THISTLE FAMILY 985 



IX. FOLTOSI. 



Heads cy lindro-campanulate ; disk about 5 mm. wide. 

 Bracts black-tipped. 



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



Bracts narrowly linear, long-acute. 35. 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. CANI. 



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 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 linear, 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 basal leaves spatulate or broadly oblanceolate; stem-leaves lanceolate 

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



44. S. canus. 



XI. TOMENTOST. 



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 pinnatifld 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. neomericanus. 



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



Basal leaves lanceolate or oblanceolate; achenes glabrous. 



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



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



All 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 hispidulous on the angles; ligules yellow. 

 Cyme dense; upper leaves usually pinnatifld 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; ligules orange. 



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



57. 5. longipetiolatus. 

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



58. S. Rydbergii. 

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



Lower stem-leaves spatulate, with broad- winged petioles; upper ones sessile 



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



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



Stem-leaves, like 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* 



