184 



PLANT STRUCTURES 



known as the seed coat, or testa (Fig. 153a). The devel- 

 opment of this testa hermetically seals the structures with- 

 in, farther development and activity 

 are checked, and the living cells pass 

 into the resting condition. This pro- 

 tected structure with its dormant cells 

 is the seed. 

 In a certain sense the seed is a transformed ovule (mega- 

 sporangium), but this is true only as to its outer configura- 



FiG. 153«. Pine seed. 



Fig. 154. Pine seedlinp^s. ehowing the long hypocotyl and the numerous cotyledons, 

 with the old seed case still attached.— After Atkinson. 



