Richard H. Zander
Merceyopsis Dixon
Plants forming a thin or thick turf, green to greenish yellow or brown distally, blackish or weakly iridescent to metallic tan or yellow-brown proximally. Stems to 4 cm, rounded-pentagonal in transverse section, hyalodermis absent, sclerodermis absent, central strand absent; axillary hairs 3--5 cells in length, proximal cell usually brownish. Cauline leaves often crowded, incurved to spreading, contorted, carinate, occasionally with undulating margins when dry, spreading when moist; lingulate to ligulate or oblanceolate, widest at midleaf or beyond, adaxial surface narrowly and deeply grooved along costa or broadly channeled, to 2.5 mm; base scarcely differentiated in shape to long-elliptic, occasionally medially constricted, proximal margins occasionally slightly decurrent; distal margins plane or somewhat recurved proximally, entire to minutely crenulate or denticulate distally, often bordered by a few rows of thicker walled cells distally; apex broadly acute or obtuse, often with a broad apiculus, occasionally rounded; costa slender, percurrent or ending 2--8 cells before the apex, occasionally excurrent as a short mucro, adaxial outgrowths absent, adaxial cells quadrate to rectangular, in 2--4 rows; transverse section semicircular to round, adaxial epidermis absent or present, adaxial stereid band absent, guide cells 2(--4) in 1 layer, hydroid strand absent, abaxial stereid band present, rounded in sectional shape, abaxial epidermis present, usually very distinct; proximal cells differentiated across leaf, extending higher medially, rectangular, occasionally inflated, scarcely wider than distal cells to inflated, 2--3:1, walls of proximal cells hyaline or deep brown; distal medial cells rounded quadrate to hexagonal or short-rectangular, ca. 8--14 µm, often heterogeneous in size, 1(--2):1, 1-stratose; papillae usually lacking, occasionally low-verrucose, cell walls thin to evenly thickened, thicker near margins, flat or somewhat bulging on adaxial surface. Specialized asexual reproduction rare, on stalks from the stem, greenish brown, clavate to ellipsoid or filamentous and branching, ca. 12 µm, of 2 or more rounded cells. Sexual condition dioicous. Perichaetia terminal, interior leaves little differentiated. [Seta 2--6 mm. Capsule stegocarpous, theca shortly elliptic to cylindric, macrostomous, 0.6--2.2 mm, annulus weakly differentiated or of 1--4 rows of vesiculose cells, deciduous in fragments; operculum conic-rostrate, erect or oblique; peristome teeth absent. Calyptra cucullate. Spores 8--13 µm.] KOH distal laminal color reaction yellow to yellowish orange.
Species 3 (2 in the flora); mountainous areas of North, Central and South America, Europe, c Africa, Asia, Pacific Islands.
This is a small genus (R. H. Zander 1993) of "copper mosses" (see reviews by A. J. Shaw and L. E. Anderson 1988 and A. J. Shaw 1993) associated with mineralized soils. Crumia is similar but is quickly distinguished by its stem central strand, intramarginal laminal border, and distal laminal cells usually distinctly papillose.
SELECTED REFERENCES
Shaw, A. J. and L. E. Anderson. 1988. Factors affecting the distribution and abundance of the "copper moss," Scopelophila ligulata, in North America. Lindbergia 14: 55--58. Shaw, A. J. 1993. Morphological uniformity among widely disjunct populations of the rare "copper moss," Scopelophila cataractae (Pottiaceae). Syst. Bot. 18: 525--537. Zander, R. H.1967 [1968]. The New World distribution of Scopelophila (= Merceya). Bryologist 70: 405--413. Zander, R. H.1994. Scopelophila. In: A. J. Sharp, H. A. Crum and P. M. Eckel (eds.), Moss Flora of Mexico. Mem. New York Bot. Gard. 69.
OTHER REFERENCES
Bartram, E. B. 1924b. Scopelophila ligulata Spruce in North America. Rev. Bryol. 51: 47--48.
Jones, G. N. 1961. The discovery of Merceya in Illinois. Bryologist 64: 263--265.
Lampton, R. K. 1966. Merceya ligulata in Georgia. Bryologist 69: 511.
Reese, W. D. 1989. Scopelophila cataractae in Texas. Bryologist 92: 413.
Shaw, A. J. 1993. Population biology of the rare copper moss, Scopelophila cataractae. Amer. J. Bot. 80: 1034-1041.
Shaw, J. and S. C. Beer. 1989. Scopelophila cataractae (Mitt.) V. F. Brotherus in Pennsylvania. Bryologist 92: 112--115.
Steen, A. J. 1986. Two collections from Calaveras County yield two mosses new to California. Evansia 3: 11.
