. The power of movement in plants . Plants; Botany. 420 MODIFIED CIROUMNUTATION. 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 CIROUMNUTATION. 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 ' ° â ' , P- , ' 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 from above. On several occasions Betavuiga'-is: circumnu- we Were much struck with this fact, tation of hypocotyi, de- whilst observing the circumnuta- flected by the light . « i ⢠i i being slightly lateral, tion 01 highly Sensitive seedlings, dassVom8 3olT*to '^^^^^ ^^re Unintentionally illu- Directionofthe minated rather obliquely, or only ii-'wt'^^'inun^iS ^* ^^"'^es^i^e intervals of time. fhStldiiruS â For instance, two young seedlings of dots. Figure reduced to ^^^ vulgaris were placed in the middle one-third of the original of a room with north-east windows, and ^"^^^^ were kept covered up, except during each observation which lasted for only a minute or two; but the result was that their hypocotyls bowed themselves to the side, whence some light occasionally entered, in lines which were. Please note that these images are extracted from scanned page image
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Keywords: ., bookcentury1800, booksubjectbotany, booksubjectplants, bookyear18
