COMPOSITAE (COMPOSITE FAMILY) 511 



long, narrowly oblong-lanceolate or linear: involucre 10-14 mm. broad, the 

 bracts acute, somewhat ciliate: rays white, about 12mm. long. Aster Xylorhiza. 

 Naked clayey saline soils; south-central Wyoming. 



la. Xylorhiza glabriuscula villosa (Nutt.) A. Nels. Intermediate between 

 the preceding and the following species: softly villous or tomentose. (X. 

 villosa Xutt. 1. c. 208.) Habitat and range of the species. 



2. Xylorhiza Parryi Gray, Am. Nat. 8: 212. 1874. Somewhat hoary with 

 a thin, loose, villous tomentum; stems several from the woody crowns, 1-2 dm. 

 high: leaves spatulate-linear, cuspidate, 3-5 cm. long: peduncles solitary: 

 involucral bracts oblong-lanceolate, long-acuminate, cinereous-pubescent : rays 

 numerous, white, 10-14 mm. long: achenes white-villous. Aster Parryi. 

 In denuded or saline soils; western Wyoming, Colorado, and adjacent Utah. 



3. Xylorhiza venusta (Jones) Heller, Cat. N. A. Plants 8. 1900. Softly 

 villous-tomentose up to the canescent involucre; stems many, erect, stout, 

 simple, shrubby at base: leaves all entire, oblanceolate or lowest spatulate, 

 scarcely petioled, 5-8 cm. long, generally apiculate, larger ones indistinctly 

 3-iuTved: peduncles monocephalous, 1-2 dm. long: involucral bracts oblong- 

 ovate and abruptly long-acuminate, in about 3 series: rays white or light 

 purple, linear-oblanceolate, 20-25 mm. long: pappus of unequal, stiff bristles; 

 achene silky. Western Colorado to Utah. 



22. ASTER L. ASTER 



Perennial or rarely annual herbs, with alternate entire or serrate leaves 

 and racemose, paniculate, or corymbose (rarely solitary) heads of flowers with 

 white, purple, or blue ray, and yellow (often changing to purple) disk corollas. 

 Heads many-flowered; the ray-flowers in a single series, not very numerous, 

 pistillate; those of the disk tubular, perfect. Bracts of the involucre more 

 or less imbricated, usually with herbaceous or foliaceous tips. Receptacle 

 flat or convex, naked. Appendages of the style (in the disk-flowers) lanceo- 

 hiti or subulate, acute. Pappus simple; of numerous, often unequal, scabrous 

 capillary bristles. Achenes usually compressed. (Includes Brachyactis 

 Ledeb., Eucephalus Nutt., and Unamia Greene.) 



ANNUALS (Brachyactis Ledeb.) 



Involucral bracts linear, acute . . 1. A. angustus. 



Involucral bracts oblong, obtuse . . . . . . . 2. A. frondosus. 



PERENNIALS (Bucephalus Nutt.) 



INVOLUCRAL BRACTS WITH PROMINKNT OR KEELED MIDRIB, DRY AND CHARTACEOUS, 

 USUALLY PURPLE-TIPPED 



Steins mostly simple below; the involucral bracts acute. 



Stmit, usually <>-15 drn. high; heads large (12-15 mm. high) . 3. A. Engelmannii. 

 Slender, 3-6 dm. high; heads smaller, with conspicuously 



purple-tipped bracts . . . . . . . 4. A elegans. 



Steins mostly branched throughout; at least the outer involucral 



bracts obtuse 5. A. glaucus. 



PERENNIALS 



INVOLUCRAL BRACTS NEITHER KEELED NOR WITH PROMINENT MIDRIB, 

 AT LEAST THE TIPS GREEN 



Stems low, usually less than 1 dm. high, monocephalous; high 



alpine. 

 1'rom a low woody crown or caudex. 



Stems and involucre lanate-pubescent .... 6. A. culminis. 



- and involucre minutely glandular . . . 7. A. Kingii. 



From filiform creeping rootstocks . . . . . . 8. A. andinus. 



Stems taller, usually more than 1 dm. high, bearing solitary, 

 few, or many heads, mostly from rootstocks which are often 

 branching and matted or tufted. 

 Peduncles and involucres glandular. 



Steins simple, rarely branching at summit. 



Heads solitary or racemed ... . 15. A. campestris. 



Heads not in racemes. 



