THISTLE FAMILY 877 



1. X. glabriuscula Nutt. Stems 1-2 dm. high, glabrous; leaves linear- 

 oblanceolate, 2-5 cm. long, glabrous; involucres 8-10 mm. high, 10-15 mm. wide; 

 bracts linear-lanceolate, acuminate, glabrous, erose on the margins; ligule rose- 

 colored, 10-12 mm. long. Alkali plains: Wyo. Je-Jl. 



2. X. villosa Nutt. Stems 1-2 dm. high; leaves 2-5 cm. long, or linear- 

 oblanceolate, villous, tipped with a callous point; involucres 8-10 mm. high, 10- 

 15 mm. broad; bracts linear-lanceolate, attenuate at the apex, villous on the 

 back, erose on the margins; ligules pale red, 8-12 mm. long. Aster Xylorrhiza 

 T. & G. Rocky places and clayey soil: Colo. Wyo. My-Je. 



3. X. venusta (M. E. Jones) Heller. Stems 2-5 dm. high; leaves entire, 

 spatulate or oblanceolate, villous, 4-6 cm. long, spinulose-tipped ; involucres 

 about 1.5 cm. high, 3 cm. broad; bracts linear-lanceolate, attenuate, villous on 

 the back, scarcely erose; ligules white or purple, 15-20 mm. long. A. venustus 

 M. E. Jones. Dry places: Colo. Utah. Son. My-Je. 



4. X. Parryi (A. Gray) Greene. Stems tomentose-villous, about 1 dm. high; 

 leaves spatulate, obtuse with a callous point, 2-3 cm. long, villous; involucres 

 8 mm. high, 15-18 mm. broad; bracts well imbricate, villous on the back, erose on 

 the margins; rays about 1 cm. long, white. A. Parryi A. Gray. Flats : Wyo. Son. 



5. X. coloradensis (A. Gray) Rydb. Stems less than 1 dm. high, 

 canescent; leaves spatulate or oblanceolate, 2-4 cm. long, spinulose-dentate, 

 hirsute-canescent; jnvolucres about 8 mm. high, 15 mm. broad; bracts lance- 

 subulate, attenuate, canescent; ligules 8-10 mm. long, violet-purple. A. colora- 

 densis A. Gray. Higher mountains: Colo. Alp. 



6. X. Brandegei Rydb. Stem almost 1 dm. high; leaves spatulate or the 

 upper oblanceolate, 3-4 cm. long, firm, closely and sharply serrate with bristle- 

 tipped teeth; disk about 3 cm. wide; bracts narrowly linear-lanceolate, attenuate; 

 rays rose-purple. High mountains: s Colo. Subalp. Alp. S. 



7. X. lanceolata Rydb. Shrubby perennial, with white stems; branches 

 more or less villous; leaves 4-6 cm. long, more or less villous, reticulately veined, 

 dentate with spinulose-subulate teeth; involucre fully 1 cm. high, 15-20 mm. 

 broad; bracts lance-subulate, villous and slightly glandular, attenuate and spinu- 

 lose-tipped; ligules purple, about 2 crn. long. Arid places: s Utah. L. Son. 



35. HERRICKIA Woot. & Standl. 



Perennial herbs, with thick rigid, spinulose-toothed, reticulate, sessile leaves. 

 Heads solitary at the ends of the branches, subsessile. Involucre turbinate- 

 campanulate; bracts in several series, conspicuously keeled, green and foliaceous 

 above, with callous points, the outer more foliaceous and passing into the leaves; 

 receptacle naked. Ligules purple. Disk-flowers perfect; corollas yellow, turn- 

 ing purplish, with short ovate lobes. Style-branches with lanceolate, acute tips. 

 Achenes compressed, striate, glabrous. Pappus simple, of long barbellate bristles. 



1. H. horrida Woot. & Standl. Stems 3 dm. high or less, hirsute-glandular; 

 leaves rigid, oblong to broadly ovate or oval, 2-4.5 cm. long, sessile or somewhat 

 cordate-clasping, reticulate, spinose-dentate, pubescent; ligules 8 mm. long. 

 Mountains: N.M. s Colo. Au. 



36. UNAMIA Greene. SNEEZEWORT ASTER. 



Perennial, caulescent herbs with horizontal rootstocks. Leaves alternate, 

 narrow, entire. Heads rather small, corymbose, radiate. Involucres turbinate- 

 campanulate; bracts narrow, not foliaceous, more or less keeled. Ray-flowers 

 pistillate; ligules white or ochroleucous. Disk-flowers yellow, perfect, numerous. 

 Appendages of the style-branches lanceolate-subulate. Achenes 4-5-angled, not 

 compressed, glabrous. Pappus of white rigid bristles, somewhat clavate at the 

 ends. 



Inner bracts ovate-lanceolate, acute, the outer lance-subulate; ligules white. 



1. U. alba. 



Inner bracts oblong or elliptic, obtuse or rounded at the apex; ligules yellowish, the 

 outer lanceolate, obtusish. 2. U. lutescens. 



