Francis E. Lloyd — 264 — Carnivorous Plants 



apparent to Darwin, Cohn, Mrs. Treat and others that animals 

 caught in the traps disintegrate, but the natural inference, that diges- 

 tion was effected by the plant, was not sustained by evidence, for a 

 few experiments done by Darwin in which he introduced minute 

 fragments of meat, albumen and cartilage into the traps, gave only 

 negative results, and he concluded that Utricularia cannot digest its 

 prey. Bijsgen fared no better — he worked with an acid medium 

 with which Luetzelburg also got meagre results. 



GoEBEL regarded Utricularia as capable of digestion because of its 

 close relationship to Pinguicula, but confessed that no evidence had 

 been forthcoming. Luetzelburg (1910), one of his students, obtained 

 evidence with sap expressed from large numbers of traps removed 

 individually, ground up with clean sand and glycerin, and perco- 

 lated. The extract thus obtained showed a sHght activity, visible 

 after 3 days, in an acid medium. It was, however, much more active 

 in an alkaline medium, and the conclusion that a trypsin was present 

 was arrived at. 



During prolonged observation of the experiments it was noticed 

 that there was never any odor of putrefaction, and culture tests 

 showed that bacteria did not grow in the presence of the expressed 

 juices, yet these could liquify gelatin in four days. The presence of an 

 agent inhibiting the growth of bacteria was inferred and this inference 

 was strengthened by experimental evidence that bacteria are only 

 feebly produced in trap fluid put on a gelatin surface. This led to the 

 discovery of benzoic acid in the trap fluid, this substance having been 

 found also in the leaves and glands of Pinguicula by Loew and Aso, 

 and in the pitchers of Cephalotus by Goebel. 



Adowa (1924) attacked the same problem. He first made sahne 

 and acid (HCl) extracts of the whole plant, and tested their efficacy 

 in digesting gelatin, fibrin, milk casein and egg-albumin. The tissues 

 of the whole plant contain, he found, two proteoclastic ferments, 

 alpha- and beta-protease, the latter active in an acid medium. The 

 former is rendered a httle more active with the addition of CaCl2 to 

 it in a neutral medium. He then made extracts of three lots of ma- 

 terial (fl) stems, {h) green (young) traps and (c) red and blue traps, 

 and tested these separately. In neutral gelatin, the effects of these 

 three extracts were in the ratios of 18.5 for green traps, 6.5 for colored 

 traps, and 3.5 for stems; in alkaline gelatin the ratios were 22, 23.5 

 and 6. In acid gelatin the effects were rapid at first but stopped quickly, 

 while in the alkahne and neutral media the action was continuous. The 

 conclusions were drawn that (/) the extract of the traps contained more 

 alpha-protease than that of the stems; (2) that of green traps affects 

 alkaline gelatine over a long period (24 days) to the same extent as 

 that of colored traps; (3) the extract of green traps acts more ener- 

 getically on neutral gelatine than that of the colored traps; {4) the 

 protease content of branches is very insignificant; (5) alkahne gela- 

 tin is the best medium for digestion by undiluted extracts, neutral 

 gelatin for diluted extracts (50% and less); {6) beta-protease both 

 from the branches and from the traps shows a weaker activity than 

 alpha-protease, and (7) extracts diluted 8-16 times act in neutral but 

 not in alkahne medium. 



