282 



BOTANY OF THE LIVING PLANT 



young. Accordingly, it is not represented as a rule in the ripe 

 seed, except by the remains of its tissue, which are crushed between 



the firm seed-coat and the endosperm 

 or embryo within. 



On the other hand, the integument, 

 or integuments, persist, developing into 

 the testa, or seed-coat. Their tissues 

 become indurated, of stony or leathery 

 texture; but there is a good deal of 

 variety in the detail. Usually the 

 outermost .layer, but not infrequently 

 some layer more deeply seated, develops 

 its cells in prismatic form and thick- 

 walled. Others may also harden : but 

 the inner, softer layers are often com- 

 pressed. The tissues lose their cell- 

 contents, serving only the purpose of 

 protection to the germ and the stores 

 within. (Fig. 224.) When this condi- 

 tion is reached in many-seeded ovaries 



FIG. 224. 



Section through testa, and mucilage- 

 endosperm of seed of Gymnocladus cana- 

 densis. a=palissade layer. s=sup- 

 porting layer. p = thick- walled fissure. 

 These form the testa. sch= mucilaginous 

 endosperm of this Leguminous seed. 

 (After Nadelmann.) 



FIG. 225. 



Young carpel, and fruit of Copaifera. 

 a indicates the arillus which spreads from 

 the micropylar end of the pendent seed. 

 (After Baillon.) 



the tissue of the funicle dries, and being brittle, the connection 

 between the seed and the parent plant is severed. It is now 

 independent, and the new individual has to fend for itself. 



Other developments, having special biological value, are sometimes formed 

 during the ripening of the seed. Superficial cells may grow into long hairs, 



