Erythrina caffra.—­A filament was fixed transversely across [page 367]

a terminal leaflet, as we wished to observe its movements when asleep.  The plant was placed in the morning of June 10th under a skylight, where the light was not bright; and we do not know whether it was owing to this cause or to the plant having been disturbed, but the leaflet hung vertically down all day; nevertheless it circumnutated in this position, describing a figure which represented two irregular ellipses.  On the next day it circumnutated in a greater degree, describing four irregular ellipses, and by 3 P.M. had risen into a horizontal position.  By 7.15 P.M. it was asleep and vertically dependent, but continued to circumnutate as long as observed, until 11 P.M.

Fig. 152.  Erythrina crista-galli:  circumnutation and nyctitropic movement of terminal leaflet, 3 3/4 inches in length, traced during 25 h.; apex of leaf 3 ½ inches from the vertical glass.  Figure reduced to one-half of original scale.  Plant illuminated from above; temp. 17 1/2o — 18 1/2o C.

Erythrina corallodendron.—­The movements of a terminal leaflet were traced.  During the second day it oscillated four times up and four times down between 8 A.M. and 4 P.M., after which hour the great nocturnal fall commenced.  On the third day the movement was equally great in amplitude, but was remarkably simple, for the leaflet rose in an almost perfectly straight line from 6.50 A.M. to 3 P.M., and then sank down in an equally straight line until vertically dependent and asleep. [page 368]

Apios tuberosa (Tribe 8).—­The leaflets sink vertically down at night.

Phaseolus vulgaris (Tribe 8).—­The leaflets likewise sink vertically down at night.  In the greenhouse the petiole of a young leaf rose 16o, and that of an older leaf 10o at night.  With plants growing out of doors the leaflets apparently do not sleep until somewhat late in the season, for on the nights of July 11th and 12th none of them were asleep; whereas on the night of August 15th the same plants had most of their leaflets vertically dependent and asleep.  With Ph. caracalla and Hernandesii, the primary unifoliate leaves and the leaflets of the secondary trifoliate leaves sink vertically down at night.  This holds good with the secondary trifoliate leaves of Ph.  Roxburghii, but it is remarkable that the primary unifoliate leaves which are much elongated, rise at night from about 20o to about 60o above the horizon.  With older seedlings, however, having the secondary leaves just developed, the primary leaves stand in the middle of the day horizontally, or are deflected a little beneath the horizon.  In one such case the primary leaves rose from 26o beneath the horizon at noon, to 20o above it at 10 P.M.; whilst at this same hour the leaflets of the secondary leaves were vertically dependent.  Here, then, we have the extraordinary case of the primary and secondary leaves on the same plant moving at the same time in opposite directions.