DARWIN'S INSECTIVOROUS PLANTS. 207 



tiveness belongs only to the glands and tips of the tentacles, 

 but is propagated thence down their stalks and across the 

 blade of the leaf through the cellular tissues ; that they accu- 

 rately and delicately discriminate animal or other nitrogenous 

 matter from anything else ; that the glands absorb such mat- 

 ter ; that when excited by contact, or by the absorption of 

 nitrogenous matter by the viscid enveloping liquid, an acid 

 secretion is poured out and a ferment analogous to pepsin, 

 the two together dissolving animal matter ; so that the office 

 and action of these glands are truly analogous to those of the 

 glands of the stomach of animals. Finally, that animal or 

 nitrogenous matter, thus absorbed and digested in the glands, 

 is taken in, and conveyed from cell to cell through the tenta- 

 cles into the body of the leaf, was made evident by ocular 

 inspection of the singular changes in the protoplasm they con- 

 tain. So particularly have the investigations been made and 

 so conscientiously recorded, that the account of those relating 

 to one species of Sundew, Drosera rotund [folia, fills 277 

 pages of the English edition, or more than half of the book. 

 After all it ends with the remark : " and we see how little 

 has been made out in comparison with what remains unex- 

 plained and unknown." The briefer examination of six other 

 Sundews follows, some of them equally and others less effi- 

 ciently fly-catchers and feeders. 



Dionaea is next treated, but with less detail. Indeed, ex- 

 cept as to the particular nature of the secreted digesting fluid, 

 there is little in this chapter that had not been made out or 

 already become familiar here. That the secretion has diges- 

 tive powers, and that it is reabsorbed along with whatever 

 has been digested, is now proved beyond reasonable doubt. 

 That the motor impulse is conveyed through the cellular par- 

 enchyma, and not through the vascular bundles, or spiral ves- 

 sels, and that the latter do not originate the secretion, as Rees 

 and Wills in a recent paper seem to suppose they must, ap- 

 pears to be shown by the facts, and was antecedently probable. 

 " The wonderful discovery made by Dr. Burdon Sanderson is 

 now universally known : namely, that there exists a normal 

 electrical current in the blade and footstalk, and that when 



