The petioles of the cotyledons of 11 young seedlings of Sinapis nigra were slightly divergent at noon, and the blades stood at right angles to the hypocotyls; at night the petioles were in close contact, and the blades considerably raised, with their bases in contact, but only a few stood sufficiently upright to be called asleep.  On the following morning, [page 302] the petioles diverged before it was light.  The hypocotyl is slightly sensitive, so that if rubbed with a needle it bends towards the rubbed side.  In the case of Lepidium sativum, the petioles of the cotyledons of young seedlings diverge during the day and converge so as to touch each other during the night, by which means the bases of the tripartite blades are brought into contact; but the blades are so little raised that they cannot be said to sleep.  The cotyledons of several other cruciferous plants were observed, but they did not rise sufficiently during the night to be said to sleep.

Githago segetum (Caryophylleae).—­On the first day after the cotyledons had burst through the seed-coats, they stood at noon at an angle of 75o above the horizon; at night they moved upwards, each through an angle of 15o so as to stand quite vertical and in contact with one another.  On the second day they stood at noon at 59o above the horizon, and again at night were completely closed, each having risen 31o.  On the fourth day the cotyledons did not quite close at night.  The first and succeeding pairs of young true leaves behaved in exactly the same manner.  We think that the movement in this case may be called nyctitropic, though the angle passed through was small.  The cotyledons are very sensitive to light and will not expand if exposed to an extremely dim one.

Anoda Wrightii (Malvaceae).—­The cotyledons whilst moderately young, and only from .2 to .3 inch in diameter, sink in the evening from their mid-day horizontal position to about 35o beneath the horizon.  But when the same seedlings were older and had produced small true leaves, the almost orbicular cotyledons, now .55 inch in diameter, moved vertically downwards at night.  This fact made us suspect that their sinking might be due merely to their weight; but they were not in the least flaccid, and when lifted up sprang back through elasticity into their former dependent position.  A pot with some old seedlings was turned upside down in the afternoon, before the nocturnal fall had commenced, and at night they assumed in opposition to their own weight (and to any geotropic action) an upwardly directed vertical position.  When pots were thus reversed, after the evening fall had already commenced, the sinking movement appeared to be somewhat disturbed; but all their movements were occasionally variable without any apparent cause.  This latter fact, as well as that of the young cotyledons not sinking nearly so much as the older ones, deserves notice. [page 303] Although the movement of the cotyledons endured for a long time, no pulvinus was exteriorly visible; but their growth continued for a long time.  The cotyledons appear to be only slightly heliotropic, though the hypocotyl is strongly so.