184 



PLANT STRUCTURES 



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

 opment of this testa hermetically seals the structures with- 

 in, further 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. 153a. Pine seed. 



FIG. 154. Pine seedlings, showing the long hypocotyl and the numerous cotyledons, 

 with the old seed case still attached. After ATKINSON. 



