644 



BOTANY 



PAUT II 



the northern hemisphere. Annual, biennial, or perennial herbs 



without milky juice. Inflorescence racemose, usually without bracts 



or bracteoles. Flowers actinomorphic, always lateral, composed of 



bimerous whorls. Floral 



formula, K 2 + 2, C 4, A 2 + 4, 



G (2) (Fig. 654). The outer 



whorl of sepals stands in the 



median plane ; the four petals 



alternate with the sepals. The 



two outer stamens are shorter 



than the four inner ones 



which stand in the median 



plane. The latter correspond 



yroo 



FIG. 657. Transverse section of the seed 

 of Brassica nigra. rail, radicle ; cot, 

 cotyledons ; proc, vascular bundles. 

 (After MOLLER.) 



FIG. 658. Seeds of Cruciferae cut across 

 to show the radicle and cotyledons. 

 A, Cheiranthus cheiri(x. S);B,Sisym- 

 brium alliaria ( x 7). (After BAILLON.) 



FIG. 659. Brassica nigra. 

 OFFICIAL. 



nat. size.) 



to two stamens branched to the base. The carpels form a superior, 

 usually pod-like, ovary, which is divided into two chambers by a 

 false septum stretching between the parietal placentas (Fig. 656 D). 

 The fruit opens by the separation from below upwards of the main 

 portion of each carpel, leaving the seeds attached by their stalks to 

 the central portion formed by the placentas together with the false 

 septum. Rarely the fruit is indehiscent (e.g. Isatis). Embryo 



