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Montana Field Guides

Rusty Lime Moss - Didymodon ferrugineus
Other Names:  A Didymodon Moss, Didymodon fallax var. reflexus

Status Under Review
Native Species

Global Rank: G5
State Rank: SU

Agency Status
MNPS Threat Rank:

External Links

General Description
Plants: Acrocarpous. Growing in open clumps of erect shoots (Lawton 1971), most often russet (FNA 2007), sometimes deep green and eventually turning russet (Crum & Anderson et al., 1981). Stems sometimes reaching 25 mm in height (FNA 2007), branched (Crum & Anderson et al., 1981), possessing a central strand; hairs of the leaf axil ca 5 cells long, the first 1 or 2 cells brown (FNA 2007).

Leaves: Typically loosely spaced (Crum & Anderson et al., 1981), upright and close to the stem to spreading (FNA 2007) up to 90 degrees, curved and twisted a little when dry (Lawton 1971), strongly curved back and downward distally and keeled when damp, 0.8-2 mm in length, deltoid to lance-shaped, with ovate tendencies through the range, narrowing to a nearly obtuse and non-deciduous apex; margins typically smooth, at mid-leaf almost flat to curved back and downward; costa extending to or shortly beyond the leaf tip, scarcely broader at the bottom than above, with a ventral channel running alongside it(FNA 2007).

Leaf Cells: Upper laminal cells isodiametric, smooth or mostly with 1-3 big, pointed papillae, in 1 cell-layer; proximal laminal cells square or short and oblong; costa with elongate ventral cells, in X-section with 1 row of guide cells (FNA 2007), the abaxial stereid band small, the guide cells and stereids sometimes not much differentiated (Lawton 1971).

Fruit ripens in winter and through spring (FNA 2007).

Diagnostic Characteristics
Merging somewhat with Didymodon fallax, but the leaves of D. fallax are typically narrower and the papillae less conspicuous; the sporophytes of D. fallax are also similar but are typically larger (FNA 2007).

Range Comments
North American Range

Canada: YT and NU, BC and AB, ON, NB and NL; USA: AK, MT, CO, AZ and NM, AR, IL, MI, NY, WV to NC; Mexico (FNA 2007). Known in Montana from Flathead, Meagher, and Judith Basin Counties (Elliott & Pipp, 2016).

Observations in Montana Natural Heritage Program Database
Number of Observations: 1

(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)

Calcareous soil, stone shelves and crags in wet areas and tundra. Occurs from 200-4590 feet (FNA 2007).

Reproductive Characteristics
Dioicous. Capsules seldom produced. Perichaetia occurring at the stem apices (FNA 2007). Seta 6-12 mm tall (FNA 2007), red (Crum & Anderson et al., 1981). Capsule 0.7-1.5 mm in length; peristome delicate and frequently missing, the 16 very slender teeth split nearly to their bottoms, spiraled anti-clockwise 1 time around to almost straight (FNA 2007).

No specialized vegetative reproduction (FNA 2007).

  • 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. 2007. Flora of North America North of Mexico. Volume 27. Bryophytes: Mosses, Part 1. Oxford University Press, Inc., NY. xxi + 713 pp.
    • Lawton, E. 1971. Moss Flora of the Pacific Northwest. Hattori Botanical Laboratory. Japan: Yamabuki-cho, Shinjuku-ku, Tokyo. 362 pages plus appendices.
  • 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:
Rusty Lime Moss — Didymodon ferrugineus.  Montana Field Guide.  .  Retrieved on , from