THISTLE FAMILY 881 



Plant glabrous or sparingly short-pubescent. 31. A. Lindleyanus. 



Basal leaf-blades lanceolate; upper stem-leaves narrowly lanceolate or those of the inflor- 

 escence lance-linear. 

 Heads few; involucres 8-9 mm. high; rays about 15 mm. long; achenes glabrous. 



32. A. MacCallae. 



Heads numerous; involucres 5-6 mm. high; rays 8-10 mm. long; achenes hispidulous- 

 strigose. 33. A. Butleri. 



XV. LAEVES. 



Bracts much shorter than the disk. 34. A. brevibracteatus. 



Bracts about equalling the disk or only slightly shorter. 

 Leaves merely scabrous-ciliate. 



Green tips of the bracts broadly rhombic; leaves of the branches much reduced. 



35. A. laevis. 



Green tips of the bracts narrowly rhombic or rhombic-oblanceolate; leaves of 



the branches gradually but not conspicuously reduced. 

 Stem-leaves lanceolate or linear-lanceolate, auricled-clasping. 



36. A. Geyeri. 

 Stem-leaves narrowly linear, not auricled. 37. A. subsalignus. 



Leaves decidedly long-ciliate ; bracts with oblong green tips. 38. A. Scribneri. 



O XVI. PORTERIANI. 



One species. 39. A. Porteri. 



XVII. SALICIFOLII. 



Inflorescence falsely racemose; leaves linear to oblanceolate ; leaves triple-nerved. 



40. A. subraccmosus. 

 Inflorescence paniculate or corymbiform; leaves not triple-nerved. 



Inflorescence elongate, not flat-topped. 



Heads numerous in a much branched panicle; involucre well imbricate. 

 Leaves distinctly toothed. 



Disk of the head about 1 cm. high and broad; leaves thickish. 



41. A. salicifolius. 

 Disk 68 mm. high and broad; leaves thin. 42. A. paniculatus. 



Leaves entire, rarely denticulate, with more or less clasping bases. 

 Disk of the Jiead nearly 1 cm. high and broad. 



Bracts linear-filiform, more or less squarrose. 43. A. hesperius. 

 Bracts linear, erect. 



Ligules purple. 44. A. fluviatilis. 



Ligules white or sometimes pinkish. 



Bracts not with white midrib; leaves narrowly linear. 



45. A. Osterhoutii. 

 Bracts with white midrib; leaves lanceolate or oblong-lanceolate. 



46. A. laetivirens. 

 Disk of the head 6-8 mm. high and broad. 



Bracts linear, nearly of the same length; leaves narrowly linear. 



47. A. longulus. 

 Bracts oblong or linear-oblong, the outer shorter; leaves broadly linear. 



48. A. roseolas. 

 Heads rather few, often solitary on the leafy branches; bracts narrowly linear, 



nearly of the same length, the outer green. 49. A. Franklinianus. 



Inflorescence more or less flat-topped. 



Leaves lanceolate to linear-lanceolate, firm; heads numerous. 



50. A. corymbiformis. 

 Leaves narrowly linear, thin; heads few. 51. A. junciformis. 



XVIII. LONCHOPHYLLI. 



Stem softly pubescent; leaves lanceolate, not pale. 



Stem crisp-puberulent above; upper stem-leaves linear, sessile, but scarcely auricled. 



52. A. lonchophyllus. 

 Stem villous above; upper stem-leaves oblong-lanceolate, auriculate-clasping. 



53. A. eriocaulis. 

 Stem hispidulous above; leaves linear, pale green. 54. A. leucopsis. 



XIX. OCCIDENTALES. 



Bracts linear-subulate, acuminate, the inner almost caudate. 



Leaves linear-oblanceolate, acuminate, or the upper linear-lanceolate. 



55. A. subcaudatus. 



Leaves linear. 49. A. Franklinianus. 



Bracts linear, acute; lower leaves oblanceolate, the upper lanceolate, acute, usually 



auriculate-clasping. 



Disk about 1 cm. broad; stem-leaves linear or lance-linear; basal-leaves linear-ob- 

 lanceolate; bracts distinctly imbricate in 3-4 series. 56. A. occidentalis. 

 Disk 1.5 cm. or more wide; leaves lanceolate or oblanceolate, entire; bracts in about 



2 series. 

 Bracts, at least the outer ones, wholly green; plant 2-4 dm. high. 



57. A. Fremontii. 

 Bracts with more or less distinct white margins below, green-tipped above. 



Bracts with conspicuous rhombic-lanceolate green tips; dark green stem- 

 leaves oblanceolate, all except the uppermost crenate and petioled; rays 

 dark blue. 58. A. Umbachii. 



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