ALLIUM CEPA 



185 



Development of the Seedling. — In germination, there is an 

 initial elongation and growth of the lower and middle parts of the 

 cotyledon resulting in the emergence of the root tip through the 

 seed coat at the micropyle. (Fig. 85.) Within 14 hours, the 

 hypocotyl has grown out through the seed coat; and the cotyledon 



1 



Fig. 85. The development of seedling: A, diagram of seed showing position of embryo; 

 B, the emergence of first foliage leaf through the cotyledonary slit. 



soon emerges except for its tip, which remains embedded in the 

 endosperm and acts as a haustorium for the absorption of food. 

 The emerging root tip is usually directed upward at first, owing to 

 the shape of the seed; but after it has attained a length of from 

 3 to 5 mm., downward curvature takes place in the elongating 

 parts of the seedling which already lie outside the seed. This 

 results in the formation of a sharp bend in the cotyledon, which 



