Amblystegium is a genus of moss in the family Amblystegiaceae (order Hypnales, class Bryopsida). Described in 1853 by Wilhelm Philippe Schimper in Bryologia Europaea, the genus contains small, green to yellowish mosses with freely and irregularly branched stems. The stem and branch leaves are erect to spreading, ovate to oblong-lanceolate, and tiny (0.5–1 mm), with a single costa typically reaching only mid-leaf. Unlike related genera, Amblystegium lacks paraphyllia and has a weak costa less than 30 µm wide at the base. The plants are autoicous (both sexes on the same plant), producing inclined to horizontal, arcuate capsules with well-developed peristomes and spores measuring 9–18 µm. The genus is nearly cosmopolitan in distribution and is terrestrial, sometimes occurring in swampy sites but never in truly aquatic habitats. The most widespread and commonly recognized species is Amblystegium serpens, a creeping feather moss found on bark, rock, and soil across much of the Northern Hemisphere.
Etymology
The name Amblystegium derives from the Greek amblys (blunt) and stege (roof), alluding to the obtuse (blunt) operculum that covers the spore capsule.
Distribution
Amblystegium has a nearly worldwide (cosmopolitan) distribution. It is a terrestrial genus, occasionally found in swampy ground, but is never truly aquatic or subaquatic. The genus occurs across much of the Northern Hemisphere, with Amblystegium serpens being the most widely recorded species.
Ecology
Amblystegium is a terrestrial moss genus, sometimes occurring in moist or swampy sites but never in aquatic or subaquatic habitats. It is distinguished from the related genus Hygroamblystegium, which occupies wetter environments, by its smaller size, weaker costa, and absence of paraphyllia.
Taxonomy
Amblystegium was described by Schimper in Bryologia Europaea (1853). The genus is placed in the family Amblystegiaceae within the order Hypnales. It is most readily distinguished from Hygroamblystegium by its smaller size, weaker and straighter costa (under 30 µm wide at base, typically ceasing at mid-leaf), and the absence of paraphyllia. Flora of North America recognizes a single species in the region, though older treatments have recognized additional taxa; the generic circumscription has narrowed over time as species have been transferred to other amblystegiaceous genera.
