Pine fern

Osmunda adiantifolia Linnaeus, Sp. Pl. 2: 1065. 1753

Stems ca. 2 mm diam. Leaves partially dimorphic (sporangia limited to proximal pair of pinnae), 17--85 × 7--35 cm, sterile leaves (excluding erect fertile pinnae) 17--60 cm. Petiole straw-colored to chestnut brown, 1/2--2/3 length of leaf, 1--1.4 mm wide, hirsute to glabrous. Blade deltate, 3-pinnate, leathery. Pinnae 10--18 pairs, alternate to subopposite, segments oblanceolate, base cuneate, margins minutely denticulate, apex obtuse, pilose with stiff white hairs. Fertile pinnae usually taller than sterile blades. Spores with ridges ± parallel, distant. 2 n = 76, 114, 152.

Terrestrial on open to lightly shaded, rocky slopes and in hammocks and pine woods, often on limestone; 0--30 m; Fla.; Mexico; West Indies in the Antilles, Trinidad; Central America; South America to Ecuador and Brazil.