. The power of movement in plants . Plants; Botany. Chap. Vni. HELIOTBOPISM. 427 ff^.ra'C no doubt, was due to its then cirounmutating in this direction. Similar cases were repeatedly observed, and a dim light rarely or never produced any eflfect until from a quarter to three- quarters of an hour had elapsed. After , by which time the light had become obscure, the hypocotyl began to circumnutate about the same spot. The contrast between the two figures (172 and 173) would have been more striking, if they had been . originally drawn on the same scale, and had been equally reduced. But
. The power of movement in plants . Plants; Botany. Chap. Vni. HELIOTBOPISM. 427 ff^.ra'C no doubt, was due to its then cirounmutating in this direction. Similar cases were repeatedly observed, and a dim light rarely or never produced any eflfect until from a quarter to three- quarters of an hour had elapsed. After , by which time the light had become obscure, the hypocotyl began to circumnutate about the same spot. The contrast between the two figures (172 and 173) would have been more striking, if they had been . originally drawn on the same scale, and had been equally reduced. But the movements shown in Fig. 172 were at first more mag- nified, and have been re- duced to only one-half of the original scale; whereas those in Fig. 173 were at first less magnified, and have been reduced to a one-third scale. A tracing made at the same time with the last of the movements of a second hypocotyl, presented a Closely analogous appear- ance ; but it did not bend quite so much towards the light, and it circumnu-. Shg'^!' tated rather more plainly. P^w^aris Canariensis: heliotropie movement Ti-L 1 ⢠n â ⢠and circumnutation of a rather old cotv- Phalaris j^^^^^ ^^^^^^, ^^H j^j^^jUgj^j^ ^^^^^. The sheath-Hke cotyledons on a horizontal glass from Sept. 16th to 17th. Figure reduced to one-third of original scale. of this monocotyledonous plant were selected for trial, because they are very sensitive to light and circumnutate well, as formerly shown (see Fig. 49, p. 63). Although we felt no doubt about the result, some seedlings were first placed before a south-west window on a moderately bright morning, and the movements of one were traced. As is so common, it moved. 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,
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Keywords: ., bookcentury1800, booksubjectbotany, booksubjectplants, bookyear18
