86 GRASSES OF IOWA. 



enzymes totally destroys the activity as a cellulose dissolving- 

 agent, and that it does not pre-exist in the resting seeds, but it 

 is a product of germination.* 



The reserve foods, as indicate:], consist of two general 

 classes, the carbo-hydrates occuring under three forms: sugar, 

 starch and cellulose, and the albuminoids occurring in the 

 form of albumoses and the vegetable globulins. Of course 

 these are very concentrated. In the aleurone cells the album- 

 inoids have received special names in different seeds. 



The outer row of cells of the embryo make up what is known 

 as the cylinder epithelium, or referred to as the epithelium. 

 (Fig. 51 A.) The embryo contains very little starch or none. Mow 

 the dissolved material of endosperm is transferred through the 

 absorptive epithelium by diffusion and transferred to the grow- 

 ing embryo within a few hours after the moistened corn is put 

 under favorable conditions for germination. The protoplasm 

 of the epiihelial cells becomes coarser in structure, and the 

 granules increase in size. The contents of the cells and 

 nucleus are less distinct; they reach their maximum change in 

 from m to 36 hours. At this stage the epithelium ceases to 

 produce its secretory enzymes. The protoplasm loses its large 

 granules and contains small refractive granules. The cell 

 contents become hyaline. The contents of the endosperm 

 become gradually absorbed, the cells having become greatly 

 elongated. The first action of the endosperm is a dissolution 

 of the cellulose and the appearance of transitory starch in the 

 scutellum or cellulose, and therefore acts first in supplying the 

 growing embryo with food. " In the first place the cellwall 

 swells up slightly, and its stratification becomes much more 

 apparent, owing to a partial separation of its constituent lamel- 

 lae. These are gradually disintegrated, but the middle lamella 

 appears to offer a somewhat greater amount of resistance than 

 the other. Ultimately the whole of the cellwall is broken 

 down into very minute spindle-shaped fragments, with their 

 long dimensions arranged tangential to the original cell- wall. 

 Owing to this arrangement, these minute fragments, when 

 viewed with low powers, gives the appearance of ghost-like 

 cellwalls for some time after the wall has really ceased to be 

 continuous. Ultimately, as the action continues, the residual 

 fragments also disappear, and there is no visible sign of sepa- 



*These writers, Research of the germination, etc. Jour. Ohem. Soc. 57: 465., give an 

 account of obtaining these enzymes. 



