Monographs Details: Amblystegium
Description:Genus Description - Plants minute, small, or medium-sized; green, yellowish green or brownish. Stem irregularly or irregularly pinnately branched in one plane; central strand present, rarely absent, often slender; hyalodermis absent; pseudoparaphyllia foliose, the outer ones occasionally filamentose; paraphyllia absent or present (in latter case ovate or ovate-lanceolate or lanceolate); rhizoids smooth, slightly to moderately branched, inserted at or just below costa insertion; axillary hairs with 1-2(-3) upper, hyaline cells, the hairs often sparse or very delicate. Stem leaves erect to spreading, straight or weakly (and gradually) curved, sometimes homomallous or spreading, more erect and sometimes weakly incurved when dry, ovate to ovate-triangular, rarely cordate, sometimes distinctly constricted at insertion, narrowing gradually or abruptly from ± far below to acumen, not plicate, concave or usually slightly concave, decurrent or not; acumen ± plane, rarely distinctly channeled, the apex obtuse or acute or acuminate or narrow-acuminate; margin plane or in lower part narrow-recurved, entire or finely denticulate to denticulate; costa single, ending 35% of way up leaf to percurrent; median laminal cells elongate-rhomboidal or elongate-hexagonal or rectangular or short-linear or sometimes linear, unistratose, thinwalled or incrassate, eporose or slightly porose, smooth; alar cells differentiated or not (when differentiated transverse-rectangular or quadrate or especially toward insertion short- to long-rectangular), not widened or sometimes inflated, slightly incrassate, eporose; alar group often indistinctly delimited, triangular or ovate or broadly ovate, sometimes extending up along margin. Branch leaves smaller and sometimes narrower than stem leaves; proximal branch leaves triangular or ovate or broadly ovate, the apex short-acuminate to broadly rounded. Autoicous. Perigonial leaves gradually narrowing from broad base to acuminate to obtuse apex. Inner perichaetial leaves gradually or abruptly narrowing to acuminate to obtuse apex, plicate or in smallest species smooth; margin bordered or not at shoulder, entire to strongly denticulate; costa single and long, ending in lower acumen to percurrent, rarely short and indistinct; vaginula with paraphyses. Calyptra naked. Seta long, only in smallest species shorter (then 5-8 mm long), reddish; capsule cylindrical, curved throughout and horizontal, or straight and erect to slightly inclined; annulus separating; operculum conical, rarely rostrate or short-rostrate. Exostome well developed to slightly reduced; teeth cross-striolate below, papillose above; margin dentate to entire above. Endostome well developed or partially reduced, with high or sometimes slightly reduced basal membrane and segments not or narrow-perforate along midline; cilia 0-3(-4), well developed to absent or vestigial, nodose or sometimes short-appendiculate. Spores 9.0-23.0 µm, finely papillose.
Note: Small specimens of somq Amblystegium species could be confused with sterile material of small members of the Leskeaceae (e.g., Pseudoleskeella spp.), but species of the latter are usually either more rigid or have large (but diffusely delimited) alar groups consisting of numerous transverse-rectangular or quadrate or short-rectangular cells, and the groups extend farther up (to ca. 35% of leaf length) along the basal margin of the leaf than in most Amblystegium species. Differences between Amblystegium and Conardia are discussed under C. compacta.
Distribution and Ecology: Amblystegium is at present a poorly understood genus, the circumscription of which varies considerably among authors. As the genus is understood in the present treatment, including Hygroamblystegium and Serpoleskea, it includes somewhere between 20 and 60 species, most likely closer to the lower than the upper end of this range. Members of the genus are widespread mainly in the northern and southern temperate zones, in the arctic and subantarctic, and at higher altitudes in tropical and subtropical areas. Eight species occur in tropical S America.