32. Centratherum Cassini, Bull. Sci. Soc. Philom. Paris. 1817: 31. 1817; in F. Cuvier, Dict. Sci. Nat. ed. 2, 7: 383. 1817.
Larkdaisy [Latin centrum, center, and atherum, prickle or awn, perhaps alluding to spine-tipped middle phyllaries of original species]
John L. Strother
Perennials (or functionally annuals), 1–3(–8+) dm (stems sometimes rooting at proximal nodes). Leaves cauline; sessile or petiolate, petioles ± winged; blades ovate to obovate, lanceolate, or linear, bases ± cuneate, margins toothed, apices acute, abaxial faces usually ± hirtellous to strigillose or tomentose, sometimes nearly glabrous, adaxial faces sparsely scabrellous or glabrate, both usually resin-gland-dotted. Heads discoid (pedunculate, each subtended by 3–8+, ± foliaceous bracts), borne singly. Involucres ± hemispheric, 6–12(–18+) mm diam. Phyllaries 24–50+ in 4–8+ series, each proximally firm, distally ± scarious, the outer ovate to deltate or lanceolate, inner oblong to lanceolate, margins entire, tips rounded to acute, usually apiculate to seta-tipped or attenuate-spinose, abaxial faces glabrous or sparsely strigillose to tomentose and usually ± resin-gland-dotted distally. Florets 30–50(–100+); corollas usually lavender to purplish (rarely white), tubes longer than funnelform throats, lobes 5, lance-linear, ± equal. Cypselae ± columnar to plumply clavate, 8–10-ribbed, glabrous, often resin-gland-dotted; pappi caducous, of 20–40 lance-linear to subulate scales. x = 16.
Species 2–4 (1 in the flora): Florida, Neotropics, Pacific Islands (Philippines), Australia.
Gleason, H. A. 1922. Centratherum. In: N. L. Britton et al., eds. 1905+. North American Flora…. 47+ vols. New York. Vol. 33, pp. 49–50. Kirkman, L. K. 1981. Taxonomic revision of Centratherum and Phyllocephalum (Compositae: Vernonieae). Rhodora 83: 1–24.