408 COMPOSITAE. Vou. 1II. 
(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, a °~2° tall; leaves 1’-3’ long. 38. A. adscendens, 
Eastern swamp plant, 2°-5° tall; leaves 2’-6' long. 39. A. novi-belgii. 
(b) Bracts in only 1 or2 series; leaves lineartolanceolate. 40. A. longifolius. 
tt Bracts of the involucre green, foliaceous; western. 
Leaves lanceolate, firm ; heads few. . A. foliaceus. 
Leaves oblong-lanceolate, thin; heads many. on A. phyllodes. 
C. Leaves sessile or petioled, not at all clasping, or scarcely so. 
1. 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. 
+ Bracts thin or coriaceous, relatively small. 
} Leaves bristly-ciliate, linear, rigid; western species. 45. A. Fendleri. 
t 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. grandiflorus, 
Leaves lanceolate to oblong, the lower sparingly dentate. 
Basal leaves with margined petioles. 
Involucre hemispheric to campanulate; heads 1’ 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”—9” 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. 
0° Involucral bracts all appressed (except i 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, sofieines purple. 
Heads unilaterally racemose. 
Stem leaves oval, oblong, or lanceolate, serrate, or chiefly so. 
Stem pubescent or glabrate. : 53. A. lateriflorus. 
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. multifiorus. 
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”-10” 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 te. 
ee 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”. le broad ; upper leaves linear. 63. A. Faxon. 
Heads numerous, 4”- broad; pet, leaves subulate. 
Involucre subhemisnherte 2i4”- ” high, 
Rays usually white; heads cn ” broad. 
Paniculately branched, fates 64. A. ericoides. 
Simple, or with slender ascending branches. 65. A. Pringlei. 
Rays purple; heads 8”’-12” broad. , 66. A. Priceae. 
Involucre top- -shoped, 24” high or less. 
Plant pilose-pubescent, 114°-2° high. 67. A. parviceps. 
Plant glabrous, very slender, 1° high or less, 68. A. depauperatus. 
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. acuminatus. 
Bracts oblong or oblong-lanceolate, obtuse or acutish; leaves narrow, entire. Pyiees 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 Trrrotium Nees.] 
Involucre campanulate ; disk-flowers more numerous than the Tays; rays tae fone. 
74 exits, 
Involucre cylindraceous ; disk-flowers fewer than the very short rays. 75. A. subulatus, 
