METABOLIC PROCESSES IN THE PLANT. 315 



113). The stem does not develop till later. The seedlings must 

 now be examined from time to time, if it is desired to obtain in- 

 formation respecting the metabolic processes taking place during 

 germination. Soon after germination begins, considerable quan- 

 tities of glucose appear in the endosperm, as can easily be deter- 

 mined by means of Copper sulphate and potash. The scutellum, 

 which during germination remains within the wheat grain, effects 

 the transfer of the whole of the plastic material from the endo- 

 sperm into the embryo, but it is important that the cells of the 

 scutellum never contain sugar. 



The columnar epithelium serves the scutellum as an absorbing 

 organ, and although the presence of starch or glucose is never to 

 be detected in the epithelial cells, yet the other cells of the 

 scutellum soon after the commencement of germination contain 

 transitory starch. The presence of this starch in the cells of the 

 scutellum may be readily proved by treating the sections with 

 potash, Acetic acid, and dilute Iodine solution. It is further to be 

 noticed here that, in order to prepare satisfactory sections, the 

 germinated wheat grains must be somewhat dried. Proteids, as 

 well as non-nitrogenous bodies, are conveyed from the endosperm 

 to the germinating seedling by the scutellum. If wheat seedlings 

 have developed for, say, five days at the usual room temperature, 

 it is easy, by treatment with Copper sulphate and potash, to detect 

 the presence of considerable quantities of proteid in the younger 

 parts of the roots, and also in the vascular bundles which stand 

 diametrically opposite one another in the sheath leaf. This last is 

 still in a state of very active growth, and is also correspondingly 

 rich in plastic material coming from the endosperm. In the 

 parenchyma of the sheath leaf, numerous starch grains are easily 

 recognised, the number of which diminishes as the growth of the 

 sheath, with progressing germination, gradually ceases. The cells 

 of the rest of the growing leaves also contain starch grains. The 

 presence of glucose I have been unable to detect at any time in 

 any part of the wheat embryo (the seedlings which I examined 

 developed in darkness) ; glucose is present only in the endosperm 

 of germinating wheat grains. It is, however, by no means im- 

 possible that under particular conditions glucose may appear also 

 in the embryo. Naturally the cells of the endosperm constantly 

 become poorer in reserve substances (proteids and starch) as the 

 development of the seedling advances, and if we tease up small 

 quantities of fairly exhausted endosperm tissue in a drop of water 



