Gymnocarpium
Gymnocarpium dryopteris
oak-fern
common fern, common oak fern, gymnocarpe fougère-du-chêne, northern oak fern, oak fern, western oakfern
long-creeping, stolons absent.
0.5–1.5 mm diam.;
scales 1–4 mm.
monomorphic, dying back in winter.
usually 12–42 cm.
ca. 1.5–3 times length of blade, base not swollen;
vascular bundles 2, lateral, ± oblong in cross section.
9–28 cm, with sparse glandular hairs distally;
scales 2–6 mm.
broadly deltate, ternate, or ovate, 2–3-pinnate-pinnatifid, reduced distally to pinnatifid apex, herbaceous.
broadly deltate, 2-pinnate-pinnatifid, 3–14 cm, lax and delicate, abaxial surface and rachis glabrous or with sparse glandular hairs, adaxial surface glabrous.
of proximal pinnae oblong, entire to crenate, apex entire, rounded.
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.
of 2d pair usually sessile with basal basiscopic pinnule longer than or equaling adjacent pinnule and about equal to basal acroscopic pinnule;
basal acroscopic pinnule equaling or slightly shorter than adjacent pinnule, often with entire, rounded apex.;
pinnae of 3d pair sessile with basal basiscopic pinnule equaling adjacent pinnule and equaling basal acroscopic pinnules;
basal acroscopic pinnule equaling or slightly shorter than adjacent pinnule.
free, simple or forked.
in 1 row between midrib and margin, ± round;
indusia absent.
brownish, rugose.
34–39 µm. 2n = 160.
apex entire, rounded.
pinnae 2–12 cm, ± perpendicular to rachis, with basiscopic pinnules ± perpendicular to costa;
basal basiscopic pinnule usually sessile, pinnatifid or rarely pinnate-pinnatifid, if sessile then with basal basiscopic pinnulet often equaling or longer than adjacent pinnulet; 2d basal basiscopic pinnule sessile, with basal basiscopic pinnulet equaling or longer than adjacent pinnulet;
basal acroscopic pinnule sessile, with basal basiscopic pinnulet longer than or equaling adjacent pinnulet.
= 40.
Gymnocarpium
Gymnocarpium dryopteris
Species 8 (5 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Gymnocarpium dryopteris is a fertile allotetraploid species that arose following hybridization between G. appalachianum and G. disjunctum (see reticulogram). Its wide distribution over much of the north temperate zone has provided ample opportunity for secondary contact between G. dryopteris and each of its diploid parents, thereby resulting in a wide-ranging composite of abortive-spored triploid crosses (G. disjunctum × G. dryopteris and G. appalachianum × G. dryopteris). These relationships are shown on the diagram. Sterile triploid plants are not restricted only to areas where the range of the tetraploid overlaps with that of either diploid. Their broad distribution could be explained in part by their spores, which are of two types: malformed, black, and with very exaggerated perispores, or round with extensive netted perispores (K. M. Pryer and D. M. Britton 1983). The latter spore type is capable of germination and presumably permits the plants to reproduce apogamously. The name G. × brittonianum (Sarvela) Pryer & Haufler has been applied to the G. disjunctum × G. dryopteris hybrid formula (K. M. Pryer and C. H. Haufler 1993). The type of G. × brittonianum has aborted and round spores, and leaves that strongly resemble those of G. disjunctum. They are large, 3-pinnate-pinnatifid, and the second and third pairs of pinnae are sessile with basal basiscopic pinnules markedly longer than the basal acroscopic pinnules. Sterile triploid plants with a morphology similar to the type of G. × brittonianum are frequent. The biology of both of these cryptic hybrid taxa needs further study, which should lead to detailed morphologic descriptions and distribution maps.
Gymnocarpium dryopteris also hybridizes with both G. jessoense subsp. parvulum and G. robertianum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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. | 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. | G. robertianum |
3. Pinnae of 2d pair and basal basiscopic pinnule of proximal pinnae stalked. | G. 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. | G. 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. | G. 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. | G. appalachianum |
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