Polypodium virginianum
Polypodium glycyrrhiza
common polypody, polypode de virginie, rock polypody, tripes-de-roches
licorice fern, licorice 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.
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.
to 40 cm.
to 75 cm.
slender, to 2 mm diam.
usually slender, 0.5–2 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.
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, less than 8 mm wide;
margins entire to crenulate;
apex rounded to broadly acute;
midrib glabrous adaxially.
linear to oblong, less than 12 mm wide;
margins serrate;
apex acute to attenuate;
midrib puberulent adaxially.
midway between margin and midrib to nearly marginal, less than 3 mm diam., circular when immature.
midway between margin and midrib or slightly closer to midrib, usually less than 3 mm diam., circular to oval when immature.
more than 52 µm, tuberculate, surface projections more than 3 µm tall.
less than 58 µm, verrucose, with surface projections less than 3 µm. 2n = 74.
free.
free.
present, usually less than 40 per sorus, heads covered with glandular hairs.
absent.
= 148.
Polypodium virginianum
Polypodium glycyrrhiza
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.)
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.)
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