. The power of movement in plants . Plants; Botany. Chap. VUL HELIOTKOPISM. 421 Fig. 169. only slightly zigzag. Although not a single eUipse was even approximately formed, we inferred from the zigzag lines—^and, as it proved, correctly—^that their hypocotyls were circunmuta- ting, for on the following day these same seedlings were placed in a completely darkened room, and were observed each time by the aid of a small wax taper held almost directly above them, and their movements were traced on a horizontal glass above; and now their hypocotyls clearly circum- nutated (Fig. 168, and Kg. 39, for
. The power of movement in plants . Plants; Botany. Chap. VUL HELIOTKOPISM. 421 Fig. 169. only slightly zigzag. Although not a single eUipse was even approximately formed, we inferred from the zigzag lines—^and, as it proved, correctly—^that their hypocotyls were circunmuta- ting, for on the following day these same seedlings were placed in a completely darkened room, and were observed each time by the aid of a small wax taper held almost directly above them, and their movements were traced on a horizontal glass above; and now their hypocotyls clearly circum- nutated (Fig. 168, and Kg. 39, formerly given, p. 52); yet they moved a short distance towards the side where the taper was held np. If we look at these diagrams, and suppose that the taper had been held more on one side, and that the hypocotyls, stiU drcumnutating, had bent themselves within the same time much more towards the light, long zigzag lines would ob- viously have been the result. Again, two seedlings of Solanum lyco- psrsicum were illuminated from above, but accidentally a little more light entered on one than on any other side, and their hypocotyls became slightly bowed towards the brighter side; they moved in a zigzag line and described in their course two little triangles, as seen in Kg. 37 (p. 50), and in another tracing not given. The sheath- like cotyledons of Zea mays behaved, under nearly similar drcumstanc&s, in a nearly similar manner, as described in our first ^''^^^^"t and dr"m- chapter (p. 64), for they bowed themselves during the whole day towards one side, making, however, in their course some conspicuous flexures. Before we knew how greatly ordinary circumnutationwas modified by a lateral light, some seedling oats, with rather old and therefore not highly sensitive cotyledons, were placed in front of a north-east window, towards which they bent all day in a strongly zigzag course. On the following day they continued to bend in the same direction (Fig. 169), but zigz
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