Grimmia reflexidens
Grimmia incurva
black grimmia, grimmia dry rock moss
1–2 cm, central strand absent.
1–2 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.
incurved and moderately contorted when dry, spreading when moist, oblong- to linear-lanceolate, tapering to a slender and acuminate, often hyaline apex, 2.5–4.5 × 0.3–0.5 mm.
arcuate, 1.5–2 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, emergent to exserted, yellowish, obloid, smooth or somewhat wrinkled when dry, exothecial cells thin-walled, annulus present, operculum conic to rostrate, peristome teeth orange, divided distally, papillose.
mitrate.
, margins plane or recurved proximally on one or both sides, awns short, often only mucronate, occasionally long and denticulate, costa projecting on abaxial side;
basal juxtacostal laminal cells long-rectangular, slightly sinuose, thick-walled;
basal marginal laminal cells short- to long-rectangular, thin-walled;
medial laminal cells rectangular, nodulose, thick-walled;
distal laminal cells 1-stratose, margins and apex 2-stratose.
Grimmia reflexidens
Grimmia incurva
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.)
The peculiar east-west disjunct distribution of Grimmia incurva in North America may reflect its preference for damp sites. Specimens have been collected in New England and in the Maritime Provinces, with a second widespread area running from the Yukon south through to California. It is uncommon in the continental interior. Grimmia incurva is a shade-loving subalpine species, characterized by rounded dark green cushions and linear, contorted leaves. The awns are visible only with a hand-lens. This species has a habit more like that of Dicranowesia crispula than of a Grimmia. H. A. Crum and L. E. Anderson (1981) reported immersed capsules, but that is not correct; they are clearly exserted (H. C. Greven 1995). Crum and Anderson also observed: “Specimens recorded from Maine can be considered a shade form of G. donniana.” However, this confusion extends beyond Maine. Greven renamed nearly all the G. donniana specimens from New York and New Hampshire in MICH to G. incurva. Hastings agrees that these specimens cannot be G. donniana because the leaf shape is virtually identical to that of G. incurva, being narrowly lanceolate and contorted. However, like G. donniana, and unlike G. incurva, the specimens are autoicous and the setae are straight. Rather than expanding the concept of either G. donniana or G. incurva to include these anomalous specimens, we propose that they represent an as yet unpublished species with a unique combination of characters. Hastings thus retains G. incurva as being dioicous and G. donniana as having oblong-lanceolate leaves.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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