CRUCIFERACEAE (MUSTARD FAMILY) 115 



DRABA (Whitlow-grass) 



Annual or perennial, low, tufted. Leaves simple, entire or toothed. 

 Flowers white or yellow. Pod elliptic to linear, flat, dehiscent. Seeds 

 wingless, in 2 rows in each cell. — (Gk. drabe = biting ; referring to the 

 sharp taste.) Too difficult for beginners. 



THYSANOCARPUS (Lace Pod) 



Annual, slender, erect, sparingly branched. Basal leaves toothed or 

 pinnatifid. Flowers minute, white or rose, in long racemes. Pod plano- 

 convex, i-celled, i-seeded. Seed somewhat flat, margined. — (Gk. thy- 

 sanos = a fringe, karpos = a fruit or body ; referring to the wing-margined 

 pod.) 



A. Upper leaves lanceolate or linear-lanceolate; pod not radiately veined; pedicels 

 4-8 mm. long. E. T. curvipes (fringed lace pod) 



AA. Upper leaves ovate-lanceolate or ovate-oblong; pod radiately veined; pedicels 

 8-1 7 mm. long. U. T. radians (radiate lace pod) 



SMELOWSKIA 



Herbs, perennial, low, caespitose ; pubescence simple or stellate. Leaves 

 i-2-pinnatifid. Flowers small, white, in terminal racemes. Petals obovate 

 or spatulate, longer than the sepals. Stigma sessile. Pod lanceolate or 

 lance-oblong ; valves sharply keeled. Seeds few. — (Evidently named after 

 some Russian.) 



A. Capsule lanceolate, attenuate at each end; petals i^ times as long as the sepals. 



W. C. E. S. calyclna 



AA. Capsule ovate, obtuse to subcordate at base, acute to attenuate at apex; petals 



ij times as long as the sepals. W. C. S. oyalis 



AAA. Capsule linear, obtuse at base, acuminate at apex; petals 3 times as long as 



the sepals. U. S. fremontli 



ARABIS (Rock Cress) 



Herbs. Flowers white or purple, in bractless racemes. Sepals equal 

 or the lateral ones saccate at base. Pod linear, flattened parallel to the 

 partition. Seeds in 1-2 rows in each cell. — (Named after Arabia, the 

 country where first found.) Too difficult for beginners. 



ERYSIMUM (Wall-flower) 



More or less pubescent or hoary. Leaves simple. Stigma lobed. Pod 

 linear. Seed oblong. — (Gk. eryein = to draw blisters ; a property of 

 the ground seeds of many plants of this family.) 



A. Petals -t-s mm, long; pod 1-2 cm. long. E. 



£. cheirantholdes (treacle mustard) 

 AA. Petals 6-25 mm. long (unknown in E. arenicola); pod 2.5-10 cm. long. 

 B. Pod terete or 4-angled. 



