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Montana Field Guides

Ambiguous Thread Moss - Ditrichum ambiguum
Other Names:  Ambiguous Ditrichum Moss

Status Under Review
Native Species

Global Rank: G4?
State Rank: SU

Agency Status
MNPS Threat Rank:

External Links

General Description
Plants: Acrocarpous, growing in open to crowded clumps of erect shoots, green, or green with yellow tones, turning somewhat brownish with yellow tones over time, not shiny. Stems single or occasionally branched a little, 7-20 mm in height, possessing a central strand; rhizoids occurring at the bottom of the stem, somewhat red (FNA 2007).

Leaves: Slightly curled, twisted, or wavy when dry, generally spreading up to ca 45 degrees, lance-shaped and sometimes very slender with a longitudinal groove from the sunken costa, the apex slender and dull to obtuse; margins widely curved back and downward in the proximal half, saw-toothed in the upper half, sometimes smooth at the leaf tip; costa extending to the leaf tip (FNA 2007).

Leaf Cells: Lamina with several bi-stratose cells dispersed in the upper half, the cells with thick walls; upper laminal cells square or nearly so to short and quadrangular, becoming both wider and longer proximally, with thinner walls; distal margins and sometimes a few adjacent cells bi-stratose; costa in X-section with guide cells in 1 row, a dorsal stereid band (FNA 2007), and several stereid cells to the inside of the guide cells (Lawton 1971).

Fruit ripens about mid-spring to mid-summer (FNA 2007).

Species Range

Range Comments
North American Range

AK, BC s to CA (FNA 2007). Known in Montana from Flathead County (Elliott & Pipp, 2016).

Observations in Montana Natural Heritage Program Database
Number of Observations: 3

(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)

Found on damp soil with a sandy or sometimes a clay texture, with habitats such as clay slopes, road banks, or sandstone bluff fissures. Elevation:330-1640 feet (FNA 2007).

Reproductive Characteristics
Dioicous. Perichaetial bracts enveloping the stem somewhat (FNA 2007), about 5 mm in length (Lawton 1971). Seta vertical, red, 10-20 mm in height, carrying the capsule beyond the perichaetial bracts. Capsule upright, straight or a little bowed, deep brown to russet, 1.5-3.2 mm in length, the base sometimes a little larger around than the rest of the capsule; peristome single, the 16 teeth split almost to the bottom, creating 2 thread-like divisions, these filaments spiraled when dry, red, strongly covered with papillae or tiny sharp points. Calyptra like a draping hood (FNA 2007), smooth (Crum & Anderson et al., 1981).

  • 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.
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Citation for data on this website:
Ambiguous Thread Moss — Ditrichum ambiguum.  Montana Field Guide.  .  Retrieved on , from