THISTLE FAMILY 267 



IV. TRTANGUL.1RES. 



Heads few; involucres 10 mm. high; lower leaf-blades cordate, the upper oval. 



14. S. variifolius. 

 Heads usually many: involucres 6-8 mm. liigh: all leaves triangular, or the upper deltoid- 

 lanceolate. 

 Stem 3-4 dm. liigh; leaves fleshy. 15. S. saliens 



Stem 4-10 dm. high: leaves thin. 16. S. triangularis. 



V. Serr.\e. 

 Heads 12-15 mm. high: disk 8-15 mm. broad; whole plant dark green. 



17. S. admirabilis. 

 Heads 8-10 mm. high: disk 5-6 ram. wide: plant light green. 



Leaves oval-deltoid to lanceolate; panicles elongate. 18. S. Solidago. 



Leaves narrowly lanceolate to almost Unear; panicles round-topped. 



Leaves, at least the lower, closely dentate; involucre cylindro-campanulate. 



19. S. serra. 

 Leaves entire; involucres turbinate-campanulate. 20. .S. lanceolatus. 



VI. Eremophiu. 



Blades of the leaves stnuately lobed, the upper cleft halfway to the midrib. 



Bracts linear-subulate, not thickened on the back. 21. S. glauciifolius. 



Bracts linear, carinate on the back. 22. S. Kingii. 



Blades of the leaves pinnatifid or laciniate, cut usually to near the midrib. 

 Leaf-blades ovate in outline: divisions toottied or lobed. 



Involucres 6-7 mm. liigh, 5-6 mm. broad; bracts black-tipped. 



2.3. S ambrosi aides. 

 Involucres 7-10 mm. high, 6-8 mm. broad. 24. S eremophilus. 



Leaf-blades narrowly oblanceolate ; divisions Unear, entire. 25.' S. Kuntzei. 



VII. LONGILOBI. 



Plant glabrous, at least in age. 



Leaves except those of the branches pinnately divided. 



Leaves oblanceolate, with lanceolate or oblong lobes or teeth. 



25. S. Kuntzei. 

 Leaves and their divisions linear-filiform. 



Bractlets one-third to one-half as long as the bracts, filiform. 



26. S. filicifolius. 

 Bractlets very short, subulate. 



Involucres campanulate; bracts 12-15. 27. S. Riddellii. 



Involucres almost cyUndrical: bracts 8-10. 28. S. mul'.icapitatus. 



Leaves entire, Unear-fiUform, or some rarely with a pair of filiform lobes. 



29. S. spartioides. 

 Plant more or less permanently tomentose. 30. S. longilobus. 



VIII. Glaucescentes. 

 Basal leaves spatulate or oblanceolate. 



Bracts long-attenuate, sUghtly if at all black-tipped; lower leaves broadly spatulate. 



31. 5. anacletus. 

 Bracts short, acute, with conspicuous black tips. 



Lower leaves broadly spatulate. 32. S. glaucescens. 



Lower leaves oblanceolate. 96. S. lapathif alius. 



Basal leaves narrowly linear-oblanceolate. 33. S. lugens. 



IX. FOLIOSI. 



Heads cylindro-campanulate; disk about 5 mm . wide. 

 Bracts black-tipped. 



Bracts broadly linear, abruptly acute. 34. S. atralus. 



Bracts narrowly hnear, long-acute. 35. S. milliflorus. 



Bracts not black-tipped. 36. S. foliasus. 



Heads openly campanulate; disk 8-10 mm. wide; upper stem-leaves much reduced. 



37. S. sphaerocephalus. 



X. C.\NI. 



Heads 7-8 mm high. 



Involucres as well as the whole plant densely white-tomentose. 



38. S. Hallii. 

 Involucres glabrate or nearly so. 



Plant densely tomentose; basal leaves short-petioled ; petioles scarcely e.xceeding 

 the blades. 

 Blades of the basal leaves obovate or spatulate. 39. S. Purshianus. 



Blades of the basal leaves linear or nearly so. 40. S. larimiensis. 



Plant finely tomentose, becoming more glabrate in age; basal leaves with slender 

 petioles, much longer than the blades. 41. S. Howellii. 



Heads 1 cm. or more high. 



Blades of the basal leaves narrowly oblanceolate: stem-leaves Unear, entire. 

 Plant 3-6 dm. high; involucres campanulate; upper leaves much reduced. 



42. S. spatulifarmis. 

 Plant 1-2 dm. high; involucres turbinate-campanulate: upper leaves not much 

 reduced. 43. S. Harbourii. 



Blades of the basal leaves spatulate or broadly oblanceolate; stem-leaves lanceolate 

 or oblong, usually more or less pinnatifid; heads hemispheric. 



44. S. canus. 



