426 



A TEXT-BOOK OF BOTANY. 



develops in such a way that the tip of the young root always 

 points in the direction of the micropyle. 



In the fully developed embryo three distinct parts may be dif- 

 ferentiated (Fig. 161) : (i) The COTYLEDONS; (2) the part below 

 the cotyledons, known as the HYPOCOTYL, the apical portion of 

 which constitutes the young root or RADICLE;-^) the part above 



pc, 



FIG. 249. Forms of embryo and distribution of endosperm in various seeds and 

 fruits. A, Ricinus seed: car, caruncle; m, micropyle; e, embryo. B, superior drupe of 

 Piper: per, pericarp; e, endosperm; p, perisperm. C, spinach fruit and D, corn cockle seed 

 (Agrostemma Githago): per, pericarp; t, seed-coat; h, hilum; p, perisperm; e, endosperm 

 C, curved embryo. A, C, D, after Harz; B, after Baillon. 



the cotyledons, known as the EPICOTYL, the apex of which con- 

 sists of a more or less developed bud spoken of as the PLUMULE. 

 The position of the embryo (Figs. 249, 250) in the seed varies 

 somewhat : in most seeds it lies in the center, as in strophanthus 

 and linum ; it may, however, be excentral, as in colchicum and 

 nutmeg. The cotyledons are usually situated above the hypocotyl, 

 but in the Cruciferse, either their edges lie against the hypocotyl, 

 as in the mustards, when they are said to be ACCUMBENT or con- 



