Grimmia reflexidens
Grimmia attenuata
1–2 cm, central strand absent.
5–10 cm, 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.
straight appressed when dry, erectopatent when moist, lanceolate, 2.7–3.5 × 0.5–0.75 mm, sharply keeled distally, margins narrowly reflexed on both sides, awns terete, firm and short, denticulate, costa 70-120 µm wide at base, channeled distally, circular, projecting on dorsal side;
basal juxtacostal laminal cells elongate with extremely thick, slightly nodulose walls;
basal marginal laminal cells in a few rows short-rectangular, thin-walled;
medial laminal cells short- to long- rectangular with extremely thick and sinuose lateral walls;
distal laminal cells 1-stratose, apex and margins 2-stratose.
cygneous, 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.]
sporadically present, exserted, yellowish brown, ovoid, smooth, exothecial cells thin-walled with incrassate corners, annulus present, operculum rostrate, peristome teeth orange, 40–60 µm wide at base, split and perforated, smooth proximally, papillose distally.
not seen.
Grimmia reflexidens
Grimmia attenuata
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.)
Of conservation concern.
Grimmia attenuata resembles forms of the extremely variable Racomitrium heterostichum (= Bucklandiella heterosticha), and because G. N. Jones (1933) mentioned five varieties of the latter, it is not surprising that in some herbaria, e.g. NY, all specimens of G. attenuata have been filed as varieties of R. heterostichum. In 1898, Kindberg realized that his species is not a Racomitrium, but a Grimmia, and wrote: “Habit of G. elatior.” In spite of Kindberg’s correct transfer to Grimmia, T. C. Frye (1917–1918) synonymized G. attenuata with R. macounii. Adding to the confusion, H. A. Möller (1929) synonymized it with G. elatior, and J. Muñoz (1999b) cited it as G. arcuatifolia, which is a synonym of G. lisae. Grimmia elatior is characterized by ellipsoid striate capsules, leaf margin broadly recurved on just one side, and an opaque 2-stratose distal lamina with rounded usually mammillose to papillose cells, the mid leaf cells quadrate to short-rectangular with slightly sinuose, thick walls. Like Grimmia leibergii, G. attenuata is characterized by its elongate to linear, strongly nodulose and thick-walled basal juxtacostal cells, its extremely thick-walled and sinuouse medial cells, leaf margins both recurved, and stem central strand absent. However, the two differ in costa shape and basal marginal cell shape.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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