NOTES ON RECENT RESEARCH. 



nectar can absorb also syrup artificially supplied. The internal pressure 

 of the secreting cells is very high ; and as they only begin to plasmolyse 

 in 10 per cent, solution of KN0 3 , it must equal at least thirty atmospheres. 

 Some interesting anatomical details are given, for which the author claims 

 no novelty any more than he does for the view that the function is 

 protective, attracting ants from the flowers &c. to the herbaceous parts, 

 which they largely preserve from caterpillars &c. — M. If. 



Digestion in Nepenthes. 



Nepenthes, Proteolytic Enzyme of. By Prof. S. EL Vines, M.A., 

 D.Sc, F.R.S. (Ann. Bot. vol. xv., No lx., p. 568). — An enzyme is a soluble 

 ferment, and one that is proteolytic decomposes proteids. The author 

 returns to the subject of the digestion of Nepenthes in order to bring to 

 notice a paper of considerable importance, by the late Georges Clautriau, 

 which is not easily accessible to English readers. Clautriau is believed 

 to have been the first to investigate the physiology of the pitchers in the 

 native habitat of the plant. The acidity of the liquid was the subject 

 of special attention, and he found that it was caused not only by the 

 introduction of any foreign body, but also by mechanical stimulation, 

 such as a vigorous shaking of the pitcher, open or unopened. This is 

 interesting because Nepenthin— the name proposed by Professor Vines for 

 this enzyme — is active only in presence of acid ; indeed the digestion of 

 Nepenthes, the author remarks (contrary to the view held by Clautriau), 

 is very much hastened by the addition of hydrochloric acid, or organic 

 acid like citric acid. Clautriau observed that living insect larva?, 

 especially those of the mosquito, are to be found in the pitchers, and he 

 rightly argued that this could not be accepted as evidence of digestive 

 inactivity, but rather that it is evidence of the special adaptation of the 

 larva; for such a situation, just as parasites may be adapted to the digestive 

 canal of an animal. Clautriau expresses a doubt as to the presence of 

 enzyme in the liquid of unopened pitchers, but the author's experience 

 entirely confirms the statement of Gorup-Basanez that this liquid is 

 very active when acidified. The really important difference of opinion 

 between Clautriau and the author is as to the nature of this proteolytic 

 enzyme. The former regarded it as a pepsin, that is, an enzyme acting on 

 the higher proteids in an acid medium, giving rise to peptones, but 

 incapable of decomposing proteids into non-proteid substances. Prof. 

 Vines, on the other hand, has found that the enzyme is a trypsin, and 

 has endeavoured to prove that digestion proceeds to the further stage of 

 producing substances characteristic of tryptic digestion. Sufficient has been 

 said to show the interest of this paper, but further remark must be made 

 in order to point out Professor Vines's suggestion that all known proteo- 

 lytic enzymes of plants are tryptic. This suggestion, he thinks, may be 

 expanded into the proposition that tryptic digestion is a property of all 

 living organisms, and that it is the more primitive form of the digestive 

 process. — B. I. L. 



ON PliOTHALLI. 



Ophioglossum pendulum and Helminthostachys zeylanica, 

 On the Prothalli Of. By William H. Lang, M.B., D.Sc, Lecturer in 



