2. P. hexagonóptera, Fée. Fronds triangular, usually broader than long (7–12´ broad), slightly pubescent and often finely glandular beneath; pinnæ lanceolate; upper segments oblong, obtuse, toothed or entire, those of the very large lowest pinnæ elongated and pinnately lobed, basal ones very much decurrent and forming a continuous many-angled wing along the main rhachis; fruit-dots near the margin; some also between the sinus and the midrib.—Rather open woods, New Eng. to Minn., and southward; common. July.—Larger and broader than the last, which it often closely resembles.
[*][*] Fronds ternate, the three divisions petioled; rhachis wingless.
3. P. Dryópteris, Fée. Fronds smooth, broadly triangular (4–6´ wide); the three triangular primary divisions all widely spreading, 1–2-pinnate; segments oblong, obtuse, entire or toothed; fruit-dots near the margin.—Rocky woods; common northward. July. (Eu.)
4. P. calcàrea, Fée. Fronds minutely glandular and somewhat rigid, the lateral divisions ascending; lowest inferior pinnæ of the lateral divisions smaller in proportion than in the last species, which it otherwise closely resembles.—Iowa and Minn.; rare. July. (Eu.)
13. ASPÍDIUM, Swartz. Shield Fern. Wood Fern. ([Pl. 19.])
Fruit-dots round, borne on the back or rarely at the apex of the veins. Indusium covering the sporangia, flat or flattish, scarious, orbicular and peltate at the centre, or round-kidney-shaped and fixed either centrally or by the sinus, opening all round the margin. Stipe continuous (not articulated) with the rootstock.—Our species have free veins and 1–3-pinnate fronds. (Name, ἀσπίδιον, a small shield, from the shape of the indusium.)
§ 1. DRYÓPTERIS. Indusium reniform, or orbicular with a narrow sinus.
[*] Veins simple or simply forked and straight; fronds annual, decaying in autumn, the stalks and slender creeping rootstocks nearly naked.
1. A. Thelýpteris, Swartz. Fronds pinnate, lanceolate in outline; pinnæ horizontal or slightly recurved, linear-lanceolate, deeply pinnatifid, the lowest pairs scarcely smaller; lobes oblong, entire, obtuse or appearing acute when in fruit from the strongly revolute margins; veins mostly forked, bearing the (soon confluent) fruit-dots near their middle; indusium minute, smooth and naked.—Marshes; common. Aug.—Stalk 1° long or more, usually longer than the frond, which is of thicker texture than the next, and slightly downy. (Eu.)
2. A. Noveboracénse, Swartz. Fronds pinnate, lanceolate in outline, tapering both ways from the middle; pinnæ lanceolate, the lowest 2 or more pairs gradually shorter and deflexed; lobes flat, oblong, basal ones often enlarged and incised; veins simple, or forked in the basal lobes; fruit-dots distinct, near the margin; indusium minute, the margin glanduliferous.—Swamps and moist thickets; common. July.—Frond pale green, delicate and membranaceous, hairy beneath along the midribs and veins.