PRUSSIC ACID IN PLANTS 49 



hydrin and the a /3-disaccharide, the latter being then resolved 

 by the further action of the enzyme into the two simple 

 glucoses. 



This essential difference shown by maltase and emulsin 

 in their methods of attacking amygdalin appears to negative 

 the view sometimes expressed that maltase and emulsin are 

 complementary to each other in activity. 



The only other glucosidolytic enzymes calling for attention 

 in the present connection are lotase, present in Lotus arabicus, 

 and gynocardase, occurring in gynocardia seeds. The activities 

 of gynocardase are very similar to, if not identical with, those 

 of emulsin. Lotase differs markedly from emulsin in activity, 

 as might be expected, since it occurs with lotusin, in which, 

 as already pointed out, the cyanogen group is associated with 

 the sugar residue. 



The Physiological Significance of Cyanogenesis 



The earlier investigators who devoted attention to cyano- 

 genesis were usually inclined to regard the production of prussic 

 acid by a plant as a means of protection, and later on this view 

 was succeeded by the belief that prussic acid and its immediate 

 precursors are merely waste products of metabolism, stored in 

 places such as barks, epidermal cells of leaves, etc., where they 

 are harmless to the plant. Recently, however, several investi- 

 gators have assigned a more important role to the acid, and 

 Treub, 1 in particular, has asserted that it is probably the first 

 recognisable product of the assimilation of the nitrogen of 

 nitrates by plants. Treub's conclusions are based principally 

 on the results of his elaborate investigations of the plants 

 Pangium edule and Phaseolus lunatus. It would take too long 

 to describe these in detail, but the most important points estab- 

 lished seem to be that in the green parts of both these plants 

 both free prussic acid and cyanogenetic glucosides occur, the 

 latter serving apparently as temporary reserve products ; and 

 that with more active assimilation in the plant, whether brought 

 about by improvement in environment or by increased supplies 

 of suitable nutrition, an increase in the amount, both of free 

 prussic acid and of cyanogenetic glucosides, follows. Some 

 confirmation of Treub's views is also afforded by the results of 

 Soave's 2 experiments with bitter almonds, which show that/;r<? 

 1 Treub, loc. cit. 2 Soave, Nuov. giorn. bot. ital. 1899, 6, 219. 



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