Flora of North America species comparison

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Gymnocarpium

Gymnocarpium robertianum

oak-fern

gymnocarpe de Robert, limestone oak fern, scented oakfern
Habit Plants terrestrial.
Stems

long-creeping, stolons absent.

1–2 mm diam.;

scales 2–4 mm.
Leaves

monomorphic, dying back in winter.

Fertile leaves

usually 10–52 cm.
Petiole

ca. 1.5–3 times length of blade, base not swollen;

vascular bundles 2, lateral, ± oblong in cross section.

5–33 cm, with numerous glandular hairs distally;

scales 2–6 mm.
Blade

broadly deltate, ternate, or ovate, 2–3-pinnate-pinnatifid, reduced distally to pinnatifid apex, herbaceous.

broadly deltate, 2–3-pinnate-pinnatifid, 5–19 cm, usually firm and robust, abaxial surface moderately to densely glandular, rachis densely glandular, adaxial surface moderately glandular.
Ultimate segments

of proximal pinnae oblong, entire to slightly crenate, apex entire, rounded.
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.

of 2d pair usually stalked, if sessile then with basal basiscopic pinnule usually shorter than adjacent pinnule and equaling basal acroscopic pinnule;

basal acroscopic pinnule shorter than adjacent pinnule, apex often entire, rounded.;

pinnae of 3d pair usually sessile with basal basiscopic pinnule shorter than adjacent pinnule and equaling basal acroscopic pinnule;

basal acroscopic pinnule equaling or shorter than adjacent pinnule.
Veins

free, simple or forked.

Sori

in 1 row between midrib and margin, ± round;

indusia absent.

Spores

brownish, rugose.

34–39 µm. 2n = 160.
Pinna

apex acute.
Proximal

pinnae 3–13 cm, ± perpendicular to rachis, basiscopic pinnules ± perpendicular to costa;

basal basiscopic pinnules either sessile or stalked, pinnate-pinnatifid or pinnatifid, if sessile then with basal basiscopic pinnulet usually shorter than adjacent pinnulet; 2d basal basiscopic pinnule sometimes stalked, if sessile then with basal basiscopic pinnulet shorter than or equaling adjacent pinnulet;

basal acroscopic pinnule sometimes stalked, if sessile then with basal basiscopic pinnulet shorter than or equaling adjacent pinnulet.
x

= 40.

Gymnocarpium

Gymnocarpium robertianum
Habitat Calcareous substrates, limestone pavement, outcrops, and cliffs, Thuja swamps
Elevation 0–1000 m (0–3300 ft)
Distribution
from USDA
North America; North temperate regions; Eurasia
[BONAP county map]
from FNA
IA; MI; MN; WI; MB; NB; NF; ON; QC; Europe; Asia in Caucasus Mountains
[WildflowerSearch map]
[BONAP county map]
Discussion

Species 8 (5 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Gymnocarpium robertianum occurs in numerous localities in eastern Canada, especially in Ontario and Quebec where it is widely distributed; populations are small. Hybrids with G. robertianum are extremely rare. Gymnocarpium × heterosporum W. H. Wagner, a putative triploid hybrid between G. robertianum and G. appalachianum, is known only from one county in Pennsylvania (plants now extirpated, K. M. Pryer 1992). Gymnocarpium × achriosporum Sarvela, a putative tetraploid hybrid between G. robertianum and G. dryopteris, is known only from Sweden and two localities in Quebec. Both hybrids resemble G. robertianum in their leaf morphology and dense glandularity but have black, malformed spores.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.
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
Source FNA vol. 2. Author: Kathleen M. Pryer. FNA vol. 2.
Parent taxa Dryopteridaceae Dryopteridaceae > Gymnocarpium
Sibling taxa
G. appalachianum, G. disjunctum, G. dryopteris, G. jessoense
Subordinate taxa
G. appalachianum, G. disjunctum, G. dryopteris, G. jessoense subsp. parvulum, G. robertianum
Synonyms Polypodium robertianum, Dryopteris robertiana, Phegopteris robertianum, Thelypteris robertiana
Name authority Newman: Phytologist 4: 371. (1851) (Hoffmann) Newman: Phytologist 4: app. 24. (1851)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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