. The power of movement in plants . Plants; Botany. Chap. VIU. HELIOTEOPISM. 4yi which, whilst young, is so extremely sensitive to light, worth giving. Cassia tora. — The cotyledons of this plant are extremely Fig. 177. 6°][).mS a. W°io'^ sensitive to light, whilst the hypocotyls are much less sensitive than those of most other seedlings, as we had often observed with surprise. It seemed therefore worth while to trace their move- ments. They were exposed to a lateral light before a north-east window, which was at first covered merely by a muslin blind, but as the sky grew brighter about 11
. The power of movement in plants . Plants; Botany. Chap. VIU. HELIOTEOPISM. 4yi which, whilst young, is so extremely sensitive to light, worth giving. Cassia tora. — The cotyledons of this plant are extremely Fig. 177. 6°][).mS a. W°io'^ sensitive to light, whilst the hypocotyls are much less sensitive than those of most other seedlings, as we had often observed with surprise. It seemed therefore worth while to trace their move- ments. They were exposed to a lateral light before a north-east window, which was at first covered merely by a muslin blind, but as the sky grew brighter about 11 , an additional linen Dlind was suspended. After 4 one blind and then the other was removed. The seedlings were protected on each side and above, but were open to the diffused light of the room in the rear. Up- right filaments were fixed to the hypocotyls of two seed- lings, which stood vertically in the morning. The accom- panying figure (Fig. 177) shows the course pursued by one of them during two days; but it should be particularly noticed that during the second day the seedlings were < kept in darkness, and they then circumnutated roxmd nefirly the same smaU space. On the first day (Oct. 7th) the hypocotj] moved from 8 to , toward the light in a zigzag line, then turned abruptly to the left and afterwards described a small ellipse. Another irregular. '7 •7°': Cassia tora; heliotropic movement aud circumnutation of a hypocotyl (IJ inch in height) traced on a horizontal glass from 8 to Oct. 7th. Also its circumnutation in darkness from 7 Oct. 8th to Oct. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Charles, 1809-1882; Darwin, Francis, Sir, 1848-1925. New York : D. Appleton
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Keywords: ., bookcentury1800, bookdecade, booksubjectbotany, booksubjectplants
