Grimmia reflexidens
Grimmia muehlenbeckii
1–2 cm, central strand absent.
1–2.5 cm, central strand present.
rare, in clusters, short-stalked, in distal leaf axils.
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.
loosely appressed, twisted when dry, erectopatent when moist, ovate-lanceolate, tapering to acute apex, 2–3 × 0.6–0.8 mm, keeled, margins recurved in mid leaf on both sides, awns short, denticulate, in perichaetial leaves stout and often decurrent, costa channeled distally, projecting at abaxial side, angled to bluntly winged;
basal juxtacostal laminal cells short- to long-rectangular, yellowish, nodulose, thick-walled;
basal marginal laminal cells short-rectangular with thickened transverse walls;
medial laminal cells quadrate to short-rectangular, sinuose, thick-walled;
distal laminal cells 1-stratose with 2-stratose ridges, margins 2-stratose.
arcuate, 2–3 mm.
dioicous, perichaetial leaves enlarged.
dioicous.
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.]
occasionally present, exserted, globose, shiny, brown, smooth to slightly striate, exothecial cells thin-walled, annulus present, operculum rostrate, peristome teeth purple, fully-developed or slightly split distally, papillose.
mitrate.
Grimmia reflexidens
Grimmia muehlenbeckii
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 muehlenbeckii is closely related to G. trichophylla, and in the past it was frequently regarded as a subspecies or variety of that taxon. H. Deguchi (1978) treated it as a distinct species, followed by A. J. E. Smith (1992). Greven agrees with those treatments. He has seen many specimens that are remarkably uniform and easy to distinguish from G. trichophylla by their small, globose, shiny, dark brown capsules with purple, entire peristome teeth. In contrast, the capsules in G. trichophylla are oblong-ovoid, larger and longer than in G. muehlenbeckii, dull, yellowish brown, and the peristome teeth are orange and cleft. The gametophyte differs from that of G. trichophylla by its blackish green tufts, angled costa with blunt wings protruding on the abaxial side, and ovate-lanceolate leaves with stout, denticulate awns that are often decurrent.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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