20. Siliques inflated or compressed parallel to septum, the replum equaling the 



silique width (21) 



21(20). Siliques globose to pyriform or ovoid, sometimes slightly longer than 

 broad or broader than long but not compressed laterally (22) 



21. Siliques compressed to strongly flattened parallel to septum (23) 



22(21). Cauline leaves sagittate-clasping stems; silicle somewhat pyriform, the 

 firm valves 1-nerved 15. Camelina 



22. Cauline leaves not sagittate; silicle globose to ovoid 7. Rorippa 



23(21). Leaves pinnately to bipinnately dissected; petals yellow 11. Selenia 



23. Leaves entire or merely lobed; petals white to lavender 13. Draba 



1. lodanthus Steud. 

 Four species from central United States and Mexico. 



1. lodanthus pinnatifidus (Michx.) Steud. Purple rocket. 



Perennial; stem usually single from base, branched above, leafy, glabrous or 

 rarely sparsely pubescent, with simple trichomes below, 3-8 dm. tall; leaves 

 glabrous, ovate to lanceolate, petiolate or the upper sessile and cuneate, irregularly 

 serrate, lower leaves usually with a winged petiole and auricles clasping the stem; 

 inflorescence narrowly racemose, elongated; sepals oblong, erect, often purplish, 

 6-8 mm. long; petals white to light-lavender, spatulate to narrowly obovate, 7-14 

 mm. long; pedicels widely spreading, glabrous, 4-10 mm. long; siliques linear, 

 widely spreading to divaricately ascending, straight, nearly terete, glabrous, 2-4 

 cm. long, sessile or with a short stipe; seeds oblong, wingless, 1-1.5 mm. long; 

 cotyledons accumbent. 



Alluvial soil of river bottoms and in rich woods, n.e. Okla. {Waterfall) and cen. 

 and e. Tex., Apr.-June; Pa. to la., Ala. and Tex. 



2. Arabis L. Rock-cress 



Annual, biennial or perennial herbs; stems erect, stiff, simple or branched, 

 glabrous to pubescent; basal leaves petiolate; cauline leaves petiolate or sessile; 

 inflorescence racemose, ebracteate; flowers tetradynamous; sepals erect, oblong; 

 petals spatulate to oblong, white, cream or lavender; siliques sessile, straight 

 to curved, erect to pendulous, flattened parallel to partition; styles evident, entire; 

 seeds orbicular to oblong, winged; cotyledons accumbent. 



About 150 species in Eurasia, North America and Africa. 



L Seeds definitely in 1 row in each locule 1. A. hirsuta. 



\. Seeds in 2 rows in each locule (2) 



2(1). Fruiting pedicels merely ascending or divaricately spreading, finely stellate- 

 pubescent or glabrous; stem finely appressed-pubescent at base 

 with forked trichomes 2. A. divaricarpa. 



2. Fruiting pedicels strictly appressed or subappressed, glabrous; stem hirsute 



at base or glabrous 3. A. Drummondii. 



1. Arabis hirsuta (L.) Scop. var. pycnocarpa (M. Hopk.) Roll. 



Stoutish biennial; stem 2-8 dm. high, slender, hirsute usually to summit with 

 spreading mostly simple hairs; radical leaves oblong to oblanceolate, 2-8 cm, 

 long, villous-hirsute to hirtellous on both surfaces; cauline leaves very numerous, 

 imbricated or nearly so, oblong to lanceolate, 1-4 cm. long, obtuse to subacute, 

 the lower auriculate- to subsagittate-amplexicaul, hirsute, the upper merely sessile 

 and less pubescent or smooth; racemes slender, becoming lax; sepals herbaceous; 

 petals whitish to ochroleucous or rarely pinkish, lanceolate, 4-6 mm. long, 0.7-1 

 mm. wide; siliques erect or appressed, flat, often moniliform, 1.5-5 cm. long, 



964 



