BFNA Title: Biantheridion
XX. BIANTHERIDION (Grolle) Konstantinova & Vilnet, Arctoa 18: 67. 2009
Jamesoniella sect. Biantheridion Grolle, Trans. Brit. Bryol. Soc. 4: 662. 1964
Marie L. Hicks
Stem not especially soft, cortex not differentiated. Leaves succubous, not especially soft, symmetrical, plane or undulate, unlobed, rounded or shallowly retuse, entire, upper base decurrent, lower base not decurrent; cell walls slightly thickened; trigones present, occasionally slightly bulging, marginal cells similar; underleaves very small or absent. Gemmae absent. Gynoecial bracts closely enveloping base of perianth; perianth persistent, oblong-ovoid, distally plicate, narrowed to mouth.
Species one (one species in the flora): Greenland; Europe; Asia.
The single species of Biantheridion has often been included in Jamesoniella (a synonym of Syzygiella, Adelanthaceae), on account of the presence of a few teeth on the bracts. Recent research has made it clear that it is not related to this primarily tropical family, but instead belongs in Scapaniaceae (Vilnet et al. 2010).
SELECTED REFERENCES. A. A. Vilnet, N. A. Konstantinova, and A. V. Troitsky. 2010. Molecular insight on phylogeny and systematics of the Lophoziaceae, Scapaniaceae, Gymnomitriaceae and Jungermanniaceae. Arctoa 19: 31--50.
1. Biantheridion undulifolium (Nees) Konstantinova & Vilnet, Arctoa 18: 67. 2009 
Jamesoniella schraderi var. undulifolia Nees, Naturg. Eur. Leberm. 1: 306. 1833; Jamesoniella undulifolia (Nees) Müller Frib., Crossogyna undulifolia (Nees) Schljakov
Plants with shoots 10--30 cm x 1--1.5 mm, prostrate to erect-caespitose when crowded, slightly laterally compressed, simple or with few branches, green to reddish-brown. Stems firm, 225--275 \um; branches terminal, long; cortical cells 14--20 µm with thin walls, medullary cells slightly larger. Leaves imbricate, orbicular, wider than long, 0.8--0.85 x 0.95--1.1 mm, slightly concave, the larger leaves tending to be undulate; margins broadly rounded, entire, emarginate leaves occasional; median leaf cells 22--26 x 25--34 \um; marginal cells 20--25 µm; cuticle faintly verruculose; cell walls slightly thickened; trigones present, occasionally slightly bulging; oil bodies 6--12 per cell, spherical to ellipsoid, 4--5 x 6--8 \um, granular. Underleaves absent or sporadically present on sterile shoots, very small, lanceolate or of slime papillae. Androecia terminal becoming intercalary; bracts in 4--6 pairs, imbricate, concave with an incurved tooth at dorsal base; antheridia two per bract, stalk 4-seriate. Gynoecia (frequently fertile) terminal on main shoot with large somewhat undulate subtending leaves; bracts large, up to 800 x 1200 \um, undulate, similar to distal leaves with small, obscure teeth on margins; bracteole free, large (to 650 \um), lanceolate with 1--2 teeth at base; perianth ovoid-oblong, inflated, contracted to plicate mouth with small 1--2 celled teeth or crenulate margin formed by elongate fingerlike cells.
Peaty soil in bogs or among mosses on tundra; low to high elevations; w and nw Greenland; Que.; n Europe; Asia (Russian Far East, Siberia).
The name Jamesoniella schraderi (Mart.) Schiffner has often been misapplied to this species.