[+][+] Indusium entirely concealed beneath the sorus, divided into very narrow segments or reduced to minute hairs.
5. W. Oregàna, D. C. Eaton. Smooth, with fronds (2–8´ high, 8–12´´ wide) elliptical-lanceolate, pinnate, the fertile ones tallest; pinnæ 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 shore of Lake Superior (Robbins), and westward.
6. W. scopulìna, D. C. Eaton. Much like the last, but the rather larger fronds puberulent 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. DICKSÒNIA, 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 Dickson, an English Cryptogamic botanist.)
1. D. pilosiúscula, Willd. Fronds minutely glandular and hairy (2–3° high), ovate-lanceolate and acuminate in outline, pale green, very thin, with strong chaffless stalks rising from slender extensively creeping naked root-stocks, mostly bipinnate; primary pinnæ 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. TRICHÓMANES, 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. radìcans, Swartz. Fronds very delicate, oblong-lanceolate in outline (4–8´ long, 6–18´´ wide), bipinnatifid; rhachis narrowly winged; pinnæ 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. SCHIZÆ̀A, Smith. ([Pl. 20.])