THE FRUIT. 195 



But sometimes the mesocarp is excessively thin, in dry fruits 

 for example, such as the pod of the pea, or the fruit of the 

 gilliflower. In the nut the three parts are blended together ; 

 in the peach they remain separate. In the latter fruit the 

 epicarp forms the skin, the mesocarp the fruit or edible part 

 of the peach, and the endocarp, the stone in its centre which 

 covers the kernel and seed. 



Whatever may be the thickness of the walls of the pericarp, 

 its anatomical constitution remains the same. It is always 

 formed of two membranes, the epicarp and the endocarp, and 

 an intermediate bed of tissue called the mesocarp, sometimes 

 thin and dry, at other times thick and succulent. Such is the 

 constitution of the leaf from which it is derived, and of which 

 it is only a peculiar modification. 



This remarkable transformation of the leaves is not peculiar 

 to fruits, for in more cases than is usually supposed, similar 

 changes take place in the other floral organs. Thus the calyx is 

 changed into a hard crustaceous body in Salsola and in Spinage; 

 and is red and juicy in the Strawberry blite and Winter- 

 green (Gaultheria), being in both instances commonly mistaken 

 for the fruit from which it is wholly distinct. In the Yew, 

 the bracts enveloping the seed become pulpy and berry-like. 

 Nearly the whole bulk of the apple is a thickened calyx. The 

 pulp of the Strawberry, as we have already intimated, is 

 nothing else but the enlarged and juicy extremity of the 

 1 flower-stalk or receptacle. Examples might be multiplied 

 proving that all the appendages of the axophyte are subject to 

 these transformations, which are erroneously imagined to be 

 peculiar to the fruit. 



The fruit, like the pistil of which it is the final development, 

 may be either simple or compound. The fruit is simple when 



