Polypodium hesperium
Polypodium saximontanum
western polypody, western polypody fern
Rocky Mountain polypody
occasionally whitish pruinose, slender to moderately stout, to 6 mm diam., acrid- to sweet-tasting: scales concolored, brown or slightly mottled, often darker near point of attachment, lanceolate, usually symmetric, margins entire to denticulate.
often whitish pruinose, slender, to 6 mm diam., acrid-tasting;
scales weakly bicolored, lanceolate, contorted distally, bases and margins light brown, sometimes with dark central stripe, margins often coarsely dentate.
to 35 cm.
to 25 cm.
slender, to 1.5 mm diam.
slender, to 1.5 mm diam.
oblong to lanceolate-ovate, occasionally deltate, pinnatifid, usually widest at or near middle, to 7 cm wide, herbaceous to somewhat leathery;
rachis sparsely scaly to glabrescent abaxially, glabrous adaxially;
scales linear-lanceolate, usually less than 6 cells wide.
oblong to linear, pinnatifid, usually widest 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 to linear-lanceolate, less than 12 mm wide;
margins entire to crenulate or obscurely serrate;
apex obtuse to acute;
midrib glabrous adaxially.
oblong, less than 12 mm wide;
margins entire to crenulate;
apex rounded to broadly acute;
midrib glabrous adaxially.
midway between margin and midrib, less than 3 mm diam., oval when immature.
midway between margin and midrib to nearly marginal, less than 3 mm diam., circular when immature.
more than 58 µm, rugose to verrucose or tuberculate, surface projections commonly less than 3 µm.
more than 58 µm, tuberculate, surface projections more than 3 µm tall.
free.
free.
absent.
present, usually less than 40 per sorus, heads with a few glandular hairs or rarely without glands.
= 148.
= 148.
Polypodium hesperium
Polypodium saximontanum
Using morphologic and chromosomal data, F. A. Lang (1971) proposed that Polypodium hesperium originated through allotetraploidy involving P. glycyrrhiza and P. amorphum, a hypothesis recently supported by electrophoretic studies (C. H. Haufler, M. D. Windham, and E. W. Rabe, unpublished). Variations in spore surface morphology and banding patterns observed in isozyme studies indicate that P. hesperium may have originated more than once from different individuals of the same species. Some collections of P. hesperium can be mistaken for P. glycyrrhiza, but the latter species is easily distinguished by its pubescent rachises, linear blade scales, and smaller spores (less than 58 µm). Although P. amorphum has sporangiasters and P. hesperium lacks them, misshapen sporangia in P. hesperium can mimic these distinctive soral structures. Therefore, it is often necessary to use a combination of soral, stem scale, and blade scale features (discussed in the key) to separate P. hesperium from P. amorphum. Hybridization occurs between P. hesperium and each of its progenitor diploids to form triploid individuals with misshapen spores (F. A. Lang 1971). Rare, sterile, tetraploid hybrids with P. saximontanum have also been detected (M. D. Windham, unpublished).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Polypodium saximontanum is an allotetraploid species whose progenitor diploid species are P. amorphum and P. sibiricum (M. D. Windham 1993). Prior to its recognition as a distinct species, collections of P. saximontanum were variously referred to P. montense F. A. Lang (= P. amorphum), P. hesperium, and/or P. virginianum. In addition to its separate geographic range, P. saximontanum can be distinguished from P. virginianum by having narrower leaves and a reduced frequency of glandular hairs on its sporangiasters. Polypodium saximontanum also has a separate range from P. amorphum and has spores with large (greater than 3 µm tall) projections. Although P. saximontanum overlaps in range with P. hesperium, the latter species has no sporangiasters. Tetraploid hybrids of these two species have misshapen spores.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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