CHAPTER XVII 



THE MORPHOLOGY OF SEEDS AND FRUITS, AND THEIR 

 DISTRIBUTION 



Seeds. A seed is the result of the changes which take 

 place in an ovule after fertilisation. The changes can be shown 

 thus : 



(1) The oospore develops into an embryo. 



(2) The embryo-sac nucleus divides up to form endosperm. 



(3) The coverings or integuments of the ovule change and 

 become fit for the protection of the embryo, and in the seed are 

 called the spermoderm (p. n.) 



Structure of Seeds. Each seed is covered with a layer, 

 the testa. It is formed from the integuments of the ovule. 

 The central portion of the seed consists of the embryo and the 

 endosperm when it is present. The opening through the testa 

 is called the micropyle (p. 10), and represents the micropyle of 

 the ovule. The parts present in albuminous and exalbuminous 

 seeds may be shown thus : 



Seeds. 



Albuminous. Exalbuminous. 



Testa. Testa. 



Embryo. Embryo. 



Endosperm. 



Comparison of an Ovule with a Seed. The corres- 

 ponding parts of the ovule and seed may be easily compared : 



