Tithonia Desf.

Small trees, shrubs or herbs; stems yellow, green, brown or purple, terete, glabrous or densely villous. Leaves alternate, occasionally opposite below, linear to deltate or 3 - 5 lobed, acute to acuminate, attenuate to auriculate or decurrent at base, pilose to subglabrous on both surfaces, serrate to crenate, petiolate or sessile. Heads solitary on fistulose, pilose to villous or subglabrous peduncles. Receptacle hemispheric to convex; paleae stiff, striate, acuminate or acute, usually with two secondary lobes embracing the achenes, persistant. Involucral bracts 2 - 5 seriate, linear to broadly rounded, rounded or acute, glabrous to pilose. Ray florets many; corolla orange or yellow. Achenes white to light tan, triangular. Pappus absent or present. Disc florets with yellow corolla, 5-lobed. Anthers black to brown. Style bifid with papillate stigma. Achenes black, brown or nottled, triangular to quadrangular. Pappus of awns or of fused squamellae or absent.

Mexico, C. America and W. Indies; ca 10 species, 2 in India.

Literature. BLAKE, S.F. (1921). Revision of the genus Tithonia. Contr. U.S. Natl. Herb. 20: 423- 436. LaDUKE, J.C. (1982). Revision of Tithonia. Rhodora 84: 453-522.

KEY TO THE SPECIES

1a. Perennials; ligules of ray florets 4.5 cm or more long

1. Tithonia diversifolia

b. Annuals; ligules of ray florets less than 3.5 cm long

2. Tithonia rotundifolia

List of Lower Taxa