BFNA Title: Leskeella
XX. LESKEELLA (Limpricht) Loeske, Moosfl. Harz. 255, 1903 (Genus Leskea and Latin -ella, diminutive)
John R. Spence
Leskea subgen. Leskeella Limpricht, Laubm. Deutschl. 2: 747, 756. 1895; Anomodon subgen. Leskeella (Limpricht) Kindberg
Plants prostrate, in thin mats or patches. Stems slender, creeping, irregularly branched, secondary branches ascending to erect, often clustered, paraphyllia absent, rhizoids in clusters arising from base of leaves, older primary stems becoming stoloniferous. Leaves of stems and branches slightly differentiated, those of prostrate stems lanceolate, symmetric, appressed to erect when dry, erect-spreading when wet; lamina smooth to weakly plicate on either side of costa, apex abruptly to gradually acuminate or subulate, margins entire to weakly serrulate distally, recurved proximally; costa strong, nearly reaching apex to percurrent, not forked or sinuose, flattening and filling acumen, somewhat obscure distally; mid-laminal cells 1--2:1, smooth, firm-walled, alar cells not well differentiated, laminal cells in acumen somewhat longer than medial cells; secondary branch leaves smaller, more ovate-lanceolate, mid-laminal cells mostly 1:1. Specialized asexual reproduction when present by clustered flagelliform branchlets in axils of distal secondary branch leaves. Sexual condition dioicous; perichaetial leaves pale translucent, longer and more acuminate. Capsule pyriform to subcylindric, erect to inclined, mostly symmetric, operculum conic, short-rostrate; peristome double, reduced, exostome teeth lanceolate or linear-lanceolate, endostome of moderately high, free, segments irregular to filiform, cilia rudimentary to absent. Spores small, finely papillose.
Species 4 (1
in the flora): Northern Hemisphere, cool-temperate, montane and
boreal-temperate regions, disjunct in
P. Wilson and D. H. Norris (1989) provide sound arguments for combining Leskeella and Pseudoleskeella. However, I have retained Leskeella pending a worldwide revision that includes all other species of the genus as well as those of Pseudoleskeella. There appear to be two main groups that do not correspond to the traditional genera, one consisting of species with lanceolate, appressed leaves and a strong costa (L. nervosa, P. rupestris, P. arizonae), and the second of species with ovate-lanceolate catenulate leaves with a short, often forked costa (P. tectorum, P. catenulata, P. papillosa).
REFERENCES Lewinsky, J. 1974. The
genera Leskeella and Pseudoleskeella in
1. Leskeella nervosa (Bridel) Loeske, Moosfl. Harz. 255. 1903
Pterigynandrum nervosum Bridel, Muscol. Recent. Suppl. 1: 132. 1806; Leskea nervosa (Bridel) Myrin; Pseudoleskeella nervosa (Bridel) Nyholm
Plants dark green to blackish green. Stems appressed to substrate, irregularly branched, secondary branches common, erect and clustered. Leaves of primary stems 0.6--1.2 mm, lanceolate, narrowed into slender acumen longer than main portion of the lamina, secondary branch leaves smaller, 0.4--0.8 mm, ovate to ovate-lanceolate, acute to subulate, leaves of stolons scale-like, distant, ovate or orbicular. Specialized asexual gemmae of clustered flagelliform branchlets common in axils of erect, distal secondary branch leaves. Capsule 2--3 mm, subcylindric. Spores 13--18 \um.
Capsules mature July--Sept., common on bark of trees, occasionally on calcareous rock, 0--3500 m; Greenland; Alta., B.C., Labr., Man., N.B., Nfld., N.S., Ont., Que.; Ariz., Colo., Idaho, Maine, Mich., Minn., Mont., N.Mex., N.C., N.Y., Pa., R.I., S.Dak., Utah, Vt., Wis.; Europe; Asia; Atlantic Islands (Iceland).