STRUCTURE OF FRUIT. 137 



from the epicarp and endocarp ; but however thin it 

 may be, we are always compelled to admit its existence, 

 since it is only by this plexus of vessels that the organ 

 is nourished. 



In the same manner as we have seen, in speaking of 

 leaves, that the more stomata there are, the thinner will 

 this plexus be ; so, among carpels we shall find three 

 particular states of the mesocarp connected with the 

 structure of the epicarp. Thus, sometimes the carpellary 

 leaf is membranous, and almost scarious, and then the 

 epicarp has no stomata, and the endocarp little or no 

 flesh, as in Amaranthus ; sometimes the epicarp has 

 stomata, and the endocarp has the ordinary foliaceous 

 texture, as in the Pea; sometimes the epicarp has no 

 stomata, and the endocarp becomes thick and fleshy, as 

 in succulent leaves ; this is what we see in the Peach 

 and other fleshy fruits. 



Fruits compared together when ripe, present different 

 kinds of adhesion or separation of the mesocarp ; thus it 

 adheres sometimes very strongly to the endocarp, as in 

 the Nectarine, or Beau ; at other times it easily separates, 

 as in the Peach, or husk of the Walnut, or in Entada, in 

 which it is detached naturally or easily, remaining free 

 from the epicarp. The adhesion of the mesocarp with 

 the epicarp is equally variable ; thus the latter is easily 

 detached in the Peach, with difficulty in the Cherry. 



The leaves which form the carpels are presented 

 under several different systems ; thus, they may be : — 



1st. Curved in the form of a cylinder, tapering to the 

 two extremities, having the two margins beveled off 

 upon one another, and the back round, as in Colchicum, 

 Delphinium, Sterculia, &c. 



2d. Curved in the form of a horn, so that the margins 

 approach each other at the base, and the upper part re- 

 mains open, as in Astrocarpus, Helleborus, Isopyrum, &c. 



