140 DROSERA ROTUNDIFOLIA. Cnap, 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 
these 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 simultancous 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, Ido 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 
Fic. 9. seen only two instances; and 
(Drosera rotundifolia.) in both of these the inflec- 
zeaf (enlarged) with all the tentacles tion was very feeble. Again 
closely inflected, from immersion in a : : 
solution of phosphate of ammonia (one with leaves the weak solu 
part to 87,500 of water). tions, the inflection of the ten. 
tacles and ‘blade often goes on 
steadily, though slowly, increasing during many hours; and 
