The Movements and Habits of Climbing Plants
The Project Gutenberg eBook, The Movement and Habits of Climbing Plants,by Charles DarwinThis eBook is for the use of anyone anywhere in the United States and mostother parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms ofthe Project Gutenberg License included with this eBook or online at www.gutenberg.org. If you are not located in the United States, you'll haveto check the laws of the country where you are located before using this ebook.Title: The Movement and Habits of Climbing PlantsAuthor: Charles DarwinRelease Date: April 21, 2015 [eBook #2485][This file was first posted on March 4, 2000]Language: EnglishCharacter set encoding: ISO-646-US (US-ASCII)***START OF THE PROJECT GUTENBERG EBOOK THE MOVEMENT AND HABITS OFCLIMBING PLANTS***
Transcribed from the 1906 John Murray edition by David Price,email [email protected]
AND HABITS OF
ByCHARLES DARWIN, F.R.S.
JOHN MURRAY, ALBEMARLE STREET.
This Essay first appeared in theninth volume of the ‘Journal of the Linnean Society,’published in 1865. It is here reproduced in a correctedand, I hope, clearer form, with some additional facts. Theillustrations were drawn by my son, George Darwin. FritzMüller, after the publication of my paper, sent to theLinnean Society (Journal, vol. ix., p. 344) some interestingobservations on the climbing plants of South Brazil, to which Ishall frequently refer. Recently two important memoirs,chiefly on the difference in growth between the upper and lowersides of tendrils, and on the mechanism of the movements oftwining-plants, by Dr. Hugo de Vries, have appeared in the‘Arbeiten des Botanischen Instituts inWürzburg,’ Heft. iii., 1873. These memoirs oughtto be carefully studied by every one interested in the subject,as I can here give only references to the more importantpoints. This excellent observer, as well as ProfessorSachs, [iv] attributes all the movements oftendrils to rapid growth along one side; but, from reasonsassigned towards the close of my fourth chapter, I cannotpersuade myself that this holds good with respect to those due toa touch. In order that the reader may know what points haveinterested me most, I may call his attention to certaintendril-bearing plants; for instance, Bignonia capreolata,Cobæa, Echinocystis, and Hanburya, which display asbeautiful adaptations as can be found in any part of the kingdomof nature. It is, also, an interesting fact thatintermediate states between organs fitted for widely differentfunctions, may be observed on the same individual plant ofCorydalis claviculata and the common vine; and these casesillustrate in a striking manner the principle of the gradualevolution of species.
APPENDIX TO PREFACE (1882).
Since the publication of thisEdition two papers by eminent botanists have appeared;Schwendener, ‘Das Winden der Pflanzen’(Monatsberichte der Berliner Akademie, Dec. 1881), and J. Sachs,‘Notiz über Schlingpflanzen’ (Arbeiten desbotanischen Instituts in Würzburg, Bd. ii. p. 719,1882). The view “that the capacity of revolving, onwhich most climbers depend, is inherent, though undeveloped, inalmost every plant in the vegetable kingdom”(‘Climbing Plants,’ p. 205), has been confirmed bythe observations on circumnutation since given in ‘ThePower of Movement in Plants.’
On pp. 28, 32, 40, 53, statements are made with reference tothe supposed acceleration of the revolving movement towards thelight. It appears from the observations given in ‘ThePower of Movement in Plants,’ p. 451, that theseconclusions were drawn from insufficient observations, and areerroneous.
THE MOVEMENTS AND HABITS OF CLIMBING PLANTS.
Introductory remarks—Description of thetwining of the Hop—Torsion of the stems—Nature of therevolving movement, and manner of ascent—Stems notirritable—Rate of revolution in variousplants—Thickness of the support round which plants cantwine—Species which revolve in an anomalous manner.
I was led to this subject by aninteresting, but short paper by Professor Asa Gray on themovements of the tendrils of some Cucurbitaceous plants.
Climbing plants may be divided into four classes. First,those which twine spirally round a support, and are not aided byany other movement. Secondly, those endowed with irritableorgans, which when they touch any object clasp it; such organsconsisting of modified leaves, branches, orflower-peduncles. But these two classes sometimes graduateto a certain extent into one another. Plants of the thirdclass ascend merely by the aid of hooks; and those of the fourthby rootlets; but as in neither class do the plants exhibit anyspecial movements, they present little interest, and generallywhen I speak of climbing plants I refer to the two first greatclasses.
This is the largest subdivision, and is apparently theprimordial and simplest condition of the class. Myobservations will be best given by taking a few specialcases. When the shoot of a Hop (Humulus lupulus)rises from the ground, the two or three first-formed joints orinternodes are straight and remain stationary; but thenext-formed, whilst very young, may be seen to bend to one sideand to travel slowly round towards all points of the compass,moving, like the hands of a watch, with the sun. Themovement very soon acquires its full ordinary velocity. From seven observations made during August on shoots proceedingfrom a plant which had been cut down, and on another plant duringApril, the average rate during hot weather and during the day is2 hrs. 8 m. for each revolution; and none of the revolutionsvaried much from this rate. The revolving movementcontinues as long as the plant continues to grow; but eachseparate internode, as it becomes old, ceases to move.
To ascertain more precisely what amount of movement eachinternode underwent, I kept a potted plant, during the night andday, in a well-warmed room to which I was confined byillness. A long shoot projected beyond the upper end of thesupporting stick, and was steadily revolving. I then took alonger stick and tied up the shoot, so that only a very younginternode, 1¾ of an inch in length, was left free. This was so nearly upright that its revolution could not beeasily observed; but it certainly moved, and the side of theinternode which was at one time convex became concave, which, aswe shall hereafter see, is a sure sign of the revolvingmovement. I will assume that it made at least onerevolution during the first twenty-four hours. Early thenext morning its position was marked, and it made a secondrevolution in 9 hrs.; during the latter part of this revolutionit moved much quicker, and the third circle was performed in theevening in a little over 3 hrs. As on the succeedingmorning I found that the shoot revolved in 2 hrs. 45 m., it musthave made during the night four revolutions, each at the averagerate of a little over 3 hrs. I should add that thetemperature of the room varied only a little. The shoot hadnow grown 3½ inches in length, and carried at itsextremity a young internode 1 inch in length, which showed slightchanges in its curvature. The next or ninth revolution waseffected in 2 hrs. 30 m. From this time forward, therevolutions were easily observed. The thirty-sixthrevolution was performed at the usual rate; so was the last orthirty-seventh, but it was not completed; for the internodesuddenly became upright, and after moving to the centre, remainedmotionless. I tied a weight to its upper end, so as to bowit slightly and thus detect any movement; but there wasnone. Some time before the last revolution was halfperformed, the lower part of the internode ceased to move.
A few more remarks will complete all that need be said aboutthis internode. It moved during five days; but the morerapid movements, after the performance of the third revolution,lasted during three days and twenty hours. The regularrevolutions, from the ninth to thirty-sixth inclusive, wereeffected at the average rate of 2 hrs. 31 m.; but the weather wascold, and this affected the temperature of the room, especiallyduring the night, and consequently retarded the rate of movementa little. There was only one irregular movement, whichconsisted in the stem rapidly making, after an unusually slowrevolution, only the segment of a circle. After theseventeenth revolution the internode had grown from 1¾ to6 inches in length, and carried an internode 1⅞ inch long,which was just perceptibly moving; and this carried a very minuteultimate internode. After the twenty-first revolution, thepenultimate internode was 2½ inches long, and probablyrevolved in a period of about three hours. At thetwenty-seventh revolution the lower and still moving internodewas 8⅜, the penultimate 3½, and the ultimate2½ inches in length; and the inclination of the wholeshoot was such, that a circle 19 inches in diameter was swept byit. When the movement ceased, the lower internode was 9inches, and the penultimate 6 inches in length; so that, from thetwenty-seventh to thirty-seventh revolutions inclusive, threeinternodes were at the same time revolving.
The lower internode, when it ceased revolving, became uprightand rigid; but as the whole shoot was left to grow unsupported,it became after a time bent into a nearly horizontal position,the uppermost and growing internodes still revolving at theextremity, but of course no longer round the old central point ofthe supporting stick. From the changed position of thecentre of gravity of the extremity, as it revolved, a slight andslow swaying movement was given to the long horizontallyprojecting shoot; and this movement I at first thought was aspontaneous one. As the shoot grew, it hung down more andmore, whilst the growing and revolving extremity turned itself upmore and more.
With the Hop we have seen that three internodes were at thesame time revolving; and this was the case with most of theplants observed by me. With all, if in full health, twointernodes revolved; so that by the time the lower one ceased torevolve, the one above was in full action, with a terminalinternode just commencing to move. With Hoyacarnosa, on the other hand, a depending shoot, without anydeveloped leaves, 32 inches in length, and consisting of seveninternodes (a minute terminal one, an inch in length, beingcounted), continually, but slowly, swayed from side to side in asemicircular course, with the extreme internodes making completerevolutions. This swaying movement was certainly due to themovement of the lower internodes, which, however, had not forcesufficient to swing the whole shoot round the central supportingstick. The case of another Asclepiadaceous plant, viz.,Ceropegia Gardnerii, is worth briefly giving. Iallowed the top to grow out almost horizontally to the length of31 inches; this now consisted of three long internodes,terminated by two short ones. The whole revolved in acourse opposed to the sun (the reverse of that of the Hop), atrates between 5 hrs. 15 m. and 6 hrs. 45 m. for eachrevolution. The extreme tip thus made a circle of above 5feet (or 62 inches) in diameter and 16 feet in circumference,travelling at the rate of 32 or 33 inches per hour. Theweather being hot, the plant was allowed to stand on mystudy-table; and it was an interesting spectacle to watch thelong shoot sweeping this grand circle, night and day, in searchof some object round which to twine.
If we take hold of a growing sapling, we can of course bend itto all sides in succession, so as to make the tip describe acircle, like that performed by the summit of a spontaneouslyrevolving plant. By this movement the sapling is not in theleast twisted round its own axis. I mention this because ifa black point be painted on the bark, on the side which isuppermost when the sapling is bent towards the holder’sbody, as the circle is described, the black point gradually turnsround and sinks to the lower side, and comes up again when thecircle is completed; and this gives the false appearance oftwisting, which, in the case of spontaneously revolving plants,deceived me for a time. The appearance is the moredeceitful because the axes of nearly all twining-plants arereally twisted; and they are twisted in the same direction withthe spontaneous revolving movement. To give