DIGESTIYE FEHMENT OF NEPENTHES. 429 



caustic potash and dilute copper sulphate (Biuretreaction). The 

 digestive process was very much accelerated by the addition of a 

 few drops of dilute hydrochloric acid (-2 per cent.). 



At the time of the publication of Von (xorup-Besanez's paper, 

 I was engaged at the Eoyal Gardens, Kew, in a series of experi- 

 ments upon Nepenthes, which, I am glad to say, are quite confir- 

 matory of his results. In dealing with the subject, I followed the 

 method of which Eiess and Will availed themselves in their inves- 

 tigation of Drosera ; that is to say, I treated the pitchers of Ne- 

 penthes (hybrida and gracilis) just as though they had been the 

 gastric mucous membrane of an animal, first with absolute alcohol, 

 and then with glycerin. I then proceeded to test the ^digestive 

 properties of the Nepenthes extract just in the same way as they 

 tested the Drosera extract. I took three test-tubes : in the first I 

 placed a little of the extract and a few drops of dilute hydrochloric 

 acid (*2 per cent.), in the second a little of the extract only, and 

 in the third some of the diluted acid ; to each I then added a 

 small piece of swollen-up fibrin and exposed them all to a tempe- 

 perature of 40° C. At the end of eight hours I found that the 

 nbrin in the first tube showed signs of the digestive action of the 

 fluid, and the filtrate gave a distinct peptone reaction. The fibrin 

 m the other two tubes was unaffected ; and their filtrates gave no 

 reaction with caustic potash and copper sulphate. 



By these experiments I have demonstrated for Nepenthes the 

 facts which Riess and Will have brought out concerning Drosera, 

 viz. that the glands of the pitchers contain a digestive ferment 

 which is soluble in glycerin, and which can exert its digestive 

 action only in the presence of acid. 



The investigations which I have here detailed form together a 

 body ef evidence which is amply sufficient to prove the fact that 

 the solution of proteids by plants, described by Dr. Hooker in his 

 Address and by Mr. Darwin in his book, was effected by a true 

 digestive process which resembles in every particular the process 

 of solution of proteids which takes place in the digestive cavity 

 of an animal. 



II. 



On comparing the results obtained by Von Gorup-Besanez, 

 w hen experimenting upon the secretion of Nepenthes, with those 

 w "ich I obtained when experimenting with the glycerin extract 



