(6.) Camellia Japonica (Camelliaceae, Fam. 32).—­A youngish leaf, which together with its petiole was 2 3/4 inches in length and which arose from a side branch on a tall bush, had a filament attached to its apex.  This leaf sloped downwards at an angle of 40o beneath the horizon.  As it was thick and rigid, and its [page 232] petiole very short, much movement could not be expected.  Nevertheless, the apex changed its course completely seven times in the course of 11 ½ h., but moved to only a very small distance.  On the next day the movement of the apex was traced during 26 h. 20 m. (as shown in Fig. 97), and was nearly of the same nature, but rather less complex.  The movement seems to be periodical, for on both days the leaf circumnutated in the forenoon, fell in the afternoon (on the first day until between 3 and 4 P.M., and on the second day until 6 P.M.), and then rose, falling again during the night or early morning.

Fig. 97.  Camellia Japonica:  circumnutation of leaf, traced from 6.40 A.M.  June 14th to 6.50 A.M. 15th.  Apex of leaf 12 inches from the vertical glass, so figure considerably magnified.  Temp. 16o — 16 1/2o C.

In the chapter on the Sleep of Plants we shall see that the leaves in several Malvaceous genera sink

Fig. 98.  Pelargonium zonale:  circumnutation and downward movement of young leaf, traced from 9.30 A.M.  June 14th to 6.30 P.M. 16th.  Apex of leaf 9 1.4 inches from the vertical glass, so figure moderately magnified.  Temp. 15o — 16 1/2o C.

at night; and as they often do not then occupy a vertical position, especially if they have not been well illuminated during [page 233] the day, it is doubtful whether some of these cases ought not to have been included in the present chapter.

(7.) Pelargonium zonale (Geraniaceae, Fam. 47).—­A young leaf, 1 1/4 inch in breadth, with its petiole 1 inch long, borne on a young plant, was observed in the usual manner during 61 h.; and its course is shown in the preceding figure (Fig. 98).  During the first day and night the leaf moved downwards, but circumnutated between 10 A.M. and 4.30 P.M.  On the second day it sank and rose again, but between 10 A.M. and 6 P.M. it circumnutated on an extremely small scale.  On the third day the circumnutation was more plainly marked.

(8.) Cissus discolor (Ampelideae, Fam. 67).—­A leaf, not nearly full-grown, the third from the apex of a shoot on a cut-down plant, was observed during 31 h. 30 m. (see Fig. 99).  The day was cold (15o — 16o C.), and if the plant had been observed in the hot-house, the circumnutation, though plain enough as it was, would probably have been far more conspicuous.

Fig. 99.  Cissus discolor:  circumnutation of leaf, traced from 10.35 A.M.  May 28th to 6 P.M. 29th.  Apex of leaf 8 3/4 inches from the vertical glass.