''Polypodium amorphum'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

with the common name irregular polypody, which grows near the

northwest coast of North America The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...

Description

''Polypodium amorphum'' grows from a creeping rhizome, usually creeping along rock crevices. The rhizome has light brown scales that darken with age. The leaves arise singly from the rhizome (not forming a centralized tuft) and are up to 30 cm but usually much shorter. The petiole is slender, to 1.5 mm diam. Leaf blades are oblong to rarely deltate, up to 4 cm wide, somewhat leathery. The rachis is sparsely scaly to glabrous. Pinnule margins are entire to crenulate, with the apex rounded to broadly acute. The leaflets are usually shorter and more rounded than other

Polypodium ''Polypodium'' is a genus of ferns in the family Polypodiaceae, subfamily Polypodioideae, according to the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The genus is widely distributed throughout the world, with the highest ...

ferns that share its range. Sori are usually apparent from the top of the leaflets as bump-like protrusions. On the leaf underside, sori are midway between pinnule margin and midrib to nearly marginal, less than 3 mm in diameter, circular when immature. Sporangiasters with abundant glands are present nestled among the

sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cyc ...

in spring and early summer, but are very small and can be seen only with close inspection with magnification. ''Polypodium amorphum'' differs from the similar ''Polypodium hesperium'' in having leaves that persist for two years and in the presence of sporangiasters.Hitchcock, C.L. and Cronquist, A. 2018. Flora of the Pacific Northwest, 2nd Edition, p. 65. University of Washington Press, Seattle.

Range

This fern is native to the Pacific Northwest of North America, ranging from southern British Columbia to northern Oregon. It grows in the Olympics and on both sides of the Cascade crest, but on the drier (east) side only in damper spots at high elevation.

Habitat

''Polypodium amorphum'' grows mostly in moist rock crevices in mountains up to the subalpine zone.

Taxonomy

References

amorphum Ferns of Canada Ferns of the United States {{Polypodiaceae-stub