-- 2. POLSTICHUM. _Indusium orbicular and entire, peltate, fixed by the depressed centre; fronds rigid and coriaceous, evergreen, very chaffy on the rhachis, etc.; pinnae or pinnules auricled at base on the upper side, crowded, the teeth or lobes bristle-tipped._

[*] _Fronds simply pinnate._

10. A. acrostichodes, Swartz. (CHRISTMAS FERN.) (Pl. 19, fig. 3, 4.) Frond lanceolate (1--2 high), _stalked; pinnae linear-lanceolate_, somewhat scythe-shaped, half-halberd-shaped at the slightly stalked base, serrulate with appressed bristly teeth; _the fertile_ (upper) _contracted and smaller_, bearing contiguous fruit-dots near the midrib, which are confluent with age, covering the surface.--Var. INCSUM is a state with cut-lobed pinnae, a not unfrequent case in the sterile fronds; sometimes with all the tips fertile.--Common in rocky woods, especially northward. July.

11. A. Lonchtis, Swartz. Frond linear-lanceolate (9--20' high), _scarcely stalked, very rigid; pinnae broadly lanceolate-scythe-shaped, or the lowest triangular_, strongly auricled on the upper side, and wedge-truncate on the lower, densely spinulose-toothed (1' or less in length), copiously fruit-bearing; fruit-dots contiguous and near the margins.--Woods, southern sh.o.r.e of Lake Superior, and northward. (Eu.)

[*][*] _Fronds bipinnate._

12. A. aculeatum, Swartz, var. Braunii, Koch. _Fronds spreading_ (1--2 long), oblong-lanceolate in outline, with a tapering base, the lower of the many pairs of oblong-lanceolate pinnae gradually reduced in size and obtuse; pinnules ovate or oblong, obtuse, truncate and almost rectangular at base, short-stalked, or the upper confluent, sharply toothed, beset with long and soft as well as chaffy hairs.--Deep woods, mountains of New Eng., N. Y., and Penn., and northward. (Eu.)

14. CYSToPTERIS, Bernhardi. BLADDER FERN. (Pl. 19.)

Fruit-dots roundish, borne on the back of a straight fork of the free veins; the delicate indusium hood-like or arched, attached by a broad base on the inner side (toward the midrib) partly under the fruit-dot, early opening free at the other side, which looks toward the apex of the lobe, and is somewhat jagged, soon thrown back or withering away.--Tufted ferns with slender and delicate 2--3-pinnate fronds; the lobes cut-toothed. (Name composed of ??st??, _a bladder_, and pte???, _fern_, from the inflated indusium.)

1. C. bulbifera, Bernh. (Pl. 19, fig. 1--3.) _Frond lanceolate, elongated_ (1--2 long), 2-pinnate; the pinnae lanceolate-oblong, pointed, horizontal (1--2' long); the _rhachis and pinnae often bearing bulblets underneath, wingless_; pinnules crowded, oblong, obtuse, toothed or pinnatifid; indusium short, truncate on the free side.--Shaded ravines, not rare from N. Eng. to Ark., commoner on calcareous rocks. July.--Specimens from Tenn. and Ark. have sometimes shorter fronds and few or no bulblets, indicating an approach to the next species.

2. C. fragilis, Bernh. _Frond oblong-lanceolate_ (4--8' long, besides the brittle stalk which is fully as long), 2--3-pinnate; the pinnae and _pinnules_ ovate or lanceolate in outline, irregularly pinnatifid or cut-toothed, mostly acute, _decurrent on the margined or winged rhachis_; indusium tapering or acute at the free end.--Shaded cliffs and rocky woods; common and greatly varying in the shape and cutting of the pinnules. July. (Eu.)

15. ONOCLeA, L. (Pl. 16 and 19.)

Sporangia borne on elevated receptacles, forming roundish sori imperfectly covered by very delicate hood-shaped indusia attached to the base of the receptacles. Fertile fronds erect, rigid, with contracted pod-like or berry-like divisions at first completely concealing the sporangia, and at last, when dry and indurated, cracking open and allowing the spores to escape. Sterile fronds foliaceous. Rootstocks creeping and constantly forming new plants. (Name apparently from ????, _a vessel_, and ??e??, _to close_, from the singularly rolled up fructification.)

-- 1. ONOCLEA proper. _Sterile frond with anastomosing veins._

1. O. sensibilis, L. (SENSITIVE FERN.) (Pl. 19, fig. 1, 2.) Fronds scattered; the sterile ones long-stalked (2--15' long), triangular-ovate, pinnatifid into a few oblong-lanceolate sinuately lobed or nearly entire segments; veins reticulated with fine meshes; fertile fronds contracted, closely bipinnate, the pinnules rolled up into berry-like bodies.--Moist meadows and thickets, very common and variable. July.--Imperfectly fertile fronds sometimes occur, with the still foliaceous pinnae cut into obovate segments with free veins and abortive sori; the so-called var. OBTUSILOBaTA.

-- 2. STRUTHIoPTERIS. _Sterile frond with free veins._

2. O. Struthiopteris, Hoffmann. (Pl. 16, fig. 1--5.) Fronds growing in a crown; sterile ones short-stalked (2--10 high), broadly lanceolate, narrowed toward the base, pinnate with many linear-lanceolate, pinnatifid pinnae; veins free, the veinlets simple; fertile frond shorter, pinnate with pod-like or somewhat necklace-shaped pinnae.

(Struthiopteris Germanica, _Willd._)--Alluvial soil, common northward.

July.--The rootstock sends out slender underground stolons, which bear fronds the next year. (Eu.)

16. WOoDSIA, R. Brown. (Pl. 19.)

Fruit-dots round, borne on the back of simply-forked free veins; the very thin and often evanescent indusium attached by its base all around the receptacle, _under_ the sporangia, either small and open, or else early bursting at the top into irregular pieces or lobes.--Small and tufted pinnately-divided ferns. (Dedicated to _Joseph Woods_, an English botanist.)

[*] _Stalks obscurely articulated some distance from the base; fronds chaffy or smooth, never glandular; indusium divided nearly to the centre into slender hairs which are curled over the sporangia._

1. W. Ilvensis, R. Brown. _Frond oblong-lanceolate_ (2--6' long by 12--18" wide), smoothish and green above, _thickly clothed underneath as well as the stalk with rusty bristle-like chaff_, pinnate; the pinnae crowded, oblong, obtuse, sessile, pinnately parted, _the numerous crowded segments oblong_, obtuse, obscurely crenate; the fruit-dots near the margin, somewhat confluent when old.--Exposed rocks; common, especially northward, and southward in the Alleghanies. June. (Eu.)

2. W. hyperbrea, R. Brown. Frond narrowly oblong-lanceolate (2--6' long by 8--12" wide), smooth above, sparingly paleaceous-hirsute beneath, pinnate; the pinnae triangular-ovate, obtuse, pinnately lobed, the lobes few and nearly entire; fruit-dots rarely confluent.--Mountain ravines, northern Vt. and N. Y., and northward; rare. (Eu.)

3. W. glabella, R. Brown. (Pl. 19, fig. 1--3.) _Smooth and naked throughout; frond linear_ and very delicate (2--5' high), pinnate; _pinnae roundish-ovate_, the lower ones rather remote (2--4" long), obtuse, crenately lobed; fruit-dots scanty; the hairs of the indusium fewer than in the last two species.--On moist mossy rocks, mountains of northern New Eng., north and westward. First found at Little Falls, N. Y., by _Dr. Vasey_. (Eu.)

[*][*] _Stalks not articulated; fronds never chaffy, often glandular-p.u.b.escent._

[+] _Indusium of a few broad segments, at first covering the sorus completely._

4. W. obtusa, Torr. (Pl. 19, fig. 4, 5.) Frond broadly lanceolate, minutely glandular-hairy (6--12' high), pinnate, or nearly twice pinnate; pinnae rather remote, triangular-ovate or oblong (1--2' long), bluntish, pinnately parted; segments oblong, obtuse, crenately toothed, the lower pinnatifid with toothed lobes; veins forked, and bearing the fruit-dots on or below the minutely toothed lobes; indusium at length splitting into several spreading jagged lobes.--Rocky banks and cliffs; not rare.

[+][+] _Indusium entirely concealed beneath the sorus, divided into very narrow segments or reduced to minute hairs._

5. W. Oregana, D. C. Eaton. Smooth, with fronds (2--8' high, 8--12"

wide) elliptical-lanceolate, pinnate, the fertile ones tallest; pinnae triangular-oblong, obtuse, pinnatifid; segments oblong or ovate, obtuse, finely toothed, and in larger fronds incised; fruit-dots near the margin; indusium very small, divided almost to the centre into a few necklace-like-jointed cilia.--Crevices of rocks, south sh.o.r.e of Lake Superior (_Robbins_), and westward.

6. W. scopulna, D. C. Eaton. Much like the last, but the rather larger fronds p.u.b.erulent beneath with minute jointed hairs and stalked glands; indusium deeply cleft into narrow segments ending in jointed hairs.--Rocky places, Minn., southward and westward.

17. d.i.c.kSNIA, L'Her. (Pl. 17.)

Fruit-dots small, globular, marginal, each placed on the apex of a free vein or fork; the sporangia borne on an elevated globular receptacle, enclosed in a membranaceous cup-shaped indusium which is open at the top, and on the outer side partly adherent to a reflexed toothlet of the frond. (Named for _James d.i.c.kson_, an English Cryptogamic botanist.)

1. D. pilosiuscula, Willd. Fronds minutely glandular and hairy (2--3 high), ovate-lanceolate and ac.u.minate in outline, pale green, very thin, with strong chaffless stalks rising from slender extensively creeping naked root-stocks, mostly bipinnate; primary pinnae lanceolate, pointed, the secondary pinnatifid into oblong and obtuse cut-toothed lobes; fruit-dots minute, each on a recurved toothlet, usually one at the upper margin of each lobe. (D. punctilobula, _Kunze_.)--Common in moist and shady places, from New Eng. to Minn.--Frond sweet-scented in drying.

18. TRICHoMANES, L. FILMY FERN.

Sporangia with a transverse entire ring, sessile on a cylindrical receptacle which is produced from the end of a vein and enclosed in a funnel-form or cup-shaped involucre of the same substance with the frond. Fronds very thin and pellucid, often consisting of a single layer of cells. (An ancient Greek name for some fern.)

1. T. radcans, Swartz. Fronds very delicate, oblong-lanceolate in outline (4--8' long, 6--18" wide), bipinnatifid; rhachis narrowly winged; pinnae triangular-ovate, the divisions toothed or again lobed; involucres tubular-funnel-shaped, margined, the mouth truncate; receptacle often much exserted.--On moist and dripping sandstone cliffs, Ky., and southward; rare.--Though the fronds are so very delicate, yet they survive for several years; they begin to fruit the second or third year, and thereafter the receptacle continues to grow and to produce new sporangia at its base. (Eu.)

19. SCHIZae'A, Smith. (Pl. 20.)

Sporangia large, ovoid, striate-rayed at the apex, opening by a longitudinal cleft, naked, vertically sessile in a double row along the single vein of the narrow divisions of the pinnate (or radiate) fertile appendages to the slender and simply linear, or (in foreign species) fan-shaped or dichotomously many-cleft fronds (whence the name, from s????, _to split_).

1. S. pusilla, Pursh. Sterile fronds linear, very slender, flattened and tortuous; the fertile ones equally slender (" wide), but taller (3--4'

high), and bearing at the top the fertile appendage, consisting of about 5 pairs of crowded pinnae (each 1--1" long).--Low grounds, pine barrens of N. J.; very local. Sept. (Also in Nova Scotia and Newf.)

20. LYGDIUM, Swartz. CLIMBING FERN. (Pl. 20.)

Fronds twining or climbing, bearing stalked and variously lobed (or compound) divisions in pairs, with mostly free veins; the fructification on separate contracted divisions or spike-like lobes, one side of which is covered with a double row of imbricated hooded scale-like indusia, fixed by a broad base to short oblique veinlets. Sporangia much as in Schizaea, but oblique, fixed to the veinlet by the inner side next the base, one or rarely two covered by each indusium. (Name from ????d??, _flexible_.)

1. L. palmatum, Swartz. Very smooth; stalks slender, flexile and twining (1--3 long), from slender running rootstocks; the short alternate branches or petioles 2-forked; each fork bearing a round-heart-shaped palmately 4--7-lobed frondlet; fertile frondlets above, contracted and several times forked, forming a terminal panicle.--Low moist thickets and open woods, Ma.s.s. to Va., Ky., and sparingly southward; rare. Sept.

21. OSMuNDA, L. FLOWERING FERN. (Pl. 20.)

Fertile fronds or fertile portions of the frond dest.i.tute of chlorophyll, very much contracted, and bearing on the margins of the narrow rhachis-like divisions short-pedicelled and naked sporangia; these are globular, thin and reticulated, large, opening by a longitudinal cleft into two valves, and bearing near the apex a small patch of thickened oblong cells, the rudiment of a transverse ring.--Fronds tall and upright, growing in large crowns from thickened rootstocks, once or twice pinnate; veins forking and free. Spores green.

(_Osmunder_, a Saxon name of the Celtic divinity, Thor.)

[*] _Sterile fronds truly bipinnate._

1. O. regalis, L. (FLOWERING FERN.) Very smooth, pale green (2--5 high); sterile pinnules 13--25, varying from oblong-oval to lance-oblong, finely serrulate, especially toward the apex, otherwise entire, or crenately lobed toward the rounded, oblique and truncate, or even cordate and semi-auriculate base, sessile or short-stalked (1--2'