400 



GENEKAL BOTANY 



CRUCIFERAE (MUSTARD FAMILY) 



The Oruciferae include some of the most important culti- 

 vated commercial varieties of plants, such as the cabbage, turnip, 

 radish, and cress. The most distinctive features of the family are 

 the acrid juice and the peculiar structure of the flowers and fruit. 



Reproduction. The parts of the flowers are in sets of four 

 members each, the petals being so related as to form a cross, 

 so that the flowers are said to be cruciate. In Fig. 251, a, the 

 flower of one of the turnips (Brassica) is shown in long section, 

 so as to illustrate the relations of the floral parts. The pistil 

 is composed of two sporophylls, or carpels, and the cavity of 



Carpel 



FIG. 251. Flowers and fruit of a cruciferous plant (Brassfca) 



a, young flower with unripe anthers; 6, older flower, anthers shedding pollen; 

 c, floral plan ; d, fruit (silique) 



the ovary is separated by a false partition, or septum, which 

 runs between the two placental ridges (see the section of the 

 ovary in the ground plan of a cruciferous flower, Fig. 251, c). 



The stamens are six in number, two short and four long, the 

 four long stamens representing two stamens which branch at 

 the base. Cross-pollination may be effected through the agency 

 of insects, or self-pollination from the anthers of the long stamens. 

 When the flowers are young (Fig. 251, a), the anthers of the long 

 stamens are often separated from the stigma by the movements 

 of the filaments. In more mature flowers () the anthers move 

 toward the stigma, so that self-pollination is effected. The fruit 

 (ef) is a pod, called a silique. When ripe the two halves of the 

 pod separate from the septum, or partition, to which the seeds 

 cling, and the seeds are then disseminated. 



