E-Flora BC: Electronic Atlas of the Flora of British Columbia

Species description:
Genus name from the hairless calyptra, compared to the hairy calyptra of Polytrichum. Species named in honour.of A. R. C. Selwyn, director of the Geological Survey of Canada from 1869 to 1895.

Reproduction:
Sporophytes common and abundant; seta and sporangium reddish-brown, maturing in late winter to early spring.

Distinguishing characteristics:
The extremely low lamellae on the midrib, the teeth in diagonal lines on the lower leaf surface, the markedly con­torted leaves when dry, combined with the smooth calyptra distinguish this genus from others related to it.

Habit:
Forming loose turfs of light to dark green plants with sporophyte-bearing plants in colonies usually somewhat separate from male plants.

Similar Species:
From A. undulatum it is most readily distinguished by the sharper marginal teeth and more sharply acute apices compared to the blunter points of A. selwynii. From A. tenellum it differs in nar­rower leaves that are more acute than in A. selwynii; the sporangium is usually also shorter in A. tenet/um. A. selwynii is the common species in non-urban sites near the coast while A. undulatum is a frequent urban "weed" of gardens and road margins. Oligotrichum parallelum of subal­pine sites has less acute teeth on the leaf margins and sporophytes are usually light green, rather than dark brown, when mature. Comments: This genus is sometimes transplanted to Japanese tea gar­dens as an attractive ground cover.