400 THE BIOLOGY OF FLOWERING PLANTS 



into the seed coats. These changes consist in growth, 

 keeping pace with the growth of the embryo, and, towards 

 the close of development, in the drying out of the seed coats 

 and in the formation of special, mechanically resistant and 

 impervious layers of cells. A hard or leathery seed coat 

 is protective in various ways ; it may protect the seed from 

 mechanical injury, from desiccation, from digestion by 

 animals using the fruit as food. It may also, as we shall see, 

 prevent immediate germination. New structures may 

 appear in connection with the seed coats in the form of an 

 outgrowth from the funicle — aril, or from the micropyle — 

 caruncle. The aril may be fleshy and brightly coloured, as 

 in the outgrowth which has earned for the seed of the yew 



AMD. 



Fig. 62.— Seeds with arils : i, nutmeg (Myristica) ; 2, African lucky bean 



(Afzelia). Nat. size. 



the courtesy title of " berry " ; or it may be dry and 

 wrinkled as in the mace of the nutmeg (Fig. 62). The 

 tufts of hair of such seeds as the cotton or willow are arillar 

 in origin. 



The aril has usually a function in connection with seed 

 distribution, though in some cases it may assist in the 

 opening of the fruit and liberation of the seed. 



The Fruit. — After fertiUsation has been effected, other 

 parts of the flower, and particularly of the ovary, enter on a 

 new phase of development, which results in the formation 

 of that structure peculiar to the angiosperms— the fruit. 

 In the simplest cases the fruit is derived from the ovary 

 alone ; but many fruits, in the common acceptance of the 



