128 PRACTICAL BOTANY 



of protoplasm : in the peripheral yellower portion of the 

 endosperm the starch-grains are more closely packed than in 

 the central whiter portion. 



iii. The embryo, which is in close apposition to the endo- 

 sperm : the part which is in contact with it is the scutellum ; 

 it extends over the whole surface of contact, and almost com- 

 pletely surrounds the body of the embryo itself. Note the 

 central attachment of the scutellum to the body of the embryo ; 

 the vascular bundles, which form a connection through it ; the 

 epithelium of peculiar structure, which faces the endosperm . 



The body of the embryo consists of 



(a) An apical bud, with several sheathing leaves, which 

 surround the apical cone. 



(t>) A radicle, having similar arrangement of the meristem to 

 that of the older root (compare p. 106). Outside the radicle, 

 and continuous with the root-cap, is a root-sheath, or coleor- 

 hiza : note that the body of the radicle is covered externally by 

 a clearly marked series of cells which gives rise to the piliferous 

 layer, and this, being enclosed by the coleorhiza, is not con- 

 tinuous with the superficial epidermis of the shoot. 



RESERVE AND TRANSITORY MATERIALS IN SEEDS, 

 TUBERS, &C. 



I. Starch from the potato tuber has already been described 

 with its reactions on p. 28 : as further examples of its 

 occurrence in seeds, cut sections of the cotyledon of the Pea or 

 Bean : stain with iodine solution, and observe the large, oval 

 starch-grains distributed through the tissue : note at the same 

 time the protoplasmic matrix, and numerous small aleurone 

 grains, which are stained yellow or brown. 



Cut sections also of the endosperm of the Maize, and treat 

 with solution of iodine. Note the polygonal starch grains 

 (blue), and the protoplasmic matrix (brown). 



Leukoplasts, or Starch-forming Corpuscles. These are to 

 be found in colourless tissues, in which a storage of starch is 

 taking place ; e.g. a young Potato, the rhizome of fris, or 

 Canna, &c. 



