Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
Polypodiaceae
Genus Description - Epiphytic, occasionally terrestrial; rhizomes long-creeping, often branched; rhizome scales concolorous to bicolorous, nonclathrate, imbricate, peltately attached, surfaces lacking hairs, margins entire to dentate; fronds simple, distant, monomorphic to dimorphic (fertile longer and narrower than sterile), stipitate, elliptic to oblong, articulate, phyllopodia obsolete to present, margins entire to undulate; blades chartaceous to subcoriaceous, glabrous or with filamentous or round (in M. percussa) scales; venation netted, with one to several free included veins in areoles; sori round to elongate, exindusiate, within costal areoles in one row on each side of costae, on end of free, included veins or at junction of several included veins (compital); paraphyses present, consisting of filiform scales or branched scales with filiform tips; sporangia glabrous; spores bilateral, verrucate to coarsely tuberculate or rugose; x=37.
Type: Microgramma persicariifolia (Schrad.) C. Presl [= Polypodium persicariifolium Schrad.]
Craspedaria Link, Fil. Spec. 117. 1841. Type: Craspedaria vacciniifolia (Langsd. & Fisch.) Link [= Polypodium vacciniifolium Langsd. & Fisch.] = Microgramma vacciniifolia (Langsd. & Fisch.) Copel. Anapeltis J. Sm., Cult. Ferns 5. 1857. Type: Anapeltis lycopodioides (L.) J. Sm. [= Polypodium lycopodioides L.] = Microgramma lycopodioides (L.) Copel. Lopholepis (J. Sm.) J. Sm., London J. Bot. 1: 195. 1842, hom. illeg., non Decne., 1839 (Poaceae). Goniophlebium sect. Lopholepis J. Sm., J. Bot. (Hook.) 4: 56. 1841. Type: Lopholepis piloselloides (L.) J. Sm. [= Polypodium piloselloides L.] = Microgramma piloselloides (L.) Copel.
Microgramma is a segregate of Polypodium s.l. and comprises ca. 20 species in the New World tropics and 1 or 2 species in Africa. The genus is usually distinguished by the subdimorphic to dimorphic fronds, reticulate veins, peltate non-clathrate rhizome scales, and uniseriate sori with paraphyses of narrow scales. The generic limits of Microgramma, as well as the other segregate genera, are in need of careful study. Polypodium percussum Cav. is often placed in Pleopeltis. Smith (1981) considered it might be closer to Microgramma because of its dense, branched receptacular scales with hair-like segments, and it is considered a Microgramma in this flora, largely on the basis of the lack of peltate scales in the sorus. In addition, molecular data ally it with other species of Microgramma, and not with Pleopeltis (Schneider et al., unpubl. data). Copeland included Polypodium muenchii in Microgramma, and Smith (1981) included it in Pleopeltis, but it is aberrant in both genera; we place it in Polypodium s.l. in this treatment. It is sometimes treated as Microphlebodium muenchii (Christ) L. D. Go´mez.