390 MODIFIED CIRCUMNUTATION. CHAP. VII 



the day or between 10 and 20 above the horizon, and at night 

 vertically upwards. They therefore rise between 70 and 90 at 

 night. The plant was placed at noon in the dark in the hot- 

 house, and on the following day the movements of the leaves 

 were traced. Between 8.40 and 10 30 A.M. they rose, and then 

 fell yreatly till 1.37 P.M. But by 3 P.M. they had again risen a 

 little, and continued to rise during the rest of the afternoon ami 

 night ; on the following morning they stood at the same level as 

 on the previous day. Darkness, therefore, during a day and a 

 half does not interfere with the periodicity of their movements. 

 On a warm but stormy evening, the plant whilst being brought 

 into the house, had its leaves violently shaken, and at night not 

 one went to sleep. On" the next morning the plant was taken 

 back to the hot-house, and again at night the leaves did not 

 sleep ; but on the ensuing night they rose in the usual manner 

 l>ctween 70 and 80. This fact is analogous with what we 

 have observed with climbing plants, namely, that much agitation 

 checks for a time their power of circumnutation ; but the effect 

 in this instance was much more strongly marked and prolonged. 

 Colocasia axtiquorum (Caladium esctihnlum, Hort.) (Aroidese). 

 The leaves of this plant sleep by their blades sinking in the 

 evening, so as to stand highly inclined, or even quite vertically 

 with their tips pointing to the ground. They are not provided 

 with a pulvinus. The blade of one stood at noon 1 beneath the 

 horizon; at 4.20 P.M., O) ; at 6 P.M., 43 ; at 7.20 P.M., 69 ; and at 

 8.30 P.M., 68 ; so it had now begun to rise ; at 10.15 P.M. it stood 

 at 65, and on the following early morning at 11 beneath the 

 horizon. Tbe circumnutation of another young leaf (with its 

 petiole only 3} inches, and the blade 4 inches in length), was 

 traced on a vertical glass during 48 h. ; it was dimly illuminated 

 through a skylight, and this seemed to disturb the proper perio- 

 dicity of its movements. Nevertheless, the leaf fell greatly 

 during both afternoons, till either 7.10 P M. or 9 P.M., when it 

 rose a little and moved laterally. By an early hour on both 

 mornings, it had assumed its diurnal position. The well-marked 

 lateral movement for a short time in the early part of the night, 

 was the only interesting fact which it presented, as this caused 

 the ascending and descending lines not to coincide, in accord- 

 ance with the general rule with circumnutating organs. The 

 movements of the leaves of this plant are thus of the most 

 simple kind; and the tracing is not worth giving. We havo 

 Keen that in another genus of the Aroideae, namely, Pistia, the 



