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Montana Field Guides

A Lime Moss - Didymodon tophaceus

Native Species

Global Rank: G5
State Rank: SNR

Agency Status
MNPS Threat Rank:

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General Description
Plants: Acrocarpous, growing in open to crowded clumps of erect shoots, russet (Crum & Anderson et al., 1981), green to olivaceous, or pale yellow-brown, frequently lime-encrusted (FNA 2007). Stems 4-40 mm in height (Crum & Anderson et al., 1981), possessing a central strand; hairs of the leaf axil about 5 cells long, the first 1 or 2 cells brown (FNA 2007).

Leaves: Sometimes a little bent or twisted (Lawton 1971) and spreading a little (seldom flat against the stem) when dry, spreading and frequently keeled when damp, 1-2 mm in length (FNA 2007), those near the top of fertile stems typically larger (Crum & Anderson et al., 1981), egg-shaped, sometimes tending toward lance-shaped, or somewhat oblong (FNA 2007) or tongue-shaped (Lawton 1971), narrowing to a nearly obtuse to curved, obtuse apex, the apex not easily broken, widely grooved along the nerve; base egg-shaped and frequently extending along the stem (FNA 2007) 5-10 cells down (Lawton 1971); margins smooth, curved back and downward to above mid-leaf; costa extending to or ending slightly before the leaf tip, seldom forked distally, frequently red (FNA 2007) or brown (Crum & Anderson et al., 1981).

Leaf Cells: Upper laminal cells arranged in 1 cell-layer, isodiametric, typically smooth, occasionally with 1-2 papillae per lumen; lower laminal cells square or very slightly lengthened longitudinally; costa with somewhat long ventral cells in the middle rows or beyond, in X-section with 1 row (FNA 2007) of 3-8 guide cells, and 2 stereid bands, the ventral band smaller (Lawton 1971).

Fruit ripens winter to spring (FNA 2007).

Diagnostic Characteristics
Didymodon nicholsonii, a western species, is also water-loving and has similarly-shaped leaves. However, its leaf margins or patches thereof, and occasionally the entire distal leaf lamina, are 2 cell-layers thick. In D. tophaceus, they are only of 1 cell-layer (FNA 2007).

Range Comments
North American Range

Canada: YT and NT, BC and AB, ON and QC; USA: most continental states except states east and north of NY and south of TN and VA; Mexico (FNA 2007). Known in Montana from Cascade, Flathead, Glacier, Lake, Lewis and Clark, Mineral, Missoula, and Stillwater Counties (Elliott & Pipp, 2016).

Damp to wet, typically calcareous soil or stone, such as seeping bluffs (Crum & Anderson et al., 1981) and waterfalls. Elevation: 0-6560 feet (FNA 2007).

Reproductive Characteristics
Dioicous. Perichaetia occurring at the stem apices (FNA 2007). Perigonia growing at the stem apices or laterally (Lawton 1971). Seta red (Crum & Anderson et al., 1981), 7-12 mm tall. Capsule 0.6-1.5 mm in length; peristome with 16 very slender teeth split nearly to their bottom and not spiraled, or teeth short or lacking (FNA 2007), ochre, sometimes with a reddish tinge, thickly papillose (Crum & Anderson et al., 1981).

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). December 20th. 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?
    • Flowers, S. 1973. Mosses: Utah and the West. Brigham Young University, Provo, Utah. 567 p.
    • 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:
A Lime Moss — Didymodon tophaceus.  Montana Field Guide.  .  Retrieved on , from