THISTLE FAMILY 985 



IX. FOLIOSI. 



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

 Bracts black-tippod. 



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



Bracts luuiowlv linear, long-acute. 35. S. milliflorun. 



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



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



37. S. sphaerocephatus. 



X. Cani. 



Heads 7-8 mm high. 



Involucres as well as the whole plant densely wliite-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 leav&s 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 liigli. 



Blades of the basal leaves narrowly oblanceolate; stem-leaves linear, entire. 

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



42. S. spatulifonnis. 

 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, vLsuaUy more or less pinnatifld; heads hemispheric. 



44. S. canus. 



XI. TOifENTOSI. 



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 roimded at the apex: plant yellowish green. 

 Basal leaves dentate; achenes hispid ulous on the angles. 



46. S. npomericanus. 

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



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 pinnatifld, with toothed segments. 



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



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. .\UREI. 



Heads radiate. 



Leaves thick, more or less fleshy. 



Basal leaves narrowly oblanceolate. 



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

 leaves short-petioled; achenes liispidulous on the angles; Ugules 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. tridenticulalus. 

 Basal leaves crenate. 56. S. oblnnceolalus. 



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



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



57. S. 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. nodes. 

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



Basal leavas angularly dentate or crenate all aroiuid, or more or less 

 lyrate. 

 Achenes glabrous. 



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



35* 



