Passiflora gracilis (Passifloracae).—­The young leaves sleep by their blades hanging vertically downwards, and the whole length of the petiole then becomes somewhat curved downwards.  Externally no trace of a pulvinus can be seen.  The petiole of the uppermost leaf on a young shoot stood at 10.45 A.M. at 33o above the horizon; and at 10.30 P.M., when the blade was vertically dependent, at only 15o, so the petiole had fallen 18o.  That of the next older leaf fell only 7o.  From some unknown cause the leaves do not always sleep properly.  The stem of a plant, which had stood for some time before a north-east window, was secured to a stick at the base of a young leaf, the blade of which was inclined at 40o below the horizon.  From its position the leaf had to be viewed obliquely, consequently the vertically ascending and descending movements appeared when traced oblique.  On the first day (Oct. 12th) the leaf descended in a zigzag line until late in the evening; and by 8.15 A.M. on the 13th had risen to nearly the same level as on the previous morning.  A new tracing was now begun (Fig. 161).  The leaf continued to rise until 8.50 A.M., then moved a little to the right, and afterwards descended.  Between 11 A.M. and 5 P.M. it circumnutated, and after the latter hour the great nocturnal fall commenced.  At 7.15 P.M. it depended vertically.  The dotted line ought to have been prolonged much lower down in the figure.  By 6.50 A.M. on the following morning (14th) the [page 384] leaf had risen greatly, and continued to rise till 7.50 A.M., after which hour it redescended.  It should be observed that the lines traced on this second morning would have coincided with and confused those previously traced, had not the pot been slided a very little to the left.  In the evening (14th) a mark was placed behind the filament attached to the apex of the leaf, and its movement was carefully traced from 5 P.M. to 10.15 P.M.

Fig. 161.  Passiflora gracilis:  circumnutation and nyctitropic movement of leaf, traced on vertical glass, from 8.20 A.M.  Oct. 13th to 10 A.M. 14th.  Figure reduced to two-thirds of original scale.

Between 5 and 7.15 P.M. the leaf descended in a straight line, and at the latter hour it appeared vertically dependent.  But between 7.15 and 10.15 P.M. the line consisted of a succession of steps, the cause of which we could not understand; it was, however, manifest that the movement was no longer a simple descending one.

Siegesbeckia orientalis (Compositae).—­Some seedlings were raised in the middle of winter and kept in the hot-house; they flowered, but did not grow well, and their leaves never showed any signs of sleep.  The leaves on other seedlings raised in May were horizontal at noon (June 22nd), and depended at a consi-[page 385] derable angle beneath the horizon at 10 P.M.  In the case of four youngish leaves which were from 2 to 2 ½ inches in length, these angles were found to be 50o, 56o, 60o, and 65o.  At the end of August when the plants had grown to a height of 10 to 11 inches, the younger leaves were so much curved downwards at night that they might truly be said to be asleep.  This is one