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. 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.

Lvs scattered along the branched, widely creeping rhizome, firm, evergreen, deeply lobed to once pinnate with sessile, broad-based pinnae, the veins free or areolate only along the costae; petiole with 3 vascular bundles below, these uniting distally; sori rotund or elliptic, borne subterminally on the vein-forks. 150+, cosmop.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.