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Montana Field Guides

A Mat Moss - Brachythecium frigidum

Native Species

Global Rank: GNR
State Rank: SNR

Agency Status


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General Description
Plants: Pleurocarpous (Vitt 1988). Forming crowded mats, brown, usually gold or dark green (FNA 2014), also green with yellow tones, generally shiny (Lawton 1971). Stems prostrate to upright, to 10 cm in length, leafy, circular in X-section, erratically branched; possessing a central strand. Branches slightly bowed or straight, to 15 mm in length, leafy, round in X-section (FNA 2014).

Leaves: Firm, spreading somewhat, those near the shoot end tending to point to one side of the stem (homomallous), deltoid and sometimes slightly egg-shaped, 1.8-3.5 mm in length, 0.6-1.5 mm in width, cupped, strongly longitudinally pleated, widest slightly above the base, extending down the stem narrowly (FNA 2014), frequently slightly auriculate (Lawton 1971); margins regularly toothed or finely so, plane, seldom curved backward and downward; apex narrowing to form a short acumen; costa strong, extending over half the leaf length (to 90%). Branch leaves smaller and more slender than the stem leaves (FNA 2014).

Leaf Cells: Alar cells fine-walled, rectangular and short, the region prominent; margin separated from alar region by slender, rectangular cells green with chlorophyll; laminal cells long and thin; basal cells arranged in several tiers (FNA 2014) with a prominent row of swollen cells running across the insertion (Lawton 1971).

Diagnostic Characteristics
The combination of firm and erect-spreading, strongly pleated leaves that also point in one direction from close to the shoot ends often distinguishes dry plants. This species has many distinctive features (FNA 2014).

Range Comments
North American Range

Common in the West. Present in AK, YT, BC and AB s to NV and UT, possibly one collection from ON; Mexico (FNA 2014). Known in Montana from Cascade, Flathead, Glacier, Lake, Lewis and Clark, Lincoln, Mineral, Missoula, Ravalli, and Sanders Counties (Elliott 2016).

Observations in Montana Natural Heritage Program Database
Number of Observations: 67

(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)

Somewhat shaded to exposed logs, rock (FNA 2014), wet soil or sand (Lawton 1971), wetlands, often emergent from springs and streams (Elliott 2016). The upright branches or stems may form thick cushions above the water (Lawton 1971).

Reproductive Characteristics
Dioicous. Seta 20-35 mm in length, russet. Capsule russet, level, to 3 mm in length, bowed; operculum cone-shaped and tall (FNA 2014), the tip black (Lawton 1971).

  • 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. 2014. Flora of North America North of Mexico. Volume 28. Bryophytes: Mosses, Part 2. Oxford University Press, Inc., NY. xxi + 702 pp.
    • 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.
    • 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.
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Citation for data on this website:
A Mat Moss — Brachythecium frigidum.  Montana Field Guide.  .  Retrieved on , from