408 COMPOSITAE. VOL. III. 



(a) Bracts in several series, unequal. 



Bracts linear-subulate ; leaves narrowly linear. 37. A. junceus. 



Bracts lanceolate, linear, or spatulate ; leaves lanceolate to linear. 



Western dry soil plant, i-2 tall; leaves i'-3' long. 38. A. adscendens. 



Eastern swamp plant, 2-5 tall; leaves z'-6' long. 39. A.novi-belgii. 



(b) Bracts in only i or 2 series; leaves linear to lanceolate. 40. A. longifolius. 

 tt Bracts of the involucre green, foliaceous ; western. 



Leaves lanceolate, firm; heads few. 41. A.foliaceus. 



Leaves oblong-lanceolate, thin ; heads many. 42. A. phyllodet. 



C. Leaves sessile or petioled, not at all clasping, or scarcely so. 



i. Leaves silky, silvery or canescent on both sides, entire. 



Heads corymbose-paniculate ; bracts oblong ; achenes glabrous. 43. A. sericeus. 



Heads in a narrow raceme ; bracts linear ; achenes silky. 44. A. concolor. 



2. Leaves neither silvery, silky nor canescent, entire or toothed. 

 * Bracts of the involucre with herbaceous tips, 

 t Bracts thin or coriaceous, relatively small, 

 t Leaves bristly-ciliate, linear, rigid ; western species. 45. A. Fendleri. 



tt Leaves not bristly-ciliate. 

 Tips of the involucral bracts spreading (little spreading in A. Radula, erect or spreading in 



A. Herveyi) ; heads large and showy ; rays violet to purple. 



Leaves linear to linear-oblong, rigid, obtuse, entire; heads 2' broad. 46. A. grandiftorus. 



Leaves lanceolate to oblong, the lower sparingly dentate. 

 Basal leaves with margined petioles. 



Involucre hemispheric to campanulate ; heads i' or more. 



Bracts of the involucre glandular. 47. A. spec abilis. 



Bracts of the involucre ciliate, or glabrous. 48. A. surculosus. 



Involucre turbinate ; heads 6"-g" broad. 49. A. gracilis. 



Basal leaves with unmargined petioles. 51. A, Herveyi. 



Leaves oblong-lanceolate, sharply serrate, rugose, the basal usually wanting. 50. A. Radula. 

 00 Involucral bracts all appressed (except in A. multiflorus and A. commutatus, small-headed species). 



A Involucre top-shaped; rays violet. 52. A. turbinellus. 



AA Involucre hemispheric to campanulate ; rays mostly white, sometimes purple. 

 Heads unilaterally racemose. 



Stem leaves oval, oblong, or lanceolate, serrate, or chiefly so. 



Stem pubescent or glabrate. 53. A. lateriflprus. 



Stem villous ; leaves narrowly lanceolate, thin. 54. A. hirsuticaulis. 



Stem leaves linear-lanceolate to linear, nearly entire ; stem glabrate. 55. A. vimineus. 



Heads not unilaterally racemose, mostly paniculate. 



Involucral bracts spatulate, mostly ciliate, somewhat spreading, at least the outer obtuse ; plants 



roughish-puberulent. 



Heads 3 "-4" broad, numerous ; rays 10-20. 56. A. multiflorus. 



Heads 5 "-8" broad, relatively few ; rays 20-30. 57. A. commutatus. 



Involucral bracts appressed, acute. 



Heads solitary at the ends of very small-leaved branchlets. 58. A. dumosus. 



Heads paniculate. 



Stem -leaves lanceolate, serrate or entire. 

 Heads 8"-io" broad. 



Plants glabrous, or sparingly pubescent above. 



Leaves firm, roughish or rough ; rays often purplish ; involucral bracts acute. 



59. A. salicifolius. 

 Leaves thin, smoothish ; rays chiefly white ; involucral bracts acuminate. 



60. A. paniculatus. 

 Plant puberulent all over. 61. A. missouriensis. 



Heads 6"-8" broad ; stem leaves narrowly lanceolate. 62. A. Tradescanti. 



Stem leaves linear-lanceolate to subulate, mostly entire. 



Heads scattered, 6"-g" broad ; upper leaves linear. 63. A. Faxoni. 



Heads numerous, 4 "-7" broad ; upper leaves subulate. 

 Involucre subhemispheric, 2^/2."-^," high. 

 Rays usually white ; heads 4"-?" broad. 



Paniculately branched, bushy. 64. A. ericoides. 



Simple, or with slender ascending branches. 65. A. Pringlei. 



Rays purple; heads 8" 12" broad. 66. A. Priceae. 



Involucre top-shoped, 2^" high or less. 



Plant pilose-pubescent, i l /2-2 high. 67. A. parviceps. 



Plant glabrous, very slender, i high or less. 68. A.depaupcratus. 



tt Bracts stiff, relatively large; leaves narrow, rigid, entire. [Genus HELEASTRUM DC.] 



69. A. paludosus. 

 ** Bracts of the involucre without herbaceous tips. 



Bracts linear-subulate, acuminate. 



Leaves firm, 3' long or less, entire or sparingly serrate. 70. A. nemoralis. 



Leaves thin, 6' long or less, sharply serrate. 71. A. acuminates. 



Bracts oblong or oblong-lanceolate, obtuse or acutish ; leaves narrow, entire. [Genus UNAMIA 



Greene.] 72. A. ptarmicoides. 



D. Leaves fleshy, narrow, entire; plants of salt marshes or saline soil (No. 74 sometimes in 



non-saline situations). 



Perennial ; heads 6"- 12" broad ; involucral bracts lanceolate, acuminate. 73. A. tenuifolius. 



Annuals; head 3" -5" broad; involucral bracts linear-subulate. [Genus TRIPOLIUM Nees.] 

 Involucre campanulate ; disk-flowers more numerous than the rays ; rays about 2" long. 



74. A. e.rilis. 

 Involucre cylindraceous ; disk-flowers fewer than the very short rays. 75. A. subulatus. 



