Chap MI 



SLEEP OF LEAVES. 



393 



during 24 h. (Fig. 167). The leaf fell from the early morning 

 till 1.50 P.M., and then rose till 6 p.m., when it was asleep. A 



Fig. 166. 



A. 



B. 



C. 



Marsilea quadrifoliala ; A, leaf during the day, seen from rertically above 

 B, leaf beginaiag to go to sleep, seen laterally ; C, the same asleep. 

 Figures reduced to one-half of natural scale. 



vertically dependent glass filament was now fixed to one of the 

 terminal and inner leaflets ; and part of the tracing in Fig. 167, 

 after 6 p.m., shows that it continued to sink, making one zigzag, 

 until 10.40 p.m. At 6.45 a.m. on the following morning, the leaf 

 was awaking, and the filament pointed above the vertical glass. 



Fig. 167. 



M'jlvxa. 



ilarsilea quadrifoUata : circumnutation and nyctitropic movement of leaflet 

 traced on vertical glass, during nearly 24 h. Figure reduced to two- 

 thirds of original scale. Plant kept at rather too low a temperature. 



but by 8.25 a m. it occupied the position shown in the figure. 

 The diagram differs greatly in appearance from most of those 

 previously given; and this is due to the leaflet twisting and 

 moving laterally as it approaches and comes into contact with 



