30 KEY TO THE SPECIES 



1. Cardaiuine vallicola Greene (Greek-bank Cress). Stems clustered, 2-4 

 dm. high, rather stout ; leaves green with a few scattered hairs on the margins, 

 deeply lyrate-pinnatiftd, the leaflets 5-9, the terminal one large; siliques erect on 

 ascending pedicels, linear, tapering to the style. 



7. PHYSARIA (Bladder-pod) 



Low perennial herbs, with entire leaves ; the yellow flowers in terminal racemes, 

 and the silique membranous-inflated, the two cavities sub-globose. 



1. Physaria didymocarpa (Hook.) Gray (Double Bladder-pod). Stel- 

 lately pubescent throughout, the several stems and numerous root-leaves crowded 

 on the crown ; leaves broadly spatulate or obovate ; flowers large ; siliques deeply 

 emarginate above and below. 



8. LESQUERELLA (Bladder-pod) 



Low herbs much like Physaria except as to the silique. which is globose or 

 ellipsoidal and much smaller. 



1. I^esquerella argentea (Pursh) MacM. (Silvery Bladder-pod). Stel- 

 late-pubescent throughout ; stems several, slender ; leaves linear or narrowly 

 oblanceolate, 3-6 cm. long ; the yellow flowers conspicuous, with petals 5-6 mm. 

 long; pedicels 1-3 cm. long, in fruit recurved ; silique globose or nearly so, with a 

 slender style as long as the silique. Common on sandy plains. 



2. Lesquerella montana (Gray) Wats. (Mountain Bladder-pod). Re- 

 sembling the preceding ; root-leaves from oblanceolate to broadly obovate, peti- 

 oled ; siliques elliptical, 5-6 mm, long, equaled by the slender style, erect, on 

 widely spreading, curved pedicels. Stony slopes and hilltops. 



3. L<esquerella condensata Aven Nelson (Compact Bladder-pod). Leaves 

 and stems very short and crowded, forming a small sub-spherical tuft, stellate- 

 pubescent throughout ; flowers crowded, the spatulate petals about 6 mm, long ; 

 silique ovate, compressed at summit, about 5 mm. long, equaled by the slender 

 style. Mostly on naked stony slopes ; flowering very early. 



9. BURSA 



Low plants with clustered pinnatifid basal leaves, arrow-shaped, sessile stem- 

 leaves, an elongating raceme of small white flowers, and an obcordate- triangular 

 silique flattened contrary to the narrow partition. 



1. Bursa Bursa-pastoris (L.) Britt. (Shepherd's Purse). Annual, 2-4 dm. 

 high, somewhat pubescent with forked hairs ; flowers small. A very common 

 weed in waste ground. Introduced from Europe. 



10. DRABA (Whitlow-grass) 



Small herbs, annual or perennial, entire toothed leaves, the yellow flowers in 

 naked racemes ; sepals equal and the silique narrowly oblong, sub-acute at both 

 ends. 



1. Draba nemoros^ L. ("Wood Whitlow-grass). Annual, sparsely pubes- 

 cent with forked hairs ; 1 or more slender stems from the base ; leaves elliptic to 

 broadly ovate, entire or toothed, sessile ; flowers small; silique 10-12 mm. long, on 

 slender, widely spreading pedicels about twice as long ; stigma sessile. Common 

 on wet grassy banks. 



