Polypodium virginianum
Polypodium calirhiza
common polypody, polypode de virginie, rock polypody, tripes-de-roches
licorice fern, nested polypody
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.
rarely whitish to glaucous, moderately stout to slender, to 8 mm diam., acrid- or slightly sweet-tasting;
scales concolored brown or slightly darker near point of attachment, lanceolate-ovate, symmetric, margins entire to erose.
to 40 cm.
to 70 cm.
slender, to 2 mm diam.
usually slender, to 3 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 below middle or occasionally at base, to 16 cm wide, leathery to herbaceous;
rachis sparsely scaly to glabrescent abaxially, puberulent adaxially;
scales lanceolate-ovate, usually more than 3 cells wide.
oblong, less than 8 mm wide;
margins entire to crenulate;
apex rounded to broadly acute;
midrib glabrous adaxially.
linear-lanceolate to oblong, usually less than 15 mm wide;
margins conspicuously serrate;
apex obtuse to acute;
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 4 mm diam., oval when immature.
more than 52 µm, tuberculate, surface projections more than 3 µm tall.
more than 58 µm, verrucose, surface projections less than 3 µm. 2n = 148.
free.
weakly to moderately anastomosing, some to many segments lacking areoles.
present, usually less than 40 per sorus, heads covered with glandular hairs.
absent.
= 148.
Polypodium virginianum
Polypodium calirhiza
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.)
Although originally considered a cytotype of Polypodium californicum, P. calirhiza is an allotetraploid involving P. californicum and P. glycyrrhiza (S. A. Whitmore and A. R. Smith 1991) and therefore should be treated as a distinct species. Some individuals of P. calirhiza can be difficult to distinguish from the two parental species (see comments under P. californicum and P. glycyrrhiza); most collections can be identified based on a combination of blade shape, venation pattern, spore size, and geographic distribution. Polypodium calirhiza hybridizes with P. glycyrrhiza to produce sterile triploid plants with misshapen spores.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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