THISTLE FAMILY 98^ 



IX. FOLTOSI. 



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

 Bracts black-tipped. 



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



Bracts narrowly linear, long-acute. 3.5. S. milliflorus. 



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



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



37. S. sphaerocephalus. 



X. Caxi. 

 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 exceeding 

 the blades. 

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



Blades of the ba.sal leaves linear or nearlj' 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 naore 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. spatuliformis. 

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

 reduced. 43. S. Harbourii. 



Blades of the ba,sal leaves spatxilate or broadly oblanceolate; stem-leaves lanceolate 

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



44. S. canus. 



XI. TOMENTOSI. 



Some of the basal leaves entire or dentate. 

 Basal leaves obovate or spatulate. 



Plant conspicuously rosulate-stoloniferous ; stem-leaves sinuately round-lobed. 



50. S. Fendleri. 

 Plant not stoloniferous ; stem-leaves pinnattfld with toothed lobes or dentate. 

 Lower stem-leaves acute; plant dark green. 45. S. plattensis. 



Lower stem-leaves obtuse or rounded at the apex ; plant yellowish green. 

 Basal leaves dentate; achenes hispidulous on the angles. 



46. S. neomeri canus. 

 Basal leaves crenate; achenes glabrous. 47. S. Leonardi. 



Basal leaves lanceolate or oblanceolate; achenes glabrous. 



Basal leaves narrowly oblanceolate. serrate. 48. S. salicinus. 



Basal leaves lanceolate, .sinuate-dentate. 49. S. canovirens. 



AU leaves pinnatifid, with toothed segments. 



Heads discoid; leaves crisp. 51. S. lanatifolius. 



Heads radiate; leaves scarcely crisp. 



Caudex subligneous; plant tomentose; bracts shorter than the disk; achenes gla- 

 brous. 50. S. Fendleri. 

 Caudex not subligneous; plant glabrate in age. 



Achenes glabrous. 52. S. uintahensis. 



Achenes hispidulous. ,53. S. multilobatus. 



XII. AUREI. 

 Heads radiate. 



Leaves thick, more or less fleshy. 



Basal leaves narrowly oblanceolate. 



Plant low, less than 2 dm. high, often with several stems from the base; basal 

 leaves short-petioled; achenes hispiduloas on the angles; ligules jellow. 

 Cyme dense; upper leaves usually pinnatifid with narrow lobes. 



54. S. densus. 

 Cyme more open; stem-leaves entire or merely crenate. 



Basal leaves subentire or 3-toothed at the apex. 



55. S. tridenticulatus. 

 Basal leaves crenate. 56. S. oblanceolatus. 



Plant about 4-6 dm. high, simple; achenes glabrous; Ugules orange. 



Leaves serrate or subentire; basal leaves 1 cm. or more, slender-jjetioled. 



57. S. longipeliolatus. 

 Stem-leaves with long, triangular lobes; basal leaves 5 cm. long or less. 



58. S. Rydbergii. 

 Basal leaves cimeate, spatulate, or broadly oblanceolate, subentire at the base. 



Lower stem-leaves spatulate, with broad-winged petioles; upper on&s sessile 



and with much enlarged bases. 72. S. dimorphophyllus. 



Stem-leaves neither broad-winged nor with much enlarged bases. 



Stem-leaves, Uke the basal ones, broadly obovate, coarsely toothed. 



59. S. oodes. 

 Stem-leaves reduced, either very narrow or else pinnatifid. 



Basal leaves angularly dentate or crenate all around, or more or less 

 lyrate. 

 Achenes glabrous. 



Basal leaves oval, crenate, or subentire. 60. S. laetiflorus. 



35* 



