464 STRUCTURE AND LIFE HISTORIES 
family. The mustard family contains many valuable 
economic plants, such as the white and black mustard, 
radish, cabbage, turnip, kohlrabi, and brussels sprouts. 
413. Rose Family (Rosaceae). One of the common 
wild roses (Rosa Carolina) illustrates a type of flower 
structure more advanced in several ways than that of 
Ranunculus. The flowers, with rare exceptions, have 
FIG. 347. Black mustard (Brassica nigra). 
sepals and petals which are borne on the margin of a 
well-developed hypanthium, formed by the enlargement 
of the torus, at the extremity of the peduncle. The 
numerous stamens are always inserted on the sepals 
(adnation of parts), and the pistils vary from one to 
many. In marked contrast to the numerous horticultural 
varieties of the rose, the wild roses are single; that is, they 
have one circle of petals (usually five). The "doubling" 
of the cultivated varieties is caused by the replacement of 
