BFNA Title: Arnelliaceae
ARNELLIA – ARNELLIACEAE
ARNELLIACEAE Nakai, Ordines, Familiae, Tribi, Genera . . . a Prof. Nakai, Edita. 1943
W. B. Schofield
Plants small to very small, ca. 1.3 cm. Stems 0.5--1 mm wide; branches few, terminal or lateral intercalary; stems soft-textured, with 1-stratose cortex similar to medulla, of thin walled cells. Leaves opposite, succubous, margins entire and plane, leaf bases often contiguous; underleaves subulate, obsolete or absent. Specialized asexual reproduction rare, by gemmae (only in Arnellia). Sexual condition dioicous; perianths poorly developed prior to fertilization, sheathed in leaves at time of fertilization, 2-labiate. Sporophytes developed within perigynium or marsupium. Capsule spherical, ellipsoid to cylindric, with 2-stratose jacket.
Genera 3: (1 in the flora): Holarctic and Temperate North America, South America, Europe, Asia, Meditteranean and w tropical Africa.
1. ARNELLIA Lindberg in S. O. Lindberg and W. H. Arnell, Kongl. Svenska Vetenskapsakad. Handl. ser. 2. 23: 35 * [For W. H. Arnell, Swedish hepaticologist, 1848--1932]
Plants in light green to whitish (rarely brownish) green, reclining to erect, as small shoots in mats or as scattered shoots, sparsely branched, branches intercalary. Leaves round to suborbicular, sometimes fused at antical base; rhizoids confined to underleaves; laminal cells with trigones, oil bodies 3--10 per cell, homogenous. Specialized asexual reproduction by 1--2 celled gemmae on proximal dorsal surface of leaves. Sexual condition: archegoniate shoots with leaves compressed; a marsupium usually produced. Sporophytes with short seta. Spores spherical l8--24 μm., papillose.
Species 1: circumpolar, often a calcicole, moist tundra, shaded cliffs, alpine to Arctic, North America, alpine and n Europe, Asia (Russia).
1. Arnellia fennica (Gottsche) H. Lindberg in H. Lindberg and W. H. Arnell, , Kongl. Svenska Vetenskapsakad. Handl. ser. 2. 23: 35. 1889
Jungermannia fennica Gottsche & Rabenhorst, Hep. Eur. 418. 1868
Plants usually as strands among mosses, mat pale green, sometimes with leaf pairs distant and decidedly asymmetrical, leaf margin with cells swollen dorsiventrally, leaf margins entire; underleaf sometimes connate with leaf.
Sporophytes infrequent. Damp to wet tundra, humid cliff shelves; 10--2000 m; Greenland; Alta., B.C., Man., Ont., N.W.T., Nunavut, Yukon; Alaska., S.Dak.; n Europe; Asia (Russia).