Gymnocarpium

Newman

Phytologist 4: 371. 1851

Common names: Oak fern
Etymology: Greek gymnos, naked, and karpos, fruit, referring to the absence of indusia
Treatment appears in FNA Volume 2.
Click plate for higher resolution version.
Illustrator: John Myers
Plants terrestrial. Stems long-creeping, stolons absent. Leaves monomorphic, dying back in winter. Petiole ca. 1.5–3 times length of blade, base not swollen; vascular bundles 2, lateral, ± oblong in cross section. Blade broadly deltate, ternate, or ovate, 2–3-pinnate-pinnatifid, reduced distally to pinnatifid apex, herbaceous. Pinnae weakly articulate to rachis but persistent, segment margins entire to crenate; proximal pinnae longest, petiolulate, usually ± inequilateral with pinnules on basiscopic side longer than those on acroscopic side; costae adaxially grooved, grooves not continuous from rachis to costae; indument lacking or of minute (0.1 mm) glands abaxially and sometimes along costae adaxially. Veins free, simple or forked. Sori in 1 row between midrib and margin, ± round; indusia absent. Spores brownish, rugose. x = 40.

Distribution

North temperate regions, North America, Eurasia.

Discussion

Species 8 (5 in the flora).

Key

1 Adaxial blade surface glabrous or moderately glandular, abaxial blade surface and rachis moderately or densely glandular. > 2
1 Adaxial and abaxial blade surfaces and rachis essentially glabrous. > 3
2 Blades glabrous on adaxial surface; proximal pinnae and basiscopic pinnules of proximal pinnae curving toward apex of leaf and apex of pinna, respectively; pinnae of 2d pair almost always sessile with basal pinnules ± equal in length to adjacent pinnules. Gymnocarpium jessoense subsp. parvulum
2 Blades moderately glandular on adaxial surface; proximal pinnae and basiscopic pinnules of proximal pinnae ± perpendicular to rachis and costa, respectively; pinnae of 2d pair usually stalked, or if sessile with basal pinnules shorter than adjacent pinnules. Gymnocarpium robertianum
3 Pinnae of 2d pair and basal basiscopic pinnule of proximal pinnae stalked. Gymnocarpium appalachianum
3 Pinnae of 2d pair sessile or rarely stalked; proximal basiscopic pinnule of basal pinnae sessile. > 4
4 Pinnae of 2d pair sessile with basal pinnules unequal in length (basiscopic markedly longer); ultimate segments of proximal pinnae slightly lobed to crenate, apex often crenulate, acute; blades 8-24 cm. Gymnocarpium disjunctum
4 Pinnae of 2d pair rarely stalked, if sessile with basal pinnules ± equal in length (basiscopic = acroscopic); ultimate segments of proximal pinnae crenate to entire, apex entire, rounded; blades 3-14 cm. > 5
5 Sessile basal basiscopic pinnule of proximal pinnae with basal basiscopic pinnulet (division of pinnule) ± equal in length to adjacent pinnulet; pinnae of 2d pair usually sessile, with basal pinnules ± equal in length to adjacent basal pinnule; spores 34-39 µm. Gymnocarpium dryopteris
5 Sessile basal basiscopic pinnule of proximal pinnae with basal basiscopic pinnulet shorter than adjacent pinnulet; pinnae of 2d pair sessile, with basal pinnules shorter than adjacent pinnule, or 2d basal pinnae rarely stalked; spores 27-31 µm. Gymnocarpium appalachianum