402. Isocarpha R. Brown, Trans. Linn. Soc. London. 12: 110. 1817.
Pearlhead [Greek iso-, same, and carphos, small dry body, evidently alluding to uniform receptacular paleae]
Guy L. Nesom
Perennials or subshrubs [annuals], 10–150 cm. Stems usually erect, sometimes basally decumbent [creeping]. Leaves cauline; mostly opposite (distal sometimes alternate) [alternate]; petiolate or sessile; blades ± 3-nerved, elliptic to narrowly lance-elliptic [ovate or lanceolate to linear], margins entire or serrulate [dentate], faces glabrate to weakly hirsutulous or pilosulous, gland-dotted. Heads discoid, borne singly or in tight, corymbiform to subcapitate [paniculiform] arrays. Involucres ± obconic, 4–6 mm diam. Phyllaries persistent, 10–15+ in 2+ series, [1–]2–3[–6]-nerved, ovate or elliptic to lanceolate or linear, ± equal. Receptacles conic to columnar, paleate (paleae similar to inner phyllaries). Florets 60–200+; corollas white or pinkish, throats funnelform (lengths ca. 2 times diams.) [cylindric or campanulate], lobes 5, ± deltate; styles: bases enlarged, glabrous [papillose], branches filiform. Cypselae prismatic, 5-ribbed, glabrous [pubescent]; pappi 0. x = 10.
Species 5 (1 in the flora): s, c United States, Mexico, West Indies, Central America, South America.
SELECTED REFERENCE
Keil, D. J. and T. F. Stuessy. 1981. Systematics of Isocarpha (Compositae: Eupatorieae). Syst. Bot. 6: 258–287.
