Source:
SSA
Description:
Annual herbs. Leaves usually alternate, simple, entire or often deeply lobed. Capitula radiate, solitary or few together; on long peduncles, thickened towards apex. Involucre hemispherical or broadly campanulate; bracts in 2-5 rows. Receptacle convex, paleate; paleae rigid, usually lobed, acuminate to aristate, embracing disc florets. Ray florets neuter; corolla yellow or orange, strap-shaped; tube somewhat compressed, linear-oblong, much shorter than lamina; lamina long-lanceolate, minutely 2- or 3-lobed. Disc florets bisexual, fertile; corolla yellow, slender, 5-toothed. Anthers linear, obtuse or very shortly sagittate, with lanceolate appendages. Style terete, globose at base; branches narrowly oblong, gradually widening upward to acutely triangular tips, pubescent on outer faces. Cypselas linear-obovate, usually 4-angled. Pappus of connate scales, sometimes with 1 or 2 awns. x = 17 (5, 8, 11) (aneuploids, polyploidy, B-chromosomes).
Distribution:
Species 11, SW United States to Costa Rica; 2 in sthn Afr.: * Tithonia diversifolia (Hemsl.) A.Gray, Northern Province, Mpumalanga, Swaziland, KwaZulu-Natal, and * T. rotundifolia (Mill.) Blake, Botswana, Northern Province, North-West, Gauteng, Mpumalanga, Swaziland and KwaZulu-Natal, introduced from America, now naturalised.
Classification:
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