30. GYROWEISIA Plate 39.

Gyroweisia Schimp., Syn. Musc. Eur., ed. 2. 38, 1876, nom. cons. Lectotype: Gyroweisia tenuis (Hedw.) Schimp.

Weisiodon Schimp., Coroll. 9, 1856, nom. rejic. Type: Weisiodon reflexus (Brid.) Schimp.

Gyroveisia Schimp. ex Luis., Broteria ser. Bot. 8: 36, 1909, orthogr. var.

Gymnostomum subg. Gymnoweisia B.&S. in BSG, Bryol. Eur. 1: 78, 1846 (fasc. 33–36 Mon. 4). Lectotype: Gyroweisia tenue Hedw.

Weissia subg. Weisiopsis BSG, Bryol. Eur. 1: 5. 1851 (fasc. 46–47. Consp. 1: VII), nom. illeg. Type: Weissia reflexa Brid.

Trichostomum sect. Weisiodon (Schimp.) Lindb., Oefv. K. Vet. Ak. Foerh. 21: 213, 1864, as “Weissiodon.” Type: Trichostomum reflexum (Brid.) Lindb.

Weissia sect. Spathulidium C. Müll., Linnaea 40: 298, 1876. Type: Weissia tophicola C. Müll.

Plants low, gregarious or forming a thin turf, green above, tan below. Stems short, branching occasionally, to 0.4 cm in length, transverse section rounded-pentagonal, central strand present or absent, sclerodermis present (substereid), hyalodermis absent; axillary hairs of ca. 5(–10) cells, basal 1–3 brownish. Leaves appressed-incurved when dry, weakly spreading, strict to reflexed when moist, narrowly ligulate to long-ovate, ca. 0.7–1.4 mm in length, upper lamina shallow-grooved along costa or flat, margins plane to weakly recurved, entire, occasionally bistratose throughout; apex rounded to rounded acute or obtuse, sometimes acuminate or apiculate by a sharp cell; base scarcely differentiated to ovate, occasionally sheathing; costa percurrent or ending ca. 4–8 cells below apex, superficial cells elongate ventrally and dorsally, 2–8 rows of cells across costa ventrally at midleaf, costal transverse section semicircular to rounded, ventral stereid band absent or weak, often superficially exposed, dorsal band present and semicircular in section when well developed, epidermis usually present ventrally, often present dorsally, guide cells 2(–6) in 1 layer, hydroid strand absent; upper laminal cells quadrate or short-rectangular, ca. 8–11 µm in width, 1–2:1, walls thin to evenly thickened, superficially flat to convex; papillae hollow, simple to indistinctly bifid, scattered, ca. 4 per lumen, occasionally absent; basal cells differentiated across leaf base in lower 1/4 to 1/2 of leaf, rectangular, commonly enlarged or inflated and hyaline, usually little wider than upper cells, 3–5:1, walls thin to evenly thickened. Propagula often present, oval to spindle-shaped, of several cells, borne on basal rhizoids, brown. Dioicous or autoicous, occasionally heteroicous. Perichaetia terminal, inner leaves lanceolate, usually well differentiated, to 1.5 mm in length, often strongly sheathing the seta, lower cells rectangular to long rhomboidal. Perigonia terminal, gemmate, on somewhat smaller plants, or as buds at base of perichaetiate plant. Seta ca. 1.5–6.0 mm in length, 1 per perichaetium, yellowish brown, twisted clockwise; theca ca. 0.8–1.5 mm in length, yellowish brown, oval to short-cylindrical, neck sometimes well differentiated, exothecial cells short-rectangular to rhomboidal, thin-walled, stomates phaneropore, occasionally somewhat enlarged, at base of capsule, annulus of 2–3 rows of highly vesiculose cells, usually revoluble but often merely persistent; peristome teeth absent or ca. 16, rudimentary, short, ligulate or oblong and much perforate, lightly papillose to closely spiculose, ca. 30–80 µm in length, with ca. 3–4 articulations, straight, basal membrane low. Operculum short-conic to narrowly rostrate, ca. 0.2–0.6 mm in length, cells straight. Calyptra cucullate, smooth, ca. 0.7–1.4 mm in length. Spores ca. 8–14 µm in diameter, light brown, smooth to papillose. Laminal KOH color reaction yellow or orange. Reported chromosome number n = 13.

Found on thin soil over calcareous rock, in widely scattered localities across North America, Europe, the Middle East, Africa and China.

Gyroweisia has long been a “wastebasket” genus (Zander 1977c) wherein several small, feature-poor species have been set aside. Generally, these taxa have ligulate leaves with subpercurrent costae and enlarged, hyaline basal cells (Pl. 39, f. 7, 19, 25–26), a vesiculose annulus, and a rudimentary peristome or sometimes none at all (Pl. 39, f. 21, 30). Little attention has been given to characters of the areolation and anatomy, which may be used to better place the species. Past work (Zander 1977c; Hill 1981) and the present study has assigned many of these taxa to more appropriate genera, and even further reduction in the size of the genus is probable.

Gyroweisia may be viewed (see also Zander & Hermann 1986) as part of a complex evolutionary series, also including Gymnostomum, Leptobarbula and Barbula sect. Convolutae, involving morphological reduction of plant size and expression of the peristome. Gyroweisia differs from a morphologically similar genus, Gymnostomum, by the occasional presence of a peristome (albeit rudimentary), the large annulus, the sterile plants (Pl. 39, f. 2) distinctly smaller than the sporophyte-bearing gametophytes, basal leaf cells differentiated higher up the leaf (lower 1/4 to 1/2) (Pl. 39, f. 7, 19, 26), the more common presence of propagula (Pl. 39, f. 11—see also Sérgio 1984), and the perichaetial leaves much larger than the cauline (Pl. 39, f. 12, 13, 20, 29). The transformation series conceived above is, however, not supported by the cladistic analysis, probably because the analysis utilizes more than just the most obvious characteristics of the taxa involved.

Additional literature: Andrews (1922c), Conard (1945b), Crundwell (1981), Egunyomi and Olarinmoye (1978), Geheeb (1906b), Sérgio (1972b), Steere (1939c), Thériot (1923).

Number of accepted species: 6.

Species examined: G. monterreia (BUF), G. reflexa (BUF, DUKE, NY), G. tenuis (BUF, DUKE, MICH, NY), G. yuenannensis (H).

New homotypic synonymy: Gyroweisia lindigii (Hampe) Broth. = Didymodon lindigii (Hampe) Zand. mixed with Didymodon tophaceus (Brid.) Lisa and Didymodon australasiae (Hook. & Grev.) Zand., judging from the several apparent isotypes that are present at FH and NY.