Old-fashioned books tell us that the mistletoe is a perfect parasite7, while the dodder is an imperfect one; and I believe almost all botanists17 will still repeat the foolish saying to the present day. But it really shows considerable haziness18 as to what a true parasite is. The mistletoe is a plant which has taken, it is true, to growing upon other trees. Its very viscid berries are useful for attaching the seeds to the trunk of the oak or the apple; and there it roots itself into the body of its host. But it soon produces real green leaves of its own, which contain the ordinary chlorophyll found in other leaves, and help it to manufacture starch8, under the influence of sunlight, on its own account. It is not, therefore, a complete drag upon the tree which it infests20; for though it takes sap and mineral food from the host, it supplies itself with carbon, which is after all the important thing for plant-life. Dodder, however, is a parasite pure and simple. Its seeds fall originally upon the ground, and there root themselves at first like those of any other plant. But, as it grows, its long twining stem begins to curl for support round some other and stouter21 stalk. If it stopped there, and then produced leaves of its own, like the honeysuckle and the clematis, there would be no great harm done: and the dodder would be but another climbing plant the more in our flora22. However, it soon insidiously23 repays the support given it by sending down little bud-like suckers, through which it draws up nourishment24 from the gorse or clover on which it lives. Thus it has no need to develop leaves of its own; and it accordingly employs all its stolen material in sending forth matted thread-like stems and bunch after bunch of bright flowers. As these increase and multiply, they at last succeed in drawing away all the nutriment from the supporting plant, which finally dies under the constant drain, just as a horse might die under the attacks of a host of leeches25. But this matters little to the dodder, which has had time to be visited and fertilised by insects, and to set and ripen26 its numerous seeds. One species, the greater dodder, is thus parasitic14 upon hops27 and nettles28; a second kind twines29 round flax; and the third, which I have here under my eyes, mainly confines its dangerous attentions to gorse, clover, and thyme. All of them are, of course, deadly enemies to the plants they infest19.
How the dodder acquired this curious mode of life it is not difficult to see. By descent it is a bind-weed, or wild convolvulus, and its blossoms are in the main miniature convolvulus blossoms still. Now, all bind-weeds, as everybody knows, are climbing plants, which twine30 themselves round stouter stems for mere31 physical support This is in itself a half-parasitic habit, because it enables the plant to dispense32 with the trouble of making a thick and solid stem for its own use. But just suppose that any bind-weed, instead of merely twining, were to put forth here and there little tendrils, something like those of the ivy33, which managed somehow to grow into the bark of the host, and so naturally graft34 themselves to its tissues. In that case the plant would derive35 nutriment from the stouter stem with no expense to itself, and it might naturally be expected to grow strong and healthy, and hand down its peculiarities36 to its descendants. As the leaves would thus be rendered needless, they would first become very much reduced in size, and would finally disappear altogether, according to the universal custom of unnecessary organs. So we should get at length a leafless plant, with numerous flowers and seeds, just like the dodder. Parasites, in fact, whether animal or vegetable, always end by becoming mere reproductive sacs, mechanisms37 for the simple elaboration of eggs or seeds. This is just what has happened to the dodder before me.
The other queer plant here is a broomrape. It consists of a tall, somewhat faded-looking stem, upright instead of climbing, and covered with brown or purplish scales in the place of leaves. Its flowers resemble the scales in colour, and the dead-nettle in shape. It is, in fact, a parasitic dead-nettle, a trifle less degenerate38 as yet than the dodder. This broomrape has acquired somewhat the same habits as the other plant, only that it fixes itself on the roots of clover or broom, from which it sucks nutriment by its own root, as the dodder does by its stem-suckers. Of course it still retains in most particulars its original characteristics as a dead-nettle; it grows with their upright stem and their curiously39 shaped flowers, so specially40 adapted for fertilisation by insect visitors. But it has naturally lost its leaves, for which it has no further use, and it possesses no chlorophyll, as the mistletoe does. Yet it has not probably been parasitic for as long a time as the dodder, since it still retains a dwindling41 trace of its leaves in the shape of dry purply scales, something like those of young asparagus shoots. These leaves are now, in all likelihood, actually undergoing a gradual atrophy42, and we may fairly expect that in the course of a few thousand years they will disappear altogether. At present, however, they remain very conspicuous43 by their colour, which is not green, owing to the absence of chlorophyll, but is due to the same pigment44 as that of the blossoms. This generally happens with parasites, or with that other curious sort of plants known as saprophytes, which live upon decaying living matter in the mould of forests. As they need no green leaves, but have often inherited leafy structures of some sort, in a more or less degenerate condition, from their self-supporting ancestors, they usually display most beautiful colours in their stems and scales, and several of them rank amongst our handsomest hot-house plants. Even the dodder has red stalks. Their only work in life being to elaborate the materials stolen from their host into the brilliant pigments45 used in the petals46 for attracting insect fertilisers, they pour this same dye into the stems and scales, which thus render them still more conspicuous to the insects' eyes. Moreover, as they use their whole material in producing flowers, many of these are very large and handsome; one huge Sumatran species has a blossom which measures three feet across. On the other hand, their seeds are usually small and very numerous. Thousands of seeds must fall on unsuitable places, spring up, and waste all their tiny store of nourishment, find no host at hand on which to fasten themselves, and so die down for want of food. It is only by producing a few thousand young plants for every one destined ultimately to survive that dodders and broomrapes manage to preserve their types at all.
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1
quaint
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| adj.古雅的，离奇有趣的，奇怪的 | |
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uncommon
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| adj.罕见的，非凡的，不平常的 | |
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lesser
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| adj.次要的，较小的；adv.较小地，较少地 | |
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4
labyrinthine
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| adj.如迷宫的；复杂的 | |
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5
windings
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| （道路、河流等）蜿蜒的，弯曲的( winding的名词复数 )； 缠绕( wind的现在分词 )； 卷绕； 转动（把手） | |
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6
parasites
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| 寄生物( parasite的名词复数 )； 靠他人为生的人； 诸虫 | |
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7
parasite
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| n.寄生虫；寄生菌；食客 | |
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starch
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| n.淀粉；vt.给...上浆 | |
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starches
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| n.淀粉( starch的名词复数 )；含淀粉的食物；浆粉v.把（衣服、床单等）浆一浆( starch的第三人称单数 ) | |
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10
veins
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| n.纹理；矿脉( vein的名词复数 )；静脉；叶脉；纹理 | |
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11
foodstuffs
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| 食物，食品( foodstuff的名词复数 ) | |
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12
destined
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| adj.命中注定的；(for)以…为目的地的 | |
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13
parasitically
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| adv.寄生地，由寄生虫引起地 | |
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14
parasitic
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| adj.寄生的 | |
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15
forth
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| adv.向前；向外，往外 | |
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16
fixed
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| adj.固定的，不变的，准备好的；(计算机)固定的 | |
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botanists
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| n.植物学家，研究植物的人( botanist的名词复数 ) | |
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18
haziness
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| 有薄雾，模糊； 朦胧之性质或状态； 零能见度 | |
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19
infest
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| v.大批出没于；侵扰；寄生于 | |
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infests
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| n.害虫、野兽大批出没于( infest的名词复数 )；遍布于v.害虫、野兽大批出没于( infest的第三人称单数 )；遍布于 | |
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21
stouter
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| 粗壮的( stout的比较级 )； 结实的； 坚固的； 坚定的 | |
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22
flora
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| n.(某一地区的)植物群 | |
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23
insidiously
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| 潜在地，隐伏地，阴险地 | |
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24
nourishment
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| n.食物，营养品；营养情况 | |
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25
leeches
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| n.水蛭( leech的名词复数 )；蚂蟥；榨取他人脂膏者；医生 | |
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26
ripen
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| vt.使成熟；vi.成熟 | |
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27
hops
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| 跳上[下]( hop的第三人称单数 )； 单足蹦跳； 齐足（或双足）跳行； 摘葎草花 | |
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28
nettles
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| n.荨麻( nettle的名词复数 ) | |
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29
twines
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| n.盘绕( twine的名词复数 )；麻线；捻；缠绕在一起的东西 | |
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30
twine
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| v.搓，织，编饰；（使）缠绕 | |
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31
mere
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| adj.纯粹的；仅仅，只不过 | |
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32
dispense
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| vt.分配，分发；配(药)，发(药)；实施 | |
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33
ivy
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| n.常青藤，常春藤 | |
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34
graft
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| n.移植，嫁接，艰苦工作，贪污；v.移植，嫁接 | |
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35
derive
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| v.取得；导出；引申；来自；源自；出自 | |
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36
peculiarities
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| n. 特质, 特性, 怪癖, 古怪 | |
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37
mechanisms
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| n.机械( mechanism的名词复数 )；机械装置；[生物学] 机制；机械作用 | |
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38
degenerate
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| v.退步，堕落；adj.退步的，堕落的；n.堕落者 | |
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39
curiously
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| adv.有求知欲地；好问地；奇特地 | |
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40
specially
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| adv.特定地；特殊地；明确地 | |
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41
dwindling
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| adj.逐渐减少的v.逐渐变少或变小( dwindle的现在分词 ) | |
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42
atrophy
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| n./v.萎缩，虚脱，衰退 | |
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43
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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44
pigment
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| n.天然色素，干粉颜料 | |
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45
pigments
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| n.（粉状）颜料( pigment的名词复数 )；天然色素 | |
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46
petals
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| n.花瓣( petal的名词复数 ) | |
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