CHAP. V. EFFECTS OF OKGANIC FLUIDS. 81 



from the time when the drops were placed on the leaves, all 

 four had almost re-expanded. They were then given little bits 

 of meat, and these acted more powerfully than the solution. 

 One part of isinglass was next dissolved in 437 of water ; tho 

 fluid thus formed was so thin that it could not be distinguished 

 from pure water. The usual-sized drops were placed on seven 

 leaves, each of which thus received -^ of a grain ('0295 mg.). 

 Three of them were observed for 41 hrs., but were in no way 

 affected ; the fourth and fifth had two or three of their exterior 

 tentacles inflected after 18 hrs.; the sixth had a few more, 

 and the seventh had in addition the edge of the leaf just 

 perceptibly curved inwards. The tentacles of the four latter 

 leaves began to re-expand after an additional interval of only 

 8 hrs. Hence the F |^ of a grain of isinglass is sufficient to affect 

 very slightly the more sensitive or active leaves. On one of the 

 leaves, which had not been acted on by the weak solution, and on 

 another, which had only two of its tentacles inflected, drops of 

 the solution as thick as milk were placed ; and next morning, 

 after an interval of 16 hrs., both were found with all their ten- 

 tacles strongly inflected. 



Altogether I experimented on sixty-four leaves 

 with the above nitrogenous fluids, the five leaves 

 tried only with the extremely weak solution of isin- 

 glass not being included, nor the numerous trials 

 subsequently made, of which no exact account was 

 kept. Of these sixty-four leaves, sixty-three had their 

 tentacles and often their blades well inflected. The 

 one which failed was probably too old and torpid. 

 But to obtain so large a proportion of successful 

 cases, care must be taken to select young and active 

 leaves. Leaves in this condition were chosen with 

 equal care for the sixty-one trials with non-nitro- 

 genous fluids (water not included) ; and we have seen 

 that not one of these was in the least affected. We 

 may therefore safely conclude that in the sixty-four 

 experiments with nitrogenous fluids the inflection of 

 the exterior tentacles was due to the absorption of 



