320. Porophyllum Guettard, Hist. Acad. Roy. Sci. Mém. Math. Phys. (Paris, 4to). 1750: 377. 1754.
[Greek poros, hole, and phyllon, leaf, alluding to gland-dotted leaf blades]
John L. Strother
Annuals, perennials, subshrubs, or shrubs, 10–120[–200+] cm. Stems erect, usually strictly branched. Leaves cauline; opposite or alternate; petiolate or sessile; blades orbiculate to linear or filiform, margins crenate or entire, faces usually glabrous (oil-glands scattered and/or at margins). Heads discoid, borne singly or in loose, ± corymbiform arrays. Calyculi 0. Involucres cylindric to campanulate [turbinate], 3–12 mm diam. Phyllaries 5–10 in ± 2 series (distinct to bases, oblong or lanceolate to linear, bearing oval to linear oil-glands). Receptacles convex to conic, pitted, epaleate. Ray florets 0. Disc florets (5–)10–80[–100+], bisexual, fertile; corollas usually yellow, sometimes whitish to greenish or purplish [brownish], tubes either very slender, much longer than funnelform throats, or stout, much shorter than narrowly cylindric throats, lobes 5, deltate to lanceolate (often unequal). Cypselae cylindric to fusiform, hirtellous to villous [glabrous]; pappi persistent, of 25–50(–100) coarse to fine bristles in 1–2+ series. x = 12.
Species ca. 25 (5 in the flora): sw United States, Mexico, West Indies (Antilles), Central America, South America.
Johnson, R. R. 1969. Monograph of the plant genus Porophyllum (Compositae: Helenieae). Univ. Kansas Sci. Bull. 48: 225–267.