CRUCIFERAE (MUSTARD FAMILY) 



193 



Kansas, northwestward to Washington ; all the Canadian prov- 

 inces from Quebec to Vancouver Island. 

 Habitat: Grain fields and grasslands, waste places. 



A native of Central Europe brought to this country in impure 

 commercial seeds ; by this agency it still travels, and no doubt jour- 

 neys farther in this way than when wind-driven about the country. 



Stem two to four feet high, slender, smooth, and exceedingly 

 branched and bushy. Leaves 

 deeply pinnatifid, the segments 

 nearly linear, toothed or entire, 

 the upper ones reduced to 

 thread-like thinness ; when the 

 plant ia young the lower leaves 

 are downy and the basal ones lie 

 on th^ ground in rosette form, 

 but these wither away and the 

 later leaves are smooth. Flowers 

 pale yellow, about a third of an 

 inch across, on elongating ra- 

 cemes that leave behind alter- 

 nating rows of stiff, diverging, 

 needle-like pods, two to four 

 inches long but hardly thicker 

 than their short pedicels. Each 

 pod usually contains more than 

 a hundred seeds the fecundity 



of the weed is almost incredible. 



i^T, ,, , FIG. 136. Tumbling Mustard (Sisym- 



When mature the stems become ^^ aUissimum ^ x i. 



very brittle, breaking away at 



the surface of the ground, and the plants are afterward the sport 

 of the winds; on the prairies they often roll for miles, but in 

 fenced and uneven ground they are battered to and fro, seeding 

 the soil the more thickly for such restriction. (Fig. 136.) 



Means of control 



Sow clean seed. Harrow seedlings out of grain fields in the spring. 

 Harvest infested meadows before the first seeds ripen. Burn over 



