140 



DROSEKA EOTUNDIFOLIA. 



Chap. VII. 



amount of inflection is utterly insignificant, as we shall here- 

 after see, compared with that caused by very weak solutions 

 of several salts of ammonia. 



Plants which have lived for some time in a rather high 

 temperature are far more sensitive to the action of water than 

 those grown out of doors, or recently brought into a warm 

 greenhouse. Thus in the above seventeen cases, in which the 

 immersed leaves had a considerable number of tentacles in- 

 flected, the plants had been kept during the winter in a very 

 warm greenhouse ; and they bore in the early spring remarkably 

 fine leaves, of a light red colour. Had I then known that the 

 sensitiveness of plants was thus increased, perhaps I should 

 not have used the leaves for my experiments with the very 

 weak solutions of phosphate of ammonia ; but my experiments 

 are not thus vitiated, as I invariably used leaves from the same 

 plants for simultaneous immersion in water. It often happened 

 that some leaves on the same plant, and some tentacles on the 

 same leaf, were more sensitive than others ; but why this should 

 be so, I do not know. 

 Resides the differences just indicated between the leaves im- 

 mersed in water and in weak 

 solutions of ammonia, the ten- 

 tacles of the latter are in most 

 cases much more closely in- 

 flected. The appearance of a 

 leaf after immersion in a few 

 drops of a solution of one grain 

 of phosphate of ammonia to 

 200 oz. of water (i.e. one part 

 to 87,500) is here reproduced : 

 such energetic inflection is 

 never caused by water alone. 

 With leaves in the weak solu- 

 tions, the blade or lamina often 

 becomes inflected ; and this is 

 so rare a circumstance with 

 leaves in water that I have 

 seen only two instances; and 

 in both of these the inflec- 

 tion was very feeble. Again, 

 with leaves in the weak solu- 

 tions, the inflection of the ten- 

 tacles and blade often goes on 

 steadily, though slowly, increasing during many hours; and 



(^Drosera rotundifoUa.) 



Leaf (enlarged) with all the tentacles 



closely inflected, from immersion in a 



solution of phosphate of ammonia (one 



part to 87,500 of water). 



