THISTLE FAMILY 265 



Involucre less than 1 cm. high, villous at the base, only slightly glandular: 

 bracts broadly lanceolate. 20. A. coloradensis. 



Involucre 12-15 mm. high, densely glandular-hirsute; bracts narrowly ob- 

 lanceolate. 21. A. ovata. 



Middle stem-leaves lanceolate, oblanceolate, or linear-lanceolate. 



Bracts oblanceolate, abruptly acuminate. 22. A. mollis. 



Bracts linear or lanceolate. 



Stem-leaves more or less sharply dentate, except at the base. 

 Leaves nearly glabrous, except the margins. 



Stem-leaves ovate-lanceolate, broad at the base. 



23. A. amplexifolia. 

 Stem-leaves oblanceolate or narrowly lanceolate, narrowed at the 

 base. 24. ^4. Macounii. 



I^eaves decidedly pubescent, both villous and glandular-granuliferous. 



25. A. rivularis. 

 Stem-leaves entire, sparingly denticulate, densely glandular-puberulent. 



26. A. subplumosa. 

 IX. FOLIOS.^E. 



Pubescence of the leaves long and soft, villous. 



Bracts obovate-oblanceolate, mostly obtuse. 27. A. tomentulosa. 



Bracts oblong-lanceolate, acute. 



Plant sparingly pubescent, with long flat hairs; leaves long-acute. 



28. A. Chamissonis. 

 Plant densely pubescent with fine hairs; leaves acute or obtuse. 



Leaves broadly oblanceolate or lanceolate. 29. A. rhizomata. 



Leaves linear or lance-linear. 30. A. foliosa. 



Pubescence of the leaves very short and fine. 



Stem-leaves linear-lanceolate, usually entire or callous-denticulate; involucre rarely 

 more than 1 cm. high. 

 Pubescence of the involucre and peduncle very short and fine. 31. A. ocreata. 

 Pubescence of the involucre and peduncle longer and coarser. 32. A. celsa. 

 Stem-leaves broadly lanceolate, more or less dentate; involucre usually more than 1 

 cm. high. 33. A. rubricaulis. 



X. Alpin.ve. 

 :Stem-leaves ovate. 20. A. coloradensis. 



.Stem-leaves hnear to lanceolate. 



Leaves glabrate in age, at least above. 



Involucre and peduncle more or less glandular-puberulent; achenes hispidulous. 



9. A. arnoglossa. 

 Involucre more or less \'illous, at least at the base; achenes canescent. 



Leaves and lower part of the stem glabrous or nearly so; leaves mostly acute; 

 bracts green. 

 Leaves strongly 3-ribbed. 34. A. Rydbergii. 



Leaves famtly 3-ribbed. 35 .4 tenuis. 



Leaves and stem vallous when yoimg; leaves mostly acuminate; Dracts purple- 

 tinged. 36. A. alpina. 

 Leaves densely villous-tomentose. 37. A. tomentosa. 



XI. Peduncul.^tae. 



:Stem with tufts of brown wool at the base. 38. -A. pedunculata. 



Stem without tufts of wool at the base. 39. A. fulgens. 



XII. Lessingianae. 



One species. 40. A. Louiseana. 



129. SENECIO L. Groundsel, Ragwort, Squaw-weed. 



Perennials with a more or less developed rootstock or caudex; if the latter is le.ss well- 

 developed, it bears numerous flbrous-fleshy roots. 

 Heads more or less nodding. 



Heads discoid; crown short, with fleshy-flbrous roots. I. PuDici. 



Heads radiate; rootstock well developed. II. Amplectextes. 



Heads not nodding. 



Heads more than 15 mm. high and 20 mm. broad, solitary (seldom 2-3). 

 Plant low, less than 2 dm. high, with rootstocks; bractlets short. 



II. Amplectextes. 

 Plant tall, "^-5 dm. high, stout, with a short crown and a cluster of tleshy- 

 flbrous roots 

 Bractlets linear-fiUform, almost equalling the involucre; bracts not black- 

 tipped. XIX. Megacephali. 

 Bractlets short; bracts usually tipped with black. 



XVIII. Integerrimi. 

 Heads less than 15 mm. high and broad. 

 Plants equally leafy throughout. 



Leaves or their divisions not narrowly linear or filiform. 

 Leaves merely toothed or entire, not pinnatifld. 



Leaf-blades oval, elliptic, or obovate, usually obtusish; heads few; 



plants cespitose. III. Occide.vtales. 



Leaf-blades triangular or ovate to linear-lanceolate, distinctly acute; 

 heads asually many. 

 Leaf-blades, at least the lower ones, triangular or cordate; plants 

 rowging in clumps, with fleshy-fibrous roots. 



IV. Triangul.\res. 



