CRUCIFER^ 339 



variety used for its green foliage, and hence is treated as an 

 annual. This type of rape is used as a fall pasture for sheep,- 

 pigs or cows, as a green manure, and as a soiUng crop, catch 

 crop, or cleaning crop. "Rape cake," made from the seeds 

 by expressing the oil, is used as a stock food, and the oil 

 itself is of some value. About 42 per cent, of the seed is 

 composed of rape oil. 



BRASSICA NIGRA (Black or Brown Mustard) 



Description. — The black mustard is an annual herb 2 to 

 7 feet tall, and freely branching. The lower leaves are hairy 

 and deeply pinnatifid, with one large, terminal lobe and 

 two to four smaller, lateral ones; the lobes are coarsely 

 toothed. The upper leaves have much shorter petioles than 

 the lower, or they are entirely sessile, and the blades are 

 entire and oblong or lanceolate. The flowers are bright yel- 

 low. The pods are slender, four-sided, oppressed against the 

 stem, and measure about }4 inch or more in length. The 

 seeds are dark brown. 



Black mustard is a native of Europe and Asia. It has 

 become naturahzed in this country and has escaped from 

 cultivation, becoming frequently a troublesome weed. 

 . Black mustard resembles charlock {Brassica arvensis), 

 one of the worst pests in grain fields of the Middle West. 

 Charlock has long, knotted pods with stout beaks, while the 

 pods of black mustard are short, four-angled, and with short 

 beaks. The pods of white mustard are somewhat bristly. 

 Charlock, black mustard and white mustard are propagated 

 by seeds. In their eradication, no attention needs to be 

 directed toward the starving out of rootstocks, which are so 

 typical of perennial weeds. Every effort is made to prevent 

 them from going to seed. Much success has attended the 

 use of chemical herbicides, chiefly iron sulfate, in eradicating 



