Steven G. Newmaster
Dicranum sect. Arctoa (Bruch & Schimper) Braithwaite
Plants in erect, dense tufts, dark green to yellowish brown, shiny. Stems (0.5--)1--2(--5) cm, branches simple, sparsely radiculose. Leaves lanceolate, subulate, erect-spreading, sometimes falcate-secund; margins erect, entire, or serrulate near the tips; costa excurrent as an awn, narrow, stereids poorly differentiated from median guide cells; distal laminal cells rectangular to subquadrate, smooth or slightly mammillose; basal laminal cells elongate, smooth, sometimes porose, alar cells sometimes differentiated and inflated. Perichaetial leaves with a sheathing base. Sexual condition autoicous. Seta solitary, 3--6 mm, erect, stout, yellow. Capsule erect, exserted or immersed in perichaetial leaves, symmetric, obovoid, constricted below mouth, furrowed when dry, urn 0.5--1.2 mm; operculum obliquely rostrate; peristome single, of 16 red-brown teeth, divided halfway into two segments, vertically or irregularly striolate. Calyptra cucullate, smooth. Spores spheric, 16--30 µm, finely roughened, green.
Species ca. 4 (3 in the flora); North America, Europe, Asia.
This rare northern and alpine genus occurs on rock or soil and is distinguished by its medium-sized, Dicranum-like habit, with poorly differentiated stereid and guide cells. It may be confused with Kiaeria, which differs by a longer seta, and capsules often strumose, with narrow mouths.
SELECTED REFERENCES
Allan, B. 1998. The Genus Arctoa ( Musci: Dicranaceae) in Maine. Evansia 15: 131--137. Grout, A. J. 1902. Mosses With Hand-Lens and Microscope. New York. Grout, A. J. 1933--1940. Moss Flora of North America. Vol 2. Newfane, Vermont. Corley, M. F. V. 1979. Notes on Some Rare Dicranaceae. J. Bryol. 10: 369--370. Lawton, E. 1971. Moss Flora of the Pacific Northwest. Nichinan, Japan. Nyholm, E. 1954. Illustrated Moss Flora of Fennoscandia. Musci II Fasc. 1. Lund, Sweden. Ochyra, R.A. and W. R. Buck. 2004. Arctoa fulvella, new to Tierra del Fuego, with notes on trans-American bipolar bryogeography. Bryologist 106: 532--538. Townsend, C. C. 1991. Arctoa anderssonii Wich. in Torneträsk, Swedish Lapland. J. Bryol. 16: 647--648.
