Chap, v.] EFFECTS OF ORGANIC FLUIDS. 65 



In 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 lat- 

 ter 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 been excited into movement by every 

 shower of rain. 



Gvtn arable. 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 instru- 

 ment. 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 arable, 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) M'ere left 

 on fourteen leaves from 32 hrs. to 48 hrs.; but no effect was pro- 

 duced. 



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 gen- 

 erally 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 wtre 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 alcohol of the above 

 strength do not become inflected. 



