Grimmia reflexidens
Grimmia serrana
1–2 cm, central strand absent.
to 3 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.
ovate-lanceolate from an ovate base, 2.5–3.5 × 0.6–0.7 mm, both margins plane, costa-like inter-marginal bands 2–4(–5)-stratose, awn to 1 mm, not decurrent, narrowly attached, acuminate, costa narrow proximally;
basal juxtacostal laminal cells short- to long-rectangular, sinuose, thick lateral-walled, dense;
basal marginal laminal cells quadrate to short-rectangular, sinuose, thick lateral-walled, not hyaline;
medial laminal cells quadrate, slightly sinuose, thick-walled;
distal laminal cells 1–3-stratose, oblate to rectangular, thick-walled.
straight to slightly arcuate, to 3.5 mm.
dioicous, perichaetial leaves enlarged.
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, pale yellow, ovoid, exothecial cells oblong, thin-walled, stomata absent, annulus of 1–2 rows of quadrate, thick-walled cells, operculum short straight, peristome fully developed, not perforate, not split.
cucullate.
leaves enlarged.
Grimmia reflexidens
Grimmia serrana
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.)
According to the original description, Grimmia serrana is known only from “localities along the western slope of the Sierra Nevada and two occurrences in the northern Coast Range.” Despite its limited distribution, H. C. Greven (2003) found it to be quite common in the area. With its thick, concave leaves with plane margins and flat costa, G. serrana is best placed in subg. Litoneuron. This is further supported by a number of other features shared by, but not unique to, all members of that subgenus, including a well-developed stem central strand, dioicous sexuality, and long-exserted capsule with a multi-layered, thick-walled annulus. Grimmia serrana is most readily identified by a prominent, costa-like, multi-layered band of cells that run along the laminal margin distally and become submarginal proximally. This inflated band is unique to this species and readily separates it from all other members of subg. Litoneuron. As stated by Muñoz et al., G. serrana is most likely to be confused with G. ovalis. Both are robust species with ovate-lanceolate leaves from an ovate base. However, the prominent intermarginal bands of G. serrana will readily separate these species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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