154 



BOTANY AND PHARMACOGNOSY. 



from its stalk and the resulting scar is called the hilum ; that 

 part of the seed corresponding to the foramen of the ovule is more 

 or less closed and is known as the micropyle ; the embryo de- 

 velops 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. 59) : (i) The cotyledotjs; (2) the part below 

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



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Fig. 93. Successive stages in the development of flower and fruit of Viola tricolor. 

 The bud is at first erect, as the flower develops the ovary assumes a horizontal position, 

 and after fertilization resumes the erect position. 



which constitutes the young root or radicle; (3) the part above 

 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. 121, 122) 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. 



