Grimmia reflexidens
Grimmia plagiopodia
grimmia dry rock moss
1–2 cm, central strand absent.
0.3–0.5(–1) cm.
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.
oblong-ovate, 1–1.7 × 0.4–0.8 mm, concave-keeled, awn 0.3–1 mm;
basal juxtacostal laminal cells quadrate to short-rectangular, straight, thin-walled;
basal marginal laminal cells quadrate to short-rectangular, straight, thin-walled;
medial laminal cells quadrate to short-rectangular, slightly sinuose, slightly thick-walled;
distal laminal cells 1-stratose, marginal cells 1–2-stratose.
sigmoid, 0.2–0.3 mm.
dioicous, perichaetial leaves enlarged.
gonioautoicous.
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, exothecial cells thin-walled, annulus absent, operculum mammillate, peristome present, fully developed, perforated and split in distal half.
Grimmia reflexidens
Grimmia plagiopodia
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 plagiopodia has a widespread and continuous distribution on calcareous rock across the northern Great Plains, reaching as far east as Illinois. It is rare in eastern North America, with a disjunct site in southern Ontario. In the west it reaches into the mountains on limestone and basic sandstone deposits, but its continuous range does not extend west of a line from Utah to south-central British Columbia. There is a disjunct location near Carson City, Nevada and Lake Tahoe, California. In the Arctic it is known from a few scattered localities extending from northwestern Greenland and nearby Ellesmere Island to the North Slope of Alaska. Compared to G. anodon, G. plagiopodia tends to occupy more prairie-like sites and is typically found at lower elevations. Commonly fertile, it is recognized by its immersed, peristomate capsule on a sigmoid seta with fully-developed teeth that are perforated and split distally. Grimmia americana is similar but has a short, straight to arcuate seta and a large annulus. The other widespread species in the group, G. anodon, has an annulus and is gymnostomous.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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