. The power of movement in plants . Plants; Botany. 420 MODIFIED CIRCUMNUTATION. Chap VIH rate of bending towards it, and the accuracy with which they point towards its source, &c., will be given. Afterwards it will be shownâand this seems to us a point of much interestâthat sensitiveness to light is sometimes confined to a small part of the plant; and that this part when stimulated by light, transmits an influence to distant parts, exciting them to bend. Heliotropism. â When a plant which is strongly heliotropic (and species differ much in this respect) is exposed to a bright lateral ligh
. The power of movement in plants . Plants; Botany. 420 MODIFIED CIRCUMNUTATION. Chap VIH rate of bending towards it, and the accuracy with which they point towards its source, &c., will be given. Afterwards it will be shownâand this seems to us a point of much interestâthat sensitiveness to light is sometimes confined to a small part of the plant; and that this part when stimulated by light, transmits an influence to distant parts, exciting them to bend. Heliotropism. â When a plant which is strongly heliotropic (and species differ much in this respect) is exposed to a bright lateral light, it bends quickly towards it, and the course pursued by the stem is quite or nearly straight. But if the light is much dimmed, or occasionally interrupted, or admitted in only a slightly oblique direction, Fig. 168. ^. â¢' ° -^ , .^ ' the course pursued is more or less zigzag; and as we have seen and shall again see, such zigzag move- ment results from the elongation or drawing out of the ellipses, loops, &c., which the plant would have de- scribed, if it had been illuminated fvoni above. On several occasions Beta vnhja â¢S: civcuranu- we were uiuch struck with this fact, tntion of hypocotyl, de- ^^â¢hilst observing the circumnuta- flected by the light . r> i â i i â¢,⢠^^⢠being slightly lateral, tion 01 highly Sensitive seedlings, traced on a horizontal ^hich were Unintentionally illu- glass from to . â¢' minated rather obliquely, or only lighted taper by which ^^ successive intervals of time. it was illuminated, shown by a line joining p^^, jjigtance, two youBg seedlings of the first and penultimate i -, ⢠â , -im dots. Figure reduced to J^eta vulgaris were p\a,cea in the jnidale one-third of the original of a'Toom with north-east windows, and *°^'^- , were kept covered up, except during o?^li observation which lasted for only a minute or two; but the rosult was that their hypocotyls bowed themselves to
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