Grimmia reflexidens
Grimmia leibergii
1–2 cm, central strand absent.
5–12 cm, repeatedly dichotomous, central strand absent.
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.
loosely appressed when dry, patent to spreading when moist, often becoming secund distally on the stem, lanceolate to ovate-lanceolate, 3–4 × 0.6–0.9 mm, keeled, margins recurved on both sides, awns denticulate, flattened proximally, sometimes decurrent, costa yellowish to pale orange proximally, wider (± 100 µm) near the base, channeled distally, semicircular on abaxial side;
basal juxtacostal laminal cells elongate to linear, weakly orange at insertion, nodulose, thick-walled;
basal marginal laminal cells in a few rows quadrate to short-rectangular, thick-walled;
medial laminal cells quadrate to short-rectangular, strongly sinuose, thin to thick oblique transverse walls and extremely thick lateral walls;
distal laminal cells 1-stratose, margins partly 2-stratose.
arcuate, 3–4 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, yellowish green, oblong-ovoid, striate, exothecial cells rather thick-walled, annulus present, operculum rostrate, peristome teeth orange to reddish, perforated, irregularly cleft at apex, nearly smooth basally, papillose distally.
mitrate.
Grimmia reflexidens
Grimmia leibergii
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 leibergii, formerly thought to be endemic to western North America, has the habit of Racomitrium heterostichum. Nearly all specimens of G. leibergii in NY, and probably also in other North American herbaria, have been filed as varieties of R. heterostichum (= Bucklandiella heterosticha). This confusion probably accounts for G. leibergii not being commonly recognized in North America. J. B. Leiberg (1893) stated that it is most closely related to G. decipiens, a species that does not occur in North America. Both taxa share broadly ovate-lanceolate leaves with both margins recurved, rectangular mid leaf cells with extremely thick and sinuose lateral walls and elongate to linear, nodulose, thick-walled basal juxtacostal cells. However, G. decipiens is autoicous, it is a much smaller species, with long, sharply denticulate awns. The gametophytes form comal tufts, so the distal leaves are 2–3 times longer than the lower leaves, and are not secund. Grimmia jacutica has been described separately from eastern Asia and Alaska but all specimens of it that we have examined are just slightly smaller forms of G. leibergii with slightly more sinouse mid leaf cells. The extension of G. leibergii into eastern Asia is a significant find and speaks to our poor knowledge of Grimmia distribution patterns on a worldwide basis.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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