Greek dryas, oak or tree, + pteris, fern; the ferns of this genus often grow in woodlands. Plants small, medium-sized, or large, terrestrial. Rhizomes decumbent to erect, scaly. Fronds medium-sized to large (rarely small), usually close and forming rosettes. Stipes grooved, usually 1/4-1/3 frond length, cross section revealing 3 or more vascular bundles arranged in a semicircle to nearly full circle. Blades 1- to 5-pinnate, deltate-ovate to lanceolate, chartaceous to coriaceous, glandular or not, bearing scales and hairlike scales but not needlelike hairs; rachises and midribs of pinnae and pinnules grooved, pinnae grooves usually not connecting with those of rachises. Pinnae lower pair often enlarged on basiscopic side. Veins free, forked. Sori round, 1 row on each side of pinnae and pinnules between margin and mid vein. Indusia kidney-shaped, attached at narrow sinuses, or round, but often absent in Hawaiian species.

A genus of about 200 species mostly from temperate regions. Represented in Hawai 'i by nine endemic and one indigenous species. There are thirteen varieties of the endemic species. There are no naturalized species.

Many of the Hawaiian endemic Dryopteris are very polymorphic, resulting in confusion and debate as to their taxonomic status. They exhibit as much or more infraspecific variation as Dryopteris anywhere else in the world. Delineating species and varieties within certain groups of Hawaiian Dryopteris is more troublesome than in any other fern genus in Hawai 'i. In most cases assignment to a species or variety is very subjective, and assignments in this treatment represent my current and hesitant opinion as to their placement. Further study is needed. A careful literature review, more fieldwork and more collections, reference to type specimens, new morphologic characters, studies with modern techniques such as scanning electron microscopy of spores, chromosome counts, and isozymes, and DNA studies will be needed to further define these groups. In addition, cultivation of the species and varieties in greenhouse common-garden conditions, with uniform media, temperature, moisture, and light, would demonstrate the relative importance of genetics versus environment. As clearer definitions of species and varieties are made, assignments of some taxa will change, and new taxa will surely be found. These studies may also resolve whether some varieties of the polymorphic species Dryopteris glabra are valid species and others, simply ecotypes.

Examination of many type specimens in recent years has revealed that some names in common usage have been misapplied. The resultant name corrections include D. mauiensis (for the misapplied D. sandwicensis), D. sandwicensis (for the misapplied D. unidentata), and D. unidentata and its varieties (for the misapplied D. acutidens). The name D. parvula has been incorrectly applied to a newly recognized variety of D. glabra, var.flynnii. Other less commonly used misapplied names are listed in the synonymy for each species. Where names have been corrected, a brief explanation is made in the discussion of that species.

The following six species are quite distinct: D. crinalis (and var. podosorus), D.fusco-atra (and var. lamoureuxii), D. hawaiiensis, D. mauiensis, D. subbipinnata, and D. wallichiana.

There are two groups of Hawaiian Dryopteris that comprise closely related, probably monophyletic taxa about which there is continuing debate:

(l) A 3- to 5-pinnate group without indusia (not including the exindusiate D. mauiensis), treated here as three species, includes D. sandwicensis, D. unidentata (with two varieties), and D. tetrapinnata. The smaller, relatively glabrous D. sandwicensis is recognized as standing apart enough to warrant recognition at the specific level. Dryopteris unidentata has variously been treated in the past as one species with four varieties, two species, three species, and as two of the varieties of a species with three varieties. The magnificent D. tetrapinnata is the largest fern in this group and more deeply cut than the closely related D. unidentata var. paleacea.

(2) The indusiate, (2-)3- to 5-pinnate Dryopteris in Hawai 'i are represented by two species, treated here as D. glabra with seven varieties (vars. alboviridis, flynnii, glabra, hobdyana, nuda, pusilla, and soripes) and the unrelated D. hawaiiensis. Previous treatments of this group have recognized D. glabra as being divided into up to six separate species (D. alboviridis, D. nuda, D. parvula, D. soripes, and D. tenebrosa), or as one species with four to six varieties. Dryopteris glabra and its varieties are in need of careful study. Some initial common-garden studies suggest that many of these varieties, in spite of their very different appearances, may simply be ecotypes.

Identification of rare taxa or those with limited geographic distributions may be aided by referring to their known habitats (recognizing that new locations for some of them will surely be found). These taxa include D. crinalis var. podosorus, D. glabra vars. alboviridis, hobdyana, pusilla,flynnii, and soripes, and D. subbipinnata.

KEY TO THE SPECIES OF DRYOPTERIS IN HAWAI'I

1. Fronds 1-pinnate-pinnatifid to occasionally 2-pinnate, inclined at an angle and arranged as a shuttlecock on erect rhizomes; stipes and rachises very scaly (2).

1. Fronds 2- to 5-pinnate, erect to drooping, arranged as a shuttlecock, or not, on creeping, decumbent, or erect rhizomes; stipes and rachises scaly or not(4).

2(1). Lower pinnae not, or only slightly, smaller than middle pinnae; ultimate segments at bases of pinnae usually not overlapping rachises; scales gray to black, long, narrow; sori on all pinnae (sometimes sparse or absent on most basal pinnae); all major islands ...................... 2. D.fusco-atra

2. Several lower pinnae tapering to 1 /3-1/2 the size of middle pinnae, or not; ultimate segments at bases of pinnae usually overlapping rachises; scales reddish brown to medium brown to dark brown, wider; sari limited to distal 1/2 offrond (3).

3(2). Medial and lower pinnae not overlapping, several lower pinnae tapering to 1/3-1/2 the length of middle pinnae; blades mostly 1-pinnate-pinnatisect; ultimate segments 8-12 x 3-5 mm, completely adnate, unlobed, lateral margins entire, tips truncate; sori mostly 2-4 pairs per segment; all major islands except Uina 'i ................................ 10. D. wallichiana

3. Medial and lower pinnae overlapping, lower pinnae the same size or only slightly smaller than the middle pinnae; blades 1-pinnate-pinnatisect to 2-pinnate-pinnatifid; ultimate segments 10--25 x 5-10 mm, often with constricted or stalked bases, lateral margins crenulate to lobed, tips rounded; sori mostly 4-7 pairs per segment; Maui, Hawai'i . 7. D. subbipinnata

4(1). Indusia present (5).

4. Indusia absent (6).

5(4). Stipes and rachises slightly to very scaly; costae and veins quite scaly on the abaxial surfaces; fronds not glandular; sori medial, larger than 1 mm diam.; all major islands except Lana'i .................... 4. D. hawaiiensis

5. Stipes and rachises nearly glabrous, or somewhat scaly at bases of stipes (D. glabra var. hobdyana quite scaly); costae and veins with few scales; fronds glandular to very glandular; sori submarginal to marginal, less than 1 mm in diameter; Kaua'i only, Maui only, or all major islands .................................... 3. D. glabra (and varieties)

6(4). Fronds medium-sized; stipes, rachises, costae, and veins clothed with dark, stiff, long, narrow scales, hairlike scales, and hairs; all major islands except Lana'i .......................... 1. D. crinalis (and var. podosorus)

6. Fronds medium-sized to large; stipes glabrous to very scaly, if large, often scaly, with larger, longer scales (7).

7(6). Fronds usually shorter than 1 m; stipes scaly only at bases; rachises nearly glabrous with few or no scattered hairlike scales; all major islands ........................................... 6. D. sandwicensis

7. Fronds usually longer than 1 m; stipes, rachises, and costae usuallyscaly along entire length with stiff, dark brown scales, or stipes with soft, reddish brown, long, linear-lanceolate scales at bases, becoming flattened against upper stipes, and rachises and costae largely naked (8).

8(7). Blades 2- to 3-pinnate, ovate-deltate to ovate-lanceolate, chartaceous, light green; scales stiff, reddish brown, long, linearlanceolate at stipe bases, becoming soft and flattened against upper stipes, rachises and costae largely naked, but with occasional small, soft, reddish brown scales or hairlike scales; all major islands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. D. mauiensis

8. Blades 3- to 4-pinnate, oblong-lanceolate to oblong-ovate, coriaceous, green to dark green; stipes, rachises, costae, and costules with scales plentiful to dense, dark, triangular to linear-lanceolate (9).

9(8). Fronds up to 2 m long; blades 3- to 4-pinnate; ultimate segments more than 2 mm wide; all major islands ................ 9. D. unidentata (and varieties)

9. Fronds up to 3 m or longer; blades 4-pinnate-pinnatisect; ultimate segments less than 1.5 mm wide; East Maui ....................... 8. D. tetrapinnata