COMPOSITION OF THE FRUIT—PERICARP. 299 
layer, being frequently of a fleshy or succulent nature, is also 
then termed the sarcocarp ; while the inner layer, from its hard- 
ness in some fruits, is likewise called the stone, putamen, or 
pyrene. When the pericarp consists simply of the matured 
walls of the ovary, its three parts correspond to the three paren- 
chymatous layers of the lamina of the carpellary leaf: thus, the 
epicarp represents the epidermis of the under surface, or that 
on the outer surface of the ovary ;, the mesocarp corresponds 
to the general parenchyma of the lamina, or of that of the 
ovary ; and the endocarp to the epidermis of the upper surface, 
or to the inner lining of the ovary. When the calyx is com- 
pletely united to the ovary, the relation of parts must necessarily 
differ, and probably somewhat 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 blade of a leaf, is traversed by 
fibro-vascular tissue. 
Fic. 662. 
Fig. 662. Foliaceous bladdery legume of the Bladder Senna (Colutea 
arborescens). 
In some cases the pericarp clearly indicates its analogy to the 
blade by remaining in a condition not very dissimilar to that 
part of a leaf folded inwards and united by its margins, as in 
the Bladder Senna (jig. 662); such a fruit is described as folia- 
ceous or leafy. Generally speaking, however, one or more of the 
layers of the pericarp become more developed, by which its re- 
semblance to the lamina of a leaf is rendered much less evident. 
The epicarp usually retains an epidermal appearance, suffering 
but little change, except in becoming slightly thickened. The 
endocarp is more liable to alteration, and frequently differs 
much in appearance from the corresponding part of the blade 
of a leaf or ovary ; thus, its cells sometimes become hardened 
by thickening layers in its interior and form a stony shell 
surrounding the seed, which is commonly called the putamen. 
The mesocarp is however the layer which commonly presents the 
greatest development, and differs most in appearance and tex- 
ture from the general parenchyma of the lamina of a leaf. 
The above remarks will be rendered more intelligible by 
being illustrated by a few examples taken from well-known 
