Dudley's sword fern

Polystichum aculeatum (Linnaeus) Roth var. dudleyi (Maxon) Jepson

Stems erect. Leaves monomorphic, arching, 2--10 dm; bulblets absent. Petiole 1/5--1/3 length of leaf, densely scaly; scales light brown, gradually diminishing in size distally. Blade broadly lanceolate, 2-pinnate, base not narrowed. Pinnae 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. Pinnules ± stalked, linear-falcate to oblique-rhombic, acroscopic auricle well developed on proximal pinnules; margins spinulose-dentate; apex acute. Indusia ciliate. Spores brown. 2 n = 82.

Moist forests; 0--100 m; Calif.

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).