Polypodium hesperium
Polypodium californicum
western polypody, western polypody fern
California 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.
dull or inconspicuously glaucous, moderately stout, to 10 mm diam., acrid or bland-tasting;
scales uniformly brown or slightly darker near point of attachment, lanceolate-ovate, symmetric, margins entire to erose.
to 35 cm.
to 70 cm.
slender, to 1.5 mm diam.
usually slender, to 3 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.
deltate to lanceolate-ovate, pinnatifid, usually widest near base, to 20 cm wide, leathery to herbaceous;
rachis sparsely scaly to glabrescent abaxially, puberulent adaxially;
scales deltate to ovate, usually more than 10 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.
linear-lanceolate to oblong, usually less than 15 mm wide;
margins serrate;
apex widely obtuse to rarely attenuate;
midrib puberulent adaxially.
midway between margin and midrib, less than 3 mm diam., oval when immature.
midway between margin and midrib or slightly closer to midrib, usually less than 3 mm diam., oval when immature.
more than 58 µm, rugose to verrucose or tuberculate, surface projections commonly less than 3 µm.
less than 58 µm, verrucose, with surface projections to 3 µm.
free.
weakly to conspicuously anastomosing, most segments containing several areoles, often forming 1 row.
absent.
absent.
= 148.
= 74.
Polypodium hesperium
Polypodium californicum
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P. amorphum, a hypothesis recently supported by electrophoretic studies (C. H. Haufler, M. D. Windham, and E. W. Rabe, unpublished).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.)
R. M. Lloyd and F. A. Lang (1964) recognized two cytotypes within Polypodium californicum. The tetraploid has proved to be an allopolyploid involving P. californicum and P. glycyrrhiza and is treated here as a separate species, P. calirhiza, following S. A. Whitmore and A. R. Smith (1991). Polypodium californicum can be confused with P. calirhiza, but it usually can be distinguished by blade shape, venation, spore size, and geographic distribution. D. S. Barrington et al. (1986) reported that spores of northern populations of P. californicum can be as large as those of P. calirhiza, but the former species has veins forming more areoles per segment than does the latter.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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