Thistle Family. 81 



t f Stem glabrous or sparingly pubescent, ab-ive. A - 



% Leave sharply serrate, sometimes in \ A. laevis. ^**^*- 



A. prenanthoides Muhl. Stem 1-3 feet high, slender, nearly glabrous or 

 hairy above; leaves thin, ovate-lanceolate, taper-pointed, sharply serrate in 

 the middle, tapering' into a slender, elongated, entire portion towards the 

 base, upper surface rough, lower smooth, base auriculate-olasping: heads 

 about % inch hig-h, on short divergent peduncles, involucral scales narrow, 

 somewhat spreading; rays light blue or whitish. Rich woods; frequent; 

 Jackson, Delaware. Mu-ieatine, and Johnson counties, reported from Fayette 

 and Story counties. 



A. laeVis L. Stem 2-1 feet high, smooth, often glaucous; leaves lanceolate 

 or oblong-lanceolate, entire or sub-serrate, thickish, radical and lower leaves 

 large, wing-petioled, the upper partly clasping by an auriculate base; heads 

 chiefly solitary on the branchlets; involucre hemispherical, scales with broad, 

 acute, ap pressed, green tips. Prairies and rocky woods; frequent and widely 

 distributed; Winneshiek, Fayette, Floyd, Delaware, Johnson, Henry. Deca- 

 Lur, Winnebago, Lyon, Dickinson, and Emmet counties, reported from Story 

 and Hamilton counties. 



X X Leaves entire or nearly so. 



A. longifolius Lam. Stem 1-3 feet high, glabrous or somewhat pubes- 

 cent, branched; leaves long-lanceolate to linear-lanceolate, entire or nearly 

 so, acuminate, base -sessile, clasping; heads numerous, about an inch broad, 

 the scales narrow, green, acute, in 1 or 3 rows. Moist soil; specimens from 

 Delaware and Henry counties referred to this species 



* * * Leaves petloled or sessi'e, not clamping or scarcely so. 

 t Leaves entire, silvery, silky or canescent or both sides. 



A. sericeus Vent. Stem 1-3 feet high, smooth, very rigid, branched; 

 leaves lanceolate or oblong, sessile, entire, silvery white on both sides; heads 

 large, mostly terminal, on slender branches; rays many, violet-purp'e; scales 

 leaf-like, tips spreading. Common on the prairies in western and southern 

 Iowa, infrequent eastward; Winneshiek, Delaware, Muscatine,, Johnson, 

 Decatur, Ringgold, Taylor, Page, Fremont, Montgomery, Pottawattamie, 

 Winnebago, Lyon, and Emmet counties; reported from Fayette, Stor3 T , 

 Buena Vista, Monona, Harrison, and Woodbury counties. 



t t Leaves open toothed, neither silvery, silky noi- canescent. 

 X Heads corymbose. 



A. ptarmicoides~(Nees) T. & G. Stems simple, tufted, 8-20 inches high, 

 smocth or sparingly pubescent; leaves linear-lanceolate, 1-3-nerved, acute, 

 entire, rough-margined, lower tapering to a short petiole; heads in a flat 

 corymb; involucral scales imbricated in 3 or 4 rows, appressed, without green 

 tips; rays white. Sandy soil; Muscatine, Emmet, and Lyon counties. 

 X X Heads solitary at the ends of the branchlets. 



A. dumosus L. Stem 1-3 feet high, glabrous, paniculately branched; 

 leaves linear or linear-lanceolate, entire, acute or obtusish, rough-margined, 

 those of the branches small and bract-like; heads many, terminating the 

 branches and branchlets; involucre campanula^, the scales in 4 rows, linear- 

 subulate, obtuse or acutish, appressed, green-tipped; rays 15-30, white to pale 

 violet. Sandy soil; reported from Benton county by Arthur; specimens from 

 Lee county have been referred to this species. 



XXX Heads paniculate, mot in 1-sided racemes. 



A. salicifolius Lam. Stem 2-5 feet high, slender, paniculately branched, 

 leafy, o-labrous or slightly pubescent above; leaves lanceolate or linear-Ian- 



