1_>-_>C, CRUCIFERAE (MUSTARD FAMILY) 



S-p:ils glabrous or nearly so. 



Silique strongly nerved, obtusish 7. A. rugocarpa. 



Silique lightly nerved, cuneately pointed . 8. A. oxylobula. 



Plants taller (more than 2 dm.); silique long (more than 4 



cm ) . . . 9. A. microphylla. 



Leaves more or less dentate; oblong to ovate .... 10. A. fructicosa. 



Cauline leaves more or less pubescent as well as the basal . 

 Biennials or perennials, but without woody caudex. 

 Siliques erect or nearly so. 



Leaves more or less hirsute, spatulate or broader. 



Mature silique short (less than 3 cm.) .... 11. A. Nuttalln. 



Mature silique long (more than 4 cm.) . . . . 12. A. hirsuta. 



Leaves densely stellate-pubescent, oblanceolate. 



Seeds in 1 row in each cell 13. A. Crandallii. 



Seeds in 2 rows in each cell 14. A. oblanceolata. 



Siliques widely spreading or deflexed. 

 Pubescence wholly stellate-canescent. 

 Flowers large (9-12 mm. long). 



Leaves linear; flowers pale flesh-color .... 15. A. formosa. 

 Leaves oblanceolate; flowers deep purple . . . 16. A. perelegans. 

 Flowers small (4-6 mm. long). 



Leaves narrowly linear, crowded at the base . . . 17. A. canescens. 

 Leaves lanceolate or oblanceolate, equably distributed. 



Seeds in 2 rows 18. A. exilis. 



Seeds in 1 row . . . . . . . . 19. A. rhodantha. 



Pubescence in part ciliate or branched-hirsute. 

 Siliques pendent, on divaricate pedicels. 



Leaves fascicled on the crown ..... 20. A. aprica. 



Leaves equably distributed 21. A. Fendleri. 



Siliques pendent on refracted pedicels . . . . 22. A. caduca. 

 Perennials, with woody caudex. 



Stems solitary from the simple crown 23. A. lignipes. 



Stems several. 



Caudex branched, lignescent. 



Leaves entire, seeds in 1 row 24. A. lignifera. 



Leaves toothed; seeds in 2 rows 25. A. Selbyi. 



Caudex simple, but stems several from the base . . .26. A. eremophila. 



1. Arabis glabra (L.) Bernh. Verz. Syst. Erf. 195. 1800. Tall, mostly 

 simple-stemmed biennial, 4-8 dm. high: glabrous and glaucous above, hirsute 

 on stem and leaves below: basal leaves oblanceolate or oblong, petioled, 

 5-30 cm. long, dentate, or even lyrate; cauline lanceolate, sessile, entire, 

 auriculate: flowers yellowish-white; the petals barely exceeding the sepals: 

 siliques linear, erect, and appressed, 5-8 cm. long: seeds in 2 rows. A. per- 

 foliata. Across the continent. 



2. Arabis Drummondii Gray, Proc. Am. Acad. 6: 187. 1866. Biennial or 

 more often perennial, sparingly pubescent below (or glabrous), the hairs hor- 

 izontal and attached by the middle: stems mostly simple, erect, 3-8 dm. high: 

 basal leaves narrowly oblanceolate, short-petioled ; cauline auriculate, oblong 

 to linear-lanceolate, 3-5 cm. long, glaucous: petals white or pinkish, twice 

 us long as the, narrow sepals: silique erect, rather broadly linear, obtuse, 

 5-8 cm. long; the valves faintly veined and with a conspicuous mid-nerve: 

 seeds in 2 rows, membranously broad-winged. (A. oxyphylla Greene' Pitt. 

 4: IDC). 1000; A. connexa Greene, 1. c. 197.) Frequent; throughout the 

 Kocky Mountains. 



3. Arabis Lyallii Wats. Proc. Am. Acad. 11: 122. 1876. Near the pre- 

 ceding hut smaller, usually less than 3 dm. high, bright green or glaucous, 

 somet lines a little pubescent below, leaves similar: flowers rose-color: siliques 

 civet or ascending, straight, only 3-4 cm. long: seeds narrowly winged, usually 

 in 1 row in each cell. In the highest mountains; in northwestern Wyoming 

 and far to the northwestward. 



}. Arabis divaricarpa A. Nels. Bot. Gaz. 30: 193. 1900. Biennial or some- 

 times more enduring, glabrous above, somewhat glaucous and tinged with 

 purple, 1 dm. high: stems simple, rarely more than one from the base: 

 basal leave! narrowly oblanceolate, petioled, with a minute branched pu- 

 hesc.-nee; cauline sagittate-clasping, linear-oblong, 1-4 cm. long: flowers pale 

 or purple: sili<|iies straight, linear, uniformly divaricate-ascending, 1-nerved, 

 \ <i cm. long, on pedicels 4-8 mm. long: seeds in 1 irregular row, margined 

 but not winged. In the mountains; northern Wyoming and probably Mon- 

 tana and Idaho. 



