11. E. scirpodes, Michx. _Stems very numerous in a tuft, filiform_ (3--6' high), _flexuous and curving, mostly 6-grooved_, with acute ridges; _sheaths 3-toothed_, the bristle-pointed teeth more persistent; central air-cavity wanting.--Wooded hillsides, N. Eng. to Penn., Minn., and northward. (Eu.)

ORDER 131. FiLICES. (FERNS.)

_Leafy plants, with the leaves_ (fronds) _usually raised on a stalk or petiole_ (stipe), _rising from a_ (sometimes greatly elongated) _rootstock, separately rolled up_ (circinate) _in the bud, and bearing on the under surface or along the margin small reticulated sporangia, which at length split open and discharge the numerous minute spores.

Prothallus green, above ground, normally moncious._

SUBORDER I. Polypodiaceae. Sporangia collected in dots, lines, or variously shaped cl.u.s.ters (_sori_ or _fruit-dots_) on the back or margins of the frond or its divisions, cellular-reticulated, stalked, the stalk running into a vertical incomplete many-jointed ring, which by straightening at maturity ruptures the sporangium transversely on the inner side, discharging the spores. Fruit dots often covered (at least when young) by a membrane called the _indusium_ (or less properly the _involucre_), growing either from the back or the margin of the frond.

(Plates 16--19.)

Tribe I. POLYPODIEae. Fructification on the back of the frond, in round or roundish fruit-dots (_sori_) placed on the veins or at the ends of the veins, without indusium of any kind. Stipes articulated to the rootstock, leaving a distinct scar when separated. Veins free (not reticulated) in our species.

1. Polypodium. Sori round, in one or more rows, on each side of the midrib or of the segments of the frond.

Tribe II. GRAMMITIDEae. Sori more or less elongated, without indusium, placed on the back of the frond, usually along the veins or near their extremities. Veins free in our species.

2. Notholaena. Sori short, of few rather large sporangia, placed near the tips of the veins; under surface of the frond usually either chaffy, woolly, or powdery.

Tribe III. PTERIDEae. Fructification marginal or intramarginal, provided with a general indusium formed of the (either altered or unchanged) margin of the frond. Stipes not articulated to the rootstock. Veins free in all our species.

[*] Sporangia at the ends of the veins, on a reflexed portion of the margin of the frond.

3. Adiantum. Midrib of the pinnules marginal or none. Stipe black and polished.

[*][*] Sporangia borne on a continuous marginal vein-like receptacle, connecting the apices of the veins, and covered by a delicate whitish indusium formed of the reflexed margin.

4. Pteris. Midrib of the pinnules central. Stipe light colored.

[*][*][*] Sporangia at or near the ends of the unconnected veins, borne on the under surface of the frond; indusium various.

5. Cheilanthes. Sori minute, at the ends of the veins; indusium continuous or interrupted. Fronds mostly chaffy, woolly, or pulverulent, rarely smooth.

6. Pellaea. Sori on the upper part of the veins, distinct, or mostly forming a confluent submarginal band of sporangia. Indusium membranaceous, continuous, rarely wanting. Sterile and fertile fronds not very unlike; stipes dark colored; fronds smooth.

7. Cryptogramme. Sori roundish or elongated and extending far down the free veins, at first covered by the very broad continuous indusium, at length exposed and confluent. Sterile and fertile fronds very different; stipes light colored; fronds smooth.

Tribe IV. BLECHNEae. Sori oblong or linear, borne on a veinlet parallel to the midrib, and covered with a special usually concave or arched indusium attached to the fruiting veinlet, and opening along the inner side.

8. Woodwardia. Sori forming a chain-like row each side of the midrib or central vein. Veins reticulated.

Tribe V. ASPLENIEae. Sori more or less elongated, occupying one or both sides of oblique veins, covered by a special indusium which is attached by one side to the fertile vein, and is free on the other. Stipes not articulated.

9. Asplenium. Sori on the upper side or rarely on both sides of a veinlet. Veins free in all our species.

10. Scolopendrium. Sori linear, confluent in pairs, each pair appearing like a single sorus with a double indusium opening down the middle.

Veins free.

11. Camptosorus. Sori oblong, variously curved, or some of them in opposite pairs. Veins reticulated.

Tribe VI. ASPIDIEae. Sori round or roundish, on the back or rarely at the apex of the vein, with a special indusium, rarely naked. Stipes not articulated to the rootstock.

[*] Indusium obsolete or none.

12. Phegopteris. Sori round, rather small. Veins free in our species.

[*][*] Indusium evident, round or roundish, covering the sporangia, at least when young. Sterile and fertile fronds not very unlike. Veins free in our species.

13. Aspidium. Indusium flat or slightly convex, orbicular or round-reniform, fixed by the centre, opening all round the margin.

14. Cystopteris. Indusium convex, fixed by a broad base partly under the sorus, commonly reflexed as the sporangia ripen.

[*][*][*] Indusium obscure, irregularly semicircular. Fertile fronds much contracted and very unlike the sterile ones.

15. Onoclea. Sporangia on an elevated receptacle; divisions of the fertile frond pod-like or berry-like.

Tribe VII. WOODSIEae. Sori round, borne on the veins; indusium fixed under the sorus, divided into segments or into slender filaments.

16. Woodsia. Small ferns with free veins. Indusium very delicate.

Tribe VIII. d.i.c.kSONIEae. Sori roundish, marginal or submarginal. Indusium cup-shaped or two-valved, the outer portion composed of a reflexed lobule of the frond, or more or less united to it.

17. d.i.c.ksonia. Indusium in our species small, membranaceous, nearly globular. Frond elongated, decompound.

SUBORDER II. Hymenophyllaceae. Sporangia sessile on a bristle-like receptacle within a cup-shaped or bivalvular involucre, the ring transverse and complete. Fronds delicately membranaceous.

18. Trichomanes. Involucres funnel-form or cup-shaped.

SUBORDER III. Schizaeaceae. Sporangia ovate, sessile, having a complete transverse articulated ring at the apex, and opening by a longitudinal slit. (Pl. 19.)

19. Schizaea. Sporangia naked, fixed in a double row to the midrib of the narrow fertile segments. Sterile fronds rigid, simple or dichotomously branched.

20. LyG.o.dium. Sporangia borne in a double row on narrow fertile segments, each sporangium seated on a separate veinlet, and provided with a special scale-like indusium. Fronds leafy, climbing.

SUBORDER IV. Osmundaceae. Sporangia naked, globose, mostly pedicelled, reticulated, with no ring or mere traces of one near the apex, opening into two valves by a longitudinal slit. Stipes winged at base and almost stipulate! (Pl. 19.)

21. Osmunda. Fertile pinnae or fronds very much contracted, bearing the abundant and large sporangia upon the margins of the very narrow segments. Veins free.

1. POLYPDIUM, L. POLYPODY. (Pl. 16.)

Fruit-dots round, naked, arranged on the back of the frond in one or more rows each side of the midrib or central vein, or irregularly scattered, each borne in our species on the end of a free veinlet.

Rootstocks creeping, branched, often covered with chaffy scales, bearing scattered roundish k.n.o.bs, to which the stipes are attached by a distinct articulation. (Name from p????, _many_, and p???, _foot_, alluding to the branching rootstock.)

1. P. vulgare, L. (Pl. 16, fig. 1--3.) Fronds evergreen, oblong, _smooth both sides_, 4--10' high, simple and deeply pinnatifid; the divisions linear-oblong, obtuse or somewhat acute, remotely and obscurely toothed; veins once or twice forked; _fruit-dots large, midway between the midrib and the margin_.--Rocks; common. July. (Eu.)

2. P. incanum, Swartz. Fronds evergreen and coriaceous, oblong, 2--6'

high, _grayish and very scurfy underneath with peltate scales_, simply pinnatifid; the divisions oblong-linear, obtuse; _fruit-dots rather small, near the margin_; veins forking, free in the N. American plant!--Rocks and trunks of trees, Va. and Ohio to Ill., and southward.

Aug.