Chapter X —161— Drosera 



Their method of obtaining the enzymes was as follows. The se- 

 cretion of the glands was taken up by filter paper and because of its 

 viscosity was diluted. That of the leaf tissues was extracted with 

 glycerin. Both were tested on edestin. 



It was found that the gland secretion, with its optimuni at pB. 

 ^.^, was far more active than that of the leaf blade, with its opti- 

 mum at 4.6, or even of the secretion, extracted from removed glands 

 with maximum activity at ^H 3.8. It is admitted that the last may 

 be due to the overlapping of the action of the two enzymes in ques- 

 tion. The authors concluded, "We have to do with a quite different 

 distribution of two enzymes, of which the one occurring in the se- 

 cretion is a proteinase for the purpose of digestion." Further it was 

 pointed out that the distinct function of a proteinase, optimum activity 

 at pB. 3.2, does not harmonize with Dernby's results who found 

 the maximum activity on acid albumin at ^H 5, nor with Okahara's 

 with carmine fibrin, maximum activity at pE. 1.4. Dernby's results 

 may have come about because he used masses of total leaf, but those 

 of Okahara's are regarded as distinctly antagonistic. This may be 

 due to the possibiUty that the Japanese plant may differ physiolog- 

 ically from the European. Merck's pepsin acted on edestin at pB. 

 1.8; therefore, the proteinase of Drosera and pepsin are not iden- 

 tical. , . o , 



Recent and still unpublished work done by A. Akerman and 

 L. G. M. Baas Becking using D. capensis yielded definite evidence 

 that peptic fermentation takes place. The method used was the fol- 

 lowing: A single tentacle on the leaf edge was plunged into distilled 

 water held in a small paraffin cup. Under these conditions the water 

 retained its initial pB. of 5.8 for at least 24 hours. When, however, 

 a solution of NH4CI (cone. 25 mgr/L) was used the ^H fell from 5.8 

 to 2.0, from which it is evident that this salt served to stimulate the 

 production of acid. Equivalent solutions of CaCl2, NaCl and MgClz 

 gave no action, while KCl produced only a very slight change in 

 pB. When egg albumin {pB 7.0) was placed on a tentacle, the pB 

 changed to 3.0. Carmine-fibrin when treated with a leaf extract was 

 digested indicating the presence of a peptic enzyme, effective at an 

 optimum pB of 2-3.0 while it has been shown by J. de Zeeuw that 

 digestion in Nepenthes takes place at about pB 4.0. Since the leaf 

 extract was not bacteria free. Prof. Baas Becking (Sept. 1935) pointed 

 out that the proof for Drosera is not absolute, and final proof will 

 require experiments with bacteria-free plants. It is further noted 

 that Drosera proteinase takes a middle position between pepsin and 

 papain {in ep.). 



Darwin observed that milk when placed on Drosera leaves was 

 soon coagulated. Green mentions this under the heading "Vegetable 

 Rennet," presumably because of the more obvious inference that milk 

 coagulation is brought about by a rennet, as perhaps is the case 

 when Galium verum is used for the preparation of curds for cheese 

 making, also mentioned by Green. As has been seen, a similar ac- 

 tion of Pinguicula in coagulating milk is not attributed to the pres- 

 ence of a rennet (Dernby 191 7), and if so, this may be equally true 

 of Drosera. Darwin does not speak of a rennet, but does remark 



