

NATURE OF FOOD STORED IN SEEDS 



19 



Living and growing cells contain the life substance (protoplasm) 

 which has a complicated structure. In some plants the proto- 

 plasmic units are not bounded off by cell walls, still in general we 

 can say that the cell is the unit of structure, at least of the tissues 

 of the higher plants. A tissue is a group of cells of one kind, or 

 in some cases of different kinds united together. (See para- 

 graph 5.) 



25. Minute structure of the coats and outer layer of food 

 reservoir in corn and wheat grains. This structure is deter- 

 mined by a study of a thin section cut from a grain and extending 

 through the outer surface and a short distance into the interior or 

 flour part, and magnified by the use of the microscope. Figure 26 







Fig. 26. 



Section through exterior part of a grain of wheat, c, cuticle, or outer layer of bran; ep, epi- 

 dermis; m, middle layer; i, i\, layers of hull next to seed coats; s, si, seed coats; p, layer contain- 

 ing protein grains; st, cells of the endosperm filled with starch. Greatly magnified. After 

 Tschirch. 



is from a wheat grain, and the parts are as follows(the fruit 

 coat extends from c to i l and is the pericarp) : The outer layer 

 of cells (ep) is the epidermis, and upon this is the cuticle (c)', 

 next are a few layers of cells (m) the middle layer of brown, and 

 next (i, i 1 ) comes the inner layer of brown.* Together these are 



* These three portions of the brown layers are not a part of the seed. 

 They are a part of the fruit and are in reality the wall of the ovary inside of 



