328 Transactions. 



The endosperm consists of a mass of starch-cells, intermingled 

 with irregular and spherical particles of nitrogenous matter, the 

 whole contained in compartments of cellulose, and forming a 

 store of foodstuff to supply the germ until it has grown suffi- 

 ciently to enable it to draw nourishment through its roots and 

 leaves. 



Immediately under the skin is a triple layer of thick-walled 

 square -shaped cells, known as the " aleurone cells." These 

 cells contain finely granulated nitrogenous matter, and also 

 small spherules of fat or oil. It is not clear what their 

 immediate function is, but, seeing they are in contact with 

 the starch-cells of the endosperm and the bulk of the germ, 

 they may take some active part in the transfer of food from 

 the former to the latter. 



Now, although the substances in the endosperm are intended 

 as a food-supply for the germ, they are in an entirely unavailable 

 condition, for, in the first place, the scutellum will prevent the 

 passage to the germ unless these substances are in a state of 

 solution, and, in the second place, such a solution must be a 

 diffusible one. Now, starch, which constitutes the bulk of the 

 endosperm, is practically insoluble, and the nitrogenous matters 

 are almost entirely so, while such portions of them as do 

 dissolve in water yield non-diffusible solutions. 



With the object of rendering the amount of foodstuff avail- 

 able for the young germ, the epithelial layer of the scutellum, 

 which I have previously described, has the property, when 

 sufficient water is present, of secreting soluble ferments, or 

 enzymes, which have the power of acting on the starch and 

 nitrogenous matter and rendering them both soluble, and the 

 solutions of which are diffusible. The enzyme which acts upon 

 starch is diastase, while that which acts upon nitrogenous matter 

 is vegetable pancreatin, and is probably similar to peptase. 



Now, although by the aid of the two ferments, diastase and 

 peptase, the two difficulties of solubility and diffusibility are 

 overcome, the foodstuffs in the endosperm are not even yet 

 available for the nutrition of the germ. I mentioned previously, 

 in speaking of the contents of the endosperm, that both the 

 starch and gluten cells were enclosed within compartments of 

 cellulose, and, as this cellulose tissue is impervious both to 

 diastase and peptiise, it is necessary that another enzyme should 

 be secreted to dissolve this cellulose. This enzyme is called 

 '" cytase," and its action, of course, precedes the action of 

 both the other ferments. Cytase is secreted in the region of 

 the scutellum, and slowly passes through the grain, and its 

 passage may be noted by the progressive softening of the corn 

 as it dissolves the cellulose, the original hardness of the grain 



