Heads many-flowered, radiate; the rays numerous, pistillate. Scales of the hemispherical involucre imbricated somewhat in 2 rows, appressed, with narrow membranaceous margins. Receptacle conical or hemispherical, naked. Achenes very flat, obovate or inversely heart-shaped, margined with a callous wing, or in the ray 3-winged, crowned with a pappus of several minute bristles and usually 2–4 longer awns.—Perennial and bushy-branched smooth herbs, pale green, with the aspect of Aster; the thickish leaves chiefly entire, often turned edgewise. Flowers autumnal; disk yellow; rays white or purplish. (Dedicated to James Bolton, an English botanist of the last century.)
[*] Heads middle-sized, loosely corymbed.
1. B. asteroìdes, L'Her. Stems 2–8° high; leaves lanceolate; involucral scales acuminate; pappus of few or many minute bristles and 2 awns or none. (B. glastifolia, L'Her., the awned form.)—Moist places along streams; Penn. to Ill., and southward to Fla. Sept., Oct.—Var. decúrrens, Engelm., a large form with the leaves alate-decurrent upon the stem and branches. Mo. (Eggert).
2. B. latisquàma, Gray. Heads rather larger; involucral scales oblong to ovate, obtuse or mucronate-apiculate; pappus-awns conspicuous.—W. Mo. and Kan.
[*][*] Heads small, panicled on the slender branches.
3. B. diffùsa, L'Her. Stem diffusely branched; leaves lance-linear, those on the branchlets very small and awl-shaped; rays short, mostly white; pappus of several very short bristles and 2 short awns.—Prairies of S. Ill. (Vasey), and southwestward. Aug.–Oct.
23. TOWNSÉNDIA, Hook.
Heads many-flowered, the numerous ray-flowers (violet to white) in a single series, fertile. Involucre broad, the lanceolate scariously margined scales imbricated in several series. Receptacle flat, naked. Achenes obovate or oblong, flattened, with thickish margins and beset with forked-capitellate hairs; pappus a single row of long awns or coarse rigid bristles, or reduced in the ray to chaffy scales.—Low scarcely caulescent herbs, with linear to spatulate entire leaves and large heads. (Named for David Townsend, botanical associate of Dr. Darlington of Penn.)
1. T. serìcea, Hook. Acaulescent silky-pubescent perennial; heads sessile, solitary or few, ½–1´ high; ray-pappus mostly bristly.—Dry plains, central Neb., north and westward. April, May.
24. SERICOCÁRPUS, Nees. White-topped Aster.