114 DROSERA ROTUNDIFOLIA. [Cuar. VIL 
taking of this movement. Hence, excepting in a few cases hereafter 
to be specified, we can judge whether a solution produces any effect 
only by observing the exterior tentacles within the first 3 or 4 hrs, 
after immersion. 
Now for a summary of the state of the 173 leaves after an immersion 
ef 3 or 4 hrs. in pure water. One leaf had almost all its tentacles 
inflected ; three leaves had most of them sub-inflected ; and thirteen 
had on an average 36:5 tentacles inflected. Thus seventeen leaves out 
of the 173 were acted on in a marked manner. Eighteen leaves had 
from seven to nineteen tentacles inflected, the average being 9°3 ten- 
tacles for each leaf. Forty-four leaves had from one to six tentacles 
inflected, generally the long-headed 
ones. So that altogether of the 
173 leaves carefully observed, 
seventy-nine were atlected by the 
water in some degree, though 
commonly toa very slight degree; 
and ninety-four were not affected 
in the least degree. This amount 
of inflection is utterly insignifi- 
cant, as we shall hereafter 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 tem- 
perature are far more sensitive to 
the action of water than those 
grown out of doors, or recently 
brought into a warm greenhouse. 
Fic. 9. Thus in the above seventeen cases, 
(Drosera rotundifolia.) in er <a reese ee oe 
: a considerable number of tentacles 
ei THaecled. dtae inifaceaion “Kr inflected, the plants had been kept 
solution of phosphate of ammonia (one during the winter in a very warm 
BAPE to ST ,D0 oF water)» greenhouse; and they bore in the 
early spring remarkably fineleaves, 
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 ten- 
tacles on the same leaf, were more sensitive than others; but why this 
should be so, I do not know. 
Besides the differences just indicated between the leaves immersed 
in water and in weak solutions of ammonia, the tentacles of the latter 
are in most cases much more closely inflected. The appearance of a 
