1903.] Cyanogenesis in Plants. 293 



compounds of this type can, by processes of reduction, be converted 

 into ammo-derivatives, which recent researches indicate as the 

 materials from which, by processes of condensation, proteids originate, 

 his supposition implies that cyanogenetic glucosides are to be 

 regarded as plastic materials, whilst the enzymes with which they 

 are associated must be considered as aplastic substances with the 

 definite function of decomposing and possibly also producing cyano- 

 genetic glucosides, since the hydrolytic action of enzymes appears to be 

 reversible. 



This suggestion may explain the occurrence of cyanogenetic gluco- 

 sides in Lotus arabicus arid Sorghum vulgare during that period of their 

 life-history in which metabolism is active and their disappearance 

 when the plants have matured and produced seeds, since this period 

 coincides with that in which the synthesis of proteid in the plant is 

 actively proceeding. Although Phaseolus lunatus resembles Lotus 

 arabicus and Sorghum vulgare in containing a cyanogenetic glucoside, 

 it differs from these plants in continuously secreting this glucoside 

 which is likewise found in the seeds. In this respect Phaseolus 

 resembles the bitter almond. The seed produced by Phaseolus lunatus 

 under cultivation, however, does not contain phaseolunatin, just as the 

 seed of the sweet almond, which there is reason to believe is produced 

 by the cultivation of Prunus amygdalus, contains no amygdalin. It is 

 impossible without further knowledge of the causes which influence 

 plants in the selection of reserve materials to offer any explanation of 

 the fact that these glucosides appear as reserve materials in the seeds 

 of PJiaseolus lunatus and in those of the bitter almond, but not in those 

 of Lotus arabicus and Sorghum vulgare. 



The reason for the disappearance of cyanogenetic glucosides from 

 the seeds of Phaseolus lunatus and the bitter almond when cultivated, 

 is probably to be found in the stimulus to metabolism resulting 

 from improved nutrition and environment. These, as is well known, 

 lead to the more rapid utilisation of plastic substances, with the 

 result that there is very little, or possibly none, of the cyanogenetic 

 glucoside available for storage as reserve material in the seeds of the 

 cultivated plant. The enzymes on the other hand are aplastic sub- 

 stances performing definite synthetical and analytical functions without 

 themselves undergoing change, and consequently it is to be expected 

 that they would be found alike in the seeds of the wild and of the 

 cultivated plants. The enzyme emulsin occurs in the seeds of the 

 cultivated Phaseolus lunatus as well as in those of the sweet almond, 

 although the cyanogenetic glucoside has disappeared under the influence 

 of cultivation. 



The observations recorded by the authors in a previous paper,* 

 with regard to the existence of the cyanogenetic glucoside dhurrin in 



* Part II, loc. cit. 



