Gymnocarpium in Flora of North America @ efloras.org

6. Gymnocarpium Newman, Phytologist. 4: 371. 1851.

Oak fern [Greek gymnos, naked, and karpos, fruit, referring to the absence of indusia]

Kathleen M. Pryer

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.

Species 8 (5 in the flora): north temperate regions, North America, Eurasia.

SELECTED REFERENCES

Pryer, K. M. 1992. The status of Gymnocarpium heterosporum and G. robertianum in Pennsylvania. Amer. Fern J. 82: 34--39. Pryer, K. M. and D. M. Britton. 1983. Spore studies in the genus Gymnocarpium. Canad. J. Bot. 61: 377--388. Pryer, K. M., D. M. Britton, and J. McNeill. 1983. A numerical analysis of chromatographic profiles in North American taxa of the fern genus Gymnocarpium. Canad. J. Bot. 61: 2592--2602. Pryer, K. M. and C. H. Haufler. 1993. Isozymic and chromosomal evidence for the allotetraploid origin of Gymnocarpium dryopteris (Dryopteridaceae). Syst. Bot. 18: 150--172. Sarvela, J. 1978. A synopsis of the fern genus Gymnocarpium. Ann. Bot. Fenn. 15: 101--106. Sarvela, J., D. M. Britton, and K. M. Pryer. 1981. Studies on the Gymnocarpium robertianum complex in North America. Rhodora 83: 421--431. Wagner, W. H. Jr. 1966b. New data on North American oak ferns, Gymnocarpium. Rhodora 68: 121--138.

1 Adaxial blade surface glabrous or moderately glandular, abaxial blade surface and rachis moderately or densely glandular. (2)

+ Adaxial and abaxial blade surfaces and rachis essentially glabrous. (3)

2 (1) 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. 4a subsp. parvulum

+ 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. 5 Gymnocarpium robertianum

3 (1) Pinnae of 2d pair and basal basiscopic pinnule of proximal pinnae stalked. 1 Gymnocarpium appalachianum

+ Pinnae of 2d pair sessile or rarely stalked; proximal basiscopic pinnule of basal pinnae sessile. (4)

4 (3) 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. 2 Gymnocarpium disjunctum

+ 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 (4) 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. 3 Gymnocarpium dryopteris

+ 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. 1 Gymnocarpium appalachianum

Lower Taxa

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