Flora of North America species comparison

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Dryopteris

Dryopteris intermedia

dryoptère, shield fern, wood-fern

dryoptère spinuleuse, evergreen wood fern, fancy fern, intermediate woodfern
Habit Plants terrestrial, rarely on rock.
Stems

short-creeping to erect, stolons absent.

Leaves

monomorphic, green through winter or dying back in winter.

monomorphic, green through winter, 32–90 × 10–20 cm.
Petiole

ca. 1/4–2/3 blade length, bases swollen or not;

vascular bundles more than 3, arranged in an arc, ± round in cross section.

1/3 length of leaf, scaly at least at base;

scales scattered, tan.
Blade

deltate-ovate to lanceolate, 1–3-pinnate-pinnatifid, gradually reduced distally to pinnatifid apex, herbaceous to somewhat leathery.

green, ovate, 3-pinnate-pinnatifid, herbaceous, glandular.
Pinnae

not articulate to rachis, segment margins entire, crenate, or serrate, spinulose or not;

proximal pinnae reduced (several pairs), same size as or enlarged relative to more distal pinnae, sessile to petiolulate, equilateral or often inequilateral with pinnules on basiscopic side longer than those on acroscopic side;

costae adaxially grooved, grooves continuous from rachis to costae to costules;

indument of linear to ovate scales abaxially, also sometimes with glands, blades ± glabrous adaxially.

± in plane of blade, lanceolate-oblong;

basal pinnae lanceolate, not reduced, basal pinnules longer than adjacent pinnules, basal basiscopic pinnule longer than basal acroscopic pinnule;

pinnule margins serrate, teeth spiny.
Veins

free, forked.

Indusia

with minute glandular hairs.
Sori

in 1 row between margin and midrib, round;

indusia round-reniform, attached at narrow sinus, persistent or caducous.

midway between midvein and margin of segments.
Spores

brownish, coarsely rugose or with folded wings.

x

= 41.

2n

= 82.

Dryopteris

Dryopteris intermedia
Habitat Moist rocky woods, especially hemlock hardwoods, ravines, and edges of swamps
Elevation 0–2000 m (0–6600 ft)
Distribution
from USDA
Mostly in temperate Asia
[BONAP county map]
from FNA
AL; CT; DE; GA; IA; IL; IN; KY; MA; MD; ME; MI; MN; MO; NC; NH; NJ; NY; OH; PA; RI; TN; VA; VT; WI; WV; NB; NF; NS; ON; PE; QC
[WildflowerSearch map]
[BONAP county map]
Discussion

The relationships of the North American species are reasonably well understood, but species identifications are complicated by the frequent presence of hybrids in field populations. Sterile hybrids can be distinguished from fertile species by their misshapen spores and intermediate morphology. They are not included in the key, but they may be identified as to parentage by combinations of characters in the key (e.g., marginal sori for Dryopteris marginalis, narrow blades for D. cristata). Relationships are shown in the accompanying reticulogram.

Species ca. 250 (14 in the flora).

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

A related taxon, Dryopteris intermedia subsp. maderensis (J. Milde ex Alston) Fraser-Jenkins, occurs on eastern Atlantic islands.

Dryopteris intermedia and the other taxa in the " D. spinulosa complex" have long confounded taxonomists. Dryopteris intermedia is diploid and is one of the parents of the allotetraploids D. carthusiana and D. campyloptera. Dryopteris intermedia hybridizes with eight species. All hybrids are easily detected by the distinctive glandular hairs on the indusia and, usually, on the costae and costules.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Blades densely scaly abaxially, aromatic-glandular; old leaves forming conspicuous gray or brown clumps; leaves 6-25(-40) cm.
D. fragrans
1. Blades glabrous to sparsely scaly abaxially, not aromatic-glandular; old leaves not persisting in conspicuous gray or brown clumps; leaves usually more than 25 cm.
→ 2
2. Blades 2-pinnate to 3-pinnate-pinnatifid at base.
→ 3
2. Blades pinnate-pinnatifid to 2-pinnate at base.
→ 7
3. Basal pinnules of basal pinnae shorter than adjacent pinnules.
→ 4
3. Basal pinnules of basal pinnae longer than adjacent pinnules.
→ 5
4. Pinnae with elongate serrate tip; blades and indusia lacking glands or sparsely glandular.
D. cinnamomea
4. Pinnae lacking elongate serrate tip; blades, at least the midrib of segments and indusia, finely glandular.
D. intermedia
5. First basal basiscopic pinnule not much wider than 1st acroscopic pinnule on basal pinnae; blades ovate-lanceolate.
D. carthusiana
5. First basal basiscopic pinnule 2 times width of 1st acroscopic pinnule on basal pinnae; blades ovate-deltate.
→ 6
6. Petiole scales tan, with dark central stripe; leaves erect to slightly arching (Rocky Mountains, n Great Lakes, ne Canada).
D. expansa
6. Petiole scales tan or dark at base, lacking distinct dark stripe; leaves widely spreading (Appalachian Mountains north to ne Canada).
D. campyloptera
7. Sori at or near margins of segments; petioles with dense tuft of pale tawny scales at base.
D. marginalis
7. Sori midway between margin and midrib or closer to midribs of segments; petioles with scattered tan to dark brown scales at base.
→ 8
8. Pinnules finely spiny with spreading teeth (Arizona and west coast of North America).
D. arguta
8. Pinnules not finely spiny, teeth blunt or incurved (e, nw North America).
→ 9
9. Petioles less than 1/4 length of leaves, scales of 2 kinds, mixed, broad and hairlike.
D. filix-mas
9. Petioles 1/4-1/3 length of leaves, scales broad to narrow, but not hairlike.
→ 10
10. Fertile pinnae narrower than vegetative pinnae, restricted to distal 1/2 of blade.
D. ludoviciana
10. Fertile pinnae same width as vegetative pinnae, occupying distal 1/2 of blade to nearly entire blade.
→ 11
11. Basal pinnae ovate; blades ovate to ovate-lanceolate; scales at base of petioles dark brown or with dark brown stripe.
→ 12
11. Basal pinnae deltate; blades lanceolate with parallel sides; scales at base of petioles tan.
→ 13
12. Blades ovate, tapering abruptly to tip; sori nearer midvein than margin of segments.
D. goldieana
12. Blades ovate-lanceolate, gradually narrowed to tip; sori about midway between midvein and margin of segments.
D. celsa
13. Basal pinnae narrowly elongate-deltate; pinnae of fertile leaves nearly in plane of blade.
D. clintoniana
13. Basal pinnae deltate; pinnae of fertile leaves twisted nearly at right angles to plane of blade.
D. cristata
Source FNA vol. 2. Authors: James D. Montgomery, Warren H. Wagner Jr.. FNA vol. 2.
Parent taxa Dryopteridaceae Dryopteridaceae > Dryopteris
Sibling taxa
D. arguta, D. campyloptera, D. carthusiana, D. celsa, D. cinnamomea, D. clintoniana, D. cristata, D. expansa, D. filix-mas, D. fragrans, D. goldieana, D. ludoviciana, D. marginalis
Subordinate taxa
D. arguta, D. campyloptera, D. carthusiana, D. celsa, D. cinnamomea, D. clintoniana, D. cristata, D. expansa, D. filix-mas, D. fragrans, D. goldieana, D. intermedia, D. ludoviciana, D. marginalis
Synonyms Aspidium intermedium, D. austriaca var. intermedia, D. spinulosa var. intermedia
Name authority Adanson: Fam. Pl. 2: 20, 551. (1763) (Muhlenberg ex Willdenow) A. Gray: Manual 630. (1848)
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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