XVII 



MORPHOLOGY OF SEEDS AND FRUIT 



225 



Structure of a Fruit. The wall of the fruit is called the 

 pericarp, and in most instances it can be divided into three 

 different layers : 



Theefocarfl, or outer layer of the fruit. (Fig. 218). 



The mesocarp, or middle layer of the fruit. 



The endocarp, or inner layer of the fruit. 



The pericarp may be hard and dry, or soft and succu- 

 lent ; in a few cases a portion may be succulent and the 

 remainder hard. In the Plum and Cherry the epicarp and 

 mesocarp are succulent, and the endocarp is hard (Fig. 218). 

 The Hazel-nut possesses a very hard pericarp which is broken 

 off when the seed within is used for food (Fig. 221). 



When the fruit is formed from a single carpel, as in the 



-R 



Ac-" 



FIG. 217. A 1 , Strawberry; B 1 , longitudinal section of Strawberry; Ac, carpel; 

 R, swollen receptacle. 



Bean and Pea, it is called a monocarpous fruit. If two or more 

 separate carpels take part in the formation of the fruit, as in the 

 Buttercup and Raspberry, the fruit is apocarpous. A syncarpous 

 fruit is formed from a syncarpous gyncecium, as in the Poppy, 

 Lily, and Wallflower. 



Fruits may dehisce or open to liberate the seeds, when they 

 are called dehiscent fruits. If the fruits do not open to liberate 

 the seeds, but the seeds germinate within, and the young plant 

 break through the wall of the fruits, they are called indehiscent 

 fruits. 



When the fruit is the result of a single gynoecium it is called 

 a simple fruit, and when produced from a number of carpels it 

 is said to be a compound fruit. Thus, both monocarpous and 

 syncarpous fruits are simple, while apocarpous fruits are 

 compound. 



Q 



