1905.] On the Germination of Seeds of the Castor- Oil Plant. 85 



metabolism. Their protoplasm grows and takes a prominent part in these 

 metabolic changes, secreting enzymes, and setting up various chemical 

 changes in the cells partly by means of the latter and partly independently 

 of them. In this renewed activity the embryo also takes a share by 

 contributing to the enzyme-formation. The result is the production of 

 a great variety of nutritive material, partly the direct product of enzyme- 

 action, partly produced by the secretory activity of the protoplasm and 

 partly by the interaction of the products of the first two agents. Two 

 varieties of sugar, lecithin, fatty acids, and the products of their oxidation, 

 proteids, and the products of their digestion, including various crystalline 

 nitrogenous bodies, amino- and amido-compounds at least are present. In 

 this mass of nutritive material the embryo is plunged, and by the delicate 

 epidermis of its cotyledons it absorbs, probably selectively, what it needs for 

 its own growth. It is not easy to follow the process of absorption in detail, 

 on account of the metabolism accompanying growth, which is very speedily 

 set up in the cells of the embryo. 



Analyses of the cotyledons show them to contain a varying quantity of 

 lecithin, amounting in some cases to l - 36 per cent, of their dry weight. 

 Both the sugars can be detected in them, the relative amounts, however, 

 varying, but cane-sugar being usually present in largest quantity. 



The reaction of the sap is acid, traces of phosphoric acid being mixed with 

 an organic acid whose nature has not been ascertained. In fact, the 

 transport of the nutritive substances to the embryo seems to be much the 

 same in character as their transport in the tissue of the endosperm. 

 Probably in both cases the presence of protoplasmic threads in the various 

 cell-walls plays an important part in the matter ; it seems at any rate 

 probable that this agency is necessary to explain the transport of lecithin to 

 the embryo. A very small quantity of lecithin can be dissolved in water or 

 exist as a fine emulsion. It is improbable, however, that it can be trans- 

 mitted through the cell -walls by dialysis alone. Dialysis no doubt plays 

 a large part in the absorptive processes, especially where the crystalline 

 substances are concerned. 



The renewed metabolism in the endosperm-cells thus furnishes a mass of 

 nutritive material on which both the endosperm-cells and the young embryo 

 feed, and there seems to be no particular difference in the manner in which 

 they are severally nourished. 



vol. lxxvii. — B. 



H 



