576 



COMPOSITAE (COMPOSITE FAMILY) 



clusters, on very short peduncles; scales of the involucre 4-5. Wyoming to 

 Idaho and Utah. 



4. Tetradymia spinosa II. & A. Bot. Beech. 360. 1840. A rigidly branched 

 shrub 6-12 dm. high; stems densely white-tomentose: primary leaves modi- 

 fied into rigid spines which may be either straight or recurved, 1-4 cm. long, 

 tomentose or glabrate; secondary fascicled leaves commonly present, small, 

 linear-clavate, glabrous or early glabrate: heads on stout peduncles arising 

 from the leaf-axils; involucre about 8 mm. high, usually 6 or 7-flowered; 

 bracts 5 or 6, the outer ones oblong, the inner ones broadly oblong to nearly 

 orbicular, all obtuse: achenes with soft white wool nearly equaling the rigid 

 pappus-bristles. Desert areas; from Wyoming and Colorado to California and 

 Oregon. 



90. SENECIO L. 



Herbs or woody plants with alternate leaves and with heads in terminal 

 cymes or rarely solitary. Heads many-flowered, radiate or discoid; flowers 

 in our species yellow. Involucre cylindrical to campanulate, of several or 

 numerous connivent-erect herbaceous equal bracts, mostly with 1 or 2 rows 

 of outer erect bracteoles at base, which are elongated and exceed the proper 

 involucre in a few species. Receptacle flat, naked. Anthers mostly rounded 

 at base. Style-branches truncate. Achenes terete. Pappus of abundant 

 white and soft bristles. 



Heads large, 15-25 mm. high, usually more or less nodding. 

 Rayless. 



Heads 15-20 mm. long 1. S. Bigelovii. 



Heads 8-12 mm. long 2. S. cernuus. 



Rays present. 



Stem leaves clasping 3. S. amplectens. 



Stem leaves usually short-petioled, not clasping. 

 Leaves tapering gradually to the petiole. 



Plant glabrous 4. S. Holmii. 



Plant arachnoid-tomentose . . . 5. S. taraxacoides. 



Leaves tapering abruptly into the petiole . . . 6. S. Soldanella. 



Heads smaller, less than 15 mm. high, not noticeably nodding. 

 Biennials or perennials. 



Leaves not at all pinnate or pinnatifid. 



Stems often numerously and always nearly equably leafy to 



the top. 

 Leaves not linear. 



Leaves obovate to elliptic, entire to repand-dentate, 

 obtuse. 



Peduncles very short 7. S. carthamoides. 



Peduncles distinctly surpassing the leaves . 8. S. Fremontii. 



Leaves triangular to lance-linear, acute. 



Some or all of the leaves triangular or lance-cordate . 9. S. triangularis. 

 None of the leaves triangular or lance-cordate. 



Stems 5-12 dm. high; leaves sessile, serrate . . 10. S. serra. 

 Stems 4 dm. or less high; leaves petioled. 



Rays preseht U.S. crassulus. 



Rays wanting 12. S. rapifolius. 



Leaves linear 40. S. spartioides. 



Stems either few-leaved or with the upper leaves reduced in 



size. 



Tall (7-15 dm.) bog-plant with glaucous, fleshy leaves . 13. S. hydrophilus. 

 Lower, 6 dm. or less high. 

 Stems more or less leafy. 



Leaves glabrous or glaucous (at least in age). 

 Leaves sharply dentate. 



Rays wanting 12. S. rapifolius. 



Rays present . . . . . . .11. S. crassulus. 



Leaves entire or callous-denticulate. 



Leaves not glaucous ..... 16. S. integerrimus. 



Leaves glaucous or glaucescent. 



Involucral bracts black-tipped . . . 14. S. glaucescens. 

 Involucral bracts not black-tipped . . 15. S. anacletus. 



Leaves and stems at first woolly-pubescent or floccose, 



but often early glabrate. 



Loosely woolly-pubescent, becoming glabrate. 

 Leaves entire; involucral bracts not black- 

 tipped . . . . . . 16. S. integerrimus. 



Leaves dentate or denticulate; involucral bract 

 black-tipped. 



