GYROTHYRA A NEW GENUS OF HEPATICAE.
Stem creeping, foliose, subsimple or somewhat sparingly branch ing, radiculose. Leaves succubous, entire, alternate ; underleaves present, free, bifid, segments narrowly lanceolate or subulate; walls of the leaf-cells with triangular thickenings at the angles. Antheridia short-stalked, in the axils of smaller saccate leaves, form ing short median or, at first, terminal spikes. Involucral leaves 2-4 pairs (commonly 3 pairs). Perianth terminal, confluent for half its length or more with the bases of the involucral leaves, the greater part of the calyptra, and the tissues of the stem, to form a thick-walled tube (perigynium), with a small bulbous or saccate base; perigynium erect or ascending, making, at maturity, nearly a right angle with the stem. Capsule cylindrical, long_exserted, dehiscing
spirally by four very long and slender valves ; capsule-valves of two layers of cells, whose walls are wholly destitute of spiral, semiannular, or other local thickenings. Elaters free, bispiral, acute or bluntly pointed ; spores minutely papillate. " Involucel lum " of the sporogonium foot well developed. (Name from rupk, twisted, and 06pa, door.)