THE FRUIT. 193 



which is formed by the walls of the ovary, and which deter- 

 mines the general form of the fruit. Since the walls of the 

 ovary constitute the pericarp, it must be constantly present in 

 all fruits. When the fruit is a single cell and contains only one 

 seed, the pericarp is so thin and is united so completely with 

 the seed, that they can hardly be distinguished from each 

 other. Such, for example, are the fruits of the grasses, Cype- 

 raceae, and syngenesious plants, which were formerly regarded 

 as seeds, but which are in reality pericarps or seed-vessels 

 enclosing a seed. 



A fruit may be usually distinguished from a seed, or other 

 organ assuming its character, by the presence of some vestige 

 of the style. Thus the carpels of the Ranunculus, (Fig. 90,) 



Fig. 90. 



Fig. 90. Carpels of the Ranunculus with a few stamens, the calyx and corolla having 

 been removed. One of the carpels magnified, showing it to be a single-seeded vessel 

 with the pericarp applied close to the seed. Such fruits resemble seeds in appearance, 

 the style and stigma, s, aid in distinguishing them from seeds. 



which are vulgarly regarded as seeds, are at once determined 

 to be seed-vessels by their apiculate summit, the vestige of the 

 style. In the same manner we discover that the strawberry is 

 not a single fruit, but an enlarged fleshy receptacle bearing the 

 simple fruits at its surface. (Fig. 91.) 



The pericarp, like the leaves from which it proceeds, is 

 composed of two plates of epidermis, between which exists a 



17* 



