THISTLE FAMILY 891 



tichophijUus Greene. Alpine peaks: Mont.— Colo.— Ore.— B.C. MonL— Sub- 

 alp, Jl-Au. 



39. OREOSTfMMA Greene. 



Subacaulescent perennials. Leaves narrow, entire, subcoriaceous. Heads 

 solitary, terminating the scapiform stems. Involucre hemispheric; bracts sub- 

 equal, in 2-3 series, herbaceous. Rays pistillate, numerous; ligules purple. Disk- 

 flowers perfect, fertile. Style-branches with subulate or lanceolate acute ap- 

 pendages. Achenes narrow, cylindric. Pappus of brittle, barbellate deciduous 

 bristles. [Oreastrum Greene.] 



1. O. Haydeni (Porter) Greene. Low perennial, with thick woody root 

 and caudex; stem 1 dm. high or less, glabrous; basal leaves many, linear 5-10 

 cm long, 2-3 mm. wide, glabrous; stem-leaves shorter; head solitary; mvolucres 

 about 1 cm. high, 10-12 mm. broad; bracts linear, glabrous, slightly tinged with 

 purple, with narrow scarious, ciliolate margins; ligules blue, about 1 cm. long. 

 Aster pulch:llus A. Gray, in part, not WiUd. A. Haydeni Porter. Mountain 

 slopes : Mont. — Wyo.— Nev. MonL—Subalp. Jl-S. 



40. ASTERIGERON Rydb. 



Low perennials, with cespitose rootstocks. Leaves alternate, the basal ones 

 numerous, the cauline ones much reduced. Heads solitary, termmal, radiate. 

 Involucres hemispheric; bracts imbricate in 3 series, those of the mner series 

 broad, lanceolate, with reddish purple-tinged scarious margins, the rest linear. 

 Ray-flowers pistillate; ligules purpUsh. Disk-flowers perfect, fertile. btyle- 

 branches with ovate or triangular, subulate-acuminate appendages. Achenes 

 flat, appressed pubescent. Pappus of many hispidulous bristles. In general 

 habit, involucre and fruit agreeing with Erigeron, but the style-tips more like 

 those of Aster. 



1. A. Watsoni (A. Gray) Rydb. Perennial, with a cespitose rootstock; 

 stems slender, decumbent, 1 dm. long or less, glabrous or nearly so; basa leaves 

 2-3 cm. long, petioled, linear-spatulate, glabrous; stem-leaves very small, 4-lU 

 mm. long; heads sohtary, peduncled; involucre about 5 mm. high and S nam. 

 broad; bracts oblong-lanceolate, acute, pruinose, and with some scattered hairs, 

 with purplish membranous margins; ligules about 4 mm. long, white or purphsh. 

 Aster Watsoni A. Gray. Mountains: Nev.— Utah. Mont. Au. 



41. DOELLINGERIA Nees. White Aster. 



Perennial caulescent herbs, with rootstocks. Leaves alternate, ciliate, entire. 

 Heads in corymbiform c>Tiies, radiate. Involucres campanulate; bracts imbri- 

 ratp in 2-4 series, narrow, appressed, not herbaceous at the tips; receptacle pitted. 

 Ra%wers few'or seve^arpisti^llate; ligules white. Disk-flowers perfect; cor- 

 ollas slender, expanded into a 5-lobed limb. Anthers obtuse at the base. Ap- 

 pendages of the style-branches subulate to ovate. Achenes slightly broader 

 above Pappus double, the outer of short bristles or squamellae, the inner of 

 capillary bristles, usually clavellate at the apex, ta^wny. 



1 D pubens (A. Gray) Rydb. Stem 5-10 dm. high, finely puberulent: 

 leaves lanceolate or ovate-lanceolate, 5-15 cni. long entire, acute green and 

 scabrous above, pale and tomentulose beneath; involucres about 5 mm. high, 

 bracts Unear-lanceolate, slightly tomentulose; ligules white, 4 mm. long. Aster 

 umhellatus p^ibens A. Gray. Meadows and open woods: Lpper Mich.— Wis.— 

 Neb.— Sask; Plain. Jl-S. 



42. lONACTIS Greene. 



narrow, entire. 



ligneous at the base. Leaves alternate, 

 ry or corymbose. Involucres turbinate; 

 firm. Ray-flowers numerous; ligul 



Set Disk-flowers perfect; corollas with campanulate throats. Style-branches 

 with subulate appendages. Achenes pubescent, flat, with strong marginal nerves. 

 plppS Xble, the inner series of capillary bristles, the outer short, setulose. 



