228 CRUCIFERAE (MUSTARD FAMILY) 



merous from the multicipital caudex, 2-3 dm. high: radical leaves oblanceolate 

 spatulate, 15-20 mm. long; the cauline similar but shorter, sessile: petals 

 obovate-cuneate, twice as long as the obtuse stellate-pubescent sepals, white 

 or rose-tinged: siliques linear, 2.5-4 cm. long, erect on ascending or erect pedi- 

 cels: seeds uniseriate in each cell. Western Colorado. 



14. Arabis oblanceolata Rydb. Bull. Torr. Bot. Club 31: 557. 1904. Re- 

 sembling the preceding, but less densely stellate and larger: stems several 

 from the base, 3 dm. high: basal leaves oblanceolate, 3 cm. or more in length, 

 sagittate-auricled ; cauline sessile, lanceolate: petals reddish-purple, twice as 

 long as the acute pubescent sepals: siliques broadly linear, glabrous, about 

 5 cm. long, ascending on ascending pedicels 1 cm. long: seeds in 2 rows. 

 Southwestern Colorado. 



15. Arabis formosa Greene, Pitt. 4: 198. 1900. Perennial, canescent with 

 a fine stellate indument throughout: stems virgate, one or more from the 

 crown, erect, 2-4 dm. high: basal leaves oblanceolate, entire, 3-4 cm. long 

 (including the rigid petiole); cauline as long, sessile by a truncate but not 

 auricled base: raceme long and loose: petals flesh-color, 10-14 mm. long, with 

 oblong-spatulate limb, 2-3 times as long as the stellate-canescent sepals: 

 silique pendulous, somewhat stellate-pubescent. New Mexico, and prob- 

 ably in southern Colorado. 



16. Arabis perelegans A. Nels. Tall biennial, more or less pubescent with 

 branched hairs below, glabrate upward: stems solitary, strict, 6-10 dm. high, 

 very leafy up to the raceme: basal leaves few and early deciduous the second 

 season; cauline entire or remotely denticulate, oblanceolate, and petioled be- 

 low, passing into lanceolate-linear auriculate forms above: flowers large, from 

 deep purple to almost white: petals twice as long as the pubescent sepals; 

 the buds erect but drooping in anthesis: siliques linear, 5-8 cm. long, divar- 

 icate, drooping, or variously twisted, on long ciliate pedicels. (A. elegans A. 

 Nels. Bot. Gaz. 30: 192. 1900.) Yellowstone Park. 



17. Arabis canescens Nutt. T. & G. Fl. N. A. 1: 83. 1838. Perennial from 

 a multicipital caudex, finely and canescently stellate-pubescent throughout: 

 stems numerous, erect, slender, 2-4 dm. high: leaves all linear, crowded on 

 the crowns and the lower part of the stems, 2-4 cm. long: flowers small, pale: 

 siliques linear, glabrous, 3-5 cm. long, pendent on reflexed or sometimes 

 refracted pedicels: seeds small, winged, in 2 rows. Western Wyoming and 

 Utah to Oregon. 



18. Arabis exilis A. Nels. Bull. Torr. Bot. Club 26: 123. 1899. Biennial 

 or sometimes perennial, minutely stellate-pubescent, more glabrate upwards: 

 stems solitary or 2 or 3 from the caudex, 2-5 dm. high: basal leaves rosulate, 

 entire or toothed, oblong, acute at both ends, on short petioles; cauline lan- 

 ceolate or linear, becoming sessile above but not auriculate-clasping: petals 

 linear-spatulate, white or purplish, exceeding the pubescent narrow sepals: 

 silique linear, 4-6 cm. long, pendent on abruptly deflexed somewhat pubescent 

 pedicels: seeds in 2 rows. A. Holboellii in part. (A. consanguinea Greene, 

 Pitt. 4: 190. 1900; A. pendulocarpa A. Nels. Bot. Gaz. 30: 192. 1900.) 

 Southern Colorado to Montana. 



19. Arabis rhodantha Greene, Pitt. 3: 155. 1897. Biennial, stellate- 

 tomentulose throughout: stem simple, stout, erect, 3-5 dm. high: basal 

 leaves cuneate-oblanceolate, entire or toothed; cauline linear, acutish, sessile 

 by an abruptly dilated auriculate base : raceme elongated, glabrous, subse- 

 cund: flowers small, pendulous: petals rose-red, barely longer than the pu- 

 bescent sepals: siliques linear, straight, long, deflexed: seeds in 1 row, narrowly 

 wing-margined. A. Holboellii in part. Subalpine; Colorado. 



20. Arabis aprica Osterh. Biennial, glabrous above, cinereous below with 

 a subhispid branched (not stellate) pubescence: stems 1-4 from the single 

 crown, ascending, 1.5-2 cm. high: basal leaves a crowded fascicle on the sum- 

 mit of the crown (the few stems arising just below or outside of the clustered 

 leaves), hispid-ciliate, narrowly oblanceolate, tapering to a slender petiole, 

 about 3 cm. long; cauline leaves few, glabrous, merely foliar lanceolate auric- 

 ulate bracts: flowers few, small: petals light rose, twice as long as the sepals: 



