THE FRUIT: PARTS OF THE FRUIT 



205 



the pea, bean, etc., so that the seed when ripe becomes free from 

 the wall of the ovary and separates by the splitting of the fruit. 



323. The fruit consists of the ripened ovary including the 

 seed, and in many cases other accessory parts of the flower. 

 The fruit may be formed of a single pistil either simple or com- 

 pound, or it may be formed of several simple pistils crowded 

 together (aggregate, or collective fruits), or there may be acces- 

 sory parts of the flower (calyx, receptacle, etc.) which reinforce 

 the fruit (accessory or reinforced fruits). 



Fig. 157- 



Section of drupe, or stone fruit of peach, showing the fleshy exocarp, stony endocarp, and 

 the "meat" or embryo within. 



324. The pericarp. The wall of the ripened ovary is called 

 the pericarp. It is the part of the fruit which envelops the seed, 

 and may consist of the carpels alone, or of the carpels and the 

 adherent part of the receptacle, or calyx. In many fruits the 

 pericarp shows a differentiation into layers, or zones of tissue, 

 as in the cherry, peach, plum, hickory nut, etc. In others there 

 is no apparent differentiation into distinct layers. Sometimes 

 the pericarp is firmly joined with the seed as in the wheat, corn, 

 etc., while in others it may be easily separated, as in the sun- 

 flower. 



