. The power of movement in plants. Plants; Botany. Ceap. X. APOGEOTROPISM. 501 Kig. 187. upwards, and rose during the first 3 h. 10 m. in a nearly straighl line (Fig. 187); but it was not possible to trace the upward move- ment on the vertical glass for the first 1 h. 10 m., so that the nearly straight line in the diagram ought to have been much longer. During the next 11 h. the hypocotyl circum- nutated, describing irregularflgures, each of which rose a little above the one previously formed. During the night and following early morn- ing it continued to rise in a zigzag course, so that apoge
. The power of movement in plants. Plants; Botany. Ceap. X. APOGEOTROPISM. 501 Kig. 187. upwards, and rose during the first 3 h. 10 m. in a nearly straighl line (Fig. 187); but it was not possible to trace the upward move- ment on the vertical glass for the first 1 h. 10 m., so that the nearly straight line in the diagram ought to have been much longer. During the next 11 h. the hypocotyl circum- nutated, describing irregularflgures, each of which rose a little above the one previously formed. During the night and following early morn- ing it continued to rise in a zigzag course, so that apogeotropism was still acting. At the close of our ob- servations, after 23 h. (represented by the highest dot in the diagram) the hypocotyl was still 32° from the perpendicular. There can be little doubt that it would ulti- mately have become upright by describing an additional number of irregular elUpses, one above the other. ApogeotropUm retarded hy Helio- tropism. — When the stem of any plant bends during the day towards a lateral Hght, the movement is opposed by apogeotropism; but as the light gradually wanes in the evening the latter power slowly gains the upper hand, and draws J^rassica oleracea: apogeotropic the stem back into a vertical position. Here then we have a good opportunity for observing how apogeotropism acts when very nearly balanced by an opposing force. For instance, the plumule of Tropceolum (see former Fig. 175) moved towards the dim evening light in a slightly zigzag Une until , it then returned on. movemenf. of hypocotyl, traced on ve]-tical glass, from Sept. 12th to l.'^th. The upper part of the figure is more magnified than the lower part, if the whole course had been traced, the straight upright line would have been much longer. Figure here reduced to one-third of the original scale. its course until. Please note that these images are extracted from scanned page images that may have been digitally enhanced for read
Size: 866px × 2885px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade, booksubjectbotany, booksubjectplants
