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Montana Field Guide

Montana Field Guides

Curved Dry Rock Moss - Grimmia incurva
Other Names:  Curved Black Rock Moss

Species of Concern
Native Species

Global Rank: G4G5Q
State Rank: S1

Agency Status
MNPS Threat Rank:

External Links

General Description
Plant: Rounded cushions. Green to black-green. Stems 1.0-2.0 cm tall. Stem X-S with a central strand.

Leaf: When dry, leaves are incurved and mildly contorted. When moist, leaves spread. Oblong to linear-lanceolate, 2.5-4.5 x 0.3-0.5 mm, keeled, and tapers to a slender and acuminate apex that is often hyaline. Awn short and often mucronate (use hand-lens). Both margins plane or one/both sides recurved proximally. Costa ends before apex and projects on abaxial side (keeled).

Leaf Cells: Basal laminal cells near costa are long-rectangular, slightly sinuose, thick-walled. Basal laminal cells near margin are short- to long-rectangular and thin-walled. Median laminal cells are rectangular, nodulose, and thick-walled. X-S: distal laminal cells are 1-layered except margins and apex are 2-layered. Costa X-S: distally semi-circular in outline (keeled).

Diagnostic Characteristics
Its distinctive characteristics include dark, round cushions with linear, contorted leaves in shaded, sub-alpine habitats. The awns are noticeable only with a hand-lens. Its habit is similar to Dicranowesia crispula.

Species Range

Range Comments
Greenland; Canada: AB, BC, NB, NL, YT; USA: CA, CO, ME, NH, NY, OR, SD, WA; Eurasia (FNA 2007). In Montana: Flathead and Ravalli Counties (Elliott 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)

Shaded, damp acidic rock. Moderate to high elevations (1,640 – 8,200 feet). It prefers shaded microsites in the sub-alpine. It is uncommon in the continental interior.

Reproductive Characteristics
Dioicous. Seta is 1.5-2.0 mm tall, arcuate, and asymmetrically attached to base of capsule. Capsules are occasionally found, emergent to exserted, yellowish, smooth or little wrinkled when dry, oblong-ovoid to cylindric.

Gemmae absent on leaves.

  • Literature Cited AboveLegend:   View Online Publication
    • 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.
  • 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.
    • Lawton, E. 1971. Moss Flora of the Pacific Northwest. Hattori Botanical Laboratory. Japan: Yamabuki-cho, Shinjuku-ku, Tokyo. 362 pages plus appendices.
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Citation for data on this website:
Curved Dry Rock Moss — Grimmia incurva.  Montana Field Guide.  .  Retrieved on , from