88 FRUIT. 



of beans, for example), but at other times it becomes hard and 

 brittle, and forms what is named the stone of the fruit. 



17. Each carpel has two edges, one named dorsal, which cor- 

 responds to the primary nerve of this appendage, and another, 

 called ventral, which results from the agglutination of these two 

 edges to each other ; and, when the edges of the carpel, in place 

 of being simply joined, are folded inwards, they constitute an in- 

 ternal partition which divides the ovarian cell or cavity into two 

 parts. 



18. The carpels are sometimes single in each flower, some- 

 times more or less numerous, and in this last case they may be 

 agglutinated to each other in different ways, and constitute com- 

 pound fruits, the appearance of which varies. Sometimes they 

 are very distinct externally, at other times are united with the 

 torus and with the calyx in such a manner that no trace of ex- 

 ternal union can be seen, and constitute a simple fruit (fig. 116). 

 In general the cells of different carpels united into a single mass, 

 are perfectly distinct, and the compound fruit consequently pre- 

 sents as many cells as there are carpels ; but sometimes the car- 

 pels are not closed along their ventral edge, and then the cells of 

 all these organs communicate with each other, and constitute a 

 single cavity, of which the circumference only is more or less 

 lobed. And it also happens sometimes that the partitions, which 

 separate the neighbouring cells, are in part destroyed by the pro- 

 gress of maturation, and all the cells of a compound fruit are 

 united into a single cavity, the centre of which is occupied by a 

 species of column formed by the remains of the ventral edge of 

 the carpels thus united. Often one or more carpels abort and 

 leave no trace of their existence. Finally, not only may the 

 carpels of the same flower be united to each other, but sometimes 

 those of neighbouring flowers approximate, and become agglu- 

 tinated into a single mass, and thus constitute what is termed an 

 aggregate fruit. Figs, and the cones of the pine tree are com- 

 posed in this way. 



19. At the period of their maturity fruits present still other 

 important differences ; some are indehiscent (from the Latin in, 

 not, and dehiscere, to gape wide open), that is, they do not open 

 spontaneously ; others, on the contrary, open of themselves, and 

 are called for this reason, dehiscent. In simple fruits, the open- 

 ing generally takes place at the agglutinated edges of the carpel, 

 or by this and the dorsal edge at the same time, so that the fruit 

 is divided into two pieces called valves. In the compound fruits, 



17. What is meant by the dorsal and ventral edges of a carpel ? 



18. Have all flowers the same number of carpels? What is meant by 

 an aggregate fruit ? 



19. What is meant by an indehiscent fruit ? What is a dehiscent fruit 1 



