Richard H. Zander
Pleuroweisia Schliephacke
Plants forming a compact turf, dark to light green, occasionally glaucous above, brown or tan below. Stems elongate, to 2[--7] cm; hyalodermis absent or occasionally weakly developed, sclerodermis absent or present, usually weak, central strand present, usually strong; axillary hairs of several 1-seriate cells, usually thin-walled or occasionally proximal 1--2 cells thick-walled. Leaves usually crowded, appressed-incurved to weakly spreading, usually twisted, occasionally tubulose when dry, spreading to spreading-recurved when moist; variously ovate, ligulate, long-oblong, linear, ovate- to linear-lanceolate, adaxial surface flat to broadly or narrowly channeled; base scarcely differentiated to elliptic-sheathing; distal margins plane to weakly recurved in proximal 1/2, entire or occasionally sinuolate, occasionally denticulate at shoulders, distal margins often 2-stratose entirely or in patches; apex broadly rounded to narrowly acute; costa ending 1--3(--6) cells before apex, percurrent, or excurrent as a stout mucro, adaxial outgrowths absent, adaxial cells quadrate to elongate, in 2--7 rows; transverse section circular, semicircular or reniform, adaxial epidermis present, adaxial stereid band absent to weak, guide cells 2--7 in 1 layer, hydroid strand absent, abaxial stereid band present, crescent-like or rounded in sectional shape, abaxial epidermis usually present, weakly developed; proximal cells differentiated across leaf or differentiated area V- or U-shaped, rectangular, little wider than the distal cells, (1--)2--5:1, walls of proximal cells thin or evenly thickened to porose; distal medial cells often irregular in shape, rounded-quadrate, oval, rounded-triangular, ca. 8--10 µm wide, 1:1; papillae crowded, low, irregular, scablike, occasionally simple to 2-fid or massively multifid, cell walls evenly thickened to weakly trigonous, flat to bulging superficially, superficial walls usually thicker than internal walls. Specialized asexual reproduction by axillary gemmae, rarely present, obovoid to spindle-shaped, ca. 35--50 µm, multicellular. Sexual condition dioicous. Perichaetia terminal on short lateral branches, interior leaves usually highly differentiated, sheathing the seta, ovate-lanceolate, usually shorter than the cauline leaves, often marginally serrulate, laminal cells rhomboid in proximal 1/2 to throughout. [Seta 0.2--0.7 cm. Capsule stegocarpous, theca ovoid to cylindric, often macrostomous, 0.6--1.5 mm, annulus of 2--3 rows of transversely elongated, hexagonal cells, weakly vesiculose; operculum long-rostrate, oblique, of untwisted cells; peristome absent. Calyptra cucullate. Spores ca. 9--12 µm.] KOH laminal color reaction yellow to yellow-orange.
Species 15 (3 in the flora); all continents except Australia and Antarctica, in montane or Arctic areas.
Molendoa has lateral perichaetia, like Anoectangium. The costa of Molendoa has two stereid bands (in robust specimens at least), and the distal lamina is commonly 2-stratose at least in patches.
SELECTED REFERENCES
Zander, R. H. 1977. The tribe Pleuroweisieae (Pottiaceae, Musci) in Middle America. Bryologist 80: 233--269. Zander, R. H. 1993. Genera of the Pottiaceae: Mosses of Harsh Environments. Bull. Buffalo Soc. Nat. Sci. 32: vi + 378 pp. Zander, R. H. 1994. Molendoa. In A. J. Sharp, H. A. Crum and P. M. Eckel, eds. Moss Flora of Mexico. Mem. New York Bot. Gard. 69: 257--259.
OTHER REFERENCES
Smith Merrill, G. L. 1992. Ozobryum ogalalense (Pottiaceae), a new moss genus and species from the American Great Plains. Novon 2: 255--258.
Zander, R. H. 1979. Molendoa hornschuchiana new to the Americas from the Pacific coast of Alaska. Bryologist 82: 487--489.
