Francis E. Lloyd — 160 — Carnivorous Plants 



proteoses and peptones, with an optimum activity at pB. 1.5, an acidity 

 high for plant enzymes and suggesting a resemblance to animal pepsin. 

 In order to determine to what extent the Drosera pepsin is identical in 

 action with animal pepsin, Okahara observed the influence of poisons 

 (quinine hydrochloride and atoxyl) on them. He failed to find a strict 

 parallel, since the enzyme activity under certain conditions was re- 

 pressed in the one and accelerated in the other. 



Okahara's second paper (1930J) is of a more general nature, deal- 

 ing with the effect of toxic substances on pepsin with a view to 

 illuminating his earher observations cited just above. Though the sub- 

 ject may be regarded as controversial, it remains true that there is a 

 substance capable of digestion of proteins in Drosera leaves. 



In a third paper (1931) Okahara gave the results of inquiry into 

 the optimum acidities of various acids for the enzyme activity. He 

 had observed the occurrence of formic acid in Drosera, and was 

 prompted to investigate the comparative effect of various acids on the 

 action of a proteolytic enzyme on edestin and found that the optimum 

 acidities for various acids differ, and that the decrease from the op- 

 timum acidity parallels the decrease of the electrical dissociation con- 

 stant. 



While Okahara's second and third papers do not immediately 

 concern Drosera, they have been mentioned in this connection since 

 their bearing will doubtless be made clear by further studies. His 

 fourth paper, however, bears directly on the controversial question, 

 do bacteria play a role in the digestion of carnivorous plants and in 

 particular of Drosera? Nepenthes was examined also in this connection. 

 The paper was published in 1933. The author isolated from the plants 

 studied a series of bacteria and moulds. Experiments with these 

 in media held at two acidities, />H 5-6 and /?H 3.3, afforded the following 

 results. Three of the moulds acted on Witte's peptone and glycocoll 

 at ^H 3.3. The other organisms attacked various nitrogenous com- 

 pounds supplied (Witte's peptone, glycylglycine, glycocoll and alanine) 

 falling into two groups which cooperate to reduce these substances to 

 ammonia. Okahara concludes, that, while the plant enzymes may 

 themselves take a leading part in the breaking down of proteins, 

 such organisms as were isolated from the plants mentioned ''may 

 also cooperate in the completion of the process." Okahara to this 

 extent supports the views of Labbe (1904) and of Stutzer (1926), 

 the former for Drosera and the latter for Utricularia. 



Following Okahara, Linderstr0m-Lang and Holter (1934) again 

 raised the question whether digestion in Drosera rotundifolia is es- 

 sentially different from that in other plants and similar to that in 

 animals, or do they depend on resorption of the products of bacterial 

 action? 



Accordingly, the secretions from the glands and from the leaf 

 tissues (from the blade, that is) were examined separately, in order 

 to answer specific questions, to wit: (i) whether proteinase is secreted 

 by the glands; (2) what position among the proteolytic enzymes 

 it takes; (3) in what quantities it occurs and how these quantities 

 behave in relation to the endoproteinase to be expected in the leaf 

 tissues. 



