52 THE FRUIT. 



the non-development of five of the ovules, while the sixth grows so rapidly as to 

 obliterate the dissepiments and occupy the whole space. The same change also 

 takes place in the hazle-nut. The ovary of the birch is two-celled and two- 

 ovuled, but, by the suppression of one cell with its ovule, the fruit becomes one- 

 celled, 



1. OF THE PERICARP. 



111. The FRUIT consists of the pericarp and the seed; the 

 former may be wanting, but the latter is essential. 



a. Truly naked seeds are found in few plants, except the Coniferse, where the 

 pollen falls directly upon the ovules without the intervention of the pistil. The 

 seeds of the sage and the borage, with their respective tribes, generally said to be 

 naked, are not so in fact, for each, seed being the product of an ovary with one 

 ovule must necessarily be a one-seeded pericarp. 



112. The PERICARP (neQi, around, xagnog, fruit) is the covering 

 or envelope of the seeds, of whatever nature it may be. It 

 consists of three different parts. 1. The epicarp (em, upon) is 

 the outer integument, or skin. 2. The endocarp (evdov, within) 

 called also putamen or shell, is the inner coat, and the sarco- 

 carp (cr>, flesh) is the intervening fleshy substance. 



a. Thus, in the peach, the skin is the epicarp, the fleshy pulp the sarcocarp, and 

 the shell of the stone the endocarp. In the apple or pear, the endocarp forms the 

 glazed lining of the cells, the epicarp the epidermis, and the sarcocarp the inter- 

 vening pulp. 



1 13. The growth of the fruit depends upon the absorption of sap from the parts 

 below. This fluid, finding no growing axis to be prolonged in the usual manner 

 into a branch, is accumulated in the pistil and adjacent parts, is condensed by 

 evaporation, and elaborated into cellular matter by the external surfaces, which 

 still perform the functions of true leaves. Thus these parts become gradually- 

 distended into the form and dimensions of the fruit. 



114. The process of ripening consists of certain chemical changes, effected by 

 the combined action of heat, light, and air. In its earliest stages, the pericarp 

 consists of a structure similar to that of leaves, being composed of cellular and 

 ligneous tissue, with an epidermis and stomata (35, 37). 



a. Secondly, the fleshy pulp, or sarcocarp, is developed, and becomes sour by 

 absorbing from the air an excess of oxygen, which is the proper acidifying prin 

 ciple. 



b. Lastly, when the fruit lias attained its full growth, the pulp becomes gradu 

 ally sweetened and softened, by the formation of sugar at the expense of the 

 acids and of the ligneous matter, which before rendered it both sour and hard. 

 These transitions are exemplified by the apple, plum, currant, c., where the 

 greater portion of nutritive matter is stored up in the pericarp ; but in the fruit of 



