SECT. V. THE FRUIT. 165 



might the more closely unite with the exterior part 

 of the fruit. 



Sometimes the shell is separable into several The pyre- 

 different divisions, each forming an enclosed cavity" 

 and containing a seed. In this case each division 

 assumes the appellation of a Pyrena, and the fruit 

 is said to be dipyrenous, tripyrenous, or polypy- 

 renous, according to the number of divisions into 

 which it separates. The partitions, however, as 

 in the compound nut, are effaced in the matured 

 fruit. 



ARTICLE 6. The Silique. The silique or pod Defim- 

 (PL VI. Fig. 6.) is a dry and elongated pericarp, 

 consisting of two valves with two opposite seams, 

 to which the seeds are alternately attached. It is 

 said to be siliculous if the transverse and longitu- 

 dinal diameters are equal, or nearly so, as in 

 Thlaspi ; and siliquose if the longitudinal diameter 

 exceeds the transverse so as to give to the pod an 

 oblong figure, as in Cheiranthus. In Brassica 

 the pod is cylindrical ; in Erysimum it is four-cor- 

 nered ; in Lepidium it is elliptical ; and in Thlaspi 

 it is inversely heart-shaped. The surface of the 

 pod is generally smooth or pubescent; but in 

 Raphanus and Sinapis it is covered with protu- 

 berances. Though the valves are generally two, yet 

 the pod of the genus Bimias is wholly without 

 valves. In Dent aria the valves open with a sudden 

 jerk, and in Cardamine, after opening, they roll 

 back spirally. Sometimes the partitions are pa- 



