A GUIDE TO THE WILD FLOWERS 135 



more nearly oblong, and the stem leaves more plentiful. Pods 

 about 13^ in. long, stiffly erect. Among rocks. New Bruns- 

 wick to Georgia, and westward. May-Sept. There are several 

 related species. 



395. Rock-cress. Arabis lyrata. A weak herb, scarcely 12 in. 

 tall. Basal leaves cut or divided, suggesting a lyre, 1-2 in. 

 long. Stem leaves not clasping the stem, practically toothless 

 and undivided, about ^ in. long. Flowers scarcely 14 ^^- wide, 

 in a terminal cluster, white. Pods about i in. long, ascending, 

 but scarcely stiffly erect. In rocky or sandy places. Ontario to 

 Tennessee, and westward. April-Sept. Fig. 395. 



396. Flowers yellow. (Nos. 397-409.) 



Leaves undivided, not cut or compound no. 405 



Leaves cut, divided, or compound 



Plants without conspicuously yellow juice 



Pods about 3 times as long as broad 



Yellow Water-cress no. 397 



Pods about 8 or 10 times as long as broad 

 Pods conspicuously pinched between the seeds 

 Pods covered with stiff hairs . . White Mustard no. 398 



Pods scarcely hairy Wild Radish no. 399 



Pods not pinched, or only slightly so 

 Pods about y> in. long 

 Leaf lobes pointing backward . Hedge Mustard no. 400 



Leaf lobes not pointing backward 



Black Mustard no. 401 



Pods I in, or more long 



Plants 2-4 ft. high Tall Sisymbrium no. 402 



Plants about 18 in, high or less . Yellow Rocket no, 403 

 Plant with conspicuously yellow juice Celandine no. 404 



397. Yellow Water-cress. Radicula palustris. A branching 

 smooth herb with deeply cut leaves, the segments toothed. 

 Lower leaves stalked, 3-6 in. long, the upper ones nearly 

 stalkless and smaller. Flowers yellow, about % in. wide, in 

 a long terminal cluster. Pods about i in. long, 3 times as long 

 as broad. Throughout North America in wet places. May- 

 August. Fig. 397. There are several related species, one of 

 them, R. hispida, has a hairy stem, and frequently grows 

 4 ft. tall. It is found in wet places from New Brunswick to 



