1912.] 



Studies on Enzyme Action. 



369 



The absence of "prunase" from the Ericaceae examined, except in the case 

 of the Whortleberry, is of interest in view of the occurrence of Arbutin in 

 this group. 



The great activity of Spanish Chestnut towards prunasin and salicin is 

 significant ; apparently no glucoside characteristic of this species is known. 



Another instance of variability is afforded by Aquilegia, Apparently 

 hydrogen cyanide is to be detected in many if not in most species of this 

 family but the amount is subject to considerable variation at different 

 seasons and as often as not it cannot be detected in cultivated garden 

 varieties of the plant. 



Mountain Ash (Pyrus aucuparia) again varies greatly in the amount of 

 hydrogen cyanide the leaf affords at various seasons ; often it cannot be detected. 



A noteworthy instance of association in habits is presented by Thalictrum 

 aquilegifolium, the leaf of which closely resembles that of aquilegia. We have 

 tested this plant in many places and always found cyanide present in the leaf ; 

 judging from tests made at Kew, other species do not contain the cyanide. 



The Yicia group presents interesting peculiarities in addition to those 

 indicated in the table. The seed of Vicia angustifolia contains a considerable 

 proportion of the cyanophoric glucoside Vicianin, which Bertrand has also 

 found in two other species,* though only in small proportion. On more than 

 one occasion we have obtained traces of hydrogen cyanide from unripe seeds 

 of V. sativa. V. villosa, in like manner, affords traces of the cyanide but 

 only at the moment when the pod blackens ; none can be obtained from the 

 ripe seeds. Whether corresponding variations take place in the enzymes 

 remains to be ascertained ; results such as these, however, are interesting 

 proof of latent peculiarities. 



We hope to be able to submit the cases mentioned to more exhaustive 

 systematic study on lines similar to those followed in the case of Lotus 

 corniculatus. It is to be expected that, when completed, such observations 

 will afford important evidence as to the possibility of differentiating botanical 

 species by chemical means and with reference to the transmission and 

 variation of chemical factors, such as enzymes and glucosides, in plants. The 

 evidence now brought forward affords renewed proof of the essentially 

 selective nature of the actions exercised by enzymes. By pursuing the 

 inquiry on the lines indicated and by using a larger number of hydrolytes, 

 we hope to be able eventually to decide both the specific character and the 

 range of activity of the various /3-glucases — but it is obvious that the task 

 will be one of extreme difficulty. 



* 'Compt. Eend.,' vol. 143, p. 970. 



