Cuap. ¢. EFFECTS OF ORGANIC FLUIDS. 77 
is kept in a room, and some of the central and sub- 
marginal tentacles are thus drawn together, giving to 
them the false appearance of having become inflected. 
This sometimes occurs with water, as it is rendered 
adhesive by mingling with the viscid secretion. 
Hence the only safe criterion, and to this alone I 
have trusted, is the bending inwards of the exterior 
tentacles, which have not been touched by the fluid, or 
at most only at their bases. In this case the move- 
ment is wholly due to the central glands having been 
stimulated by the fluid, and transmitting a motor 
impulse to the exterior tentacles. The blade of the 
leaf likewise often curves inwards, in the same manner 
as when an insect or bit of meat is placed on the 
disc. This latter movement is never caused, as far 
as I have seen, by the mere drying up of an ad- 
hesive fluid and the consequent drawing together of 
the tentacles. 
First for the non-nitrogenous fluids. As a pre- 
liminary trial, drops of distilled water were placed on 
between thirty and forty leaves, and no effect whatever 
was produced; nevertheless, in some other and rare 
cases, a few tentacles became for a short time in- 
flected; but this may have been caused by the 
glands having been accidentally touched in getting 
the leaves into a proper position. That water should 
produce no effect might have been anticipated, as 
-otherwise the leaves would have been excited into 
movement by every shower of rain. 
Gum arabic.—Solutions of four degrees of strength were made ; 
one of six grains to the ounce of water (one part to 78); a second 
rather stronger, yet very thin; a third moderately thick, and a 
fourth so thick that it would only just drop from a pointed 
instrument. These were tried on fourteen leaves; the drops 
being left on the discs from 24 hrs. to 44 hrs.; generally about 
