Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
Lygodiaceae
Species Description - Rhizomes short-creeping, 1–2 mm diam., hairs brown; stipes and rachises stramineous, wiry; axes glabrescent to densely hairy with short stiff hairs; pinna axes very short; pinnule axes pinnate, the segments alternating, each segment trifid to quinquifid, the central lobe much the largest, 3–10 x 0.5–1.4 cm, margins finely serrulate; veins free, sparsely strigose to densely hairy, hairs 0.5 mm long, whitish; fertile lobes ca. 1 mm wide, indusia with many 0.5 mm long white hairs; 2n=116 (Trin).
Lectotype (chosen by Proctor, Fl. L. Antill. 2: 51. 1977). Brazil. Breynius s.n. (S?).
Lygodium venustum is easily distinguished from L. heterodoxum by its free veins, pubescent laminae, and palmately 3–5- parted pinnules. Mexican specimens have often been named L. mexicanum and L. polymorphum (Cav.) Kunth, based on degree of pubescence, but these variants are merely part of the wide variation in this species. The name L. polymorphum is probably misapplied to this species; the type is from the Philippines, fide Christensen (Dansk. Bot. Ark. 9(3): 3–32. 1937), and probably referable to L. flexuosum (L.) Sw. In any case, L. polymorphum is illegitimate, since Cavanilles cited Ophioglossum scandens L. as a synonym (see Alston & Holttum, Reinwardtia 5: 15. 1959). A putative hybrid of L. heterodoxum and L. venustum, with malformed spores, was collected in Oaxaca (Mickel 4179, NY). It has some free and some anastomosing veins, fertile lobes with associated whitish hairs, pinnules of intermediate width (11–14 mm wide), pinnule axes flexuous, and inequilaterally 2–4 palmately lobed pinnules.