5. Dryopteris Adans. (shield fern, wood
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.