Chapter 5

WEBVTT
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Chapter five of the Movement and Habits of Climbing Plants
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by Charles Darwin. This LibriVox recording is in the public domain.
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Chapter five, Hook and root Climbers, concluding remarks Plants climbing
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by the aid of hooks or merely scrambling over other plants,
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root climbers, adhesive matterscreted by the rutlets, General conclusions with
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respect to climbing plants and the stages of their development
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hook climbers. In my introductory remarks, I stated that besides
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the two first great classes of climbing plants, namely those
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which twine round a support and those endowed with irritability
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enabling them to seize hold of objects by means of
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their petioles or tendrils, there are two other classes, hook
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climbers and root climbers. Many plants. Moreover, as Fritz Muller
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has remarked, climb or scramble up thickets in a still
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more simple fashion without any special aid, excepting that their
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leading shoots are generally long and flexible. It may, however,
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be suspected from what follows, that these shoots in some
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cases tend to avoid the light. The few hook climbers
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which I have observed, namely Gallium aparine Rubus australis, and
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some climbing roses, exhibit no spontaneous revolving movement. If they
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had possessed this power and had been capable of twining,
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they would have been placed in the class of twiners.
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For some twiners are furnished with spines or hooks which
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aid them in their ascent. For instance, the hop which
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is a twiner, has reflexed hooks as large as those
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of the gallium. Some other twiners have stiff, reflexed hairs,
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and Dipladinia has a circle of blunt spines at the
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base of its leaves. I have seen only one tendril
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bearing plant, namely its milax aspera, which is furnished with
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reflexed spines, but this is the case with several branch
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climbers in South Brazil and Ceylon, and their branches graduate
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into true tendrils. Some few plants apparently depend solely on
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their hooks for climbing, and yet do so efficiently as
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certain palms in the New and Old worlds. Even some
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climbing roses will ascend the walls of a tall house
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if covered with a trellis. How this is affected, I
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know not, For the young shoots of one such rose,
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when placed in a pot in a window, bent irregularly
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towards light during the day and from the light during
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the night, like the shoots of any common plant, so
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that it is not easy to understand how they could
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have got under a trellis close to the wall. Rute climbers.
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A good many plants come under this class and are
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excellent climbers. One of the most remarkable is the Markgravia umbellata,
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the stem of which, in the tropical forests of South America,
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as I hear from mister spruce rose in a curiously
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flattened manner against the trunks of trees here and there
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it puts forth claspers roots which adhere to the trunk, and,
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if the latter be slender, completely embrace it. When this
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plant has climbed to the light, it produces free branches
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with rounded stems clad with sharp, pointed leaves, wonderfully different
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in appearance from those borne by the stem as it
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remains adherent. This surprising difference in the leaves I have
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also observed in a plant of Margravia dubia in my
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hothouse roof climbers, as far as I have seen, namely
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the Ivy, Hederahalia, Phycus ripens and F. Barbatas, have no
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power of movement, not even from the light to the dark.
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As previously stated, the Hoya carnosa as clepidacia is a
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spiral twiner and likewise adheres by rootlets even to a
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flat wall. The tendril bearing Bignonia tridiana admits roots which
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curve half round and adhere to thin stee The Tacoma
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ratiican's Bignonacea, which is closely allied to many spontaneously revolving species,
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climbs by rootlets. Nevertheless, its young shoots apparently move about
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more than can be counted for by the varying action
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of the light. I have not closely observed many root climbers,
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but can give one curious fact. Vicus rappens climbs up
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a wall just like Ivy, and when the young rootlets
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are made to press lightly on slips of glass, they
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emit after about a week's interval. As I observe several
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times minute drops of clear fluid, not in the least milky,
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like that exuded from a wound. This fluid is slightly vicid,
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but cannot be drawn out into threads. It has the
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remarkable property of not soon drying. A drop about the
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size of half a pin's head was slightly spread out
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on glass, and I scattered on it some minute grains
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of sand. The glass was left exposed in a drawer
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during hot and dry weather, and if the fluid had
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been water, it would certainly have dried in a few minutes.
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But it remained fluid closely surrounding each grain of sand
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during one hundred and twenty eight days. How much longer
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it would have remained I cannot say. Some other rootlets
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were left in contact with the glass for about ten
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days or a fortnight, and the drops of secreted fluid
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were now rather larger and so visied that they could
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be drawn out into threads. Some other rootlets were left
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in contact during twenty three days, and these were firmly
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cemented to the glass. Hence we may conclude that the
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rootlets first secrete a slightly visited fluid subsequently absorbed the
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watery parts. For we have seen that the fluid will
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not dry by itself and ultimately leave a cement. When
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the rootlets were torn from the glass. Atoms of yellowish
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matter were left on it, which were partly dissolved by
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a drop of bi sulfide of carbon, and this extremely
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volatile fluid was rendered much less volatile by what it
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had dissolved, as the bisulfide of carbon has a strong
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power of softening endured Chao chok. I soaked in it
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during a short time several rootlets of a plant which
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had grown up a plastered wall, and I then found
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many extremely thin threads of transparent, not vised excessively elastic
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matter precisely like kaochok, attached to two sets of rootlets
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on the same branch. These threads proceeded from the bark
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of the rootlet at one end, and at the other
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end were firmly attached to particles of silex or mortar
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from the wall. There could be no mistake in this observation,
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as I played with the threads for a long time
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under the microscope, drawing them out with my dissecting needle
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and letting them spring back. Yet I looked repeatedly at
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other rootlets similarly treated, and could never again discover these
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elastic threads. I therefore inferred that the branch in question
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must have been slightly moved from the wall at some
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critical period whilst the secretion was in the act of
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drying through the absorption of its watery parts. The genus
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Pycus abounds with chaochok, and we may conclude from the
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facts just given that this substance, at first in solution
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and ultimately modified into an unelastic cement, is used by
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the Phycus ripens to cement its rootlets to any surface
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which it ascends. Whether other plants which climb by their
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rootlets emit any cement, I do not know. But the
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rootlets of the ivy placed against glass rarely adhere to it,
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yet secreted a little yellowish matter. I may add that
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the rootlets of the Margravia dubia can adhere firmly to
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smooth painted wood. Vanilla aromatica emits aerial roots a foot
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in length, which point straight down to the ground. According
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to Mole, page forty nine, these crawl into crevices when
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when they meet with a thin support, wind round it,
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as do tendrils. A plant which I kept was young
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and did not form long roots, but on placing thin
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sticks in contact with them, they certainly bent a little
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to that side. In the course of about a day,
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and adhered by their rootlets to the wood, But they
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did not bend quite round the sticks, and afterwards they
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re pursued their downward course. It is probable that these
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slight movements of the root are due to the quicker
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growth of the side exposed to the light in comparison
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with the other, and not because the roots are sensitive
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to contact in the same manner as true tendrils. According
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to Mole, the rootlets of certain species of Lycopodium act
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as tendrils. Concluding remarks on climbing plants, plants become climbers
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in order, as it may be presumed, to reach the
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light and to expose a large surface of their leaves
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to its action and to that of the free air.
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This is effected by climbs with wonderfully little expenditure of
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organized matter in comparison with trees, which have to support
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a load of heavy branches by a massive trunk. Hence,
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no doubt it arises that there are so many climbing
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plants in all quarters of the world, belonging to so
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many different orders. These plants have then arranged under four classes,
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disregarding those which merely scramble over bushes without any special aid.
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Hook climbers are the least efficient of all, at least
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in our temperate countries, and can climb only in the
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midst of an entangled mass of vegetation. Root climbers are
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excellently adapted to ascend naked faces of rock or trunks
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of trees. When, however, they climb trunks, they are compelled
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to keep much in the shade. They cannot pass from
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branch to branch and thus cover the whole summit of
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a tree, for their rootlets require long, continued and close
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contact with a steady surface in order to adhere. The
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two great classes of twiners and of plants with sensitive organs,
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namely leaf climbers and tendril bearers, taken together, far exceed
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in number and in the perfection of their mechanism. The
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climbers of the two first classes, those which have the
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power of spontaneously revolving and of grasping objects with which
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they come in contact, pass easily from branch to branch
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and securely ramble over a wide sunlit surface. The divisions
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containing twining plants, leaf climbers, and tendril bearers graduate to
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a certain extent into one another. And nearly all have
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the same remarkable power of spontaneously revolving. Does this gradeation
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it may be asked to indicate that plants belonging to
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one subdivision have actually passed during lapse of ages, or
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can pass from one state to the other, as for instance,
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any tendril bearing plant assumed its present structure without having
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previously existed as a leaf climber or a twiner. If
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we consider leaf climbers alone, the idea that they were
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primortively twiners is forcibly suggested. The internodes of all, without exception,
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revolve in exactly the same manner as twiners. Some few
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can still twine well, and many others in an imperfect manner.
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Several leaf climbing genera are closely allied to other genera
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which are simple twiners. It should also be observed that
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the possession of leaves with sensitive petioles and with the
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consequent power of clasping the object, would be of comparatively
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little use to a plant unless associated with revolving internodes
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by which the leaves are brought into contact with the support,
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although no doubt a scrambling plant would be apt. As
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Professor Jeger has remarked to rest on other plants by
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its leave. On the other hand, revolving internodes without any
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other aid suffice to give the power of climbing, so
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that it seems probable that leaf climbers were in most
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cases at first twiners and subsequently became capable of grasping
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a support. And this, as we shall see, is a
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great additional advantage. From analogous reasons, it is probable that
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all tendril bearers were primordially twiners, that is, our descendants
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of plants having this power and habit. For the internodes
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of the majority revolve, and in a few species the
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flexible stem still retained the capacity of spirally twining round
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and upright. Stick tentril bearers have undergone much more modification
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than leaf climbers. Hence it is not surprising that their
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supposed primordial habits of revolving and twining have been more
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frequently lost or modified than in the case of leaf climbers.
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The three great tendril bearing families in which this loss
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has occurred in the most marked manner of the Kukurbetasia, Passifloracia,
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and Vitasia. In the first, the internodes revolve, but I
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have heard of no twining form, with the exception according
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to Palm page twenty nine fifty two of Momordica balsamina,
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and this is only an imperfect twiner. In the two
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other families I can hear of no twiners, and the
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internodes rarely have the power of revolving, this power being
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confined to the tendrils. The internodes, however, of Passiflora gracillus,
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have the power in a perfect manner, and those of
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the common vine in an imperfect manner, so that at
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least a trace of the supposed primordial habit has been
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retained by some members of all the larger tendril bearing groups.
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On the view here given, it may be asked why
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had the species which were aboriginally twiners been converted into
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so many groups into leaf climbers or tendril bearers. Of
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what advantage has this been to them? Why did they
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not remain simple twiners. We can see several reasons. It
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might be an advantage to a plant to acquire a
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thicker stem with short internodes bearing many or large leaves,
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and such stems are ill fitted for twining. Anyone who
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will look during windy weather at twining plants will see
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that they are easily blown from their support. Not so
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with tendril bearers or leaf climbers, where they quickly and
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firmly grasp the support by a much more efficient kind
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of movement. In those plants which still twine but at
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the same time possess tendrils or sensitive petioles, as some
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species of Bignonia hermatus and Tropelium, it can readily be
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observed how incomparably better they grasp an upright stick than
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do simple twiners. Tendrils from possessing this power of grasping
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an object can be made long and thin, so that
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little organic matter is inxibended in their development, and yet
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they sweep a wide circle in search of support. Tendril
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Bearers can from their first growth ascend along the outer
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branches of any neighboring bush, and they are thus always
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fully exposed to the light. Twiners, on the contrary, are
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best fitted to ascend bare stems and generally have to
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start in the shade. Within tall and dense tropical forests.
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Twining plants would probably succeed better than most kinds of
237
00:15:14.559 --> 00:15:18.039
tendril bearers, but the majority of twiners, at least in
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00:15:18.080 --> 00:15:21.399
our tempered regions, from the nature of their revolving movement,
239
00:15:21.759 --> 00:15:25.679
cannot ascend thick trunks, whereas this can be affected by
240
00:15:25.720 --> 00:15:28.799
tendril bearers if the trunks are branched or bare twigs,
241
00:15:29.120 --> 00:15:32.600
and by some species if the bark is rugged. The
242
00:15:32.679 --> 00:15:35.320
advantage gained by climbing is to reach the light and
243
00:15:35.399 --> 00:15:39.000
free air with as little expenditure of organic matter as possible.
244
00:15:39.720 --> 00:15:42.919
Now with twining plants, the stem is much longer than
245
00:15:43.000 --> 00:15:46.320
is absolutely necessary. For instance, I measured the stem of
246
00:15:46.360 --> 00:15:49.360
a kidney bean, which had ascended exactly two feet in height,
247
00:15:49.679 --> 00:15:52.639
and it was three feet in length. The stem of
248
00:15:52.639 --> 00:15:54.799
a pea, on the other hand, which had ascended to
249
00:15:54.840 --> 00:15:57.320
the same height by the aid of its tendrils, was
250
00:15:57.360 --> 00:16:00.960
but little longer than the height reached. That this saving
251
00:16:01.000 --> 00:16:03.799
of the stem is really an advantage to climbing plants.
252
00:16:04.120 --> 00:16:07.159
I infer from the species that still twine, but are
253
00:16:07.200 --> 00:16:11.559
aided by clasping petioles or tendrils, generally making more open
254
00:16:11.639 --> 00:16:16.240
spires than those made by symbol twiners. Moreover, the plants
255
00:16:16.360 --> 00:16:19.720
thus aided, after taking one or two turns in one direction,
256
00:16:20.120 --> 00:16:23.639
generally ascend for a space straight and then reverse the
257
00:16:23.679 --> 00:16:27.440
direction of their spire. By this means they ascend to
258
00:16:27.480 --> 00:16:30.799
a considerably greater height with the same length of stem
259
00:16:31.120 --> 00:16:34.000
than would otherwise have been possible, and they do this
260
00:16:34.120 --> 00:16:37.200
with safety, as they secure themselves at intervals by their
261
00:16:37.240 --> 00:16:41.200
clasping petioles or tendrils. We have seen that the tendrils
262
00:16:41.240 --> 00:16:45.080
consist of various organs in a modified state, namely leaves,
263
00:16:45.159 --> 00:16:49.559
flower peduncles, branches, and perhaps stipules. With respect to leaves,
264
00:16:49.679 --> 00:16:53.279
the evidence of their modification is ample. In young plants
265
00:16:53.320 --> 00:16:57.799
of Ignonia. The lower leaves often remain quite unchanged, whilst
266
00:16:57.840 --> 00:17:02.480
the upper ones have their terminal leaflets converted into perfect tendrils.
267
00:17:02.960 --> 00:17:06.480
In ecromycarpus, I have seen a single lateral branch of
268
00:17:06.519 --> 00:17:11.200
a tendril replaced by a perfect leaflet. In Visiersativa, on
269
00:17:11.240 --> 00:17:15.559
the other hand, leaflets are sometimes replaced by tendril branches,
270
00:17:15.920 --> 00:17:19.279
and many other such cases could be given. But he
271
00:17:19.359 --> 00:17:22.759
who believes in the slow modification of species will not
272
00:17:22.839 --> 00:17:26.480
be content simply to ascertain the homological nature of different
273
00:17:26.559 --> 00:17:29.240
kinds of tendrils. He will wish to learn as far
274
00:17:29.279 --> 00:17:33.160
as as possible by what actual steps leaves, flower, peduncles,
275
00:17:33.160 --> 00:17:36.559
et cetera, have had their functions wholly changed and have
276
00:17:36.640 --> 00:17:40.599
come to serve merely as prehensile organs. In the whole
277
00:17:40.640 --> 00:17:44.119
group of leaf climbers, abundant evidence has been given that
278
00:17:44.200 --> 00:17:47.599
an organ still subserving the functions of a leaf may
279
00:17:47.640 --> 00:17:51.640
become sensitive to a touch and thus grasp an adjoining object.
280
00:17:52.400 --> 00:17:56.200
With several leaf climbers, the true leaves spontaneously revolve, and
281
00:17:56.279 --> 00:17:59.920
their petioles, after clasping the support, grow thicker and strong.
282
00:18:00.839 --> 00:18:03.960
We thus see that leaves may acquire all the leading
283
00:18:04.039 --> 00:18:09.359
and characteristic qualities of tendrils, namely sensitiveness, spontaneous movement, and
284
00:18:09.480 --> 00:18:14.119
subsequently increased strength. If their blades or lamina were to abort,
285
00:18:14.400 --> 00:18:18.079
they would form true tendrils, and this process of abortion
286
00:18:18.279 --> 00:18:21.240
we can follow every step until no trace of the
287
00:18:21.240 --> 00:18:25.680
original nature of the tendril is left. In Buttisia calmatis,
288
00:18:25.920 --> 00:18:29.920
the tendril in shape and color closely resembles the petiole
289
00:18:30.000 --> 00:18:33.279
of one of the ordinary leaves, together with the mid
290
00:18:33.400 --> 00:18:36.920
ribs of the leaflets, but the vestiges of the laminae
291
00:18:37.119 --> 00:18:41.920
are still occasionally retained. In four genera of the Fumeriacea,
292
00:18:42.359 --> 00:18:46.400
we can follow the whole process of transformation. The terminal
293
00:18:46.480 --> 00:18:51.000
leaflets of the leaf climbing Fumaria officionalus are not smaller
294
00:18:51.039 --> 00:18:54.279
than the other leaflets. Those of the leaf climbing and
295
00:18:54.400 --> 00:19:00.440
Lumiacerosa are greatly reduced. Those of Corridalus claviculata, a plant
296
00:19:00.440 --> 00:19:03.119
which may indifferently be called a leaf climber or a
297
00:19:03.119 --> 00:19:07.599
tendril bearer, are either reduced to microscopical dimensions or have
298
00:19:07.680 --> 00:19:11.119
their blade wholly aborted, so that this plant is actually
299
00:19:11.160 --> 00:19:14.720
in a state of transition. And finally, in the dicentra,
300
00:19:15.079 --> 00:19:20.160
the tendrils are perfectly characterized. If therefore we could behold
301
00:19:20.519 --> 00:19:24.279
at the same time all the progenitors of Dicentra, we
302
00:19:24.319 --> 00:19:27.680
should almost certainly see a series like that now exhibited
303
00:19:27.920 --> 00:19:32.640
by the above named three genera. In Tropalium trichlorum we
304
00:19:32.720 --> 00:19:35.839
have another kind of passage, for the leaves which are
305
00:19:35.880 --> 00:19:39.079
first formed on the young stems are entirely destitute of
306
00:19:39.160 --> 00:19:43.279
laminae and must be called tendrils, whilst the latter formed
307
00:19:43.359 --> 00:19:47.720
leaves have well developed laminae. In all cases, the acquirement
308
00:19:47.920 --> 00:19:51.119
of sensitiveness by the mid rips of the leaves appear
309
00:19:51.240 --> 00:19:54.240
to stand in some close relation with the abortion of
310
00:19:54.279 --> 00:19:59.200
their laminae or blades. On the view here given, leaf
311
00:19:59.240 --> 00:20:04.359
climbers or primordially twiners and tendril bearers when formed of
312
00:20:04.440 --> 00:20:09.640
modified leaves, were primordially leaf climbers. The latter therefore are
313
00:20:09.720 --> 00:20:13.440
intermediate in nature between twiners and tendril bearers, and ought
314
00:20:13.480 --> 00:20:17.400
to be related to both. This is the case. Thus
315
00:20:17.519 --> 00:20:22.839
the several leaf climbing species of Antineae of Solanum, Coculus
316
00:20:23.000 --> 00:20:26.759
and Gloriosa have within the same family, and even within
317
00:20:26.799 --> 00:20:31.880
the same genus, relatives which are twiners. In the genus Micania,
318
00:20:32.200 --> 00:20:36.279
there are leaf climbing and twining species. The leaf climbing
319
00:20:36.319 --> 00:20:40.079
species of Climatis are very closely allied to the tendril
320
00:20:40.119 --> 00:20:45.160
bearing Naravelia. The Femiaica include closely allied genera which are
321
00:20:45.240 --> 00:20:50.160
leaf climbers and tendril bearers. Lastly, a species of Bignonia
322
00:20:50.440 --> 00:20:53.079
is at the same time both a leaf climber and
323
00:20:53.160 --> 00:20:57.079
a tendril bearer, and other closely allied species are twiners.
324
00:20:58.039 --> 00:21:02.519
Tendrils of another kind consist of modified flower peduncles. In
325
00:21:02.680 --> 00:21:07.079
this case, we likewise have many interesting transitional states. The
326
00:21:07.200 --> 00:21:10.960
common vine, not to mention the Cardiospermum gives us every
327
00:21:11.039 --> 00:21:14.759
possible gradation between a perfectly developed tendril and a flower
328
00:21:14.759 --> 00:21:18.839
peduncle covered with flowers, yet furnished with a branch forming
329
00:21:18.960 --> 00:21:23.119
the flower tendril when the latter itself bears a few flowers,
330
00:21:23.400 --> 00:21:26.559
as we know sometimes is the case, and still retains
331
00:21:26.599 --> 00:21:29.400
the power of clasping a support. We see an early
332
00:21:29.440 --> 00:21:32.839
condition of all those tendrils which have been formed by
333
00:21:32.839 --> 00:21:37.480
the modification of flower peduncles. According to Mole and others,
334
00:21:37.839 --> 00:21:42.359
some tendrils consist of modified branches. I have not observed
335
00:21:42.400 --> 00:21:46.000
any such cases and know nothing of their transitional states,
336
00:21:46.400 --> 00:21:50.039
but these have been fully described by Fritz Muller. The
337
00:21:50.079 --> 00:21:54.680
genus Bufospermum also shows us how such a transition is possible,
338
00:21:55.000 --> 00:22:00.319
for its branches spontaneously revolved and are sensitive to contact. Hence,
339
00:22:00.400 --> 00:22:02.279
if the leaves on some of the branches of the
340
00:22:02.359 --> 00:22:06.640
Lofus firmam were to abort, these branches would be converted
341
00:22:06.720 --> 00:22:10.880
into true tendrils. Nor is there anything improbable in certain
342
00:22:10.920 --> 00:22:15.839
branches alone being thus modified, whilst others remain unaltered. For
343
00:22:16.000 --> 00:22:19.559
we have seen with certain varieties of Phasiolus that some
344
00:22:19.640 --> 00:22:23.240
of the branches are thin, flexible and twine, whilst others
345
00:22:23.279 --> 00:22:26.039
on the same plant are stiff and have no such power.
346
00:22:26.960 --> 00:22:30.039
If we inquire how a petiole, a branch or flower
347
00:22:30.079 --> 00:22:33.680
pedungle first became sensitive to a touch and acquired the
348
00:22:33.720 --> 00:22:37.079
power of bending towards the touched side, we get no
349
00:22:37.240 --> 00:22:42.759
certain answer. Nevertheless, an observation by Hoffmeister well deserves attention,
350
00:22:43.359 --> 00:22:46.480
namely that the shoots and leaves of all plants, whilst young,
351
00:22:46.920 --> 00:22:51.559
move after being shaken. Kerner also finds, as we have seen,
352
00:22:51.799 --> 00:22:54.599
that the flower peduncles of a large number of plants,
353
00:22:54.680 --> 00:22:58.079
if shaken or gently rubbed, bend to this side, and
354
00:22:58.240 --> 00:23:02.319
it is young petioles and ten whatever their homological nature
355
00:23:02.359 --> 00:23:06.119
may be, which move on being touched. It thus appears
356
00:23:06.160 --> 00:23:09.720
that climbing plants have utilized and perfected a widely distributed
357
00:23:09.759 --> 00:23:13.519
and incipient capacity, which capacity, as far as we can see,
358
00:23:13.599 --> 00:23:17.200
is of no service to ordinary plants. If we further
359
00:23:17.319 --> 00:23:20.960
inquire how the stems, petules, tendrils, and flower peduncles of
360
00:23:21.000 --> 00:23:25.920
climbing plants first acquired their power of spontaneously revolving, or
361
00:23:26.079 --> 00:23:29.640
to speak more accurately, of successively bending to all points
362
00:23:29.680 --> 00:23:33.039
of the compass, we are again silenced, or at least
363
00:23:33.079 --> 00:23:37.160
can only remark that the power of moving both spontaneously
364
00:23:37.200 --> 00:23:40.759
and from various stimulants is far more common with plants
365
00:23:40.920 --> 00:23:43.200
than is generally supposed to be the case by those
366
00:23:43.200 --> 00:23:46.839
who have not attended to the subject. I have given
367
00:23:46.920 --> 00:23:51.200
one remarkable instance, namely that of the Morandia semper florins,
368
00:23:51.640 --> 00:23:55.200
the young flower peduncles of which spontaneously revolve in very
369
00:23:55.240 --> 00:23:59.279
small circles and bend when gently rubbed to the touched side.
370
00:23:59.599 --> 00:24:02.480
Yet this plant certainly does not profit by these two
371
00:24:02.519 --> 00:24:07.440
feebly developed powers. A rigorous examination of other young plants
372
00:24:07.559 --> 00:24:11.799
would probably show slight spontaneous movement in their stems, petioles
373
00:24:11.880 --> 00:24:16.279
or peduncles, as well as sensitiveness to touch. We see
374
00:24:16.319 --> 00:24:19.359
at least that the Morandia might, by a little augmentation
375
00:24:19.480 --> 00:24:22.200
of the powers which it possesses, come first to grasp
376
00:24:22.279 --> 00:24:25.920
the support bias flower peduncles, and then, by the abortion
377
00:24:26.039 --> 00:24:29.119
of some of its flowers, as with Vitus or cardiospermam,
378
00:24:29.440 --> 00:24:34.079
acquire perfect tendrils. There is one other interesting point which
379
00:24:34.119 --> 00:24:37.720
deserves notice. We have seen that some tendrils owe their
380
00:24:37.759 --> 00:24:41.440
origin to modified leaves, and others to modified flower peduncles,
381
00:24:41.759 --> 00:24:45.000
so that some are folia and others axial in their nature.
382
00:24:45.720 --> 00:24:47.920
It might therefore have been expected that they would have
383
00:24:48.000 --> 00:24:51.400
presented some difference in function. This is not the case.
384
00:24:51.920 --> 00:24:55.119
On the contrary, they present the most complete identity in
385
00:24:55.160 --> 00:25:00.440
their several characteristic powers. Tendrils of both kinds spontaneously revolve
386
00:25:00.519 --> 00:25:04.200
at about the same rate. Both when touched, bent quickly
387
00:25:04.240 --> 00:25:07.160
to the touched side, and afterwards recover themselves and are
388
00:25:07.200 --> 00:25:11.319
able to act again. In both the sensitiveness is either
389
00:25:11.359 --> 00:25:14.519
confined to one side or extends all round the tendril.
390
00:25:15.160 --> 00:25:18.440
Both are either attracted or repelled by the light. The
391
00:25:18.519 --> 00:25:21.880
latter property is seen in the foliar tendrils of Bignonia
392
00:25:21.920 --> 00:25:26.799
capriolata and in the axial tendrils of Amphlopsis. The tips
393
00:25:26.799 --> 00:25:30.000
of the tendrils in these two plants become, after contact
394
00:25:30.160 --> 00:25:33.559
enlarged into disks, which are at first adhesive by the
395
00:25:33.599 --> 00:25:37.880
secretion of some cement. Tendrils of both kinds, soon after
396
00:25:37.960 --> 00:25:42.160
grasping the support contract spiderly. They then increase greatly in
397
00:25:42.240 --> 00:25:46.200
thickness and strength. When we add to these several points
398
00:25:46.240 --> 00:25:50.480
of identity the fact that the petule of the Solanum jasminides.
399
00:25:50.759 --> 00:25:53.279
After it has classed, the support assumes one of the
400
00:25:53.279 --> 00:25:57.079
most characteristic features of the axis, namely a closed ring
401
00:25:57.119 --> 00:26:00.319
of woody vessels. We can hardly avoid asci whether the
402
00:26:00.359 --> 00:26:04.240
fundamental difference between folia and axial organs can be of
403
00:26:04.319 --> 00:26:08.440
so fundamental a nature as is generally supposed. We have
404
00:26:08.480 --> 00:26:11.079
attempted to trace some of the stages of the genesis
405
00:26:11.079 --> 00:26:14.519
of climbing plants. But during the endless fluctuations of the
406
00:26:14.559 --> 00:26:18.039
conditions of life to which all organic beings have been exposed,
407
00:26:18.400 --> 00:26:21.000
it might be expected that some climbing plants would have
408
00:26:21.079 --> 00:26:24.279
lost the habit of climbing. In the cases given of
409
00:26:24.359 --> 00:26:28.599
certain South African plants belonging to great twining families, which
410
00:26:28.599 --> 00:26:31.640
in their native country never twine, but we assume this
411
00:26:31.759 --> 00:26:34.599
habit when cultivated in England. We have a case in
412
00:26:34.720 --> 00:26:39.000
point in the leaf climbing Climatis flamula, and in the
413
00:26:39.000 --> 00:26:41.839
tender bearing vine. We see no loss in the power
414
00:26:41.839 --> 00:26:44.799
of climbing, but only a remnant of the revolving power,
415
00:26:44.799 --> 00:26:48.000
which is indispensable to all climbers, and it is so
416
00:26:48.119 --> 00:26:52.160
common as well as so advantaged to most climbers. In
417
00:26:52.200 --> 00:26:55.960
Tacoma raticans, one of the bignoniasia. We see a last
418
00:26:56.000 --> 00:26:59.200
and doubtful trace of the power of the revolving with
419
00:26:59.279 --> 00:27:03.119
respect to the abortion of tendrils. Certain cultivated varieties of
420
00:27:03.200 --> 00:27:07.759
Kucurbita popos have, according to Nauden, either quite lost these
421
00:27:07.880 --> 00:27:12.079
organs or bear semi monstrous representatives of them. In my
422
00:27:12.200 --> 00:27:15.559
limited experience, I have met with only one apparent instance
423
00:27:15.599 --> 00:27:19.279
of their natural suppression, namely in the common being. All
424
00:27:19.359 --> 00:27:23.279
the other species of vissier I believe tendril bearers, but
425
00:27:23.480 --> 00:27:26.039
the being is stiff enough to support its own stem.
426
00:27:26.359 --> 00:27:28.559
And in this species, at the end of the petiole,
427
00:27:28.640 --> 00:27:32.319
where according to analogy, a tendril ought to have existed,
428
00:27:32.839 --> 00:27:35.759
a small pointed filament projects about a third of an
429
00:27:35.759 --> 00:27:40.319
engine length, and which is probably the rudiment of a tendril.
430
00:27:40.440 --> 00:27:42.960
This may be the more safely inferred, as in young
431
00:27:43.000 --> 00:27:47.319
and unhealthy specimens of other tendril bearing plants, similar rudiments
432
00:27:47.359 --> 00:27:51.240
may occasionally be observed in the bean. These filaments are
433
00:27:51.319 --> 00:27:54.240
variable in shape, as is so frequently the case with
434
00:27:54.359 --> 00:27:58.480
rudimentary organs. They are either cylindrical or fallaceous, or are
435
00:27:58.519 --> 00:28:02.039
deeply furrowed on the upper so they have not retained
436
00:28:02.079 --> 00:28:05.759
any vestige of the power of revolving. It is curious
437
00:28:05.799 --> 00:28:09.079
fact that many of these filaments, when fallaceous, have on
438
00:28:09.160 --> 00:28:13.440
their lower surfaces dark colored glands led those on the stipules,
439
00:28:13.640 --> 00:28:16.960
which excrete a sweet fluid, so that these rudiments have
440
00:28:17.039 --> 00:28:22.680
been feebly utilized. One other analogous case, though hypothetical, is
441
00:28:22.720 --> 00:28:27.359
worth giving. Nearly all the species of Lathyrus possess tendrils,
442
00:28:27.640 --> 00:28:31.839
but l. Nissolea is destitute of them. This plant has
443
00:28:31.920 --> 00:28:35.279
leaves which must have struck everyone with surprise who has
444
00:28:35.440 --> 00:28:38.440
noticed them, for they are quite unlike those of all
445
00:28:38.519 --> 00:28:44.039
common papillonaceaus plants, and resemble those of a grass. In
446
00:28:44.119 --> 00:28:48.640
other species l Africa, the tendril, which is not highly developed,
447
00:28:48.720 --> 00:28:52.160
for it is unbranched and has no spontaneous revolving power,
448
00:28:52.640 --> 00:28:56.000
replaces the leaves, the latter being replaced in function by
449
00:28:56.079 --> 00:28:59.559
large stipules. Now, if we suppose the tendrils of el
450
00:28:59.640 --> 00:29:03.559
Paca to become flattened and fallacious like the little rudimentary
451
00:29:03.640 --> 00:29:06.599
tendrils of the bean, and the large stipules to become
452
00:29:06.720 --> 00:29:09.799
at the same time reduced in size from not being
453
00:29:09.839 --> 00:29:14.680
any longer wanted, we should have the exact counterpart of L. Missolia,
454
00:29:15.079 --> 00:29:18.720
and its curious leaves are at once rendered intelligible to us.
455
00:29:18.920 --> 00:29:21.400
It may be added, as serving to sum up the
456
00:29:21.480 --> 00:29:24.839
foregoing views on the origin of tendril bearing plants, that
457
00:29:25.039 --> 00:29:29.240
Lnssolia is probably descended from a plant which was primordially
458
00:29:29.319 --> 00:29:32.799
a twiner. This then became a leaf climber, and the
459
00:29:32.880 --> 00:29:37.720
les afterwards converted by degrees into tendrils, with the stipules
460
00:29:37.759 --> 00:29:42.279
greatly increased in size through the law of compensation. After
461
00:29:42.319 --> 00:29:45.240
a time, the tendrils lost their branches and became simple.
462
00:29:45.759 --> 00:29:48.599
They then lost their revolving power, in which state they
463
00:29:48.640 --> 00:29:51.720
would have resembled the tendrils of the existing el faca,
464
00:29:52.200 --> 00:29:56.519
and afterwards losing their prehensile power and becoming fallacious, would
465
00:29:56.599 --> 00:30:00.279
no longer be thus designated. In this last stage that
466
00:30:00.319 --> 00:30:04.279
of the existing L. Nissoleia, the former tendrils would reassume
467
00:30:04.359 --> 00:30:07.720
the original function of leaves, and the stipules, which were
468
00:30:07.799 --> 00:30:12.599
recently much developed, being no longer wanted, would decrease in size.
469
00:30:12.680 --> 00:30:15.559
If species become modified in the course of ages, as
470
00:30:15.599 --> 00:30:20.319
almost all naturalists now admit, we may conclude that Lnisolia
471
00:30:20.440 --> 00:30:23.240
has passed through a series of changes in some degree
472
00:30:23.599 --> 00:30:27.839
like those here indicated. The most interesting point in the
473
00:30:27.960 --> 00:30:31.160
natural history of climbing plants is the various kinds of
474
00:30:31.240 --> 00:30:34.799
movements which they display in manifest relation to their wants.
475
00:30:35.319 --> 00:30:40.200
The most different organs, stems, branches, flower, peduncles, petioles, mid
476
00:30:40.279 --> 00:30:44.079
ribs of the leaves and leaflets, and apparently aerial roots
477
00:30:44.119 --> 00:30:47.920
all possess this power. The first action of a tendril
478
00:30:48.000 --> 00:30:51.359
is to place itself in a proper position. For instance,
479
00:30:51.440 --> 00:30:55.440
the tendril of the Kobea first rises vertically up, with
480
00:30:55.519 --> 00:30:58.960
its branches divergent and with the terminal hooks turned outwards.
481
00:30:59.559 --> 00:31:01.920
The young shoot at the extremity of the stem is
482
00:31:01.960 --> 00:31:04.920
at the same time bend to one side so as
483
00:31:04.960 --> 00:31:08.039
to be out of the way. The young leaves of Chromatis,
484
00:31:08.160 --> 00:31:11.359
on the other hand, prepare for action by temporarily curving
485
00:31:11.359 --> 00:31:16.319
itself downwards so as to serve as grapnels. Secondly, if
486
00:31:16.319 --> 00:31:19.599
the twining plant or tendril gets by any accident into
487
00:31:19.599 --> 00:31:24.119
an inclined position, it soon bends upwards, though secluded from
488
00:31:24.200 --> 00:31:27.680
the light. The guiding stimulus, no doubt is the attraction
489
00:31:27.720 --> 00:31:30.480
of gravity. As Andrew Knite showed to be the case
490
00:31:30.519 --> 00:31:34.400
with germinating plants. If a shoot of any ordinary plant
491
00:31:34.440 --> 00:31:36.839
be placed in an inclined position in a glass of
492
00:31:36.920 --> 00:31:39.720
water in the dark, the extremity will in a few
493
00:31:39.759 --> 00:31:43.200
hours bend upwards, and if the position of the chute
494
00:31:43.279 --> 00:31:47.720
be then reversed, the downward chote reverses its curvature. But
495
00:31:47.799 --> 00:31:50.720
if the stolen of a strawberry, which has no tendency
496
00:31:50.720 --> 00:31:53.839
to grow upwards, be thus treated, it will curve downwards
497
00:31:53.839 --> 00:31:56.759
in the direction of instead of in opposition to the
498
00:31:56.839 --> 00:32:01.000
force of gravity, as with the very so it is
499
00:32:01.200 --> 00:32:05.200
generally with the twining shoots of the Hibertia dentata, which
500
00:32:05.240 --> 00:32:08.599
climbs laterally from bush to bush. For these shoots, if
501
00:32:08.640 --> 00:32:12.279
placed in positioning climbed downwards, show little and sometimes no
502
00:32:12.359 --> 00:32:17.000
tendency to curve upwards. Thirdly, climbing plants, like other plants,
503
00:32:17.039 --> 00:32:20.039
bend towards the light by a movement mostly analogous to
504
00:32:20.079 --> 00:32:23.880
the incurvation which causes them to revolve, so that their
505
00:32:23.880 --> 00:32:27.799
revolving movement is often accelerated or retarded in traveling to
506
00:32:27.960 --> 00:32:30.559
or from the light. On the other hand, in a
507
00:32:30.599 --> 00:32:35.400
few instances, tendrils bend towards the dark. Fourthly, we have
508
00:32:35.440 --> 00:32:39.839
the spontaneous revolving movement, which is independent of any outward stimulus,
509
00:32:40.079 --> 00:32:42.400
but is contingent on the youth of the part and
510
00:32:42.480 --> 00:32:45.759
on vigorous health. And this again, of course, depends on
511
00:32:45.799 --> 00:32:51.400
a proper temperature and other favorable conditions of light. Fifthly, tendrils,
512
00:32:51.519 --> 00:32:54.559
whatever their homological nature may be, and the petioles or
513
00:32:54.640 --> 00:32:58.880
tips of the leaves of leaf climbers, and apparently certain roots,
514
00:32:58.920 --> 00:33:02.400
all have the power of movement when touched and bend
515
00:33:02.480 --> 00:33:07.680
quickly towards the touched side. Extremely light pressure often suffices.
516
00:33:08.279 --> 00:33:10.680
If the pressure be not permanent, The part in question
517
00:33:10.799 --> 00:33:15.759
straightens itself and is again ready to bend on being touched. Sixthly,
518
00:33:15.799 --> 00:33:19.359
and lastly, tendrils, soon after clasping the support, but not
519
00:33:19.559 --> 00:33:23.400
after a mere temporary curvature, contract spirally. If they have
520
00:33:23.519 --> 00:33:26.680
not come into contact with any objects. They ultimately contract
521
00:33:26.720 --> 00:33:30.359
spirally after ceasing to evolve, but in this case the
522
00:33:30.400 --> 00:33:33.839
movement is useless and occurs only after a considerable lapse
523
00:33:33.839 --> 00:33:37.000
of time. With respect to the means by which these
524
00:33:37.079 --> 00:33:40.079
various movements are affected, there can be little doubt from
525
00:33:40.079 --> 00:33:43.319
the researches of Sax and h debrees that they are
526
00:33:43.480 --> 00:33:47.960
due to unequal growth, but from the reasons already assigned,
527
00:33:48.000 --> 00:33:51.519
I cannot believe that this explanation applies to the rapid
528
00:33:51.559 --> 00:33:56.039
movements from a delicate touch. Finally, climbing plants are sufficiently
529
00:33:56.160 --> 00:33:59.559
numerous to form a conspicuous feature in the vegetable kingdom,
530
00:34:00.160 --> 00:34:05.240
especially in tropical forests America, which so abounds with arboreal animals,
531
00:34:05.279 --> 00:34:08.960
as mister Bates remarks, likewise abounds, according to Mole and
532
00:34:09.039 --> 00:34:12.360
Palm with climbing plants, and of the tendril bearing plants
533
00:34:12.400 --> 00:34:15.760
examined by me, the highest developed kinds are natives of
534
00:34:15.800 --> 00:34:22.079
this grand continent, namely the several species of Bignonia, achromocarpus, Cobea,
535
00:34:22.519 --> 00:34:26.639
and Empelopsis. But even in the thickets of our temperate regions,
536
00:34:26.639 --> 00:34:30.039
the number of climbing species and individuals is considerable, as
537
00:34:30.079 --> 00:34:32.840
will be found by counting them. They belong to so
538
00:34:32.960 --> 00:34:36.679
many and wildly different orders. To gain some rude idea
539
00:34:36.719 --> 00:34:39.639
of their distribution in the vegetable series, I marked for
540
00:34:39.760 --> 00:34:42.760
the lists given by Mole and Palm, adding a few.
541
00:34:42.840 --> 00:34:46.199
Myself and a competent botanist, no doubt could have added
542
00:34:46.199 --> 00:34:50.559
many more all those families in Lindley's Vegetable Kingdom which
543
00:34:50.559 --> 00:34:56.320
include twiners, leaf climbers, or tender bearers. Lindley divides phenerogamic
544
00:34:56.400 --> 00:35:00.199
plants into fifty nine alliances. Of these, no legs less
545
00:35:00.239 --> 00:35:03.360
than thirty five include climbing plants of the above kinds,
546
00:35:03.639 --> 00:35:07.480
hook and root climbers being excluded. To these, A few
547
00:35:07.599 --> 00:35:11.679
cryptogamic plants must be added. When we reflect on the
548
00:35:11.679 --> 00:35:14.599
wide separation of these plants in the series, and when
549
00:35:14.599 --> 00:35:16.719
we know that in some of the largest and well
550
00:35:16.719 --> 00:35:23.320
defined orders, such as the Compositae Rubasia, Scropophilariae, cia, the Lasia,
551
00:35:23.519 --> 00:35:27.320
et cetera, species in only two or three genera have
552
00:35:27.400 --> 00:35:30.760
the power of climbing, the conclusion is forced on our
553
00:35:30.800 --> 00:35:34.599
minds that the capacity of revolving on which most climbers depend,
554
00:35:34.880 --> 00:35:38.239
is inherent, though undeveloped, in almost every plant in the
555
00:35:38.320 --> 00:35:42.800
Vegetable Kingdom. It has often been vaguely asserted that plants
556
00:35:42.840 --> 00:35:46.159
are distinguished from animals by not having the power of movement.
557
00:35:46.760 --> 00:35:49.440
It should rather be said that plants acquire and display
558
00:35:49.480 --> 00:35:52.559
this power only when it is of some advantage to them,
559
00:35:52.920 --> 00:35:55.840
and this being of comparatively rare occurrence. As they are
560
00:35:55.840 --> 00:35:57.960
fixed to the ground and food is brought to them
561
00:35:58.079 --> 00:36:01.199
by the air and rain. We see how high in
562
00:36:01.239 --> 00:36:04.119
the scale of organization a plant may rise. When we
563
00:36:04.159 --> 00:36:07.159
look at one of the more perfect tendril bearers, it
564
00:36:07.239 --> 00:36:10.840
first places its tendrils ready for action, as a polypus
565
00:36:10.880 --> 00:36:14.480
places its tentacula. If the tendril be displaced, it is
566
00:36:14.559 --> 00:36:17.400
acted on by the force of gravity and rights itself.
567
00:36:17.800 --> 00:36:20.199
It is acted on by the light and bends towards
568
00:36:20.280 --> 00:36:23.079
or from it, or disregards it, whichever may be the
569
00:36:23.119 --> 00:36:27.599
most advantageous. During several days, the tendrils or internodes or
570
00:36:27.679 --> 00:36:32.519
both spontaneously revolve with a steady motion. The tendril strikes
571
00:36:32.519 --> 00:36:35.760
some object and quickly curls round and firmly grasps it.
572
00:36:36.519 --> 00:36:39.320
In the course of some hours it contracts into a spire,
573
00:36:39.679 --> 00:36:44.440
dragging up the sidam and forming an excellent spring. All
574
00:36:44.480 --> 00:36:48.440
movements now cease. By growth, the tissue soon become wonderfully
575
00:36:48.480 --> 00:36:51.760
strong and durable. The tendril has done its work, and
576
00:36:51.880 --> 00:36:57.639
has done it in an admirable manner. End of Chapter five.
577
00:36:58.679 --> 00:37:01.920
End of the Movement and Habits of Climbing Plants by
578
00:37:02.000 --> 00:37:02.880
Charles Darwin,