generally supposed? 46
We have attempted to trace some of the stages in the genesis of climbing plants. But, during the endless fluctuations92 of the conditions of life to which all organic beings have been exposed, it might be expected that some climbing plants would have lost the habit of climbing. In the cases given of certain South African plants belonging to great twining families, which in their native country never twine, but reassume this habit when cultivated in England, we have a case in point. In the leaf-climbing Clematis flammula, and in the tendril-bearing Vine, we see no loss in the power of climbing, but only a remnant of the revolving power which is indispensable to all twiners, and is so common as well as so advantageous93 to most climbers. In Tecoma radicans, one of the Bignoniaceae, we see a last and doubtful trace of the power of revolving.
With respect to the abortion of tendrils, certain cultivated varieties of Cucurbita pepo have, according to Naudin, 47 either quite lost these organs or bear semi-monstrous representatives of them. In my limited experience, I have met with only one apparent instance of their natural suppression, namely, in the common bean. All the other species of Vicia, I believe, bear tendrils; but the bean is stiff enough to support its own stem, and in this species, at the end of the petiole, where, according to analogy, a tendril ought to have existed, a small pointed filament94 projects, about a third of an inch in length, and which is probably the rudiment95 of a tendril. This may be the more safely inferred, as in young and unhealthy specimens96 of other tendril-bearing plants similar rudiments97 may occasionally be observed. In the bean these filaments98 are variable in shape, as is so frequently the case with rudimentary organs; they are either cylindrical99, or foliaceous, or are deeply furrowed100 on the upper surface. They have not retained any vestige76 of the power of revolving. It is a curious fact, that many of these filaments, when foliaceous, have on their lower surfaces, dark-coloured glands101 like those on the stipules, which excrete a sweet fluid; so that these rudiments have been feebly utilized.
One other analogous case, though hypothetical, is worth giving. Nearly all the species of Lathyrus possesses tendrils; but L. nissolia is destitute of them. This plant has leaves, which must have struck everyone with surprise who has noticed them, for they are quite unlike those of all common papilionaceous plants, and resemble those of a grass. In another species, L. aphaca, the tendril, which is not highly developed (for it is unbranched, and has no spontaneous revolving-power), replaces the leaves, the latter being replaced in function by large stipules. Now if we suppose the tendrils of L. aphaca to become flattened and foliaceous, like the little rudimentary tendrils of the bean, and the large stipules to become at the same time reduced in size, from not being any longer wanted, we should have the exact counterpart of L. nissolia, and its curious leaves are at once rendered intelligible102 to us.
It may be added, as serving to sum up the foregoing views on the origin of tendril-bearing plants, that L. nissolia is probably descended103 from a plant which was primordially a twiner; this then became a leaf-climber, the leaves being afterwards converted by degrees into tendrils, with the stipules greatly increased in size through the law of compensation. 48 After a time the tendrils lost their branches and became simple; they then lost their revolving-power (in which state they would have resembled the tendrils of the existing L. aphaca), and afterwards losing their prehensile power and becoming foliaceous would no longer be thus designated. In this last stage (that of the existing L. nissolia) the former tendrils would reassume their original function of leaves, and the stipules which were recently much developed being no longer wanted, would decrease in size. If species become modified in the course of ages, as almost all naturalists104 now admit, we may conclude that L. nissolia has passed through a series of changes, in some degree like those here indicated.
The most interesting point in the natural history of climbing plants is the various kinds of movement which they display in manifest relation to their wants. The most different organs — stems, branches, flower-peduncles, petioles, mid-ribs of the leaf and leaflets, and apparently aerial roots — all possess this power.
The first action of a tendril is to place itself in a proper position. For instance, the tendril of Cobaea first rises vertically105 up, with its branches divergent and with the terminal hooks turned outwards106; the young shoot at the extremity107 of the stem is at the same time bent to one side, so as to be out of the way. The young leaves of Clematis, on the other hand, prepare for action by temporarily curving themselves downwards108, so as to serve as grapnels.
Secondly109, if a twining plant or a tendril gets by any accident into an inclined position, it soon bends upwards110, though secluded111 from the light. The guiding stimulus112 no doubt is the attraction of gravity, as Andrew Knight113 showed to be the case with germinating114 plants. If a shoot of any ordinary plant be placed in an inclined position in a glass of water in the dark, the extremity will, in a few hours, bend upwards; and if the position of the shoot be then reversed, the downward-bent shoot reverses its curvature; but if the stolen of a strawberry, which has no tendency to grow upwards, be thus treated, it will curve downwards in the direction of, instead of in opposition115 to, the force of gravity. As with the strawberry, so it is generally with the twining shoots of the Hibbertia dentata, which climbs laterally116 from bush to bush; for these shoots, if placed in a position inclined downwards, show little and sometimes no tendency to curve upwards.
Thirdly, climbing plants, like other plants, bend towards the light by a movement closely analogous to the incurvation which causes them to revolve, so that their revolving movement is often accelerated or retarded117 in travelling to or from the light. On the other hand, in a few instances tendrils bend towards the dark.
Fourthly, we have the spontaneous revolving movement which is independent of any outward stimulus, but is contingent118 on the youth of the part, and on vigorous health; and this again of course depends on a proper temperature and other favourable119 conditions of life.
Fifthly, tendrils, whatever their homological nature may be, and the petioles or tips of the leaves of leaf-climbers, and apparently certain roots, all have the power of movement when touched, and bend quickly towards the touched side. Extremely slight pressure often suffices. If the pressure be not permanent, the part in question straightens itself and is again ready to bend on being touched.
Sixthly, and lastly, tendrils, soon after clasping a support, but not after a mere1 temporary curvature, contract spirally. If they have not come into contact with any object, they ultimately contract spirally, after ceasing to revolve; but in this case the movement is useless, and occurs only after a considerable lapse of time.
With respect to the means by which these various movements are effected, there can be little doubt from the researches of Sachs and H. de Vries, that they are due to unequal growth; but from the reasons already assigned, I cannot believe that this explanation applies to the rapid movements from a delicate touch.
Finally, climbing plants are sufficiently120 numerous to form a conspicuous121 feature in the vegetable kingdom, more especially in tropical forests. America, which so abounds with arboreal122 animals, as Mr. Bates remarks, likewise abounds according to Mohl and Palm with climbing plants; and of the tendril-bearing plants examined by me, the highest developed kinds are natives of this grand continent, namely, the several species of Bignonia, Eccremocarpus, Cobaea, and Ampelopsis. But even in the thickets of our temperate regions the number of climbing species and individuals is considerable, as will be found by counting them. They belong to many and widely different orders. To gain some rude idea of their distribution in the vegetable series, I marked, from the lists given by Mohl and Palm (adding a few myself, and a competent botanist123, no doubt, could have added many more), all those families in Lindley’s ‘Vegetable Kingdom’ which include twiners, leaf-climbers, or tendril-bearers. Lindley divides Phanerogamic plants into fifty-nine Alliances; of these, no less than thirty-five include climbing plants of the above kinds, hook and root-climbers being excluded. To these a few Cryptogamic plants must be added. When we reflect on the wide separation of these plants in the series, and when we know that in some of the largest, well-defined orders, such as the Compositae, Rubiaceae, Scrophulariaceae, Liliaceae, &c., species in only two or three genera have the power of climbing, the conclusion is forced on our minds that the capacity of revolving, on which most climbers depend, is inherent, though undeveloped, in almost every plant in the vegetable kingdom.
It has often been vaguely124 asserted that plants are distinguished125 from animals by not having the power of movement. It should rather be said that plants acquire and display this power only when it is of some advantage to them; this being of comparatively rare occurrence, as they are affixed126 to the ground, and food is brought to them by the air and rain. We see how high in the scale of organization a plant may rise, when we look at one of the more perfect tendril-bearers. It first places its tendrils ready for action, as a polypus places its tentacula. If the tendril be displaced, it is acted on by the force of gravity and rights it self. It is acted on by the light, and bends towards or from it, or disregards it, whichever may be most advantageous. During several days the tendrils or internodes, or both, spontaneously revolve with a steady motion. The tendril strikes some object, and quickly curls round and firmly grasps it. In the course of some hours it contracts into a spire, dragging up the stem, and forming an excellent spring. All movements now cease. By growth the tissues soon become wonderfully strong and durable127. The tendril has done its work, and has done it in an admirable manner.
The End
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mere
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| adj.纯粹的；仅仅，只不过 | |
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scrambling
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| v.快速爬行( scramble的现在分词 )；攀登；争夺；（军事飞机）紧急起飞 | |
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adhesive
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| n.粘合剂；adj.可粘着的，粘性的 | |
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secrete
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| vt.分泌；隐匿，使隐秘 | |
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secreted
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| 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 | |
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twine
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| v.搓，织，编饰；（使）缠绕 | |
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irritability
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| n.易怒 | |
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scramble
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| v.爬行，攀爬，杂乱蔓延，碎片，片段，废料 | |
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ramble
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| v.漫步，漫谈，漫游；n.漫步，闲谈，蔓延 | |
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thickets
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| n.灌木丛( thicket的名词复数 )；丛状物 | |
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revolving
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| adj.旋转的，轮转式的；循环的v.（使）旋转( revolve的现在分词 )；细想 | |
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possessed
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| adj.疯狂的；拥有的，占有的 | |
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13
twiner
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| n.缠绕植物；搓绳机 | |
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spines
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| n.脊柱( spine的名词复数 )；脊椎；（动植物的）刺；书脊 | |
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ascent
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| n.(声望或地位)提高；上升，升高；登高 | |
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hop
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| n.单脚跳，跳跃；vi.单脚跳，跳跃；着手做某事；vt.跳跃，跃过 | |
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apparently
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| adv.显然地；表面上，似乎 | |
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18
solely
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| adv.仅仅，唯一地 | |
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19
efficiently
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| adv.高效率地，有能力地 | |
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20
ascend
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| vi.渐渐上升，升高；vt.攀登，登上 | |
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21
bent
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| n.爱好，癖好；adj.弯的；决心的，一心的 | |
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22
remarkable
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| adj.显著的，异常的，非凡的，值得注意的 | |
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curiously
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| adv.有求知欲地；好问地；奇特地 | |
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24
flattened
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| [医]（水）平扁的，弄平的 | |
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forth
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| adv.向前；向外，往外 | |
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pointed
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| adj.尖的，直截了当的 | |
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27
fully
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| adv.完全地，全部地，彻底地；充分地 | |
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28
remains
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| n.剩余物，残留物；遗体，遗迹 | |
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29
adherent
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| n.信徒，追随者，拥护者 | |
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30
ivy
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| n.常青藤，常春藤 | |
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31
previously
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| adv.以前，先前（地） | |
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32
allied
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| adj.协约国的；同盟国的 | |
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33
interval
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| n.间隔，间距；幕间休息，中场休息 | |
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34
milky
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| adj.牛奶的，多奶的；乳白色的 | |
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35
exuded
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| v.缓慢流出，渗出，分泌出( exude的过去式和过去分词 )；流露出对（某物）的神态或感情 | |
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36
drawn
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| v.拖，拉，拔出；adj.憔悴的，紧张的 | |
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scattered
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| adj.分散的，稀疏的；散步的；疏疏落落的 | |
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38
watery
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| adj.有水的，水汪汪的；湿的，湿润的 | |
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volatile
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| adj.反复无常的，挥发性的，稍纵即逝的，脾气火爆的；n.挥发性物质 | |
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40
softening
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| 变软，软化 | |
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41
transparent
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| adj.明显的，无疑的；透明的 | |
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42
elastic
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| n.橡皮圈，松紧带；adj.有弹性的；灵活的 | |
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precisely
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| adv.恰好，正好，精确地，细致地 | |
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44
mortar
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| n.灰浆，灰泥；迫击炮；v.把…用灰浆涂接合 | |
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45
secretion
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| n.分泌 | |
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46
abounds
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| v.大量存在，充满，富于( abound的第三人称单数 ) | |
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47
ascends
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| v.上升，攀登( ascend的第三人称单数 ) | |
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48
vanilla
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| n.香子兰，香草 | |
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49
crevices
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| n.（尤指岩石的）裂缝，缺口( crevice的名词复数 ) | |
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50
expenditure
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| n.(时间、劳力、金钱等)支出；使用，消耗 | |
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51
temperate
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| adj.温和的，温带的，自我克制的，不过分的 | |
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52
entangled
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| adj.卷入的；陷入的；被缠住的；缠在一起的v.使某人（某物/自己）缠绕，纠缠于（某物中），使某人（自己）陷入（困难或复杂的环境中）( entangle的过去式和过去分词 ) | |
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53
mechanism
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| n.机械装置；机构，结构 | |
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54
lapse
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| n.过失，流逝，失效，抛弃信仰，间隔；vi.堕落，停止，失效，流逝；vt.使失效 | |
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55
primordial
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| adj.原始的；最初的 | |
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56
primordially
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| adv.原始地，最初地 | |
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57
revolve
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| vi.(使)旋转；循环出现 | |
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58
analogous
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| adj.相似的；类似的 | |
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59
modification
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| n.修改，改进，缓和，减轻 | |
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60
expended
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| v.花费( expend的过去式和过去分词 )；使用（钱等）做某事；用光；耗尽 | |
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61
dense
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| a.密集的，稠密的，浓密的；密度大的 | |
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62
affected
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| adj.不自然的，假装的 | |
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63
twigs
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| 细枝，嫩枝( twig的名词复数 ) | |
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64
rugged
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| adj.高低不平的，粗糙的，粗壮的，强健的 | |
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65
ascended
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| v.上升，攀登( ascend的过去式和过去分词 ) | |
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66
spires
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| n.（教堂的） 塔尖，尖顶( spire的名词复数 ) | |
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67
spire
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| n.(教堂)尖顶，尖塔，高点 | |
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68
considerably
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| adv.极大地；相当大地；在很大程度上 | |
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69
intervals
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| 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 | |
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70
lateral
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| adj.侧面的，旁边的 | |
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71
ascertain
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| vt.发现，确定，查明，弄清 | |
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72
prehensile
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| adj.（足等）适于抓握的 | |
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73
abort
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| v.使流产，堕胎；中止；中止(工作、计划等) | |
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74
abortion
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| n.流产，堕胎 | |
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75
vestiges
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| 残余部分( vestige的名词复数 )； 遗迹； 痕迹； 毫不 | |
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76
vestige
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| n.痕迹，遗迹，残余 | |
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77
transformation
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| n.变化；改造；转变 | |
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78
microscopical
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| adj.显微镜的，精微的 | |
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79
aborted
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| adj.流产的，失败的v.（使）流产( abort的过去式和过去分词 )；（使）（某事物）中止；（因故障等而）（使）（飞机、宇宙飞船、导弹等）中断飞行；（使）（飞行任务等）中途失败 | |
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80
perfectly
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| adv.完美地，无可非议地，彻底地 | |
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81
behold
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| v.看，注视，看到 | |
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82
progenitors
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| n.祖先( progenitor的名词复数 )；先驱；前辈；原本 | |
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83
entirely
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| ad.全部地，完整地；完全地，彻底地 | |
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84
destitute
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| adj.缺乏的；穷困的 | |
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85
utilized
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| v.利用，使用( utilize的过去式和过去分词 ) | |
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86
incipient
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| adj.起初的，发端的，初期的 | |
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87
accurately
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| adv.准确地，精确地 | |
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88
stimulants
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| n.兴奋剂( stimulant的名词复数 )；含兴奋剂的饮料；刺激物；激励物 | |
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89
repelled
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| v.击退( repel的过去式和过去分词 )；使厌恶；排斥；推开 | |
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90
axis
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| n.轴，轴线，中心线；坐标轴，基准线 | |
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91
vessels
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| n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人 | |
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92
fluctuations
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| 波动，涨落，起伏( fluctuation的名词复数 ) | |
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93
advantageous
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| adj.有利的；有帮助的 | |
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94
filament
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| n.细丝；长丝；灯丝 | |
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95
rudiment
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| n.初步；初级；基本原理 | |
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96
specimens
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| n.样品( specimen的名词复数 )；范例；（化验的）抽样；某种类型的人 | |
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97
rudiments
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| n.基础知识，入门 | |
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98
filaments
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| n.（电灯泡的）灯丝( filament的名词复数 )；丝极；细丝；丝状物 | |
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99
cylindrical
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| adj.圆筒形的 | |
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100
furrowed
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| v.犁田，开沟( furrow的过去式和过去分词 ) | |
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101
glands
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| n.腺( gland的名词复数 ) | |
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102
intelligible
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| adj.可理解的，明白易懂的，清楚的 | |
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103
descended
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| a.为...后裔的，出身于...的 | |
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104
naturalists
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| n.博物学家( naturalist的名词复数 )；（文学艺术的）自然主义者 | |
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105
vertically
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| adv.垂直地 | |
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106
outwards
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| adj.外面的，公开的，向外的；adv.向外；n.外形 | |
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107
extremity
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| n.末端，尽头；尽力；终极；极度 | |
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108
downwards
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| adj./adv.向下的（地），下行的（地） | |
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109
secondly
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| adv.第二，其次 | |
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110
upwards
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| adv.向上，在更高处...以上 | |
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111
secluded
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| adj.与世隔绝的；隐退的；偏僻的v.使隔开，使隐退( seclude的过去式和过去分词) | |
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112
stimulus
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| n.刺激，刺激物，促进因素，引起兴奋的事物 | |
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113
knight
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| n.骑士，武士；爵士 | |
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114
germinating
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| n.& adj.发芽（的）v.（使）发芽( germinate的现在分词 ) | |
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115
opposition
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| n.反对，敌对 | |
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116
laterally
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| ad.横向地；侧面地；旁边地 | |
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117
retarded
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| a.智力迟钝的，智力发育迟缓的 | |
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118
contingent
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| adj.视条件而定的；n.一组，代表团，分遣队 | |
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119
favourable
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| adj.赞成的，称赞的，有利的，良好的，顺利的 | |
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120
sufficiently
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| adv.足够地，充分地 | |
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121
conspicuous
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| adj.明眼的，惹人注目的；炫耀的，摆阔气的 | |
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122
arboreal
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| adj.树栖的；树的 | |
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123
botanist
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| n.植物学家 | |
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124
vaguely
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| adv.含糊地，暖昧地 | |
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125
distinguished
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| adj.卓越的，杰出的，著名的 | |
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126
affixed
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| adj.[医]附着的，附着的v.附加( affix的过去式和过去分词 )；粘贴；加以；盖（印章） | |
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127
durable
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| adj.持久的，耐久的 | |
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