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BFNA | Family List | BFNA Vol. 1 | Dicranaceae | Dicranum | Dicranum fuscescens

Dicranum fuscescens var. fuscescens

Plants in loose tufts. Stems 1--6 (--10) cm, tomentose with white or reddish brown rhizoids. Leaves falcate-secund, usually densely foliate; margins serrulate to strongly serrate in distal half; costa papillose to spinose distally on adaxial surface; proximal leaf cells elongate, pitted, (25--)43--62(--93) ´ (2--)6--8(--12) μm; distal laminal cells short-rectangular to quadrate, not pitted, (8--)18--23(--31) ´ (5--)8--12(--14) μm. Seta 1--3.5 cm.

Capsules mature in spring. Coniferous or deciduous tree trunks and bases of trees, rotten logs, stumps, soil, boulders, rock outcrops, cliff shelves, and humus in woodlands, or sometimes bogs; 10--2300 m; Greenland; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Nun., Ont., P.E.I., Que., Sask., Yukon; Alaska, Calif., Colo., Ga., Idaho, Ky. (Snider et al. 1988), Maine, Mass. (Hilferty 1960), Mich., Minn., Mont., N.H., N.Mex., N.Y., N.C., Ohio (Snider & Andreas 1996), Oreg., Pa., S.Dak., Tenn., Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; Asia.

The var. fuscescens is highly variable but is best known by the loose tufts of green to brownish green, dull plants, the slender, falcate-secund leaves ending in a slender, keeled subula, slightly to strongly crisped when dry, the strongly serrated, often 2-stratose distal leaf margins, the excurrent costa that is conspicously rough above with papillae and spines on the abaxial surface, the nonpitted, short-rectangular, quadrate or irregularly angled distal leaf cells, and the solitary, often strumose, capsules that are inclined to horizontal.

Some plants of D. fuscescens, especially those in the northern part of Canada, may be confused with D. acutifolium. The latter, however, usually has a few undulations on the leaves and the leaf cross section often reveals larger, more rounded bulging cell walls between the lamina cells and fewer 2-stratose regions on the margins than D. fuscescens. Dicranum sulcatum Kindberg, considered a synonym here and by R. S. Williams (1913), has been recognized by W. Peterson (1979) as a distinct species. The diagnostic features are duller color due to a greater degree of papillosity, long-excurrent costa, wider costa at mid-leaf, and presence of more rows of stereid cells, 3--5 rows compared to 2--3 rows in D. fuscescens. Dicranum sulcatum is reported to occur usually on living coniferous trees in the Pacific Northwest, from southern Alaska south to central California, inland to northern Idaho and northwestern Montana. All of the diagnostic characters are too variable to be important in maintaining this species. Furthermore, they are all quantitative characters, which makes it difficult to establish a distinct species without at least one good qualitative character. Further studies could help to establish it as a variety.


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