[*][*] Veins, at least the lowest, more than once forked or somewhat pinnately branching; fruit-bearing veinlets often obscure or vanishing above the fruit-dot; fronds, at least the sterile ones, often evergreen; stalks and apex of the thickened rootstock scaly or chaffy, and often the main rhachis also.
[+] Fronds small, pinnate; pinnæ pinnatifid; indusia very large, persistent.
3. A. fràgrans, Swartz. Fronds (4–12´ high) glandular and aromatic, narrowly lanceolate, with linear-oblong pinnately-parted pinnæ; their crowded divisions (2´´ long) oblong, obtuse, toothed or nearly entire, nearly covered beneath with the very large thin imbricated indusia, which are orbicular with a narrow sinus, the margin sparingly glanduliferous and often ragged.—On rocks, especially near waterfalls, mountains of northern New Eng., west and northward.—Rootstock stout, nearly erect, densely chaffy, as are the crowded stipes and rhachis. (Asia, and barely reaching S. E. Eu.)
[+][+] Large (1–2½° high), the fronds mostly twice pinnate with variously toothed and incised pinnules; indusia rather small, shrivelled in age, or deciduous.
4. A. spinulòsum, Swartz. Stipes with a few pale-brown deciduous scales; frond ovate-lanceolate, twice pinnate; pinnæ oblique to the rhachis, elongated-triangular, the lower pairs broadly triangular; pinnules set obliquely on the midribs, connected by a very narrow wing, oblong, acute, incisely serrate or pinnatifid with spinulosely-toothed lobes; indusium smooth and without marginal glands.—In damp woods, New Eng. to Ky., and northward. July.—The common European type, rare in North America. (Eu.)
Var. intermèdium, D. C. Eaton. Scales of the stipe few, brown with a darker centre; frond broadly oblong-ovate, twice or often thrice pinnate; pinnæ spreading, oblong-lanceolate, the lower unequally triangular-ovate; pinnules crowded, ovate-oblong, spreading, pinnately divided; the oblong lobes spinulose-toothed at the apex; margin of the indusium denticulate and beset with minute stalked glands.—Woods, everywhere.
Var. dilatàtum, Hook. Scales of the stipe large, brown with a dark centre; frond broader, ovate or triangular-ovate in outline, oftenest thrice pinnate; pinnules lance-oblong, the lowest often much elongated; indusium (in the North American plant) smooth and naked.—A dwarf state, fruiting when only 5–8´ high, answers to var. dumetorum.—N. New Eng. to Minn., chiefly in mountain woods, and northward. (Eu.)
5. A. Boòttii, Tuckerman. Scales of the stipe pale-brown; fronds (1–2½° long) elongated-lanceolate in outline, somewhat narrowed at base; lowest pinnæ triangular-ovate, the upper longer and narrower; pinnules oblong-ovate, sharply spinulose-serrate or the lower pinnatifid; indusium minutely glandular. (A. spinulosum, var. Boottii, of last ed. A. cristatum, var. uliginosum, Milde.)—Wet thickets and about ponds, New Eng. to Del. and Minn. July.—Sterile fronds much smaller and simpler than the fertile. (Eu.)
[+][+][+] Large (2–4° high); fronds once pinnate and the pinnæ deeply pinnatifid, or nearly twice pinnate; fruit-dots not very near the margin; the indusium large, thinnish and flat, persistent.
6. A. cristàtum, Swartz. Frond linear-oblong or lanceolate in outline (1–2° long); pinnæ short (2–3´ long), triangular-oblong, or the lowest nearly triangular-ovate, from a somewhat heart-shaped base, acute, deeply pinnatifid; the divisions (6–10 pairs) oblong, very obtuse, finely serrate or cut-toothed, the lowest pinnatifid-lobed; fruit-dots as near the midvein as the margin; indusium round-reniform, the sinus mostly shallow, smooth and naked.—Swamps, etc.; common. July.—Stipes and the stout creeping rootstock bearing broad and deciduous chaffy scales. (Eu.)