Perennials, 6-35+ cm. Caudices ± branched, branches notably thickened distally. Stems 1-10, erect, unbranched. Leaves all basal, new leaves tightly clustered; blades spatulate or oblanceolate to linear-oblanceolate, entire, glabrous or sparsely to rarely moderately hairy, moderately to densely gland-dotted. Heads 1-10 per plant, borne singly. Peduncles 5-35 cm, ± hairy proximally, densely hairy distally. Involucres 10-15 × 12-20 mm. Outer phyllaries 8-12, 5-7.5 mm, margins 0-0.2 mm wide, sometimes slightly scarious, abaxial faces ± hairy. Ray florets 14-27; corollas 11.8-20 mm. Disc florets 50-100+; corollas yellow, 3.4-4 mm. Cypselae 2.4-3.4 mm; pappi of 4-7 obovate, usually non-aristate scales 1.9-2.2 mm. 2n = 28. Flowering (Apr-)May-Jun(-Oct). Alvars (limestone flats), openings in woods; 200 m; Ont.; Ill., Ohio. Tetraneuris herbacea is in the Center for Plant Conservation´s National Collection of Endangered Plants.
Perennial from a stout, ±fibrous-rooted caudex; lvs tufted, all basal, oblanceolate, 1-8 cm נ1.5-10 mm, ±densely villous or sericeous when young, soon glabrate, strongly punctate; scape 5-25 cm; head solitary, the disk 8-20 mm wide; invol bracts broadly rounded at the tip; rays 0.5-2 cm; 2n=28. Rare and local in prairie remnants and in open, rocky places about Lake Erie; Ill. to O. and s. Ont. May, June. (Actinea h.; Tetraneuris h.; Hymenoxys acaulis var. glabra, misapplied)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.