I04 THE STRUCTURE OF ECONOMIC PLANTS 



mericarps split apart, each one resembling an akene in general 

 structure. This type is characteristic of the Umbelliferae and is 

 also found in the Geraniaceae. Where the mericarp is winged 

 (maple), the mericarp is called a samara or key. In the nut., the 

 structure resembles an akene, but the dry pericarp becomes thick 

 and hard. The term has been loosely applied to many fruits (al- 

 mond, walnut, cocoanut); seeds (Brazil-nut); and to legumes 



Fig. 39. Fruit types; A, B, akene; C, capsule of Iris; D, pod or legume of pea; E, tran- 

 section of same; F, G, the drupe, plum. 



(peanut); but among the true nuts are the acorn, chestnut, and 

 hazelnut. 



The principal dehiscent dry fruits are the follicle, legume, capsule, 

 and silique. The follicle and legume fruit are developed from single 

 carpels, and differ from each other primarily in their manner of 

 dehiscence. In the follicle, there is a single line of dehiscence which 

 occurs along the suture on its adaxial surface; while, in the legume, 

 two sutures are formed and the fruit splits along both at maturity. 

 (Fig. 39, D, £.) The capsule develops from two or more carpels 

 and may involve a portion of the axis as well (Iris). (Fig. 39, C) 

 The dehiscence in the capsule may be loculicidal or septicidal or both; 

 and in the poppy, it occurs by means of pores. In the loculicidal 

 type, the lines of dehiscence bisect each carpel longitudinally in 

 the region of the abaxial bundle; in the septicidal type, the lines 



