CRUCIFERAE (MUSTARD FAMILY) 



175 



Canada. It is immensely prolific and its seeds have long vitality. 

 Cold does it no harm and chemical sprays that kill other 

 Mustards do not in the least affect it. Other crops cannot crowd 

 it out, for it is the better crowder, seeding in dense timothy sod 

 almost as readily as in a mellow fallow. Blooming "from snow 

 to snow" and constantly developing fruit, 

 it requires and absorbs much of the food 

 and moisture in the soil, starving the ac- 

 companying crops almost to worthless- 

 ness. T. N. Willing, Chief Weed Inspector 

 of the Northwest Territory, says, "It 

 will pay well to drop all other work and 

 fight this weed when it is first noticed." 

 (Fig. 120.) 



Stem six inches to two feet tall, smooth, 

 bright green, often simple but usually 

 branching at the top. Root-leaves long 

 oval, broadest at tip, with long petioles; 

 stem-leaves lance-shaped and clasping 

 with a pair of pointed ears at the base ; 

 all leaves coarsely toothed. When bruised, 

 the plant exhales a most disgusting gar- 

 licky odor; if it is eaten by milch cows, 

 the dairy products are spoiled. Flowers 

 clear white, very small, in thick, flat 

 terminal clusters ; beginning to mature at 

 the bottom of the cluster, they leave be- 

 hind a long raceme of the fruits, standing 

 out on slender, wiry, upcurved pedicels 

 about as long as themselves. Silicles flat, 

 about three-fourths of an inch across, 

 pale green at first, broadly winged at the 

 sides, notched at the top, two-celled, the division being across 

 the narrowest part, as in Shepherd's Purse ; each side contains 

 two to eight seeds. As the pods ripen they turn to a rusty 

 orange color, making the weed very conspicuous when grow- 

 ing with grain or clover. Seeds deep reddish brown, flattened 

 ovoid, roughened with fine curved ridges about a central groove. 



FIG. 120. Penny Cress 

 (Thlaspi arvense). X i 



