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Montana Field Guides

Ribbed Mountain Moss - Conostomum tetragonum
Other Names:  Helmet Conostomum Moss

Native Species

Global Rank: G5
State Rank: SNR

Agency Status
MNPS Threat Rank:

External Links

General Description
Plants: Acrocarpous (Vitt 1988). Growing in crowded clumps of erect shoots (FNA 2014), typically a waxy green (Lawton 1971), occasionally noticeably blue (Crum & Anderson et al. 1981). Stems unbranched or forked once, 5-sided in X-section, brown (FNA 2014), 5-30 mm; possessing a central strand (Lawton 1971) and a hyalodermis; rhizoids forming a tangled mat below, smooth (FNA 2014).

Leaves: Rigid, upright and overlapping when dry or wet, 5-ranked, slender and lance-shaped, narrowing to form a short acumen or seldom bluntly tipped, 1-1.5 mm in length, sharply creased longitudinally in the middle; margins rolled back and under in the top half; finely saw-toothed; costa extending to or beyond the apex (occasionally not reaching it in lower leaves), the dorsal side mammillose (FNA 2014).

Leaf Cells: Alar cells not distinct; basal laminal cells quadrangular, fine-walled and swollen when wet; upper laminal cells quadrangular or short and diamond-shaped, thick-walled, smooth or with mammillae at the upper end of the cell dorsally and ventrally (FNA 2014).

Fruit ripens in summer (FNA 2014).

Diagnostic Characteristics
C. tetragonum has a distinctive appearance with its glaucous, upright, 5-ranked leaves and the exostome teeth fused distally to form a cone (FNA 2014).

Range Comments
North American Range

AK to NU, s to WA and MT, also CO, QC, NB and NL, NY, NH and ME (FNA 2014). Known in Montana from Flathead County (Elliott 2016).

Moist soil and rock, thin soil on rocky shelves, and areas with snow thawing late. Elevation to 7220 feet (FNA 2014).

Reproductive Characteristics
Dioicous (Crum & Anderson et al. 1981). Perigonia bud-like or cup-shaped, intermingling with somewhat club-shaped, partitioned hairs; perichaetial bracts with a subula, bigger than the stem leaves. Seta 8-25 mm tall, red with yellow tones to brown. Capsule 2-2.5 mm in length (FNA 2014), widely ovoid and short, green or pink when immature, becoming brown and ribbed when dry (Lawton 1971); beak thick and tilted on the operculum (FNA 2014); exostome sections dark brown with a slender yellow edges (Crum & Anderson et al. 1981), perforated, joined at the tip to form a cone (FNA 2014).

  • Literature Cited AboveLegend:   View Online Publication
    • Crum, H.A. and L.E. Anderson. 1981. Mosses of Eastern North America. 2 volumes. Columbia University Press, New York. 1328 pp.
    • 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
    Do you know of a citation we're missing?
    • 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.
    • Malcolm, B., N. Malcolm, J. Shevock, and D. Norris. 2009. California Mosses. Nelson, New Zealand: Micro-Optics Press. 430 pp.
    • Smith, A.J.E. 1980. The Moss Flora of Britain and Ireland. Cambridge University Press, Cambridge. 705 pp.
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Citation for data on this website:
Ribbed Mountain Moss — Conostomum tetragonum.  Montana Field Guide.  .  Retrieved on , from