48 Chapters in Modern Botany chap. 



The secretion of the glands, Hke the gastric juice of animals, 

 contains a digestive ferment and several acids, as Frank- 

 land, Rees and Will, Lawson Tait, and others have shown. 

 But this is corroborated by what happens to little pieces 

 of organic material placed upon the leaves. Darwin fed 

 numerous plants with roast meat and minute cubes of 

 boiled white of Q.gg^ and by way of check placed similar 

 cubes in wet moss. Those in the moss putrefied, while 

 those on the sundew were dissolved. Pollen -grains had 

 their protoplasmic contents dissolved, and seeds were 

 usually killed. It is interesting to notice further that the 

 secretion obtained from tentacles stimulated by fragments 

 of glass was not able to digest, showing that the ferment 

 is not secreted until the glands have absorbed a trace of 

 animal matter. Moreover, while the leaves were able to 

 digest beef, ^%g^ cheese, and the like, they could not 

 digest horn, chitin, cellulose, and other such substances — 

 thus completing the analogy with the gastric digestion of 

 animals. 



Movements. — As to the movements of the tentacles, 

 experiments showed that pricking the leaf or the leaf-stalk 

 did not induce any response, that the stalks of the glands 

 were not stimulated by food, that in fact the glands alone 

 were sensitive. When a tentacle receives an impulse either 

 from its own gland or from the central tentacles, it bends 

 towards the middle of the leaf, the short tentacles on which 

 do not bend at all ; in all other cases all the tentacles, 

 even those of the centre, bend towards the point whence 

 the stimulus comes. Thus all the tentacles of a leaf may 

 be made to converge into two symmetrical groups by 

 placing a fragment of phosphate of ammonia in the middle 

 of each half of the blade. 



Vivisection showed that the motor impulse travels 

 through the cellular tissue, and not through the fibro- 



