Cuap. V.] EFFECTS OF ORGANIC FLUIDS. 65 
this case the movement 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 adhesive fluid and the consequent 
drawing together of the tentacles. 
First for the non-nitrogenous fluids. As a preliminary 
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 inflected; 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 bean 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 73); 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 30 hrs. Inflection was never thus caused. 
It is necessary to try pure gum arabic, for a friend tried a solution 
bought ready prepared, and this caused the tentacles to bend; 
but he afterwards ascertained that it contained much animal matter, 
probably glue. 
Sugar.—Drops of a solution of white sugar of three strengths (the 
weakest containing one part of sugar to 73 of water) were left on 
fourteen leaves from 32 hrs. to 48 hrs.; but no effect was produced. 
Starch—A mixture about as thick as cream was dropped on six 
leaves and left on them for 30 hrs., no effect being produced. I am 
surprised at this fact, as I believe that the starch of commerce 
generally contains a trace of gluten, and this nitrogenous substance 
causes inflection, as we shall see in the next chapter. 
Alcohol, Diluted.—One part of alcohol was added to seven of water, 
and the usual drops were placed on the discs of three leaves. No 
inflection ensued in the course of 48 hrs. To ascertain whether these 
leaves had been at all injured, bits of meat were placed on them, and 
after 24 hrs. they were closely inflected. I also put drops of sherry- 
wine on three other leaves; no inflection was caused, though two of 
them seemed somewhat injured. We shall hereafter see that cut-off 
leaves immersed in diluted alcvhol of the above strength do not become 
inflected. 
F 
