CHAP. IV. DICOTYLEDONS 241 



longer period ; although, as we have seen, a young leaf com- 

 pleted a fairly large ellipse in 2 h. A drop of an infusion of 

 raw meat was then placed on the leaf, and within 2 h. the glass 

 filament rose a little ; and this implies that the lobes had begun 

 to close, and perhaps the petiole to rise. It continued to rise 

 with extreme slowness for the next 8 h. 30 m. The position of 

 the pot was then (7.15 P.M., Sept. 24th) slightly changed and 

 an additional drop of the infusion given, and a new tracing 

 was begun (Fig. 107). By 10.50 P.M. the filament had risen 

 only a little more, and it fell during the night. On the follow- 

 ing morning the lobes were closing more quickly, and by 5 P.M. 

 it was evident to the eye that they had closed considerably ; by 

 8.48 P.M. this was still plainer, and by 10.45 P.M. the marginal 

 spikes were interlocked. The leaf fell a little during the night, 

 and next morning (25th) at 7 A.M. the lobes were completely 

 shut. The course' pursued, as may be seen in the figure, was 



Fig. 107. 



Dioncc-i mu.^ci}>ula : closure of ihe lobes and circumnutation of a full-grown 

 leaf, whilst absorbing an infusion of raw meat, traced in darkness, from 

 7.15 P.M. Sept. 24th to 9 A.M. 26th. Apex of leaf 8 inches from the 

 vertical glass. Figure here reduced to two-thirds of original scale. 



strongly zigzag, and this indicates that the closing of the lobes 

 was combined with the circumnutation of the whole leaf; 

 and there cannot be much doubt, considering how motionless 

 the leaf was during 2 h. 30 m. before it received the infusion, 

 that the absorption of the animal matter had excited it to 

 circumnutate. The leaf was occasionally observed for the next 

 four days, but was kept in rather too cool a place ; nevertheless, 

 it continued to circumnutate to a small extent, and the lobes 

 remained closed. 



It is sometimes stated in botanical works that the lobes close 

 or sleep at night ; but this is an error. To test the statement, 

 very long glass filaments were fixed inside the two lobes of 

 three leaves, and the distances between their tips were measured 

 in the middle of the day and at night ; but no difference could 

 be detected. 



The previous observations relate to the movements of the 

 whole leaf, but the lobes move independently of the petiole, and 



