Polypodium glycyrrhiza
Polypodium sibiricum
licorice fern, licorice polypody fern
polypode de sibérie, Siberian polypody, Siberian polypody fern
not whitish pruinose, slender to moderately stout, to 6 mm diam., intensely sweet, licorice-flavored;
scales concolored, brown or slightly darker near point of attachment, lanceolate to lanceolate-ovate, symmetric, margins entire.
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 75 cm.
to 25 cm.
usually slender, 0.5–2 mm diam.
slender, to 1 mm diam.
lanceolate-ovate to oblong, pinnatifid, widest near middle or just below, to 16 cm wide, herbaceous, rarely slightly leathery;
rachis sparsely scaly to glabrescent abaxially, puberulent adaxially;
scales linear, usually less than 3 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.
linear to oblong, less than 12 mm wide;
margins serrate;
apex acute to attenuate;
midrib puberulent adaxially.
oblong, less than 7 mm wide;
margins entire to crenulate;
apex rounded to broadly acute;
midrib glabrous adaxially.
midway between margin and midrib or slightly closer to midrib, usually less than 3 mm diam., circular to oval when immature.
midway between margin and midrib to nearly marginal, less than 3 mm diam., circular when immature.
less than 58 µm, verrucose, with surface projections less than 3 µm. 2n = 74.
less than 52 µm, tuberculate with tubercles, surface projections more than 3 µm tall.
free.
free.
absent.
present, less than 40 per sorus, heads normally without glandular hairs.
= 74.
Polypodium glycyrrhiza
Polypodium sibiricum
Polypodium glycyrrhiza hybridizes with P. calirhiza and with P. hesperium to produce sterile triploids with misshapen spores. Polypodium glycyrrhiza was involved in the origin of both of these allotetraploid species, and some individuals can be difficult to identify. Free versus anastomosing venation distinguishes this species from P. calirhiza; the presence of adaxial hairs on the rachis separates it from P. hesperium. An additional character for distinguishing these taxa is spore length, which is less than 58 µm in diploid P. glycyrrhiza and more than 58 µm in the two tetraploid species. Reports of P. glycyrrhiza occurring in Arizona (T. Reeves 1981; D. B. Lellinger 1985) are based on misidentified specimens.
(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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OR, 
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