CHAPTER XVI. 

 SEED AND FRUIT DISPERSAL 



SEEDS 



SEEDS are immature dormant plants containing or sur- 

 rounded by reserve food and covered by a protective outer 

 layer or testa. In the seed stage plants accomplish many 

 things and live through conditions which would be impossible 

 at other stages. At this stage the plant is distributed fre- 

 quently at great distances from its parent. Seeds are the 

 only means annual plants have of perpetuating themselves; 

 they survive the winter season, the periods of no rainfall 

 and other conditions adverse to plant growth. 



The seed originates in the fertilization of the egg cell and 

 endosperm nucleus in the ovule. As a result the parts of the 

 ovule become modified to form the seed. The testa or seed- 

 coats, the reserve food, and the embryo are the parts of the 

 seed. 



Testa, The testa is essentially a protective layer, but in 

 some seeds it is modified as a wing or spine. These modifi- 

 cations are the means of bringing about a wide distribution. 

 In castor-oil seed an enlargement occurs on the testa known 

 as a caruncle while the seed of nutmeg has a larger anastamos- 

 ing partially attached outer coat or aril, which when separated 

 from the seed forms mace, the well known spice of commerce. 



The texture of the testa varies in different seeds. In most 

 seeds it is very thick, hard, and resistive to cutting and 

 crushing. The hardness is usually due to the stone cells 



