Grimmia reflexidens
Grimmia pulvinata
grey-cushion grimmia, pulvinate dry rock moss
1–2 cm, central strand absent.
1–3 cm, central strand present.
absent.
ovate to oblong-lanceolate, 0.1–1.15 × 0.3–0.5 mm, keeled, not plicate, margins plane, awns 1–2 mm, very long, smooth to slightly denticulate, flattened basally, long-decurrent, costal transverse section prominent, semi-circular;
basal juxtacostal laminal cells rectangular, sometimes nodulose, thin- to thick-walled;
basal marginal laminal cells rectangular with thickened transverse walls, pellucid in 2–4 rows;
medial laminal cells rounded-quadrate, slightly sinuose, thick-walled;
distal laminal cells yellowish green, 1-stratose with 2-stratose ridges, not bulging, marginal cells 2-stratose, not bulging.
flexuose when dry, erect when moist, lanceolate, 1–1.7 × 0.3–0.6 mm, keeled, margin recurved on both sides nearly from base to apex, rarely only one margin recurved, abruptly contracted into short to long, smooth to denticulate awn, costa weak proximally, projecting on abaxial side;
basal juxtacostal laminal cells quadrate to short-rectangular, thin-walled;
basal marginal laminal cells quadrate to short-rectangular, thin- or thick-walled;
medial laminal cells rounded-quadrate, slightly sinuose, thin-walled;
distal laminal cells 1-stratose, margins 2-stratose.
arcuate, 3–4 mm.
dioicous, perichaetial leaves enlarged.
autoicous.
absent in northern hemisphere material, emergent to shortly exserted, yellowish brown, oblate, exothecial cells irregularly short-rectangular, thin-walled, stomata absent, annulus of 1 row of quadrate, thick-walled cells, operculum mammillate to rostrate, peristome present, nearly fully-developed, split and perforated only in apex, papillose.]
usually present, exserted, ellipsoid to obloid, brownish and ribbed when empty and dry, exothecial cells thin-walled, annulus present, operculum rostrate, peristome teeth reddish, fully-developed, papillose.
mitrate.
Grimmia reflexidens
Grimmia pulvinata
Of conservation concern.
Previous to its discovery in Iceland, as Grimmia grisea (H. C. Greven 1998), G. reflexidens was known from only the Southern Hemisphere. It had previously been collected east of East Bay, Newfoundland, now the only known locality in North America, but was not recognized as G. reflexidens. The latter is similar to G. asperitricha Dixon & Sainsbury of New Zealand, and the two species have been confused by G. O. K. Sainsbury (1945) as well as by R. Ochyra (1993). J. Muñoz (1998b) synonymized G. reflexidens with G. sessitana. However, the former is readily separated from the latter by: (1) enlarged perichaetial leaves, (2) decurrent awns, (3) non-bulging laminal cells, and (4) dioicous sexual condition. Capsules are unknown from Northern Hemisphere material, but G. reflexidens lacks stomata while they are present for G. sessitana. Although G. reflexidens and G. teretinervis both have decurrent awns they are easily separated by a number of characters: G. reflexidens grows in compact cushions, has long awns, and a semicircular costa; G. teretinervis grows in loose clumps, is hyaline-tipped to short-awned, and has a unique costa that is distally almost completely circular in transverse section.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Grimmia pulvinata is the most common species of the genus. It has a nearly cosmopolitan distribution, and is a pioneer on various substrates, even on the trunks of trees. However, in the eastern part of North America, it occurs only in a few scattered localities (H. A. Crum 1977). It is easily recognized by its neat hemispherical cushions with abundant capsules. It may be confused with G. orbicularis, which grows in similar habitats and is known to co-occur with G. pulvinata. However, as discussed under G. orbicularis, it differs in gametophytic as well as sporophytic characters. Some forms with more acuminate leaf tips may be confused with G. trichophylla, but the thin-walled, short-rectangular basal cells and the small, rounded mid leaf cells distinguish G. pulvinata.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC - Local Web sites:
CalFlora, CalPhotos, 
Flora NW, 
KS Wildflowers, 
MD Biodiversity, 
MI Flora, 
MO Plants, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
