152 REPORTS ON THE STATE OF SCIENCE. 



Maliase. 



This partially liydrolyses amygdalin, forming mandelic nitrile gluco- 

 side, and decomposes phaseolunatin, yielding acetone, prussic acid, and 

 a -dextrose. 



Since the mixture of enzymes prepared from the beans of Phaseolus 

 lunatus completely liydrolyses both amygdalin and phaseolmiatin, it must 

 be assumed that these beans contain at least two enzymes, the one 

 identical with or siuiilar to the emulsin of almonds, and the other identical 

 with or similar to the maltase of yeast. Fischer has shown ' that 

 maltase only liydrolyses glucosides containing an a-dextrose residue, 

 and in confirmation of this it has been shown ■^ that phaseolunatin yields 

 f«-dextrose on hydrolysis by one of the enzymes associated with it in the 

 beans of Fhaseolus lunatus, which must therefore be of the maltase type. 



Mention may also be made of the enzyme isolated by Power and 

 Gornall ^ from the seeds of Tarakiogenos Ktirzii, which has the property 

 of hydrolysing amygdalin, but differs from emulsin in also decomposing 

 potassium myronate, the characteristic glucoside of white mustard seed. 



It is of interest also to record that an emulsin-like enzyme, capable of 

 decomposing amygdalin and mandelic nitrile glucoside,' occurs in yeast,^ 

 and that substances exerting similar activities have been noted by 

 Bourquelot in various fungi. 



Physiological Significance of Cyanogenesis, 



In the literature relating to cyanogenesis three main ideas as to the 

 significance of the production of prussic acid in plants may be traced. 

 At first it was regarded as merely a waste product of no metabolic 

 importance ; later tlie \iew that it was possibly a means of protection was 

 suggested ; and more recently a small number of botanists and chemists 

 have put forward the idea that tlie acid is an intermediate product in the 

 synthesis of proteids. 



Evidence in favour of this last view has been accumulated mainly in 

 three ways. 



1. Jji/ 2^^''ysiological experiments on plants in which cyanogenesis 

 occiirs. — Two notable contributions liave been made to this side of the 

 subject by Dr. Treub, who has studied especially Pangium cdule * and 

 Phaseolus lunatus.'' In both these plants prussic acid appears to occur 

 free, and also in the form of a compound (phaseolunatin in the case of 

 P. lunaiiis), from wliich the acid may be readily released, and which 

 appears to serve as a temporary reserve of the acid, and with more 

 active assimilation in the plants, wliether brought about by improve- 

 ment in nutrition or in environment, there is an increase in the total 

 amount of the acid available in the plant. Whilst Treub has conclusively 

 established that the living plant of Phaseolus lunatus develops more 

 prussic acid under conditions of improved nutrition, it seems to be equally 

 certain that prussic acid and the cyanogenetic glucoside, phaseolunatin, 

 may be completely eliminated from the seeds or beans of the plant by 

 careful cultivation. Bonarae showed ' that of the variously coloured 



Dunsf.in, Henry, and Aiild, Proc. Boy. Son., 1906. ' Loc. cit. ' Loo. cit. 



* Henry and Aiild, Proc. Hoy. Soc, 1905, B, 76, 5G8. Compare Husemanrj, 

 Plianzen Stoffe, p. 1020. ^ Loc. cit. 



' Ann. jard. Bot. Buit., If 05, ii. 4, 86. 

 . ' Bap. Stat Ayr on. Afaurice, 1900, 94. 



