11. Gyroweisia Schimper, Syn. Musc. Eur. ed. 2. 38. 1876.
[Greek gyrus, circle, and genus Weissia, alluding to resemblance and well-developed, persistent annulus]
Richard H. Zander
Plants gregarious or forming a thin turf, green distally, tan proximally. Stems to 0.4[-3] cm, branching occasionally; rounded-pentagonal in transverse section, hyalodermis absent, sclerodermis present as substereids, central strand present or absent; rhizoids few; axillary hairs of ca. 5(-10) cells, the basal 1-2 brownish. Leaves appressed-incurved when dry, weakly spreading reflexed when moist; narrowly ligulate or rectangular to long-ovate, adaxial surface nearly flat, 0.25-1.4 mm; base scarcely differentiated to ovate [sheathing]; distal margins plane to weakly recurved, entire, 1-stratose [2-stratose]; apex rounded to rounded acute or obtuse, sometimes apiculate by a sharp cell; costa ending ca. 4[-8] cells below apex [percurrent], adaxial outgrowths absent, adaxial cells elongate in 2-8 rows, abaxial cells elongate; transverse section of costa semicircular to ovate, adaxial epidermis usually present, adaxial stereid band absent or weak, exposed, guide cells 2 in 1 layer, hydroid strand absent, abaxial stereid band present, crescentiform or round in sectional shape, abaxial epidermis present or commonly absent; basal cells differentiated across leaf base in proximal 1/4-1/2 of leaf, little wider than distal cells or somewhat bulging [inflated], 3-5:1, walls of basal cells thin to evenly thickened; distal medial cells quadrate or shortly rectangular, ca. 8-11 µm wide, 1(-2):1, papillae absent or hollow, simple to indistinctly 2-fid, cell walls thin to evenly thickened, superficially flat to convex. Specialized asexual reproduction when present by oval to spindle-shaped gemmae, of several cells, borne on basal rhizoids, green or brown. Sexual condition dioicous [autoicous, occasionally heteroicous]; perigonia appear as buds at plant base or terminal, gemmate; perichaetia terminal, inner leaves often strongly sheathing seta, lanceolate, to 1.5 mm, laminal cells often rectangular to rhomboid. Seta yellow-brown, ca. 1.5-3[-6] mm, twisted clockwise. Capsule yellow-brown, ovate to short-cylindric, [neck differentiated,] 0.8-1 mm, exothecial cells shortly rectangular to rhomboid, thin-walled, annulus of 2-3 rows of highly vesiculose cells, revoluble and deciduous in pieces; operculum short-conic [narrowly rostrate], ca. 0.2-0.3[-0.6] mm, cells in straight rows; peristome teeth absent [16, rudimentary, short, spreading, ligulate or oblong and highly perforate, straight, articulations ca. 3-4, ca. 30-80 µm, lightly papillose to closely spiculose, basal membrane low]. Calyptra cucullate, ca. 0.7-1[-1.4] mm, smooth. Spores ca. 9-11 µm, smooth to papillose, light brown. KOH laminal color reaction yellow, rarely orange.
Species 6 (1 in the flora): North America, Europe, Asia (China, Middle East), Africa.
Gyroweisia species have ligulate leaves with subpercurrent costae and enlarged, hyaline basal cells, a vesiculose annulus, and peristome absent or rudimentary peristome. Gyroweisia differs from the similar Gymnostomum by the occasional presence of a rudimentary peristome (outside the flora area), the large annulus, sterile plants distinctly smaller than the sporophyte-bearing gametophytes, basal leaf cells differentiated more strongly (often in the basal 1/4 to 1/2), and the more common presence of gemmae.
Andrews, A. L. 1922b. The status of Gyroweisia in North America. Bryologist 25: 97-100. Conard, H. S. 1945. Gyroweisia reflexa in North America. Bryologist 48: 28-29. Manierre, W. R. 1998. Gyroweisia reflexa, a moss new for the United States. Evansia 15: 30-31. Mogensen, G. S. and R. H. Zander. 1999. Four moss species new to Greenland: Barbula amplexifolia, Didymodon brachyphyllus, D. michiganensis, and Gyroweisia tenuis (Pottiaceae, Musci). Lindbergia 24: 77-83. Steere, W. C. 1939. Gyroweisia tenuis in North America. Bryologist 42: 16-23.