If 



MOTIONS IN PLANTS. 



MOTIONS IN PLANTS. 



018 



in a plate, and bUok bell-glut U inverted over them in such a 

 manner that iti edges) do uot quite touch the plat*, the OacilUtoriai 

 will remove from where they were first placed, and glide out on the 

 aide of the bell-glass which ia exposed to light The late Captain 

 Carmichael observed their motiona with great care, and sufficiently 

 proved that they were not owing to external causes of any kind ; 

 especially not to agitation of the water in which the Oscillatorias are 

 plaord. Let, he says, a small portion of the stratum be plaoed in a 

 watch-glad nearly filled with water, and covered with a circular film 

 of Ulc, *o that ita edge may touch the ghua ; the water will be rendered 

 ai fixed aa if it wa a piece of ice. The glaat may now be plaoed 

 under the microscope, and the oscillation of the filaments viewed 

 without riak of disturbance from the agitation of the water. By 

 following thia course, it will be speedily perceived that the motion in 

 quettion U entirely independent of that cause. The action of light, 

 aa a cause of motion, cannot be directly disproved, because we cannot 

 view our specimens in the dark ; but indirectly there is nothing easier. 

 If a watch-glass, charged as above, be laid aside for a night, it will be 

 found that, by the next morning, not only a considerable radiation has 

 taken place, but that multitudes of the filaments have entirely escaped 

 from the stratum, both indicating motion independent of light 

 Rapidity of growth will show itself in a prolongation of the filaments, 

 but will not account for this oscillation to the right and left ; and still 

 less for their travelling, in the course of a few hours, to the distance 

 of ten times their own length from the stratum. This last is a kind 

 of motion almost unexampled in the vegetable kingdom. 



Another kind of locomotion has been seen in the reproductive 

 particles or spores of Conferva. At a particular period of their life 

 these spores move about spontaneously inside the tubes in which they 

 are generated, and at length force themselves out into the water 

 wherein the mother-plant is floating. Once plunged in this element, 

 the spores move about with velocity, in a gyratory manner, till they 

 reach a shaded place, when they fix themselves by one end, produce a 

 root, and lose all power of after-motion, so that such plants have 

 locomotion when young, and are destitute of it when old. Many such 

 phenomena are known to occur in plants of the same low kind of 

 organisation. [ALGA; FUCACE.K ; ACIILYA.] 



But while locomotion thus unquestionably occurs among some 



are more commonly confined to 



kinds of plants, vegetable movements ar 

 the limbs, in which they are visible in 



motion occurs in roots, although not perceptibly, except by its effects. 

 Many kinds of Orchidaceous plants appear one season in a spot at 

 some distance from that which they occupied in the previous season, 

 and thus appear to travel ; in such cases however the shifting of place 

 is effected by means of underground suckers, annually formed by the 

 parent, which projects them to a certain distance from herself, and 

 then perishes. The cormi, or bulbs, as they are called, of many 

 Iridaceous plants exhibit the same kind of property, raising them- 

 selves upwards year after year, so that if originally buried some inches 

 under ground, they at last travel upwards into the air; this is effected 

 by each oonnus forming a bud at its apex, which bud grows into a 

 new cormus, and kills ita parent, forming a new cormus at its own 

 apex, and then perishing iu its turn. This power of rising upwards 

 is possessed in a most singular manner by palms, but in those plants 

 takes place in a different way. Some palm-trees, which originally had 

 their stem resting by its base on the surface of the ground, force it 

 upwards by protruding the bases of their roots, till at last a kiud of 

 plinth is formed of many irregular arches, upon which the column or 

 trunk of the palm-tree is upheaved. A case of this kiud is mentioned 

 by M. Pofteau, in the ' Annals of the Horticultural Society of Paris,' 

 voL iv. p. 4, f. 16, where the arches of the roots were high enough to 

 allow a man to pass beneath them. Here it is evident that the eleva- 

 tion of the trunk is caused by the extension of the roots, which 

 exercise that power in the direction of least resistance, namely, of the 

 air, rather than of the solid earth. 



The phenomena of flowers unfolding or closing under sunshine, of 

 which everybody is aware, are strictly referrible to the class of vege- 

 table motions. With the unfolding and closing of flowers must also 

 be arranged those singular motions in the parts of fructification which 

 occur upon their being touched. If the filaments of the Barberry 

 [BKRBEBIS] are irritated, they rise up and strike the anthers against 

 the stigina ; if the sexual column of Stylidium, which is bent over one 

 side of the flower, is touched, it swings over instantly to the other 

 side. Several case* <rf this power of motion occur in Orcliidacea : if 

 the caudicula of the pollen masses of Cataictum is disturbed, it springs 

 up so violently as to separate itself from the column on which it 

 grows, and to dart to a considerable distance. A very singular 

 instance of motion in the flowers of another plant of this kind 

 growing in the Swan River Colony, has been described by Mr. Drum- 

 mood. ('Gardeners' Gazette, voL xiv., p. 428.) The lower lip, he 

 ys, in which the anthers are placed, U a boat-shaped box ; the upper 

 lip, which he suppose* to be the stigma, forms a lid which exactly fits 

 it ; the hinge on which the lid moves springs from the upper part of 

 the flower, and is attached to 1U centre ; and when it opens the upper 

 part turns round within the box, comes out at the bottom, turns up 

 sad back ; so that when fully expanded it stands fairly over the flower. 

 The moment a small insect touches the point of the lid it makes a 

 sudden revolution, brings in the point of the lid at tho bottom of the 



box, so that it has to pass the anthers in its way, and makes prisoner 

 any small insect which the box will hold. When it catches an insect 

 it remains shut while the insect moves about; but if the insect be not 

 caught the box soon opens again. 



Another kind of motion, more resembling spontaneous action, 

 especially aa it is not apparently connected with the application of 

 stimuli, is that which occurs in the sexual apparatus of many plants 

 at the period of impregnation. In Armrria, at this time, a short 

 column below the stigmata lengthens, so as to close up the foramen of 

 the ovule, and at the same moment the cord on which the ovule is 

 suspended slips aside and elevates the ovule, so as to enable it to pre- 

 sent its foramen to the column. The same phenomena are visible in 

 Daphne Laureola and other plants ; and something of on analogous 

 nature occurs in Zygnemata, which at the period of fructification 

 bring themselves together, and effect a kind of spontaneous vegetable 

 copulation. The most striking phenomena of this nature occur bow- 

 ever in Aiclepiadacta, which have their pollen-grains closely packed 

 in bags, from which it would seem that there is no escape : at the 

 period of impregnation each of these pollen grains projects one tube 

 from its side, and these tubes all direct themselves spontaneously 

 towards a thin space on the side of the bag that holds them. Piercing 

 this bag, they succeed in extricating themselves and reaching the 

 vicinity of the stigma, but are still at some distance from it; they 

 then direct themselves towards that organ, and succeed in reaching it, 

 wherever it may be, cither by directing themselves at right angles, or 

 downwards, or eve* upwards, aa the peculiar structure and location of 

 the stigma may require. 



In the Sensitive Plants, various species of Mimota [Mmosx], espe- 

 cially if. pudica, the leaves fold up on being touched, and this so 

 slowly, that it is easy to perceive that the folding is effected by the 

 gradual communication from leaflet to leaflet of the shock produced 

 by the touch. If a portion of tho end of oue of the leaflets of the 

 Mimosa is cut off the whole of the leaflets of that pinna gradually 

 fold up, one after the other, from the point to the base ; then the 

 neighbouring pinwc will fold up their leaflets from the base to the 

 point, and presently the petiole itself will suddenly bow itself down 

 whereupon the folding up of the remainder of the pinnae will take 

 place. Sometimes, after a little space, the leaves above and below 

 will also close up, all under the influence of the one original iujury. 

 These curious phenomena have been watched with care by Dutrochet, 

 iu whose little book (' Sur la Motilito' des Plautea') a long and particu- 

 lar account of the phenomena will be found. Many other plants 

 possess this kind of sensitive power in their leaves : Smilhia icntitica, 

 jEichynomcne tensitiva, Porlicria hygromctrica, and Biophytum senri- 

 livum are well-known cases ; and it is recorded that in Senegal there 

 grows a plant which the natives call by a name equivalent to ' How 

 d'ye do?' as if it offered a friendly salutation by its bowing to those 

 who touch it (See De Candolle's ' Physiologic Ve'ge'tale,' p. 857, 

 where several of the modes are enumerated iu which leaves having 

 motion close up.) The 'sleep of the leaf,' that is, their folding up and 

 drooping at night, while they raise themselves and unfold by day, are 

 powers of motion in the limbs of plants, which are doubtless of the 

 same nature as that of the Sensitive Plant and its allies. To the some 

 class also must be assigned the fly-catching leaves of Dionita. 

 [DION.EA.] This plant, which grows wild in the marshes of Carolina, 

 has a leaf which is bordered with a row of strong teeth, and when 

 spread open is strikingly similar to one of the toothed iron traps when 

 set as used for catching game, that ia, it consists of two roundish 

 sides, each furnished with a row of strong teeth. Near the middle of 

 each side there grow three stiff bristles, placed in the form of a 

 triangle ; if one of these bristles is touched by an insect or any other 

 means, the two sides of the leaf spring up instantly, the. teeth cross 

 each other, and the insect is held so fast that it can only be extricated 

 by forcing the sides of the leaf asunder, an operation of some diffi- 

 culty, so great is tho muscular force with which tho contraction is 

 effected. These movements are all owing to a specific irritability 

 resident in the moving organ, and must be distinguished from the 

 following, which takes place, to all appearance, spontaneously. 



Damodium gyrant, the Oora-Chand of liongal, was first mentioned 

 in systematical botany by the younger Linnteus, who speaks of it as 

 a wonderful plant, on account of its singular motion. " No sooner,' 

 he says, " hod the plants he raised from seed acquired their ternate 

 leaves, than they began to be in motion in every direction. This move- 

 ment did not cease during tho whole course of their vegetation, nor 

 were they observant of any time, order, or direction. One leaflet 

 frequently revolved, while the other on the same petiole was quiescent ; 

 sometimes a few leaflets only were hi motion, then almost all of them 

 would be in movement at once. Tho whole plant was very seldom 

 agitated, and that only during tho first year. It continued to move 

 in the stove during tho second year of its growth, and was not at rest 



; even in the winter." 



" The irritability of the Damodium," Burnett adds, "is never so 



', great, even in our best houses, as it is said to be in its native climate, 

 and its motions here are very seldom so lively as those described by 



; Linnams. Warmth appears essential, for it* movements are always 

 the most observable when the heat is greatest; that they are not 

 attributable to the sun's rays, nor to any currents of air, i* shown 



1 from the fact that the plant loves the shade, and that the motion is 



