Family POLYTRICHACEAE

Microhabitat

This moss is found on soil which may be sandy or disturbed, such as on upturned tree roots and beside roads, paths, and waterways. It is found in shaded to open areas. It is most common at low elevations close to the Pacific coast.

Distribution

Atrichum selwynii is only in western North America. In Canada its range extends from coastal British Columbia east to Manitoba. In the US it grows in coastal Alaska, Washington, Oregon, and California, and east to Montana, South Dakota, Colorado, and Missouri.

Clump of gametophytes with sporophytes
Photo Credit: Yan Zhuang

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Morphology

The moss mats are loosely interwoven and light to dark green in colour. The species is dioicous and the male plants are as large as or larger than female plants. Stems are usually 1-4 cm high, and the leaves are 2.5-8.5 x 1-2 mm. The spore-bearing portion of the sporophyte (called the capsule) is 2-7.5 mm long, and the seta is 1.2-5 cm long. Generally 1-8 sporophytes arise from the end of female stems in this acrocarpous moss. Capsules mature in late winter to early spring. It has a smooth calyptra (even compared to other Atrichum species).

Key identifying features

There are several other species of Atrichum present in BC, one of which is frequently confused with A. selwynii. Atrichum undulatum is either polyoicous or monoicous, the calyptra tip is hairy, and there are never more than three sporophytes per stem. East of Manitoba, specimens labeled A. selwynii are inevitably A. altecristatum (formerly considered a variety of A. undulatum) which is monoicous and absent in western North America. Atrichum crispum, which is similar in many respects to A. selwynii, lacks spines on the underside of the leaf. Other species present in BC are A. angustatum and A. tenellum.

Interesting notes

The genus name means ‘without hair’ which is in reference to the genus belonging to the family Polytrichaceae (‘many hairs’ present on the calyptra). The specific epithet refers to A.R.C. Selwyn who was director of the Geological Survey of Canada from 1869 to 1895. The genus has 15 widely spread species. Atrichum is present in both the Northern and Southern Hemispheres and typically inhabits temperate climates. Atrichum selwynii is sometimes used in Japanese gardens as a ground cover.

Selected References

Ireland, R.R. 1969. Taxonomic studies on the genus Atrichum in North America. Can. J. Bot. 47: 353-368.

Lawton, E. 1971. Moss flora of the Pacific Northwest. The Hattori Botanical Laboratory, Ninchinan, Miyazaki, Japan.

Nyholm, E. 1971. Studies in the genus Atrichum P. Beauv. a short survey of the genus and the species. Lindbergia 1: 1-33.

Schofield, W.B. 1992. Some common mosses of British Columbia, 2nd ed. Royal British Columbia Museum, Victoria, Canada.

By Will Iles

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© 2006 Department of Botany, University of British Columbia