Flora of North America species comparison

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Polystichum imbricans

Polystichum setigerum

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

Alaska holly fern, Alaska sword fern
Stems

ascending to erect.

erect.
Leaves

erect to arching back at tip, 2–8 dm;

bulblets absent.

arching, 4–10 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.

1/8–1/5 length of leaf, densely scaly;

scales light brown, gradually diminishing in size distally.
Blade

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

lanceolate, deeply 1-pinnate-pinnatifid to 2-pinnate, base narrowed.
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.

lanceolate, not overlapping, in 1 plane, 4–8 cm, base oblique, margins incised to costa on middle pinnae, serrulate-spiny with teeth spreading-ascending, apex acute-apiculate with subapical and apical teeth same size;

microscales filiform, sparse abaxially, confined to costa adaxially.
Indusia

entire to sharply dentate.

erose-ciliate.
Spores

dark brown.

brown.
2n

= 246.

Polystichum imbricans

Polystichum setigerum
Habitat Forest floor in lowland coastal forests
Elevation 0–250 m (0–800 ft)
Distribution
from FNA
CA; OR; WA; BC; only in the flora
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; BC
[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 setigerum is disjunct on Attu Island at the western tip of the Aleutian Archipelago. It is presumed to be of hybrid origin, the result of a cross between P. munitum and P. braunii (D. H. Wagner 1979). This hybrid has been produced experimentally (A. Sleep and T. Reichstein 1967) and is reported from British Columbia (see discussion under P. braunii).

(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. aleuticum, P. andersonii, P. braunii, P. californicum, P. dudleyi, P. imbricans, P. kruckebergii, P. kwakiutlii, P. lemmonii, P. lonchitis, P. microchlamys, P. munitum, P. scopulinum
Subordinate taxa
P. imbricans subsp. curtum, P. imbricans subsp. imbricans
Synonyms Aspidium munitum var. imbricans, P. munitum subsp. imbricans, P. munitum var. imbricans Nephrodium setigerum, P. braunii subsp. alaskense, P. braunii var. alaskense
Name authority (D. C. Eaton) D. H. Wagner: Pteridologia 1: 50. (1979) (C. Presl) C. Presl: Tent. Pterid. 83. (1836)
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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