THE LOC A LIS ATIOS OF ENZYMES IN PLANTS. 345 



(6). Guignard has noted similar granularity in cells proved 

 by other means to contain emulsin, in the almond and the 

 laurel (7). In the cells which cover the embryo in various 

 palms, and which eat into the horny endosperm in which 

 this structure is impacted, the same granularity may by 

 appropriate treatment be made visible. 



Mere granularity, however, is not a sufficient test for 

 the existence of the enzymes. Various staining reactions have 

 also been used, though not with uniform results. Wiesner 

 (8) nearly ten years ago advocated the use of an alcoholic 

 solution of orcin, supplemented by boiling the tissue with 

 strong hydrochloric acid. He obtained thus a definite color- 

 ation of the contents of the cells in which various ferments 

 occurred, the colour varying with the nature of the'ferment. 

 By this method he thought he would be able to determine, 

 not only the presence of an enzyme, but to identify it. The 

 method was later shown to be inconclusive, as many other 

 bodies give similar colour reactions. It cannot therefore be 

 relied on, unless the cells examined are known to contain 

 none of these, a very difficult matter, as most of the known 

 carbohydrates are among the bodies which give the reaction. 

 Hydrochloric acid by itself gives distinctive colours with the 

 different enzymes ; diastase turns red, and later on brown, 

 emulsin becomes violet, papain orange-red, trypsin greenish- 

 yellow. Again, however, experiments with other bodies 

 show by their behaviour that the results are not to be 

 relied upon as distinctive. The cells generally contain, in 

 addition to the enzymes, considerable quantities of proteids, 

 and these are affected in various ways, giving rise to colour 

 reactions that resemble those first described. It thus be- 

 comes difficult or impossible to say with confidence what 

 body is the one to which ^any particular colour reaction 

 is due. Though we cannot give any general test of this 

 kind for the presence of an enzyme, yet particular ones may 

 be detected by careful experiments. The most success- 

 ful investigations in this direction are those which have 

 recently been carried out by Guignard (9) on the glucoside- 

 splitting ferments yielded by the Cruciferai and the Rosacea^. 

 He detected them first in the leaf of the cherry laurel. 



