2. Polypodium Linnaeus, Sp. Pl. 2: 1082. 1753; Gen. Pl. ed. 5, 485, 1754.
Polypody [Greek poly, many, and pous, podion, little foot, in allusion to numerous knoblike prominences of the stem]
Christopher H. Haufler
Michael D. Windham
Frank A. Lang
S. A. Whitmore
Plants on rock, occasionally terrestrial or epiphytic. Stems creeping, usually branched, 3--15 mm diam., sometimes whitish pruinose; scales concolored to bicolored, lanceolate to ovate-acuminate, not clathrate to strongly clathrate, glabrous, margins entire to denticulate. Leaves monomorphic, closely spaced to distant, not conspicuously narrowed at tip, to 90 cm. Petiole articulate to stem, straw-colored, somewhat flattened or grooved to nearly terete, winged distally. Blade broadly ovate to deltate, pinnatifid to 1-pinnate at base, not pectinate, usually with fewer than 25 pairs of pinnae, not glaucous or conspicuously scaly; rachis sparsely scaly to glabrescent abaxially, puberulent to glabrous adaxially; scales ovate-lanceolate to linear, not peltate or clathrate. Segments linear to oblong; margins entire to serrate; apex rounded to attenuate. Venation free to anastomosing, if strongly anastomosing, then never with more than 1 included veinlet in fertile areoles. Sori often confined to distal region of leaf, discrete, circular to oval when immature, borne at tips of single veins, in 1--3 rows on either side of midrib; indument absent or of modified sporangia (sporangiasters), often bearing glandular hairs on bulbous head. Spores monolete, rugose to tuberculate. x = 37.
Species ca. 100 (11 in the flora): worldwide.
Some species traditionally included in Polypodium are treated here in other genera, for example, Pleopeltis and Pecluma .
Except for the tropical species Polypodium triseriale , North American Polypodium is a complex assemblage of interactive species. The North American species have ties to European taxa (e.g., P . vulgare sensu stricto, which probably originated by allopolyploidy between P . glycyrrhiza and P . sibiricum ) but are quite distinct from them. Morphologic comparisons and continuing biochemical and molecular studies indicate that two groups of diploid species occur within the North American P . vulgare complex. One group includes P . glycyrrhiza and P . californicum ; the second, P . amorphum , P . appalachianum , and P . sibiricum . Allopolyploid species have originated following hybridizations within a species group (i.e., P . calirhiza from P . glycyrrhiza × californicum , P . saximontanum from P . amorphum × sibiricum , and P . virginianum from P . appalachianum × sibiricum ) as well as between members of the two groups (i.e., P . hesperium from P . amorphum × glycyrrhiza ). These reticulate relationships are summarized in the reticulogram. We consider P . scouleri to be peripheral to the "core" diploids even though hybrids have been reported.
We have not included the European Polypodium cambricum Linnaeus [ P . australe Fée], reported from San Clemente Island, California (R. M. Lloyd and J. E. Hohn 1969), in the North American flora because, since the single, original collection, efforts to relocate specimens in nature have failed (R. M. Lloyd et al. 1992).
Because taste is a characteristic used in the descriptions, the reader is cautioned to taste clean rhizomes from uncontaminated soils.
Cranfill, R. and D. M. Britton. 1983. Typification within the Polypodium virginianum complex (Polypodiaceae). Taxon 32: 557--560. Evans, A. M. 1971. Polypodium. In: A. M. Evans, ed. 1971. A Review of Systematic Studies of the Pteridophytes of the Southern Appalachians. Blacksburg. Haufler, C. H. and M. D. Windham. 1991. New species of North American Cystopteris and Polypodium, with comments on their reticulate relationships. Amer. Fern J. 81: 7--23. Haufler, C. H. and Wang Z. R. 1991. Chromosomal analyses and the origin of allopolyploid Polypodium virginianum. Amer. J. Bot. 78: 624--629. Lang, F. A. 1971. The Polypodium vulgare complex in the Pacific Northwest. Madroño 21: 235--254. Whitmore, S. A. and A. R. Smith. 1991. Recognition of the tetraploid, Polypodium calirhiza (Polypodiaceae), in western North America. Madroño 38: 233--248.