io6 THE STRUCTURE OF ECONOMIC PLANTS 



Dry-Fleshy Fruits. — Several of the major fruit types are in 

 part dry and in part fleshy. In this intermediate group are the 

 drupe, pome, aggregate, and multiple types. The drupe or stone fruit 

 develops from a single carpel in v^^hich the pericarp is differentiated 

 into a thin epicarp or skin of the fruit, a fleshy mesocarp, and an 

 endocarp which is hard and stony (plum, apricot, peach). (Fig. 39, 

 F, G.) The mature fruit commonly contains a single seed, but two 

 ovules generally arise, one of them aborting as the fruit develops. 

 The term drupe in a less restricted sense is also applied to the fruits 

 of some members of the Caprifoliaceae (elder. Viburnum) which are 

 tricarpellate and may have one to three seeds. 



In the pome (apple) the fleshy outer portion is formed by the 

 undiverged floral parts which surround the ovary, together with 

 the carpels in whole or in part. The pericarp consists of a papery 

 endocarp forming the inner limit of the core, and a fleshy mesocarp 

 and exocarp. (Fig. 40, C, D.) The aggregate fruit is composed of 

 several simple fruits developed from a flower having several simple 

 pistils. In some instances, the axis does not comprise a part of the 

 edible structure. The raspberry represents a form in which the re- 

 ceptacle is readily separated from the small edible drupes; while, in 

 the blackberry, it is not. In the strawberry, the edible tissue is the 

 fleshy receptacle on which a large number of small akenes are borne. 



The multiple fruit differs from the aggregate in that it is the 

 product of the conjoint development of several flowers, rather than 

 being derived from several pistils of a single flower. While the 

 multiple types resemble one another in this principle of organiza- 

 tion, they may be quite variable with respect to the manner of 

 differentiation and the number of accessory parts that enter into 

 the fruit structure. In the fig, the fleshy receptacle is a hollow 

 chamber on the inner surface of which the flowers are borne. The 

 flower cluster may contain both staminate and carpellate flowers or 

 these may occur in separate inflorescences. This type of multiple 

 fruit is sometimes called a synconium. In the mulberry, the stami- 

 nate and carpellate flowers develop in separate inflorescences; and, 

 in the latter, each flower develops a fruit which is nut-like and 

 surrounded by a fleshy pericarp. As the fruits develop, they be- 

 come closely aggregated; and, together with the fleshy receptacle 

 or axis, form a multiple fruit or pseudocarp. 



A third multiple type is the pineapple. Ananas, in which the 

 flowers are also borne in dense heads that are crowned by a tuft of 



