Marie L. Hicks
Jungermannia sect. Gymnocolea Dumortier
Plants creeping with ascending apices, mat forming or erect when crowded, green to blackish brown or scorched in insolated sites. Stems 7 8 cells in diameter, branching terminal, lateral or ventral intercalary, from older stems, cortical cells thin walled, 20 25 µm, little differentiated from medullary; rhizoids very sparce, scattered along ventral stem, colorless. Leaves succubous oblique, bilobed, the lobes obtuse to rounded, occasionally acute, often concave; leaf cells subisodiametric, small, 22 30 µm; cuticle smooth, occasionally slightly verruculose; walls without distinct trigones; oil bodies smooth to slightly granulate. Underleaves absent or occasional and small, of 1 3 cells from narrow ventral merophytes of 2 4 cells. Specialized asexual propagation by detached inflated perianths that float on water; gemmae absent or very rare, angular, brown, 1 2 celled. Sexual condition dioecious. Androecia terminal, spicate, becoming intercalary, of ventricose bracts similar to leaves but smaller; antheridia one per bract; stalk 1 seriate. Gynoecia terminal on main stem or branch, often with subfloral innovations; bracts similar to leaves; bracteole absent; perianth exerted, inflated, smooth, the mouth contracted; perigynium absent. Sporophyte seta cross section of 8 exterior cells and 4 interior cells; capsule ovoid, brown, valves 2 cells thick, the walls with nodular thickenings; elaters 120 200 × 6 9 µm, 2 spiral, brown; spores 10 18 µm, finely papillate, brown.
Species 6 (2 in the flora); cool parts of the Northern Hemisphere and South America.
Schuster, R. M. 1969. The Hepaticae and Anthocerotae of North America, Vol. II. New York.