Flora of North America species comparison

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Polystichum imbricans subsp. imbricans

Polystichum imbricans
Photo is of parent taxon

imbricate fern, imbricate sword fern, narrow-leaf sword fern, rock sword fern

imbricate sword-fern, narrow-leaf sword fern, rock sword-fern
Stems

decumbent to ascending.

ascending to erect.
Leaves

stiffly erect, 2.5–5 dm.

erect to arching back at tip, 2–8 dm;

bulblets absent.
Petiole

1/4–1/3 length of leaf;

scales abruptly diminishing in size distally and falling off early but retaining conspicuous tuft of brown scales at base.
Blade

linear-lanceolate to linear, 1-pinnate, base not or slightly narrowed.
Pinnae

lanceolate-oblong, less than 5 times longer than wide, twisted out of plane of blade (adaxial surfaces facing upward like Venetian blinds), base usually cupped, apex cuspidate.

oblong, slenderly lanceolate, or falcate, usually overlapping, in 1 plane or twisted out of plane of blade, 2–4 cm;

base oblique, auricles well developed;

margins serrulate-spiny with teeth ascending;

apex cuspidate or apiculate with subapical teeth smaller than apical tooth;

microscales lanceolate to linear with straight or sharply angular projections, sparse, on abaxial surface only.
Indusia

entire.

entire to sharply dentate.
Spores

dark brown.

Polystichum imbricans subsp. imbricans

Polystichum imbricans
Habitat Rooted at base of boulders or in cliff crevices in drier sites of mesic montane forests
Elevation 0–2500 m (0–8200 ft)
Distribution
from FNA
CA; OR; WA; BC
[BONAP county map]
from FNA
CA; OR; WA; BC; only in the flora
[WildflowerSearch map]
[BONAP county map]
Discussion

Polystichum imbricans subsp. imbricans grows in the Coast Ranges and the Sierra-Cascade axis. It is isolated in the Wallowa Mountains of eastern Oregon.

Sun forms of Polystichum munitum are often mistaken for P. imbricans; characteristics of the distal petiolar scales and indusial margins are more reliable than gross morphologic features for distinguishing them. Polystichum imbricans has narrow distal petiolar scales that fall off early; P. munitum has wide distal petiolar scales (the largest more than 1 mm wide) that are persistent. Polystichum imbricans hybridizes readily with P. munitum, the hybrids usually being sterile but in some places forming hybrid swarms because of partial fertility of the hybrids (D. H. Wagner 1979). The hybrids with P. californicum are discussed under that species.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Polystichum imbricans is one of the postulated ancestors of two allopolyploids, P. californicum and P. scopulinum (D. H. Wagner 1979). Relationships to P. munitum are discussed under that species.

Subspecies 2.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Pinnae oblong, less than 5 times longer than wide, adaxial surfaces facing upward and twisted out of plane of blade; leaves stiffly erect to tip; at base of boulders or in cliff crevices in exposed sites; California to British Columbia.
subsp. imbricans
1. Pinnae narrowly lanceolate, more than 5 times longer than wide, generally in 1 plane; leaf tips arching back; on forest floor in shade; only in California.
subsp. curtum
Source FNA vol. 2. FNA vol. 2.
Parent taxa Dryopteridaceae > Polystichum > Polystichum imbricans Dryopteridaceae > Polystichum
Sibling taxa
P. imbricans subsp. curtum
P. acrostichoides, P. aleuticum, P. andersonii, P. braunii, P. californicum, P. dudleyi, P. kruckebergii, P. kwakiutlii, P. lemmonii, P. lonchitis, P. microchlamys, P. munitum, P. scopulinum, P. setigerum
Subordinate taxa
P. imbricans subsp. curtum, P. imbricans subsp. imbricans
Synonyms P. munitum subsp. nudatum Aspidium munitum var. imbricans, P. munitum subsp. imbricans, P. munitum var. imbricans
Name authority (D. C. Eaton) D. H. Wagner (D. C. Eaton) D. H. Wagner: Pteridologia 1: 50. (1979)
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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