68 DROSERA ROTUNDIFOLIA. [Cuar. V. 
isinglass would act. One part was dissolved in 218 parts of distilled 
water, and drops were placed on four leaves. After 5 hrs. two of these 
were considerably and two moderately inflected; after 22 hrs. the 
former were greatly and the latter much more inflected. In the course 
of 48 hrs. from the time when the drops were placed on the leaves, atl 
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; the fluid thus formes 
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 51, 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 tertacles of the four 
latter leaves began to re-expand after an additional interval of only 
8 hrs. Hence the 515 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 tentacles 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 isinglass 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-nitrogenous 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 nitro- 
genous matter by the glands of the tentacles on the disc. 
Some of the leaves which were not affected by the non- 
nitrogenous fluids were, as above stated, immediately after- 
wards tested with bits of meat, and were thus proved to be 
in an active condition. But in addition to these trials, 
twenty-three of the leaves, with drops of gum, syrup, or 
starch, still lying on their discs, which had produced no effect 
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