Polypodium virginianum
Polypodium sibiricum
common polypody, polypode de virginie, rock polypody, tripes-de-roches
polypode de sibérie, Siberian polypody, Siberian polypody fern
often whitish pruinose, slender, to 6 mm diam., acrid-tasting;
scales weakly bicolored, lanceolate, contorted distally, base and margins light brown, sometimes with dark central stripe, margins denticulate.
often whitish pruinose, slender, to 6 mm diam., acrid-tasting;
scales concolored to weakly bicolored, uniformly dark brown, often lighter near base, lanceolate, contorted distally, margins denticulate.
to 40 cm.
to 25 cm.
slender, to 2 mm diam.
slender, to 1 mm diam.
oblong to narrowly lanceolate, pinnatifid, usually widest near middle, occasionally at or near base, to 7 cm wide, somewhat leathery;
rachis sparsely scaly to glabrescent abaxially, glabrous adaxially;
scales lanceolate-ovate, usually more than 6 cells wide.
oblong-linear, pinnatifid, usually widest at or near middle, to 4 cm wide, somewhat leathery;
rachis sparsely scaly to glabrescent abaxially, glabrous adaxially;
scales lanceolate-ovate, usually more than 6 cells wide.
oblong, less than 8 mm wide;
margins entire to crenulate;
apex rounded to broadly acute;
midrib glabrous adaxially.
oblong, less than 7 mm wide;
margins entire to crenulate;
apex rounded to broadly acute;
midrib glabrous adaxially.
midway between margin and midrib to nearly marginal, less than 3 mm diam., circular when immature.
midway between margin and midrib to nearly marginal, less than 3 mm diam., circular when immature.
more than 52 µm, tuberculate, surface projections more than 3 µm tall.
less than 52 µm, tuberculate with tubercles, surface projections more than 3 µm tall.
free.
free.
present, usually less than 40 per sorus, heads covered with glandular hairs.
present, less than 40 per sorus, heads normally without glandular hairs.
= 148.
= 74.
Polypodium virginianum
Polypodium sibiricum
Traditionally, two cytotypes have been recognized within Polypodium virginianum (I. Manton and M. Shivas 1953). Recent research has demonstrated that the tetraploid cytotype, which properly bears the name P. virginianum (R. Cranfill and D. M. Britton 1983), is an allopolyploid produced by hybridization between the diploid cytotype (here called P. appalachianum) and P. sibiricum (C. H. Haufler and M. D. Windham 1991; C. H. Haufler and Wang Z. R. 1991). Although sometimes similar to its diploid parents in overall leaf morphology, P. virginianum has consistently larger spores, typically more than 52 µm (see additional comments under P. appalachianum and P. sibiricum). Frequent hybridizations between P. virginianum and P. appalachianum form morphologically intermediate, triploid individuals with misshapen spores. Sterile triploids also result from hybridization between P. virginianum and P. sibiricum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
This boreal diploid has traditionally been identified as Polypodium virginianum (T. M. C. Taylor 1970; F. A. Lang 1971), but recent investigations indicate that it is conspecific with the eastern Eurasian species P. sibiricum (C. H. Haufler and M. D. Windham 1991). The sporangiasters of P. sibiricum normally lack glands, but some collections have sporangiasters with a few glandular hairs. Although such collections could be misidentified, the spores of P. sibiricum are less than 52 µm and clearly distinguish it from P. virginianum, P. amorphum, and P. saximontanum. Hybridization occurs between P. sibiricum and P. virginianum where these species overlap in Canada, forming triploid individuals with misshapen spores (C. H. Haufler and Wang Z. R. 1991).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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