Gyroweisia Schimper, Syn. Musc. Eur., ed. 2. 38. 1876.
[Greek gyrus, circle, and Weisia; a Weissia-like moss with a well-developed
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 proximal1/4--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(--2), 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 long, 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): widely scattered across North America, Europe, Middle East, Asia (China), Africa, on thin soil over calcareous rock.
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 region), 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), the more common presence of gemmae, and the perichaetial leaves much larger than the cauline.
Gyroweisia pusilla (Kindberg) Brotherus was treated as a synonym of Gymnostomum calcareum Smith by L. E. Andrews (1922).
The peristomate Gyroweisia reflexa (Bridel) Schimper is known for the flora area only from a single collection in Grey Co., Owen Sound, Ontario (Moxley, May 1924, CANM!). The specimen is indeed that but bryologists (H. A. Crum and L. E. Anderson 1981) have questioned the report suggesting a confusion of specimens by Moxley (as reviewed by W. R. Manierre 1998). The region of the original station, now built over, has been examined by others, but no additional sites discovered. The Michigan collection (MO!) reported by W. R. Manierre (1998) is Tortula obtusifolia (Schwägrichen) Mathieu, which, though similar in the ligulate leaves and rudimentary peristome, differs significantly in the crowded, short-ovate leaves, and the single stereid band and enlarged adaxial superficial cells of the costa in section. Although it would be difficult to demonstrate the absence of this species, given the circumstances it is now appropriate to exclude the species from the New World.
Additional literature: Andrews, A. L. 1922 . 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. 2000. Four moss species new to Greenland: Barbula amplexifolia, Didymodon brachyphyllus, D. michiganensis, and Gyroweisia tenuis (Pottiaceae, Musci). Lindbergia 24: 77--83. 1999. Steere, W. C. 1939. Gyroweisia tenuis in North America. Bryologist 42: 16--23.