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Show 56 CIRCU:M:NUTATION OF SEEDLINGS. CHAP. I. this was in parts straight and in parts decidedly zigzag, indicating circnmnutation. On the following day the other secondary shoot was observed; it was a little more advanced in age, for the upper part, instead Fig. 42. ~i ~~ (~ ·'~ Gory/us avellana: circumnutation of a young shoot emitted from the epicotyl, the apex of which had been injured, traced on a horizontal glass, from 9 A.M. Feb. 2nd to 8 A.M. 4th. Movement of bead magnified about 27 times. of depending vertically downwards, stood at an angle of 45° above tho horizon. Tho tip of tho shoot projected obliquely ·4 of an jnch above the ground, but by the close of our observations, which lasted 47 h., it had grown, chiefly towards its baRe, to a height of · 85 of an inch. Tho filament was fixed transversely to the basal and almost upright half of the shoot, close beneath the lowest scale-like appendage. Tho circumnutating course pursued is shown in tho accompanying figure (Fig. 42). The actual distance traversed from side to side was about · 04 of an inch. Pinus pinaster (Coniferro).- A young hypocotyl, with the tips of tho cotyledons still enclosed within the seed-coats, waR at first only · 35 of an inch in height; but the upper part grew so rapidly that at the end of our observations it was · 6 in height, Fig. 48. ..------~--------------- Pinus pinaster: circumuutation of hypocotyl, with filament fixed ncross its summit, traced on horizontal <r]ass, from 10 A.M. March 21st to 9 A.M. 23rd. Seedling kept in darkn"e.s. Movement of bead magnified about 35 times. · OuAP. I. PINUS AND CYCAS. 57 and by this time tho filament was attached some way clown the little stem. From some unknown canso, the hypocotyl moved far towards the left, but thoro could bo no doubt (Fig. 43) that it circumnntated. Another hypocotyl was similarly observed, and it likewise moved in a strongly zigzag line to the same side. This lateral movement was not caused by the attachment of tho glass filaments, nor by the action of light; for no light was allowed to entt·r when each observation was made, except from vertically al>ove. The bypocotyl of a seedling was secured to a little stick; it bore nino in appearance distinct cotyledons, arranged in a circle. The movements of two nearly opposite ones wore observed. The tip of one was painted white, with a mark place l below, and the figure described (Fig. 4.4, A) shows that it made an irregular Fig. 44. I \ I \\'-------.. /~ \ )' A. n. Pinus pinaster: circumnutation of two opposite cotyledons, traced on horizontal glass iu darkness, from 8.45 A.M. to 8.05 P.M. Nov. 25th. Movement of tiJ..l in A magnifieu about 22 times, here reduced to onehalf of original scale. circle in the course of about 8 h. During tho night it travelled to a considerable distance in the direction indicated by the broken line. A glass filament was attached longitudinally to tho other cotyledon, and this nearly completed (Fig. 44, B) an irregular circular figure in about 12 hours. During tho night it also moved to a considerable distance, in the direction indicated by tho broken line. Tho cotyledons therefore circumnutato independently of the movement of the h!pocotyl. Although they moved much during tho night, they did not approach each other so as to stand more vertically than during tho clay. |