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FNA | Family List | FNA Vol. 27 | Dicranaceae

2. Arctoa Bruch & Schimper, Bryol. Europ. 1: 151. 1846.

[Greek arktos, bear, alluding to an arctic or northern distribution]

Steven G. Newmaster

Dicranum sect. Arctoa (Bruch & Schimper) Braithwaite

Plants in 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 ┬Ám, finely roughened, green.

Species ca. 4 (3 in the flora): North America, Europe, Asia.

A rare northern and alpine genus, Arctoa 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 REFERENCE

Allen, B. H. 1998. The genus Arctoa (Musci: Dicranaceae) in Maine. Evansia 15: 131-137.


1 Peristome teeth not wide-spreading; distal leaf cells 1-2:1; costa short-excurrent.   3 Arctoa hyperborea
+ Peristome teeth wide-spreading; distal leaf cells 2-5:1; costa long-excurrent   (2)
       
2 (1) Capsule straight, immersed; seta short; awn entire.   1 Arctoa anderssonii
+ Capsule curved, exserted; seta long; awn toothed.   2 Arctoa fulvella

Lower Taxa


 

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