Pleopeltis

Authority

Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.

Family

Polypodiaceae

Scientific Name

Pleopeltis

Description

Genus Description - Epiphytic, less commonly epipetric; rhizomes long-creeping, branched, rhizome scales concolorous to bicolorous, nonclathrate to rarely clathrate, peltate at bases, surfaces hairy (comose) or glabrous, margins entire to fimbriate or erose; fronds simple to pinnatifid, rarely pinnate-pinnatifid, distant to clumped, monomorphic to subdimorphic, stipitate, articulate; blades firm to coriaceous, sparsely to densely scaly with peltate, round to ovate-lanceolate scales; veins netted, rarely free, areoles with 1-3 free included veins; sori round to oblong, within costal areoles in one row on each side of midribs, at junction of several included veins (compital), exindusiate, with round, peltate scales, at least in immature sori; sporangia glabrous; spores yellowish, bilateral, with perispore shallowly to prominently verrucate; x = 34, 35, 37?

Discussion

Type: Pleopeltis angusta Humb. & Bonpl. ex Willd.

xPleopodium Schelpe & Anthony, Bothalia 15: 557. 1985. Type: xPleopodium simianum Schelpe & Anthony [= Pleopeltis macrocarpa x Polypodium polypodioides subsp. ecklonii (Kunze) Schelpe].

Pleopeltis is a segregate of Polypodium and as treated herein comprises 15–20 species (excluding Lepisorus of Asia). The distribution of the genus thus construed is primarily New World, with a few species in Africa to India and Sri Lanka. Pleopeltis is usually distinguished by the blades and sori with peltate, round scales, the areoles with free, included veins, and sori at the junction of several included veins. The generic limits of Pleopeltis have long been in need of careful scrutiny (Windham, 1993). Morphologically, a few species resemble species of Microgramma, but other species are more similar to scaly species of Polypodium. On the basis of molecular evidence, it is now believed that all scaly-bladed species treated herein as Polypodium are more appropriately placed in Pleopeltis, and that the circumscription of Polypodium should be restricted to those species that have essentially scaleless blades (Smith et al., ms. in prep.; Schneider et al., unpubl. data). The implications of that for the Mexican fern flora are that the following taxa will ultimately need transfer to Pleopeltis: Polypodium alansmithii R. C. Moran; P. collinsii Maxon; P. cryptocarpon Fe´e; P. fallacissimum Maxon; P. furfuraceum Schltdl. & Cham.; P. guttatum Maxon; P. lepidotrichum (Fe´e) Maxon; P. lindenianum Kunze; P. madrense J. Sm.; P. platylepis Mett. ex Kuhn; P. plebeium Schltdl. & Cham.; P. polypodioides (L.) Watt var. knoblochianum Mickel; P. pyrrholepis (Fe´e) Maxon; P. remotum Desv.; P. rosei Maxon; P. rzedowskianum Mickel; P. sanctae-rosae (Maxon) C. Chr.; and P. villagranii Copel. Combinations in Pleopeltis already exist for Polypodium muenchii, P. polypodioides (L.) Watt var. aciculare and var. michauxianum, P. riograndense, and P. thyssanolepis, but in this work we treat them in the genus Polypodium, pending future publications. Polypodium fallax is treated here in Pleopeltis on the basis of the caducous, peltate, circular paraphyses on the blades. Polypodium percussum Cav., which is often placed in Pleopeltis (e.g, by Tryon & Tryon, 1982; Tryon and Stolze, 1993), is here treated in Microgramma (which see for further discussion). Several species of Pleopeltis appear to hybridize with species of Polypodium (as treated in this flora) to produce abortivespored or fertile species in the hybrid genus xPleopodium, which we treat here as a synonym of Pleopeltis, pending further study of generic limits of Pleopeltis and Polypodium. One such putative hybrid, xPleopodium fallacissimum (Maxon) Mickel & Beitel was thought to be the putative hybrid between Pleopeltis polylepis var. erythrolepis and Polypodium guttatum. However, we now consider this taxon to be a good species, and treat it under Polypodium, even though its proper position we anticipate will eventually be in Pleopeltis. The distribution and density of the peltate scales on the blades are important characters for distinguishing species in Pleopeltis. In the key and species descriptions, the terms used to describe the scales are defined as follows: sparse = scales rarely touching and often space between scales for two or more similar scales; scattered = some scales touching and often space between scales for a single similar scale; dense = most scales overlapping other scales and with little or no space for any additional scales.