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Montana Field Guides

Catherine's Moss - Atrichum selwynii

Native Species

Global Rank: G5
State Rank: SNR

Agency Status


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General Description
Plants: Acrocarpous (Vitt 1988), in open tufts or solitary (Flowers 1973), commonly conspicuously rosulate, pale to deep green, becoming brown below with age (FNA 2007). Stems simple, seldom branched (Flowers 1973), 1-4 cm (FNA 2007), upright, possessing a central strand (Lawton 1971).

Leaves: Contorted when dry, spreading and flat to slightly concave when moist, lanceolate or tongue-shaped, frequently with rows of teeth, their bases fused, arising from diagonal ripples on the back of the leaf surface, 2.5-8.5 mm in length, 1-2 mm in width; apex acute or occasionally obtuse; margins often 2-layered, differentiated with 1 or 2 rows of long narrow cells, congested with erratically-spaced teeth distally to mid-leaf or below, mostly double-toothed, occasionally single- or rarely triple-toothed; costa ending at or a few cells shy of the apex, smooth or toothed on back side near apex, seldom extending below mid-leaf, bearing lamellae on front surface; lamellae 2-6, each usually 8-12(-14) cells high, occasionally fewer (2-5) (FNA 2007).

Leaf Cells: Lamina of 1 layer of cells (except for margins) (Lawton 1971); basal cells usually oblong and clear (Flowers 1973), median laminal cells 6-sided, occasionally oddly-angled or rounded, usually thin-walled, sometimes thickened at the corners (FNA 2007).

Capsules ripen March-September (FNA 2007).

Diagnostic Characteristics
Young plants lacking sex organs may be hard to tell apart from A. undulatum (Lawton 1971). The latter is the largest species of the genus and tends to have longer, narrower leaves than A. selwynii (Vitt 1988).

Range Comments
Canada: AB, BC, MB, NT, SK; USA: AK, AZ, CA, CO, ID, MT, NM, OR, SD, UT, WA, WY; Central America (FNA 2007). In Montana, known from Cascade, Choteau, Flathead, Gallatin, Glacier, Granite, Lake, Lincoln, Madison, Missoula, Ravalli, and Sanders Counties (Elliott 2016).

Observations in Montana Natural Heritage Program Database
Number of Observations: 53

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Bare soil on disturbed sites, often root masses of overturned trees (Elliott 2016), from exposed to shaded areas. Low to high elevations (FNA 2007).

Reproductive Characteristics
Dioicous; male plants same size or larger than female plants, ovate or nearly round, frequently each plant with more than one bud (FNA 20007).

Seta 1-3(-8) arising from each perichaetium, 5 cm or less in height, upright or a little wavy. Capsule cylindric, a little rounded and slightly tilted, occasionally straight and upright; 2-7.5 mm in length, 0.5-1 mm in width (FNA 2007), the neck short; operculum a long slender beak, frequently almost as long as the urn (Flowers 1973).

  • Literature Cited AboveLegend:   View Online Publication
    • Elliott, J.C. and A.K. Pipp. 2018. A Checklist of Montana Mosses (1880-2018). Updated 3 January, 2020. Montana Natural Heritage Program, Helena, Montana. 73 pp.
    • Flora of North America Editorial Committee, eds. 2007. Flora of North America North of Mexico. Volume 27. Bryophytes: Mosses, Part 1. Oxford University Press, Inc., NY. xxi + 713 pp.
    • Flowers, S. 1973. Mosses: Utah and the West. Brigham Young University, Provo, Utah. 567 p.
    • Lawton, E. 1971. Moss Flora of the Pacific Northwest. Hattori Botanical Laboratory. Japan: Yamabuki-cho, Shinjuku-ku, Tokyo. 362 pages plus appendices.
    • Vitt, D. J. Marsh, and R. Bovey. 1988. Mosses, Lichens & Ferns of Northwest North America. Seattle, WA: University of Washington Press. 296 p.
  • Additional ReferencesLegend:   View Online Publication
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    • Elliot, J. C. 1993. Second checklist of Montana mosses. Unpublished report. U.S. Forest Service, Region 1. Missoula, MT. 45 pp.
    • Ireland, R.R. 1969. Taxonomic Studies on the Genus Atrichum in North America. Canadian Journal of Botany 47: 353-368.
    • Lawton, E. 1971. Keys for the Identification of the Mosses on the Pacific Northwest. Reprinted from 'Moss Flora of the Pacific Northwest'. Published as Supplement No. 2 of the Journal of the Hattori Botanical Laboratory. Nichinan, Miyazaki, Japan. 66 pp.
    • Schofield, W.B. 1969. Phytogeography of Northwestern North America: Bryophytes and Vascular Plants. Madron 20(3):155-207.
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Catherine's Moss — Atrichum selwynii.  Montana Field Guide.  .  Retrieved on , from