Flora of North America species comparison

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Polypodium hesperium

Polypodium amorphum

western polypody, western polypody fern

irregular polypody, irregular polypody fern, Pacific polypody
Stems

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.
Leaves

to 35 cm.

to 30 cm.
Petiole

slender, to 1.5 mm diam.

slender, to 1.5 mm diam.
Blade

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 rarely deltate, pinnatifid, usually widest near middle, occasionally at or near base, to 4 cm wide, somewhat leathery;

rachis sparsely scaly to glabrescent abaxially, glabrous adaxially;

scales lanceolate-ovate, usually more than 6 cells wide.
Segments

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.
Sori

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.
Spores

more than 58 µm, rugose to verrucose or tuberculate, surface projections commonly less than 3 µm.

more than 58 µm, rugose to verrucose, surface projections less than 3 µm tall.
Venation

free.

free.
Sporangiasters

absent.

present, usually less than 40 per sorus, heads covered with glandular hairs.
2n

= 148.

= 74.

Polypodium hesperium

Polypodium amorphum
Phenology Sporulating summer–fall. Sporulating summer–fall.
Habitat Cracks and ledges on cliffs, on a variety of noncalcareous substrates, rarely on limestone Cliffs and rocky slopes, usually on igneous substrates
Elevation 300–3500 m. (1000–11500 ft.) 0–1800 m (0–5900 ft)
Distribution
from FNA
AZ; CA; CO; ID; MT; NM; NV; OR; UT; WA; BC; Mexico in Chihuahua; Baja California
[WildflowerSearch map]
[BONAP county map]
from FNA
OR; WA; BC
[WildflowerSearch map]
[BONAP county map]
Discussion

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.)

The diploid Polypodium amorphum is one of the progenitors of allotetraploid P. hesperium, and these two species are occasionally sympatric. Although P. amorphum can be mistaken for P. hesperium, consistent differences exist for separating these two species (see comments under P. hesperium). Hybridization between P. amorphum and P. hesperium results in triploid individuals with misshapen spores (F. A. Lang 1971).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 2. FNA vol. 2.
Parent taxa Polypodiaceae > Polypodium Polypodiaceae > Polypodium
Sibling taxa
P. amorphum, P. appalachianum, P. californicum, P. calirhiza, P. glycyrrhiza, P. saximontanum, P. scouleri, P. sibiricum, P. triseriale, P. virginianum
P. appalachianum, P. californicum, P. calirhiza, P. glycyrrhiza, P. hesperium, P. saximontanum, P. scouleri, P. sibiricum, P. triseriale, P. virginianum
Synonyms P. prolongilobum, P. vulgare subsp. columbianum, P. vulgare var. columbianum, P. vulgare var. hesperium P. montense
Name authority Maxon: Proc. Biol. Soc. Wash. 13: 200. (1900) Suksdorf: Werdenda 1: 16. (1927)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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