Polystichum braunii
Polystichum aleuticum
Braun's holly-fern, polystic de Braun
Aleutian holly fern
erect.
erect.
monomorphic, arching, 2–10 dm;
bulblets absent.
monomorphic, erect, 1–1.5 dm;
bulblets absent.
1/8–1/6 length of leaf, densely scaly;
scales light brown, gradually diminishing in size distally.
1/6–1/4 length of leaf;
scales tan, sparse or falling off early.
broadly lanceolate, 2-pinnate;
base narrowed.
linear-lanceolate, 1-pinnate, gradually tapered to base.
oblong-lanceolate or falcate, proximal pinnae ± rectangular, not overlapping, in 1 plane, 2–10 cm;
base oblique except proximal 3–4 pinnae, where auricles not developed;
apex acute, subapical and apical teeth same size;
microscales filiform to linear, lacking projections, dense abaxially, sparse adaxially.
± 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.
ciliate.
entire to minutely erose-dentate.
brown.
brown.
± stalked, short-falcate to oblique-rhombic, acroscopic auricle well developed on proximal pinnules;
margins dentate, with slender bristle tips;
apex broadly acute.
= 164.
Polystichum braunii
Polystichum aleuticum
Because no diploid ancestors have been found, Polystichum braunii is thought to be an ancient tetraploid. Its sterile hybrid with P. acrostichoides, P. × potteri, is discussed under P. acrostichoides. Polystichum braunii × lonchitis has been reported from southeast Alaska (S. L. Welsh 1974). This hybrid has been cytologically confirmed in Europe and named P. × meyeri Sleep & Reichstein (A. Sleep and T. Reichstein 1967). It has narrower and less divided leaves than P. braunii and poorly developed auricles. Polystichum braunii × lonchitis was described by J. Ewan (1944), but the type (from British Columbia) is P. braunii × munitum (A. Sleep and T. Reichstein 1967). This latter hybrid is the postulated progenitor of P. setigerum (D. H. Wagner 1979). North American P. braunii has been segregated as var. purshii Fernald, distinguished from European populations (var. braunii) by having broader microscales.
(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.)
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