CHAP. Til. 



SLEEP OF LEAVES. 



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 posi- 

 tion, describing a figure which 

 represented two irregular el- 

 lipses. On the next day it 

 circumnutated in a greater 

 degree, describing four irre- 

 gular ellipses, and by 3 P.M. 

 had risen into a horizontal po- 

 sition. By 7.15 P.M. it was 

 asleep and vertically depen- 

 dent, but continued to circum- 

 nutate as long as observed, 

 until 11 P.M. 



Erythrina corallo'It-n/L on . 

 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 ampli- 

 tude, 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. 



Fig. 152. 



6'40'a.M 



9-f.tn. 



of terminal leaflet, 3J inches in 

 length, traced during 25 h. ; apex 

 of leaf 3 J inches from the vertical 

 glass. Figure reduced to one-half 

 of original scale. Plant illumi- 

 nated from above; temp. 17A- 

 18* C. 



