22() CRUCIFERAE (MUSTARD FAMILY) 



Sepals 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. Nuttallii. 



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, petiole'd, 

 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 

 as 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: 196. 1900; A. connexa Greene, 1. c. 197.) Frequent; throughout the 

 Rocky Mountains. 



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

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

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

 erect 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. 



4. Arabis divaricarpa A. Nels. Bqt. Gaz. 30: 193. 1900. Biennial or some- 

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

 purple, 4-6 dm. high: stems simple, rarely more than one from the base: 

 basal leaves narrowly oblanceolate, petioled, with a minute branched pu- 

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

 or purple: siliques straight, linear, uniformly divaricate-ascending, 1-neryed, 

 4-6 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. 



