THE LOCALISATION OF ENZYMES IN PLANTS. 347 



the protoplasm was only tinted pink. Various aniline 

 dyes also stained the granules. The determination and 

 identification of the proteid did not, however, establish the 

 existence of the enzyme. Subsequent experiments of a 

 different character were necessary to show its presence. 

 These, however, did demonstrate the fact of its occurrence 

 with the proteid, so that the latter formed a test for the 

 ferment, and enabled its whereabouts to be ascertained. 



The second line of investigation indicated above, viz., 

 the obtaining of evidence of the action of the ferment, 

 by putting the suspected tissues into the necessary position 

 for such activity, also presents special difficulties. Such a 

 line was followed by Guignard in the experiments last 

 referred to. The difficulties are mainly mechanical, and 

 consist of the delicate manipulation necessary to isolate the 

 cells which are suspected to contain the enzyme. In the 

 laurel leaf these cells, as we shall see later, occur in a 

 sort of band or sheath round the fibrovascular bundles, and 

 it is possible to cut sections of the leaf consisting of but 

 little besides this sheath. The property possessed by this 

 ferment, emulsin, is the decomposition of the glucoside 

 amygdalin into sugar, benzoyl-aldehyde and hydrocyanic 

 acid, the latter two of which possess characteristic odours. 

 Thin sections taken, including the cells of the sheath, were 

 kept for a short time in a 1 per cent, solution of amygdalin 

 at 50 C., and speedily the peculiar smell gave evidence of 

 the action of the enzyme. Instead of sections being made 

 through the tissue in which the sheath lay, the sheath itself 

 was afterwards dissected carefully out and treated similarly, 

 when very rapidly the odour made itself evident. 



The same method of treatment was adopted in testing 

 for the enzyme in the Cruciferae. This ferment is myrosin, 

 and the glucoside on which it acts yields on decomposition 

 sulphocyanate of allyl, the aromatic principle found in oil of 

 mustard. The special cells which give the reactions already 

 mentioned can be separated in a definite layer in the wall- 

 flower, and the piece of tissue so dissected out causes the 

 evolution of this odour when digested for a short time with 

 a solution of the irlucoside. 



