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Show 14 CIRCUMNUTATION OF SEEDLINGS. CHAP. I. age to circumnutate irregularly. On the first day tho greater movement (from right to left in the figure) was not in the plane of the vertical and arched hypocotyl, but at right angles to it, or in the plane of the two cotyledons, which were still in close contact. The basal leg of the arch at the time when the filament was affixed to it, was already bowed considerably backwards, or from the cotyledons; had tho filament been affixed before this bowing occurred, the chief movement would have been at 1·ight angles to that shown in the figure. A filament was attached to another buried hypocotyl of the same age, and it moved in a similar general manner, but the line traced was not so complex. This hypocotyl became almost straight, and the cotyledons were dragged from beneath the ground on the evening of the second day. Brassica oleracea: circumnutating movement of buried and arched hypocotyl, with the two legs of the arch tied together, traced on horizontal glass during 33k hours. Movement of the bead of filament magnified · about 26 times, and here reduced to one-half original scale. Before the above observations were made, some arched hypocotyls buried at the depth of a quarter of an inch were uncovered ; and in order to prevent the two legs of the arch from beginning to separate at once, they were tied together with fine silk. This was done partly because we wished to ascertain how long the hypocotyl, in its arched condition, would continue to move, and whether the movement when not masked and disturbed by the straightening process, indicated circumnuta. tion. Firstly, a filament was fixed to the basal leg of an arched hypocotyl close above the summit of the mdicle. The cotyledons were still partially enclosed within the seed-coats. The movement was traced (Fig. 4) from 9.20 A.M. on Dec. CHAP. I. BRASSICA. 15 23rd to 6.45 A.M. on Dec. 25th. No doubt the natural movement was much disturbed by the two legs having been tied ~getJ~er; but we see that it was distinctly zigzag, first in one directwn and then in an almost opposite one. After 3 P.M. on the 24th _the arch~d hypocotyl sometimes remained stationary for a considerable time, and when moving, moved far slower than before. Therefore, on the morning , of the 25th, the glass filament was removed from the base of the basal leg, and was fixed horizontally on the summit of tho arch, which, from the legs having been tied, had grown broad and almost fiat. The movement was now traced during 23 hours (Fig. 5), and we Fig. 5. ·~ -------------- ---- ------------ -------; /_/ I ~ Brassica oleracea: circm:nnutating movement of the crown of a buried and arched hypocot;:l, w1t.h the two legs tied together, traced on a horizonta~ glass dunng 23 hours. Movement of the bead of the filament magmfied about 58 t1mes, and here reduced to one-half origin~] scale. sec ~hat the co~rse was still zigzag, which indicates a tendency to mrcumnutatwn. The base of the basal leg by this timo had almost completely ceased to move. As soon as the cotyledons have been naturally dragged from beneath the ground, and tho hypocotyl has stmightoned itself ?Y growth ~long the inner or concave surface, there is nothing to mterf~re With the free movements of the parts; and the circumnutatiOn n~w becomes much more regular and clearly displayed, as shown m the following cases :-A seedling was placed in front and near a north-east window with a line joining the |