ORGANS OF REPRODUCTION. 801 



in some fruits, is then termed the stone or pulamen. When the 

 pericarp consists simply of the matured walls of the ovary, its 

 three parts correspond to the three parenchymatous layers of the 

 carpellary leaf : thus the epicarp represents the epidermis of the 

 under surface of a true leaf, or that on the outer surface of the 

 ovary; the mesocarp corresponds to the general parenchyma of 

 a leaf, or that of the ovary ; and the endocarp to the epidermis 

 on the upper surface of a leaf, or to the epithelium or inner hning 

 of the ovary. When the calyx is completely united to the ovary, 

 the relation of parts must necessarily differ, and probably some- 

 what vary according to circumstances : thus in the Apple, which 

 we may take as an illustration of an inferior fruit, the epicarp 

 corresponds to the epidermis of the under surface of the calyx; 

 the mesocarp to the rest of the calyx, and the whole of the ovary 

 except the inner lining, which corresponds to the endocarp. 

 The parenchyma of the fruit, like that of the ovary and the true 

 leaf, is traversed by fibro-vascular bundles. 



In some cases the pericarp clearly indicates its analogy to 

 theleaf, by remaining j'm. 647. 



in a condition not 

 very dissimilar to 

 that organ folded in- 

 wards and united by 

 its margins, as in 

 the Bladder Senna 



\ /£ cA-?\ Fig.Ml. Foliaceons bladdery legume of the 



Cens), \Jig. 647) ; Bladder Senna {Colutta arhorescem). 



such a fruit is de- 

 scribed as/oliaceous or leafy. Generally speaking, however, one 

 or more of the layers of the pcricarj} become more developed, by 

 which its resemblance to the leaf is rendered much less evident. 

 The epicarp generally retains an epidermal appearance, suffering 

 but little change, except in becoming slightly thickened. The 

 endocarp is more hable to alteration, and frequently differs much 

 in appearance from the corresponding part of the leaf or ovary. 

 Thus its cells sometimes become hardened by secondary de- 

 posits, and form a stony shell surrounding the seed, called the 

 putamen, as already noticed.- The mesocarp is the layer which 

 commonly presents the greatest development, and differs most 

 in appearance and texture from the general parenchyma of 

 the leaf. 



The above remarks will be rendered more intelligible by being 

 illustrated by a few examples taken from well-known fruits. 

 In the Peach, Apricot, Cherry, Plum, &c.. the separable skin is 

 the epicarp; the pulpy part, which is eaten, the mesocarp or sar- 

 cocarp ; and the stone enclosing the seed, the endocarp or 

 putamen. In the Almond, the seed is enveloped by a thin woody 

 shell, constituting the endocarp, which is itself surrounded by si 



