ROSE FAMILY 483 
pistil forms a pod known as the silique. The four petals, when 
opened out, suggest the Greek cross, — whence the name Cru- 
ciferae (Fig. 429). 
To this family belong such useful plants as the Cabbage, 
Turnip, Kohlrabi, Brussels Sprouts, and Rape. 
A number of plants of this family, such as Peppergrass, 
Shepherd’s Purse, White and Black Mustard, Tumbling Mus- 
tard, Indian Mustard, and Charlock are weeds. Their seeds 
Fic. 429.— The character of the Fic. 430. — 
plant, flowers, and fruit of the Black One of the Pop- 
Mustard (Brassica nigra). At the pies, showing 
right, a plant in flower (X75), and a the character of 
mature pod about natural size; at the the flowers and 
left, above, a flower, and below, an pod. After Le- 
open pod. After Vasey and Nature. comte. 
are troublesome impurities in commercial seeds, and the seeds 
of some are poisonous. 
Associated with the Mustard family is the Poppy family 
(Papaveraceae), characterized by a milky juice and represented 
by Bloodroot, common in the woods, and by the California 
Poppy from the juice of which opium is obtained (Fig. 430). 
Rose Family (Rosaceae). — To this family belong about 2000 
species of herbs, shrubs, and trees. In most plants of this 
family, there is an indefinite number of stamens and one to 
many separate carpels. The flowers of Strawberries and Black- 
berries, for example, have many stamens and many separate 
