594 Prof. H. E. Armstrong and Dr. E. F. Armstrong, [Apr. 29, 



salts. It can scarcely be supposed that such substances directly determine 

 the liberation of the enzyme from the protoplasm — in other words, that 

 initially action takes place merely because of the breakdown of a zymogen 

 oinder their immediate influence. 



It is generally considered that, in plant tissues, enzyme and glucoside are 

 either contained in different cells or in different vacuoles in the same 

 ■cell. According to Guignard,* in the cherry laurel the enzyme is stored 

 in the endodermis of the veins ; the glucoside is distributed in the 

 parenchyma of the leaf. Even if the enzyme were liberated, it is 

 improbable that it would travel any distance or through a cellular membrane. 

 It is more likely that the glucoside is caused to travel to the enzyme ; 

 in such an event, the enzyme might still be active while forming part of the 

 protoplasmic complex, if it were exposed at the surface. 



We gather that this is the view held by Guignard, as after calling attention 

 to cases in which drops of liquid appear on the surface of the leaf exposed to 

 the anaesthetic, he proceeds to say : — 



" On pent done dire que le contenu cellulaire subit una veritable deshydra- 

 tation, puisqu'une partie du liquide passe k I'exterieur de la cellule. 



" De meme, dans le cas des plantes k glucosides, tels que le myronate 

 ■de potassium ou I'amygdaline, ces principes sont entraint^s avec I'eau qui les 

 tient en solution et arrivent au contact des ferments, localises dans des 

 cellules speciales: d'oil le dedoublement produisant soit de I'essence de 

 moutarde, soit de I'acide cyanhydrique." 



And, in summarising his observations, he remarks : — 



" II y a Ik, en sonime, une methode g^n^rale de recherche de certains 

 composes dont la formation resulte de Taction r&iproque d'un ferment et 

 d'un glucoside arrivant au contact I'un de I'autre par I'intermcidiare de I'eau. 

 Les observations de M. Mirande sont un exemple tres interessant de son appli- 

 cation k la recherche des plantes ci acide cyanhydrique." 



But it appears to us to be necessary to go somewhat further. 



Modern experience would lead us to suppose that, in the living cell, 

 the formation of various hydrolytes is promoted by sympathetic liydrolysts 

 under conditions of concentration which are unfavourable to the occurrence 

 of hydrolysis ; from this point of view, the conditions of concentration in the 

 cells sliould entirely determine the process of change in citiier the one 

 or the other direction — that of hydrolysis or the reverse. 



In the case of the laurel leaf, we have no hesitation in attributing the 

 liberation of hydrogen cyanide by neutral substances which enter as vapours, 

 l)rimarily, to the influence these exercise in causing alterations in concentration 

 • 'Journal de Botanique,' 1890, vol. 4, p. 3. 



