loi THE STRUCTURE OF ECONOMIC PLANTS 



The Fruit. — The jruit of the angiosperms consists of the ovary 

 together with any closely associated parts. The ovary may be 

 simple, as in the akene (buttercup), pod (pea), and the drupe (plum); 

 or it may involve two or more carpels, as in the silique (radish), 

 the berry (tomato), and many others. Associated structures which 

 may be a part of the fruit in certain types include the receptacle, 

 sepals, basal portions of the stamens, and the axis itself. In some 

 special cases (artichoke), the floral bracts and all the floral parts 

 may constitute the fruit if the whole head is considered as 

 such. 



There are several systems of classification of fruit. These vary, 

 depending upon the point of view upon which the classification is 

 based, and the characters which are regarded as determinative. On 

 the basis of the texture of the pericarp, and accessory parts when 

 present, fruits may be classified as being dry (papery, stony), fleshy, 

 or an intermediate combined type. In the dry types, the entire 

 pericarp or ovary wall becomes desiccated as the fruit matures. 

 Such fruits may be further subdivided into dehiscent and indehiscent 

 types, dependent upon whether they do or do not open at maturity. 



In the completely fleshy types, the entire pericarp, together with 

 accessory structures in special cases, becomes succulent. In the 

 intermediate dry-fleshy forms, part of the pericarp becomes desic- 

 cated; or, in some cases, hardened; while other regions of the 

 ovary wall may remain fleshy. In such types (drupe) the pericarp 

 consists of an outer fleshy portion or exocarp and the endocarp, 

 which forms a stony pith. These categories may be further subdi- 

 vided on the basis of the number of carpels and accessory structures 

 involved in the development of the fruit. (Table II.) 



Dry Fruits. — The principal indehiscent dry fruits are the cary- 

 opsis or grain, the akene, the schizpcarp, and the nut. The caryopsis 

 develops from a single carpel and contains a single seed. In its 

 development, the integuments may be partially disorganized and 

 the remainder of the seed coat becomes so closely appressed to the 

 pericarp that the two structures cannot be readily separated in the 

 mature grain. The akene may be the product of the development of 

 one or two carpels, the former being the case in the Ranunculaceae, 

 and the latter obtaining in the Compositae, in which the receptacle 

 is also a part of the fruit. (Fig. 39, A, B.) The fruit is one-seeded, 

 differing from the caryopsis in that the pericarp can be removed 

 from the mature seed. 



