52 SELECTED WESTERN FLORA 



3. THLASPI. Penny Cress. 



Pod obcordate, flattened, with, the partition forming the short axis ; 

 seeds 2-8 in a cell. Low plants with the stem leaves clasping, and 

 racemes of small white flowers. 



1. T. arvense, L. Frenchweed or Stinkweed. 



A smooth annual or winter annual with wings on the petioles of the lower 

 leaves, and a broadly winged pod -with a deep notch at the top. Fields and 

 waste places, a very troublesome introduced weed. 



4. LEPIDIUM. Pepper Grass. 



Pods small, round, slightly notched at the top, flattened as in the 

 preceding, with a solitary seed in each cell; flowers minute. 



1. L. apetalum, Willd. 



Leaves toothed or pinnatified ; pod slightly winged ; petals usually want- 

 ing. Dry waste places, Man'-Alta. 



6. CAPSELLA. Shepherd's Purse. 



Pod triangular, flattened, wingless; seeds nu- 

 merous ; petals white. 



1. C. Bursa-pastfiris, (L.) Medic. 

 Fig. 40. — Capsella Stem leaves arrow-shaped, sessile ; root leaves form- 

 Bursa-pastoris. ing a rosette, but extremely variable. A common weed 

 in cultivated places, particularly about dwellings. 



6. NESLIA. Ball Mustard. 

 Pod globular, slightly beaked, with a single seed ; flowers yellow. 



1. N. paniculElta, (L.) Desv. 



A slender annual with simple stem, sagittate clasping leaves, and an 

 elongated raceme of small yellow flowers. Grain fields and waste places, 

 introduced. 



7. BRASSICA. Turnip, Mustard. 



Pod stout, sometimes 4-sided, with a stout beak; leaves lyrate 

 to pinnatifld ; annuals or winter annuals'. 



1. B. arvensis, "(L.) Ktze. Wild Mustard, Charlock. 



Erect, 1-2 ft. high, usually hairy, branching above ; lower leaves petioled, 

 lyrate ; upper leaves sessile, entire or nearly so ; flowers large, bright yellow ; 



