Dioneta Muscipula, Ellis, 1 5 



of too delicate a nature to effect movement of the halve as 

 they now exist. Ready proof of the general irritability <>t 

 the leaf can be adduced by scraping or tapping the outer or 

 inner surfaces; but the best demonstration can be given by 

 use of ordinary steel forceps. 



It can be predicted, that if one give a sharp but rather 

 gentle forceps-snip to any part of a leaf-half, there will be no 

 closure of the leaf; but, according apparently to the strength 

 of the snip, a more or less pronounced propagation along it 

 of the rhythmic undulations already referred to. If a second 

 snip be given within fifty to seventy seconds rapid closure, 

 within at most ten seconds after stimulus, will ensue. Every 

 part of each leaf-half may be tested in this manner with 

 uniform result. 



Summation stimuli may similarly be communicated. A 

 medium sized leaf was chosen and operated on as follows: 



First snip stimulus no effect. 



Second snip stimulus after ninety seconds " 



Third " " " seventy " " 



Fourth " " " sixty " very slight closure. 



Fifth " " " " " slight closure. 



Sixth " " " fifty " leaf half closed. 



Seventh" " " forty five " leaf closed. 



A vigorous leaf behaved thus : 



First snip stimulus no effect. 



Second snip stimulus, after three minutes " 



Third " " "two " " 



Fourth '• " " " " very slight closure. 



Fifth " " " ninety seconds.... " 



Sixth " " " " " slight closure. 



Seventh " " " sixty " 



Eighth " " " " " leaf now half closed. 



Ninth " " " forty-five " leaf closed. 



These and other experiments performed at Edinburgh show 

 what was more strikingly verified in Philadelphia, that the 

 effect of forceps-snip stimuli was more powerfully retained 

 than when irritation — even the most violent — was communi- 

 cated through the hairs. The extremely slow closing move- 

 ments of the leaf-halves was equally marked. Thus after the 

 eighth stimulus in the last experiment, the visible range of 

 the movement occupied twenty-one seconds. 



