Polystichum dudleyi
Polystichum acrostichoides
Dudley's sword fern
Christmas fern, polystic faux-acrostic
erect.
erect.
monomorphic, arching, 2–10 dm;
bulblets absent.
dimorphic (only in this species);
fertile pinnae distal, much contracted;
sterile leaves arching, 3–8 dm;
bulblets absent.
1/5–1/3 length of leaf, densely scaly;
scales light brown, gradually diminishing in size distally.
1/4–1/3 length of leaf, densely scaly;
scales light brown, diminishing in size distally.
broadly lanceolate, 2-pinnate, base not narrowed.
linear-lanceolate, 1-pinnate;
base narrowed.
narrowly lanceolate, not overlapping, in 1 plane, 3–13 cm;
base oblique, apex acute with subapical and apical teeth same size;
microscales filiform, lacking projections, sparse abaxially, but longer than in other Polystichum species, forming loosely tangled network over blade and sori (such network only in this species), sparse adaxially.
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.
ciliate.
confluent, completely covering abaxial surface of pinnae (only in this species);
indusia entire.
brown.
light brown.
± stalked, linear-falcate to oblique-rhombic, acroscopic auricle well developed on proximal pinnules;
margins spinulose-dentate;
apex acute.
= 82.
= 82.
Polystichum dudleyi
Polystichum acrostichoides
Polystichum dudleyi is confined to coastal central California. Hybrids with P. californicum are relatively frequent where these species occur together. These hybrids would key here but, unlike P. dudleyi, they are less divided and have aborted sporangia. The sterile diploid hybrid with P. munitum is also frequent in areas of sympatry. It is indistinguishable from P. californicum except for malformed sporangia and chromosome number (W. H. Wagner Jr. 1973).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.)
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