lO SEEDS : STRUCTURE AND GER.MINATIOX 



becomes root and stem is its primary axis. The part of the 

 primary axis which is below the point where the cotyledons 

 are attached is known as the radicle, and consists of a very small 

 piece of stem, the hypocotyl, at the end of which is a root. Where 



the stem ends and the root 

 begins cannot be determined 

 in the bean seedling without 

 the aid of the microscope and 

 examination of the internal 

 structure of the axis of the 

 plant. 



The curved end of the 

 primary axis above the cotyle- 

 dons is the plumule of the 

 embryo, and consists of a 

 very short piece of stem, 

 the epicotyl, on the top of 

 which is a bud. From the 

 latter is derived the ordinary 

 stem which comes above 

 ground with its green leaves 

 and flowers. 



In the early stages of the 



growth of the embryo from 



the seed the hypocotyl grows 



r , ^ . ^ very little, the part of the 



Fig. 4- — riean embryo after four days growth. 



One cotyledon has been removed, c Coty- Stem which grOWS moSt being 

 ledon *, r primary root ; b epicotyl with . . , . 



bud at its tip. the epicotyl. It IS on account 



Compare with Fig. 3. c ..l. \ ..■<■, ■ 



of the elongation of this 

 portion of the plantlet that the plumule with its young leaves 

 are driven above ground, the cotyledons remaining below en- 

 closed within the seed-coat. 



The upper part of the stem bearing the plumule comes out of 

 the seed bent, as in Fig. 4, and it maintains this curved shape for 



