288 THE FRUIT. 



out but soft within, as in a pepo ; or fleshy or berry-like without, 

 but indurated within, as in all stone-fruits, such as the cherry 

 and peach. 



541. When the walls of a pericarp consist of two layers of dis- 

 similar texture (as in a peach) the outer layer is called EXOCARP, 

 the inner ENDOCARP, these terms meaning exterior and interior 

 parts of a fruit. When the external layer is a comparatively thin 

 stratum or film, it is sometimes termed the EPICARP. When it is 

 fleshy or pulpy it is named S ARCOCARP. When the endocarp within 

 a sarcocarp is hard and bony or crustaceous, forming a shell or 

 stone, this is termed a PUT AMEN. When three concentric layers are 

 distinguishable in a pericarp, the middle one is called MESOCARP. 



542. Fruits may be divided into two kinds, in reference to 

 their discharging or retaining the contained seeds. They are 

 dehiscent when they open regularly to this end ; indehiscent when 

 they remain closed. There is a somewhat intermediate condi- 

 tion, when they rupture or burst irregularly, as in Datura Metel, 

 &c. Dry pericarps with single seeds are commonly indehiscent ; 

 those with several or many seeds mostly dehiscent. Seeds pro- 

 vided with a wing or coma or any analogous help to dispersion 

 are always in indehiscent pericarps. Permanently fleshy peri- 

 carps are indehiscent, stone-fruits as well as berries. But in 

 some stone-fruits (i. e., with indurated endocarp and fleshy 

 exocarp), such as those of Almond (Fig. 640) and Hickory, 

 the barely fleshy exocarp or sarcocarp dries or hardens, instead 

 of softening, as maturity is approached, and at length separates 

 from the putamen by dehiscence. 



543. Dehiscence, the opening of a pericarp for the discharge 

 of the contained seeds, is vgular or irregular; or, better, is 

 normal and abnormal. For most of the abnormal or non-typical 

 modes are as determinate and uniform in occurrence as the typi- 

 cal modes. A good English name for dehiscent pericarps in 

 general is that of POD. 



544. Regular or normal dehiscence is that in which a pericarp 

 splits vertically, for its whole or a part of its length, on lines 

 which answer to sutures or junctions, that is, along lines which 

 correspond to the margins or midribs of carpellary leaves, or to 

 the lines and surfaces (or commissures) of coalescence of con- 

 tiguous carpels. The pieces into which a pericarp is thus sun- 

 dered are termed VALVES. 



545. The normal dehiscence of a carpel is by its inner, ven- 

 tral, or ovuliferous suture, that is, by the disjunction of the 

 leaf-margins, as in Fig. 618. Its only other line of normal 

 dehiscence is by the opposite or dorsal suture, that is, down 



