Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
Pteridaceae
Genus Description - Epiphytic; rhizomes short-creeping, rarely erect, dorsiventral, protostelic, with strongly clathrate scales at the apices; fronds small to medium-sized, linear, monomorphic, clumped; stipes short to nearly absent, greenish or greenish brown, somewhat flattened; blades linear, entire, subcoriaceous to coriaceous, with a conspicuous to inconspicuous midrib, glabrous; veins obscure, anastomosing and forming a single row of areoles between midrib and blade margins, on each side of midrib; sori in a narrow submarginal lines, one on each side of midrib, immersed in a groove, indusia absent; paraphyses present, filiform to slightly clavate; spores tetrahedral or bilateral in one species, clear to pale yellowish, relatively smooth with scattered spherical deposits; gametophytes with paired gemmae; x=60.
Type: Vittaria lineata (L.) Sm. [=Pteris lineata L.].
Vittaria, as recently redefined by Crane (1997), is primarily a genus of the Neotropics (5 spp., 4 in Mexico), plus a single species in Africa and offshore islands in the Indian Ocean. Formerly the genus included also many paleotropical species from Asia, Polynesia, and Africa, but Crane’s work has shown that the genus as traditionally construed appears to be polyphyletic. The Old World species once included in Vittaria are now placed in Haplopteris (ca. 20 spp.), with the exception of Vittaria isoetifolia Bory, in Africa and offshore islands. Vittaria sensu stricto (shoestring ferns) grows in wet forests of low to high elevation. Two of the Mexican species are widespread, the other two of narrower distribution in Mexico and Central America. The genus is distinct in its narrow, undivided fronds, linear, submarginal sori, and single row of areoles between midribs and margins. Vittaria appalachiana Farrar & Mickel, described only recently, is a species in the eastern United States, and is known primarily from gametophytic populations; the sporophytes (embryos), if formed at all, are generally abortive, or very weak and small (Farrar & Mickel, 1991). It would not be surprising if this species were to be found eventually in northeastern Mexico, in appropriate habitats (dark, moist cavities and rock shelters in non-calcareous formations).