4. RÁDULA, Dumort. ([Pl. 24.])
Leaves large, complicate-bilobed, incubous; lower lobe small, bearing root-hairs; underleaves none. Diœcious, rarely monœcious. Fruit usually terminal. Involucral leaves 2, slightly smaller than the cauline, 2-lobed; perianth tubular, compressed or nearly terete, truncate, entire or crenate. Calyptra pyriform, persistent. Capsule oval-cylindric. Elaters slender, free. Spores large, globose, minutely tuberculate. Antheridia in the ventricose bases of spicate leaves. (Radula, a scraper or spatula, in allusion to the form of the perianth.)
[*] Lower lobe subquadrate, barely incumbent on the stem.
1. R. complanàta, Dumort. Creeping, widely subpinnately branching; leaves imbricate, spreading, rounded, the lower lobe obtuse or acute; monœcious; perianth obconic, compressed, the mouth entire, truncate; antheridia in the bases of 2–3 pairs of strongly imbricate tumid leaves.—On rocks aud roots of trees; common. (Eu.)
2. R. obcónica, Sulliv. ([Pl. 24.]) Smaller, indeterminately branched; leaves somewhat remote, round-obovate, convex; monœcious; perianth clavate-obconic, obliquely truncate; antheridia axillary on short lateral branches rising near the terminal involucre.—On trees in cedar swamps, N. J. to Ohio.
[*][*] Lower lobe small, rounded, more or less transversely adnate.
3. R. tènax, Lindb. Stems brownish-green, rigid, tenacious; leaves remote, scarcely decurrent, obliquely elliptic-ovate, opaque, the cells round and strongly chlorophyllose; diœcious; the antheridial spike lateral below the keel of a leaf, long, linear, somewhat obtuse. (R. pallens, Sulliv.; not Gottsche.)—On rotten trunks, in the Catskill Mts., and southward, especially in the mountains.
5. PORÉLLA, Dill. ([Pl. 24.])
Leaves large, incubous, complicate-bilobed; lower lobe ligulate, suberect; underleaves similar, decurrent at base, the apex entire. Diœcious. Fruit on a short lateral branch. Involucral leaves usually 4, 2-lobed, the margin ciliate or denticulate; perianth somewhat oval, compressed, bilabiate, incised or entire. Calyptra globose, persistent. Capsule globose, reddish, short-stalked. Elaters very numerous, 2–3-spiral, free. Spores large, rough. Antheridia solitary in the saccate bases of leaves, crowded in short spikes. (Name a diminutive of porus, an opening.)
[*] Leaves more or less remote; stems bipinnate.