the apex now crossed two divisions in 6 m. 18 s.; that is, at very nearly the same rate as before.  After another interval of an hour in darkness, it crossed two divisions in 4 m. 15 s., therefore at a quicker rate.  In the afternoon, after a longer interval in the dark, the apex was motionless, but after a time it recommenced moving, though slowly; perhaps the room was too cold.  Judging from previous cases, there can hardly be a doubt that this seedling was circumnutating.

Fig. 37.  Solanum lycopersicum:  circumnutation of hypocotyl, with filament fixed across its summit, traced on horizontal glass, from 10 A.M. to 5 P.M.  Oct. 24th.  Illuminated obliquely from above.  Movement of bead magnified about 35 times, here reduced to one-third of original scale.

Solanum lycopersicum (Solaneae).—­The movements of the hypocotyls of two seedling tomatoes were observed during seven hours, and there could be no doubt that both circumnutated.  They were illuminated from above, but by an accident a little light entered on one side, and in the accompanying figure (Fig. 37) it may be seen that the hypocotyl moved to this side (the upper one in the figure), making small loops and zigzagging in its course.  The movements of the cotyledons were also traced both on vertical and horizontal glasses; their angles with the horizon were likewise measured at various hours.  They fell from 8.30 A.M. (October 17th) to about noon; then moved laterally in a zigzag line, and at about 4 P.M. began to rise; they continued to do so until 10.30 P.M., by which hour they stood vertically and were asleep.  At what hour of the night or early morning they began to fall was not ascertained.  Owing to the lateral movement shortly after mid-day, the descending and ascending lines did not coincide, and irregular ellipses were described during each 24 h.  The regular periodicity of these movements is destroyed, as we shall hereafter see, if the seedlings are kept in the dark. [page 51]

Solanum palinacanthum.—­Several arched hypocotyls rising nearly .2 of an inch above the ground, but with the cotyledons still buried beneath the surface, were observed, and the tracings showed that they circumnutated.  Moreover, in several cases little open circular spaces or cracks in the argillaceous sand which surrounded the arched hypocotyls were visible, and these appeared to have been made by the hypocotyls having bent first to one and then to another side whilst growing upwards.  In two instances the vertical arches were observed to move to a considerable distance backwards from the point where the cotyledons lay buried; this movement, which has been noticed in some other cases, and which seems to aid in extracting the cotyledons from the buried seed-coats, is due to the commencement of the straightening of the hypocotyl.  In order to prevent this latter movement, the two legs of an arch, the

Fig. 38.  Solanum palinacanthum:  circumnutation of an arched hypocotyl, just emerging from the ground, with the two legs tied together, traced in darkness on a horizontal glass, from 9.20 A.M.  Dec. 17th to 8.30 A.M. 19th.  Movement of bead magnified 13 times; but the filament, which was affixed obliquely to the crown of the arch, was of unusual length.