Monographs Details: Amblystegium pseudosubtile Hedenäs
Synonyms:Amblystegium subtile (Hedw.) Schimp.
Description:Species Description - Plants minute; green. Stem irregularly branched; central strand present, slender; cortex (including epidermis) of 1-2 layers of small incrassate cells, the basic tissue of large thin-walled cells; pseudoparaphyllia ovate or narrow-ovate; paraphyllia absent; rhizoids smooth, slightly branched, inserted at or just below leaf costa insertion, reddish brown; axillary hairs 1 per axil, basal cell short-rectangular, pale brown (upper part of hairs lost in studied stems). Stem leaves 0.3-0.4 mm long, erect-patent (erect or almost so when dry), straight, ovate or ovate-triangular, narrowing abruptly or gradually to acumen, constricted at insertion, not plicate, slightly concave, not decurrent; apex acuminate; margin plane, unbordered, denticulate or finely denticulate (at least in larger parts of leaves); costa single, extending 40-50% of way up leaf or sometimes less, 16.521.0 µm wide at base, smooth or ending in a small obtusely projecting cell end on back, the cells on both ad- and abaxial sides linear or short-linear and longer than adjoining laminal cells; median laminal cells 17.033.5 × 6.5-8.5 µm, elongate-rhomboidal or short-linear, unistratose, incrassate or slightly incrassate, eporose, smooth; basal cells quadrate or short-rectangular, wider than median laminal cells, slightly incrassate, eporose; alar cells transverse-short-rectangular or quadrate or (especially toward insertion) short-rectangular, slightly incrassate, eporose; alar group somewhat indistinctly delimited, triangular or ovate, extending ca. 35% of way up along margin and inward almost to costa; apical leaf cells elongate-rhomboidal, slightly incrassate, eporose. Branch leaves smaller and more ovate than stem leaves; proximal branch leaves ovate, short-acuminate. Autoicous. Perigonia inserted laterally on stem, below and above perichaetia; perigonial leaves narrowing gradually from ovate base to acuminate or short-acuminate apex; margin entire, bordered; paraphyses present. Perichaetia lateral on stem; inner perichaetial leaves straight and erect, or slightly flexuose above, narrowing gradually or abruptly from elongate-oblong or elongate-ovate base to acuminate apex, not plicate; margin plane, strongly denticulate at shoulder, denticulate in acumen, unbordered; costa absent or very short and indistinct; vaginula with 2-8-celled, thin-walled paraphyses. Calyptra naked, 3-4-stratose, cells homogeneous. Seta long (6-8 mm); red, at least in basal part; central strand present, slender; cortex of 2-3 layers of small and incrassate cells, slightly rough from jointly projecting meeting cell ends; dextrorse when dry. Capsule cylindrical, straight or almost so, not furrowed, constricted below mouth when dry, erect or slightly inclined. Annulus separating, of 2 rows of cells; exothecial cells 27.5-56.5 × 14.5-27.5 µm, short-rectangular to short-linear, slightly incrassate, not collenchymatous; cells below mouth in 1-3 rows, smaller, transverse-elongate to short-rectangular; stomata long- or ovate-pored, the surrounding cells ± radial. Operculum rostrate; basal cells ± radial and thinwalled. Exostome almost perfect, spreading when dry; yellow brown; outside below cross-striolate, not furrowed; outside above papillose; margins above weakly dentate with border widened or slightly widened at zone of transition in outer peristomial layer pattern; ridges of primary peristomial layer normal or slightly reduced. Endostome slightly specialized; yellow; sparsely papillose above, smooth below; basal membrane height 23-28% of total endostome height; cilia absent or vestigial (if vestigial only 1 present); segments narrow, not perforated. Spores 18.0-23.0 µm, finely papillose.
Discussion:This species is similar to Amblystegium subtile, but its leaf margin is more strongly denticulate; the costa of the inner perichaetial leaves is absent or very indistinct; the seta is slightly rough from projecting, meeting cell ends; the operculum is rostrate; the exostome margin is widened at the middle of the teeth; and the spores are larger. Amblysteium pseudosubtile was earlier confused with A serpens (Buck, 1998), from which it differs in having no or a very indistinct perichaetial leaf costa, a shorter and rough seta, a straight and erect capsule, a rostrate operculum, an endostome with a lower basal membrane and no cilia, and larger spores. Amblystegium pseudosubtile seems to be the only species of the Amblystegiaceae where a rough seta has evolved.
Distribution:Haiti South America
| Sud-Est Haiti South America