3. Leucolepis Lindberg, Not. Sallsk. Fauna Fl. Fenn. Förh. 9: 80. 1868. • [Greek leucos, white, and lepis, scale, alluding to stem leaves].
Terry T. McIntosh, Steven G. Newmaster
Plants 3-8(-10) cm, in tufts or mats. Stems reddish brown to black, erect, branched distally, dendroid; rhizoids brown, macronemata matted proximally, occasionally along stem into branched portion of stem, micronemata absent. Leaves dimorphic, pale to dark green or reddish brown to hyaline, slightly contorted or crisped when dry, appressed or spreading, flat or keeled when moist, ovate-lanceolate, (1.3-)2-3(-4) mm; base decurrent; margins plane, green, hyaline, or reddish brown, 1-stratose, usually toothed to near base, teeth single, sharp; apex acute or long-acuminate, cuspidate or not; costa subpercurrent or percurrent, distal abaxial surface strongly toothed; medial laminal cells elongate, short-elongate, short-rhombic, or ± isodiametric, 17-50µm, sometimes in longitudinal or diagonal rows, not or weakly collenchymatous, walls not pitted; marginal cells differentiated, linear, short-linear, or rhomboidal, in 1 or 2 rows. Specialized asexual reproduction absent. Sexual condition dioicous. Seta single or rarely double (or 3), reddish brown, 4-5 cm, somewhat flexuose. Capsule pendent, yellow-brown or brown, cylindric, 6-8 mm; operculum hemispheric; exostome yellow-brown; endostome yellow-brown. Spores 28-30 µm.
Species 1: w North America.
Leucolepis is distinguished by a dendroid growth form and strongly differentiated stem leaves. Morphological (T. J. Koponen 1968) and cytological (R. J. Lowry 1948; W. C. Steere et al. 1954) research supports the split of Leucolepis from Mnium. The chromosome number of Leucolepis is n= 5, whereas Mnium is n= 6, 7, and 12.