Chap. I.] ACTION OF THE PARTS. 11 



The length of time during which the tentacles as' well as 

 the blade remain inflected over an object placed on the disc, 

 depends on various circumstances; namely on the vigour 

 and age of the leaf, and, according to Dr. Nitschke, on the 

 temperature, for during cold weather, when the leaves are 

 inactive, they re-expand at an earlier period than when the 

 weather is warm. But the nature of the object is by far the 

 most important circumstance; I have repeatedly found that 

 the tentacles remain clasped for a much longer average time 

 over objects which yield soluble nitrogenous matter than over 

 those, whether organic or inorganic, which yield no such mat- 

 ter. After a period varying from one to seven days, the ten- 

 tacles and blade re-expand, and are then ready to act again. 

 I have seen the same leaf inflected three successive times over 

 insects placed on the disc; and it would probably have acted a 

 greater number of times. 



The secretion from the glands is extremely viscid, so that 

 it can be drawn out into long threads. It appears colourless, 

 but stains little balls of paper pale pink. An object of any 

 kind placed on a gland always causes it, as I believe, to 

 secrete more freely; but the mere presence of the object 

 renders this difiicult to ascertain. In some cases, however, 

 the effect was strongly marked, as when particles of sugar 

 were added; but the result in this case is probably due 

 merely to exosmose. Particles of carbonate and phosphate 

 of ammonia and of some other salts, for instance sulphate of 

 zinc, likewise increase the secretion. Immersion in a solu- 

 tion of one part of chloride of gold, or of some other salts, to 

 437 of water, excites the glands to largely increased secretion ; 

 on the other hand, tartrate of antimony produces no such 

 effect. Immersion in many acids (of the strength of one part 

 to 437 of water) likewise causes a wonderful amount of secre- 

 tion, so that, when- the leaves are lifted out, long ropes of ex- 

 tremely viscid fluid hang from them. Some acids, on the 

 other hand, do not act in this manner. Increased secretion is 

 not necessarily dependent on the inflection of the tentacle, for 

 particles of sugar and of sulphate of zinc cause no movement. 



It is a much more remarkable fact, that when an object, 

 such as a bit of meat or an insect, is placed on the disc of a 

 leaf, as soon as the surrounding tentacles become considerably 

 inflected, their glands pour forth an increased amount of 



