CRUCIFER^— MUSTARD FAMILY 



BLACK MUSTARD 



Brdssica nigra 



Annual. A large, branching plant bearing many 

 yellow crucifer flowers, common in fields, roadsides, and 

 waste places. A well-known weed in California. Natural- 

 ized from Europe. June-November. 



Stem. — Two to seven feet high, branching widely. 



Leaves. — Alternate, petioled, large, coarse, rough, dark 

 green. Lower leaves are eight to twelve inches long and 

 consist of a central midrib which bears two or three 

 pairs of small irregular divisions and a large terminal 

 lobe which is very irregularly lobed and toothed. The 

 upper leaves are less divided and the uppermost are linear, 

 entire, and commonly drooping. 



Flowers. — Yellow crucifers, in long, dense racemes, 

 both terminal and lateral. 



Sepals. — Four, pale yellow, narrow, widely spreading. 



Petals. — Four, with long claw and spreading blade. 



Stamens. — Six, four long and two short. 



Pistil. — Ovary two-celled. Pods narrowly linear, closely 

 oppressed to the axis of the raceme, one-half to three- 

 fourths of an inch long. Seeds dark brown, pungent. 



Pollinated by flies and bees. Nectar-bearing. Stamens 

 mature before the stigma. 



Three common Mustards linger in our fields and 

 wander along our roadsides. The first is an April 

 blossom continuing into May. This is the Winter 



71 



