COMPOSITAE. 1025 



in the southern and western parts of North America. Our species known as 

 Groundsel, Ragwort, or Squaw-weed. 



* Heads conspicuously radiate (except in forms of Nos. 9, 10 and 16). 



(a) Heads solitary or few, 12-25 mf n- high ; northern species. 



Stout; leaves 1-2 dm. long; heads 4-5 cm. broad. i. S. Pseudo-Arnica. 



Low; leaves 3-5 cm. long; heads 2-3 cm. broad. 2. S.frigidus. 



(b) Heads several or numerous, corymbose, mostly smaller, 

 f At least the lowest leaves entire or dentate, not pinnatifid (or sometimes pinnatifid 



in Nos. 7 and 14). 

 \ None of the leaves cordate. 

 Heads 10-14 mm - high; plants 3-15 dm. tall; northwestern species. 



Involucral bracts acuminate; leaves mostly entire. 3. S. intcgerrimus. 



Bracts acute or obtuse, mostly black-tipped; leaves denticulate. 



4. S. atriapiculatus. 

 Heads 6-10 mm. high; plants 1.5-7 dm. tall. 



Leaves and stems persistently more or less tomentose or woolly. 



Achenes glabrous. 5. S. Purshianus. 



Achenes hispidulous or glandular. 



Basal leaves long-petioled, crenate-dentate or sometimes pinnatifid; plants 

 tall. 



Basal leaves crenate-dentate; eastern. 6. S. tomentosus. 



Stem-leaves, and often also the basal, pinnatifid; western. 



7. S. Plattensis. 



Basal leaves short-petioled, much tufted, oval, few-toothed or entire; plant 

 low. 8. S. antennaritfolius. 



Leaves glabrous or nearly so; stem often woolly, especially below. 

 Basal leaves obovate, spatulate, or oval; achenes glabrous. 



Basal leaves obovate or suborbicular, crenate or dentate; involucral bracts 



4-5 mm. long. 9. S. obovatus. 



Basal leaves ovate to oval; involucral bracts 6-iomm. long. 



Rays usually wanting, northern species. 10. S. discotdeus. 



Rays large and conspicuous. u. S. Crawfordi. 



Basal leaves oblong; achenes glabrous or hispidulous. 



Heads few or several, 6-8 mm. high; basal leaves 2-7 cm. long. 



12. S. Balsamitae. 

 Heads numerous, 4-5 mm. high; basal leaves 7-15 cm. long. 



13. S. Smallii. 

 Basal leaves linear-cuneate, entire or 3-toothed at apex. 



14. S. compactus. 

 \ \ Basal leaves cordate or subcordate; plants mostly glabrous. 



Basal leaves lanceolate or oblong-lanceolate. 15. S. Robbinsii. 



Basal leaves orbicular or ovate-oval. 16. S. aureus. 



ft Leaves narrowly linear, entire. 17. S. spartioides. 



ftt Leaves all pinnatifid or coarsely sinuate-dentate; plants glabrous, or somewhat 



woolly when young. 



Leaves sinuate-dentate, lanceolate; heads 8-10 mm. high. 19. S. palustris. 



Leaves pinnatifid. 



Segments narrowly linear, entire. 18. S. Fremontii. 



Segments not linear. 



Leaves pinnately divided; segments dentate; heads 4-6 mm. high. 



20. S. lobatus. 

 Leaves 2-pinnatifid; heads 6 mm. high ; introduced species. 



21. S.Jacobaea. 

 * * Heads discoid, the rays none, or minute; introduced species. 



Leaves pinnatifid; plants glabrous or puberulent; achenes canescent. 

 Heads 6-8 mm. high; involucre naked, or nearly so at the base. 



22. S. sylvaticus. 

 Heads 8-12 mm. high; involucre with several short outer bracts. 



23. S. vulgaris. 



Leaves pinnatifid ; plant viscid-pubescent; achenes glabrous. 24. S. vtscosus. 

 Basal leaves obovate, orbicular, or spatulate, merely dentate. 



Nos. 9, 10 and 16. 



i. Senecio Pseudo-Arnica Less. SEA-BEACH SENECIO. (I. F. f. 4033.) 

 Perennial, somewhat fleshy; stem stout- mostly simple, very leafy, 1.5-9 dm. high. 

 Leaves oblong-obovate, or the lower spatulate, acute or obtuse at the apex, densely 

 tomentose beneath, at least when young, repand-dentate or denticulate, narrowed 

 to a sessile and partly clasping base, or the lowest into margined petioles; heads 

 stout-peduncled, nearly 25 mm. high; involucre broadly campanulate, its bracts 



