Pinus pinaster (Coniferae).—­A young hypocotyl, with the tips of the cotyledons still enclosed within the seed-coats, was 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. 43.  Pinus pinaster:  circumnutation of hypocotyl, with filament fixed across its summit, traced on horizontal glass, from 10 A.M.  March 21st to 9 A.M. 23rd.  Seedling kept in darkness.  Movement of bead magnified about 35 times. [page 57]

and by this time the filament was attached some way down the little stem.  From some unknown cause, the hypocotyl moved far towards the left, but there could be no doubt (Fig. 43) that it circumnutated.  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 the glass filaments, nor by the action of light; for no light was allowed to enter when each observation was made, except from vertically above.

The hypocotyl of a seedling was secured to a little stick; it bore nine in appearance distinct cotyledons, arranged in a circle.  The movements of two nearly opposite ones were observed.  The tip of one was painted white, with a mark placed below, and the figure described (Fig. 44, A) shows that it made an irregular

Fig. 44.  Pinus pinaster:  circumnutation of two opposite cotyledons, traced on horizontal glass in darkness, from 8.45 A.M. to 8.35 P.M.  Nov. 25th.  Movement of tip in A magnified about 22 times, here reduced to one-half of original scale.

circle in the course of about 8 h. during the night it travelled to a considerable distance in the direction indicated by the broken line.  A glass filament was attached longitudinally to the other cotyledon, and this nearly completed (Fig, 44, B) an irregular circular figure in about 12 hours.  During the night it also moved to a considerable distance, in the direction indicated by the broken line.  The cotyledons therefore circumnutate independently of the movement of the hypocotyl.  Although they moved much during the night, they did not approach each other so as to stand more vertically than during the day. [page 58]

Cycas pectinata (Cycadeae).—­The large seeds of this plant in germinating first protrude a single leaf, which breaks through the ground with the petiole bowed into an arch and with the leaflets involuted.  A leaf in this condition, which at the close of our observations was 2 ½ inches in height, had its movements traced in a warm greenhouse by means of a glass filament bearing paper triangles attached across its tip.  The tracing (Fig. 45) shows how large, complex, and rapid were the circum-

Fig. 45.  Cycas pectinata:  circumnutation of young leaf whilst emerging from the ground, feebly illuminated from above, traced on vertical glass, from 5 P.M.  May 28th to 11 A.M. 31st.  Movement magnified 7 times, here reduced to two-thirds of original scale.