20. Lygodium. 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. Osmundàceæ. 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 pinnæ or fronds very much contracted, bearing the abundant and large sporangia upon the margins of the very narrow segments. Veins free.
1. POLYPÒDIUM, 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 knobs, to which the stipes are attached by a distinct articulation. (Name from πολύς, many, and ποῦς, foot, alluding to the branching rootstock.)
1. P. vulgàre, 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. incànum, 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.
2. NOTHOLÆ̀NA, R. Brown. Cloak-fern.
Fruit-dots roundish or oblong, placed near the ends of the veins, soon more or less confluent into an irregular marginal band, with no proper involucre. Veins always free. Fronds of small size, 1–4-pinnate, the lower surface almost always either hairy, tomentose, chaffy, or covered with a fine waxy white or yellow powder. (Name from νόθος, spurious, and λαῖνα, a cloak, the woolly coating of the original species forming a spurious covering to the sporangia.)
1. N. dealbàta, Kunze. Fronds triangular-ovate, 1–3´ long, 3–4-pinnate; rhachis and branches straight, black and shining; ultimate pinnules scarcely a line long, white and powdery on the lower surface.—Clefts of calcareous rocks, Mo., Kan., and southwestward. July–Aug.