266 DROSERA ROTUNDIFOLIA. CHAP. XL 



one part of the leaf to another must be different 

 from that which actually induces aggregation. The 

 process does not depend on the glands secreting 

 more copiously than they did before ; and is inde- 

 pendent of the inflection of the tentacles. It con- 

 tinues as long as the tentacles remain inflected, and as 

 soon as these are fully re-expanded, the little masses 

 of protoplasm are all redissolved ; the cells becoming 

 filled with homogeneous purple fluid, as they were 

 before the leaf was excited. 



As the process of aggregation can be excited by a 

 few touches, or by the pressure of insoluble particles, 

 it is evidently independent of the absorption of any 

 matter, and must be of a molecular nature. Even when 

 caused by the absorption of the carbonate or other 

 salt of ammonia, or an infusion of meat, the process 

 seems to be of exactly the same nature. The proto- 

 plasmic fluid must, therefore, be in a singularly un- 

 stable condition, to be acted on by such slight and 

 varied causes. Physiologists believe that when a 

 nerve is touched, and it transmits an influence to other 

 parts of the nervous system, a molecular change is 

 induced in it, though not visible to us. Therefore it 

 is a very interesting spectacle to watch the effects on 

 the cells of a gland, of the pressure of a bit of hair, 

 weighing only y-g-'-jn, f a grain and largely supported 

 by the dense secretion, for this excessively slight 

 pressure soon causes a visible change in the proto- 

 plasm, which change is transmitted down the whole 

 length of the tentacle, giving it at last a mottled 

 appearance, distinguishable even by the naked eye. 



In the fourth chapter it was shown that leaves 

 placed for a short time in water at a temperature of 

 110 Fahr. (43 0> 3 Cent.) become somewhat inflected ; 

 they are thus also rendered more sensitive to the action 



