Dioncea Miiscipula, lillis. 2 1 



would have closed, but instead of doing so they diverged ;i 

 little. I then took another fine leaf with the lobes standing 

 at an angle of nearly 8o° to each other ; and on immersing it 

 as before, the angle suddenly increased to 90 . A third leaf 

 was torpid from having recently re-expanded after having 

 caught a fly, so that repeated touches of the filaments caused 

 not the least movements ; nevertheless, when similarly 

 immersed, the leaves separated a little. As these leaves 

 were inserted perpendicularly into the boiling water, both 

 surfaces and the filaments must have been equally affected, 

 and I can understand the divergence of the lobes only by 

 supposing that the cells on the lower side, owing to their 

 state of tension, acted mechanically, and this suddenly drew 

 the lobes a little apart, as soon as the cells on the upper 

 surface were killed and lost their contractile power." One 

 may best lead up to the above by considering the effect of 

 gradually increasing temperature. All of the experiments 

 described below were made on leaves attached to living 

 plants. 



Water was heated to 50 C, and a dropping pipette was 

 similarly heated by immersion in the water. Three drops 

 were then let fall on an open leaf, but produced no effect after 

 ten seconds. A second and then a third application was made, 

 when the leaf closed. Four other leaves behaved thus, but 

 a sixth required four applications. Naturally, the water on 

 exposure to the atmosphere and colder leaf surface, would 

 lose some of its heating power, so that we may regard the 

 actual temperature for stimulation as having ranged from 

 45 to 48 C. 



Water at 58 C. produced no movement after ten seconds, 

 but on a second application four leaves closed after an 

 interval of five to eight seconds. At 65 C. six leaves were 

 tried, and two of these closed, one after seven seconds, the 

 other after nine, while the remaining four closed at once on a 

 second application. At 75° C. five leaves were once treated, 

 and all closed after intervals of six to nine seconds. 



Boiling water was then used on the remaining ones, but as 

 regards its action on the leaf substance, it should first be 



