BLACK, BROWN, OR RED MUSTARD 381 



Brassica to each other is not clear, as hybrids and crosses are 

 frequent. Possibly all are derived from one species : some 

 authorities are, however, disposed to notice two species with 

 varieties, thus : — 



Species i. Brassica campesins L. 



Oil-yielding summer variety : form annua, (a) Summer turnip-like Rape. 



Do. winter do. : form oleifera. \jb) Winter do. do. 



Variety with thick fleshy ' root ' form rapifera 1 , . „ „^>i „ 



= B. Rapa L. Y'^ Common White Turnip. 



Species z. Brassica Napus L. 



Oil-yielding summer variety : [orm annua, (o) Summer Swede-like Eape. 

 Do. winter do. : form oleifera (i) Winter do. do. 



Variety with thick fleshy ' root ' ; form rapifera : Swede Turnip : 



B. Napo-brassica D.C. i. white-fleshed. 



B. Rutabaga. 11. yellow- do. 



13. Black, Brown, or Red Mustard {Brassica nigra Koch.= 

 Sinapis nigra L.). — An annual plant grown for its seeds. The 

 latter are ground and the 'flour,' after removal of the dark- 

 coloured testas, is used as a condiment, namely, ordinary table 

 mustard. 



The seeds contain oil which is sometimes extracted and used 

 for burning in lamps, in the same manner as rape or colza 

 oil. 



The plant is a wild indigenous plant in this country, but most 

 frequently met with under hedges and in waste places as an 

 escape from cultivation. The seeds have the property of re- 

 maining in the ground for several years without germinating, 

 and when a crop is once allowed to seed, some of the shed seed 

 is certain to give rise to plants in many of the subsequent crops 

 grown on the same land. It may thus become a troublesome 

 pest of arable land. 



Seed and Germination. — The seeds are oval with a 

 reddish-brown coloured testa when well harvested, and the 



