Seeds and Seedlings. 



23 



a fact of great importance, since the action of the ferments 

 is hindered or entirely pre- 

 vented if their products are 

 allowed to accumulate within 

 their field of action. 



A very notable example 

 of the enlargement of the 

 cotyledon while serving as 

 an absorbing organ is seen 

 in the cocoanut. Here the 

 embryo is relatively small 

 and lies embedded in the 

 fleshy reserve food at the 

 pointed end of the nut. As 

 germination proceeds, a part 

 of the cotyledon grows out 

 through one of the three 

 openings in the shell, and 

 carries the plumule and hy- 

 pocotyl out with it, while 

 the greater part of the coty- 

 ledon remains within the 

 seed, and as it absorbs the 

 reserve materials it enlarges 

 and fills the cavity (see Fig. 6). 



13. Direction of Growth. — 

 The root of the seedling 

 grows downward into the 

 soil, and the shoot (stem and 

 leaves) upward into the sun- 

 light and air, and it matters 

 not in what direction the 

 seed may be lying in the soil. 



Fig. s. 



Stages in the germination of a Date Seed : 

 I, the young plant still attached to the 

 seed ; 2, cross section through a seed 

 showing the small embryo to the left 

 embedded in the hard cellulose endo- 

 sperm ; 3, cross section of a seed in an 

 early stage of germination ; 4, section 

 through a seedling in an advanced stage 

 of germination. The cotyledon remains 

 in the seed and enlarges as the endo- 

 sperm is absorbed. The stem or peti- 

 ole of the cotyledon depending from the 

 seed enlarges at its base and covers the 

 plumule. The tapering end below the 

 plumule is the hjpocotyl. 5, a later 

 stage showing the endosperm nearly ex- 

 hausted and the cotyledon filling the 

 cavity ; 6, surface view of a seed in an 

 early stage of germination. After SACHS. 



The hypocotyl may be 



