5. Dryopteris Adans. (shield fern, wood fern)

Rhizomes erect to prostrate and short-creeping, scaly. Leaves monomorphic to slightly dimorphic. Petioles straw-colored, shorter than the leaf blade, scaly, the bases with 4–9 vascular bundles. Rachises glabrous or scaly, lacking stalked glands. Leaf blades lanceolate to deltoid or ovate in outline, less commonly obovate, 1–3 times pinnately compound, the pinnules toothed, often deeply lobed. Veins not anastomosing. Sori circular or nearly so. Indusia kidney-shaped to circular-cordate, attached at the base of the notch. Spores 64 per sporangium, monolete, 38–64 mm long, brown. About 225 species, nearly worldwide, but most diverse in Asia.

The North American species of Dryopteris form a large complex involving past hybridization and polyploidy. The hybrid origin of most of the fertile polyploids can make determinations in the genus difficult in some cases. Elsewhere, numerous sterile hybrids have been described; however, none of these has been reported from Missouri to date. The taxa present in the state are sufficiently uncommon that there is little chance of hybridization between them. However, a few of the most likely hybrids potentially to occur in Missouri are listed below under their parental species. Students of the flora should be aware that anywhere that two or more species of Dryopteris grow together the potential for sterile hybrids exists.

Among the Missouri species, most are deciduous. However, the leaves of D. marginalis are evergreen, and those of D. intermedia tend to overwinter but often partially turn brown and shrivel.