The Movements and Habits of Climbing Plants Part 9

{8} It is well known that the stems of many plants occasionally become spirally twisted in a monstrous manner; and after my paper was read before the Linnean Society, Dr. Maxwell Masters remarked to me in a letter that "some of these cases, if not all, are dependent upon some obstacle or resistance to their upward growth." This conclusion agrees with what I have said about the twisting of stems, which have twined round rugged supports; but does not preclude the twisting being of service to the plant by giving greater rigidity to the stem.

{9} The view that the revolving movement or nutation of the stems of twining plants is due to growth is that advanced by Sachs and H. de Vries; and the truth of this view is proved by their excellent observations.

{10} The mechanism by which the end of the shoot remains hooked appears to be a difficult and complex problem, discussed by Dr. H. de Vries (ibid. p. 337): he concludes that "it depends on the relation between the rapidity of torsion and the rapidity of nutation."

{11} Dr. H. de Vries also has shown (ibid. p. 321 and 325) by a better method than that employed by me, that the stems of twining plants are not irritable, and that the cause of their winding up a support is exactly what I have described.

{12} Dr. H. de Vries states (ibid. p. 322) that the stem of Cuscuta is irritable like a tendril.

{13} See Dr. H. de Vries (ibid. p. 324) on this subject.

{14} Comptes Rendus, 1844, tom. xix. p. 295, and Annales des Sc. Nat 3rd series, Bot., tom. ii. p. 163.

{15} I am much indebted to Dr. Hooker for having sent me many plants from Kew; and to Mr. Veitch, of the Royal Exotic Nursery, for having generously given me a collection of fine specimens of climbing plants. Professor Asa Gray, Prof. Oliver, and Dr. Hooker have afforded me, as on many previous occasions, much information and many references.

{16} Journal of the Linn. Soc. (Bot.) vol. ix. p. 344. I shall have occasion often to quote this interesting paper, in which he corrects or confirms various statements made by me.

{17} I raised nine plants of the hybrid Loasa Herbertii, and six of these also reversed their spire in ascending a support.

{18} In another genus, namely Davilla, belonging to the same family with Hibbertia, Fritz Muller says (ibid. p. 349) that "the stem twines indifferently from left to right, or from right to left; and I once saw a shoot which ascended a tree about five inches in diameter, reverse its course in the same manner as so frequently occurs with Loasa."

{19} Fritz Muller states (ibid. p. 349) that he saw on one occasion in the forests of South Brazil a trunk about five feet in circ.u.mference spirally ascended by a plant, apparently belonging to the Menispermaceae. He adds in his letter to me that most of the climbing plants which there ascend thick trees, are root-climbers; some being tendril-bearers.

{20} Fritz Muller has published some interesting facts and views on the structure of the wood of climbing plants in 'Bot. Zeitung,' 1866, pp. 57, 66.

{21} It appears from A. Kerner's interesting observations, that the flower-peduncles of a large number of plants are irritable, and bend when they are rubbed or shaken: Die Schutzmittel des Pollens, 1873, p. 34.

{22} I have already referred to the case of the twining stem of Cuscuta, which, according to H. de Vries (ibid. p. 322) is sensitive to a touch like a tendril.

{23} Dr. Maxwell Masters informs me that in almost all petioles which are cylindrical, such as those bearing peltate leaves, the woody vessels form a closed ring; semilunar bands of vessels being confined to petioles which are channelled along their upper surfaces.

In accordance with this statement, it may be observed that the enlarged and clasped petiole of the Solanum, with its closed ring of woody vessels, has become more cylindrical than it was in its original unclasped condition.

{24} Never having had the opportunity of examining tendrils produced by the modification of branches, I spoke doubtfully about them in this essay when originally published. But since then Fritz Muller has described (Journal of Linn. Soc. vol. ix. p. 344) many striking cases in South Brazil. In speaking of plants which climb by the aid of their branches, more or less modified, he states that the following stages of development can be traced: (1.) Plants supporting themselves simply by their branches stretched out at right angles--for example, Chiococca. (2.) Plants clasping a support with their unmodified branches, as with Securidaca. (3.) Plants climbing by the extremities of their branches which appear like tendrils, as is the case according to Endlicher with Helinus. (4.) Plants with their branches much modified and temporarily converted into tendrils, but which may be again transformed into branches, as with certain Papilionaceous plants. (5.) Plants with their branches forming true tendrils, and used exclusively for climbing--as with Strychnos and Caulotretus. Even the unmodified branches become much thickened when they wind round a support. I may add that Mr. Thwaites sent me from Ceylon a specimen of an Acacia which had climbed up the trunk of a rather large tree, by the aid of tendril-like, curved or convoluted branchlets, arrested in their growth and furnished with sharp recurved hooks.

{25} As far as I can make out, the history of our knowledge of tendrils is as follows:- We have seen that Palm and von Mohl observed about the same time the singular phenomenon of the spontaneous revolving movement of twining-plants. Palm (p. 58), I presume, observed likewise the revolving movement of tendrils; but I do not feel sure of this, for he says very little on the subject. Dutrochet fully described this movement of the tendril in the common pea. Mohl first discovered that tendrils are sensitive to contact; but from some cause, probably from observing too old tendrils, he was not aware how sensitive they were, and thought that prolonged pressure was necessary to excite their movement. Professor Asa Gray, in a paper already quoted, first noticed the extreme sensitiveness and rapidity of the movements of the tendrils of certain Cucurbitaceous plants.

{26} Fritz Muller states (ibid. p. 348) that in South Brazil the trifid tendrils of Haplolophium, (one of the Bignoniaceae) without having come into contact with any object, terminate in smooth shining discs. These, however, after adhering to any object, sometimes become considerably enlarged.

{27} Comptes Rendus, tom. xvii. 1843, p. 989.

{28} 'Lecons de Botanique,' &c., 1841, p. 170.

{29} I am indebted to Prof. Oliver for information on this head. In the Bulletin de la Societe Botanique de France, 1857, there are numerous discussions on the nature of the tendrils in this family.

{30} 'Gardeners' Chronicle,' 1864, p. 721. From the affinity of the Cucurbitaceae to the Pa.s.sifloraceae, it might be argued that the tendrils of the former are modified flower-peduncles, as is certainly the case with those of Pa.s.sion flowers. Mr. R. Holland (Hardwicke's 'Science-Gossip,' 1865, p. 105) states that "a cuc.u.mber grew, a few years ago in my own garden, where one of the short p.r.i.c.kles upon the fruit had grown out into a long, curled tendril."

{31} Trans. Phil. Soc. 1812, p. 314.

{32} Dr. M'Nab remarks (Trans. Bot. Soc. Edinburgh, vol xi. p. 292) that the tendrils of Amp. Veitchii bear small globular discs before they have came into contact with any object; and I have since observed the same fact. These discs, however, increase greatly in size, if they press against and adhere to any surface. The tendrils, therefore, of one species of Ampelopsis require the stimulus of contact for the first development of their discs, whilst those of another species do not need any such stimulus. We have seen an exactly parallel case with two species of Bignoniaceae.

{33} Fritz Muller remarks (ibid. p. 348) that a related genus, Serjania, differs from Cardiospermum in bearing only a single tendril; and that the common peduncle contracts spirally, when, as frequently happens, the tendril has clasped the plant's own stem.

{34} Prof. Asa Gray informs me that the tendrils of P. sicyoides revolve even at a quicker rate than those of P. gracilis; four revolutions were completed (the temperature varying from 88 degrees- 92 degrees Fahr.) in the following times, 40 m., 45 m., 38.5 m., and 46 m. One half-revolution was performed in 15 m.

{35} See M. Isid. Leon in Bull. Soc. Bot. de France, tom. v. 1858, p. 650. Dr. H. de Vries points out (p. 306) that I have overlooked, in the first edition of this essay, the following sentence by Mohl: "After a tendril has caught a support, it begins in some days to wind into a spire, which, since the tendril is made fast at both extremities, must of necessity be in some places to the right, in others to the left." But I am not surprised that this brief sentence, without any further explanation did not attract my attention.

{36} Sachs, however ('Text-Book of Botany,' Eng. Translation, 1875, p. 280), has shown that which I overlooked, namely, that the tendrils of different species are adapted to clasp supports of different thicknesses. He further shows that after a tendril has clasped a support it subsequently tightens its hold.

{37} Annales des Sc. Nat. Bot. 4th series, tom. xii. p. 89.

{38} It occurred to me that the movement of notation and that from a touch might be differently affected by anaesthetics, in the same manner as Paul Bert has shown to be the case with the sleep-movements of Mimosa and those from a touch. I tried the common pea and Pa.s.siflora gracilis, but I succeeded only in observing that both movements were unaffected by exposure for 1.5 hrs. to a rather large dose of sulphuric ether. In this respect they present a wonderful contrast with Drosera, owing no doubt to the presence of absorbent glands in the latter plant.

{39} Text-Book of Botany, 1875, p. 779.

{40} Journal of Linn. Soc. vol. ix. p. 348. Professor G. Jaeger has well remarked ('In Sachen Darwin's, insbesondere contra Wigand,'

1874, p. 106) that it is highly characteristic of climbing plants to produce thin, elongated, and flexible stems. He further remarks that plants growing beneath other and taller species or trees, are naturally those which would be developed into climbers; anti such plants, from stretching towards the light, and from not being much agitated by the wind, tend to produce long, thin and flexible shoots.

{41} Professor Asa Gray has explained, as it would appear, this difficulty in his review (American Journal of Science, vol. xl. Sept.

1865, p. 282) of the present work. He has observed that the strong summer shoots of the Michigan rose (Rosa setigera) are strongly disposed to push into dark crevices and away from the light, so that they would be almost sure to place themselves under a trellis. He adds that the lateral shoots, made on the following spring emerged from the trellis as they sought the light.

{42} Mr. Spiller has recently shown (Chemical Society, Feb. 16, 1865), in a paper on the oxidation of india-rubber or caoutchouc, that this substance, when exposed in a fine state of division to the air, gradually becomes converted into brittle, resinous matter, very similar to sh.e.l.l-lac.

{43} Fritz Muller informs me that he saw in the forests of South Brazil numerous black strings, from some lines to nearly an inch in diameter, winding spirally round the trunks of gigantic trees. At first sight he thought that they were the stems of twining plants which were thus ascending the trees: but he afterwards found that they were the aerial roots of a Philodendron which grew on the branches above. These roots therefore seem to be true twiners, though they use their powers to descend, instead of to ascend like twining plants. The aerial roots of some other species of Philodendron hang vertically downwards, sometimes for a length of more than fifty feet.

{44} Quoted by Cohn, in his remarkable memoir, "Contractile Gewebe im Pflanzenreiche," 'Abhandl. der Schlesischen Gesell. 1861, Heft i.

s. 35.

{45} Such slight spontaneous movements, I now find, have been for some time known to occur, for instance with the flower-stems of Bra.s.sica napus and with the leaves of many plants: Sachs' 'Text-Book of Botany' 1875, pp. 766, 785. Fritz Muller also has shown in relation to our present subject ('Jenaischen Zeitschrift,' Bd. V.

Heft 2, p. 133) that the stems, whilst young, of an Alisma and of a Linum are continually performing slight movements to all points of the compa.s.s, like those of climbing plants.

{46} Mr. Herbert Spencer has recently argued ('Principles of Biology,' 1865, p. 37 et seq.) with much force that there is no fundamental distinction between the foliar and axial organs of plants.

{47} Annales des Sc. Nat. 4th series, Bot. tom. vi. 1856, p. 31.

{48} Moquin-Tandon (Elements de Teratologie. 1841, p. 156) gives the case of a monstrous bean, in which a case of compensation of this nature was suddenly effected; for the leaves completely disappeared and the stipules grew to an enormous size.