Polystichum acrostichoides
Polystichum microchlamys
Christmas fern, polystic faux-acrostic
attu hollyfern
erect.
erect.
dimorphic (only in this species);
fertile pinnae distal, much contracted;
sterile leaves arching, 3–8 dm;
bulblets absent.
arching, 3–8 dm;
bulblets absent.
1/4–1/3 length of leaf, densely scaly;
scales light brown, diminishing in size distally.
1/8–1/4 length of leaf, densely scaly;
scales brown, diminishing in size distally.
linear-lanceolate, 1-pinnate;
base narrowed.
broadly lanceolate, 1-pinnate-pinnatifid, base slightly narrowed.
oblong to falcate, not overlapping, in 1 plane, 2–6 cm;
base oblique, acroscopic auricles well developed;
margins serrulate-spiny with teeth ascending;
apex acute or blunt with subapical and apical teeth same size;
microscales filiform, lacking projections, dense, on abaxial surface only.
narrowly lanceolate, not overlapping, in 1 plane, 3–13 cm;
base oblique, proximal acroscopic segments enlarged;
margins incised to costa but segments sessile and adnate to costa for at least 2 mm, segments excised and decurrent, serrulate-spiny with teeth spreading to ascending;
apex acute with subapical and apical teeth same size;
microscales filiform, dense abaxially, sparse adaxially.
erose-dentate.
confluent, completely covering abaxial surface of pinnae (only in this species);
indusia entire.
light brown.
color unknown.
= 82.
Polystichum acrostichoides
Polystichum microchlamys
Polystichum acrostichoides is a common species most closely related to P. munitum (G. Yatskievych et al. 1988), which also occurs extensively on forest floors.
The dimorphic pinnae of Polystichum acrostichoides are not unique to the genus; they are found also in some Asian species. Numerous variants have been named, mostly as forms, but none are of taxonomic consequence. Hybrids are known with P. braunii (P. × potteri Barrington) and P. lonchitis (P. × hagenahii Cody). The latter hybrid is rare, known only from its type locality in Ontario, where it grows with both parents. It is recognized by its intermediate morphology (leaves wider than P. lonchitis, narrower than P. acrostichoides, with slightly contracted sorus-bearing pinnae) and malformed sporangia and spores. Polystichum × potteri is much more widespread, from Nova Scotia, New Brunswick, and Quebec through New England to Pennsylvania. It resembles P. braunii but has narrower leaves bearing malformed sporangia.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Polystichum microchlamys is found in the flora only on Attu, at the western tip of the Aleutian Archipelago.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Go Botany
IL Wildflowers
KS Wildflowers
LA Plants
MD Biodiversity
MI Flora
MN Wildflowers
MO Plants
WildflowerSearch
iNaturalist
USDA Plants Database
