Flora of North America species comparison

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Polystichum imbricans

Polystichum aleuticum

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

Aleutian holly fern
Stems

ascending to erect.

erect.
Leaves

erect to arching back at tip, 2–8 dm;

bulblets absent.

monomorphic, erect, 1–1.5 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.

1/6–1/4 length of leaf;

scales tan, sparse or falling off early.
Blade

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

linear-lanceolate, 1-pinnate, gradually tapered to base.
Pinnae

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.

± deltate to ovate, slightly overlapping, in 1 plane, 4–8 mm;

base truncate, acroscopic auricle well developed;

margins denticulate, not spiny;

apex rounded, not dentate;

microscales linear, lacking projections, dense on both surfaces.
Indusia

entire to sharply dentate.

entire to minutely erose-dentate.
Spores

dark brown.

brown.

Polystichum imbricans

Polystichum aleuticum
Habitat Growing in crevices of rocks
Elevation 0–400 m (0–1300 ft)
Distribution
from FNA
CA; OR; WA; BC; only in the flora
[WildflowerSearch map]
[BONAP county map]
from FNA
AK
[BONAP county map]
Discussion

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.)

Polystichum aleuticum is known only from Atka and Adak islands, Alaska. Its nearest relatives are in southwest China. Polystichum aleuticum resembles the dwarfed plants of P. kruckebergii, but it differs, especially, in its smaller, more rounded pinna apices and more abundant scales.

Of conservation concern.

(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 Dryopteridaceae > Polystichum
Sibling taxa
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
P. acrostichoides, P. andersonii, P. braunii, P. californicum, P. dudleyi, P. imbricans, 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 Aspidium munitum var. imbricans, P. munitum subsp. imbricans, P. munitum var. imbricans
Name authority (D. C. Eaton) D. H. Wagner: Pteridologia 1: 50. (1979) C. Christensen: in Hultén, Svensk Bot. Tidskr. 30: 515, fig. 1a. (1936)
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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