BFNA Title: Trachybryum
XX. Trachybryum (Brotherus) W. B. Schofield, J. Hattori Bot. Lab. 31: 222. 1968 * [literally “rough moss”]
Camptothecium sect. Trachybryum Brotherus in Engler & Prantl, Nat. Pfl. 1(3): 1140. 1980.
W. B. Schofield
Plants robust, forming loose mats, usually yellow-green but in deep shade often dark green, glossy. Stems prostrate, with central strand, densely terete-foliate, regularly to irregularly (and remotely in grassy habitats) pinnate branched in one plane, flattened when wet, coiling upward when dry; branches pointed to strongly attenuate; axillary hairs 4--5-celled; juvenile branch leaves acuminate. Stem leaves imbricate when dry, erect, ovate-lanceolate to lanceolate, broadest in proximal 1/10 leaf length, gradualy tapered along most of its length and rather shortly acuminate, very slightly tapered to base, very shortly decurrent, slightly concave, strongly plicate, margins plane or recurved at places, entire or with sparse, indistinct blunt teeth; costa strong, extending nearly to leaf tip, often with 1--2 teeth at end; basal cells near costa in 2--3 rows shorter and wider, with strongly incrassate and porose cell walls; cells just proximal to decurrency somewhat broader, rectangular, thick-walled, forming a small, more or less distinct group not reaching leaf margin or sometimes indistinct; mid leaf cells very narrow, linear, smooth. Branch leaves smaller and narrower than stem leaves, less attenuate, serrulate or at places almost subentire; alar cells few, often inconspicuous, median leaf cells narrow, 10--20:1. Sexual condition dioicous or phyllodioicous; sporophytes uncommon; perichaetial leaves reflexed, gradually acuminate from a sheathing base, entire or occasionally serrulate, costa weak and short, reaching to about half of basal part of leaf. Seta red-brown, rough. Capsule red-brown, horizontal, ovoid-oblong, swollen at base, tapering to mouth, curved; annulus separating by fragments; operculum long-conic; peristome perfect. Calyptra naked. Spores 19--20 \um, nearly smooth.
Trachybryum is distinct in its large size, lack of rhizoids due to dense stem foliage, stem leaves that are considerably larger than branch leaves, weakly differentiated alar cells, and a distinctive ecology, occurring usually in conifer forests on litter, not on rocks and trunks as do most Homalothecium species.
1. Trachybryum megaptilum (Sullivant) Schofield, J. Hattori Bot. Lab. 31: 222. 1968
Camptothecium megaptilum Sullivant, Icon. Musc. Suppl., 102. 1874; Homalothecium megaptilum (Sullivant) H. Robinson
Stems 1--12 cm, branches 10--15 mm. Stem leaves 3.5--5 x 1.3--1.8 mm; basal cells near costa 30--60 x 9--12 \um wide, just proximal to decurrency 25--40 x 9--12(--14) \um; mid-leaf cells 60--130 x 4--6 \um. Branch leaves 1.8--2.5 x 0.8--1.2 mm; mid-leaf cells 50--90 x 4--6 \um. Seta 2--2.5 cm. Capsule 2--2.5 mm.
Litter in coniferous forest, among grasses in open sites, rarely logs and rocks; (60--)300-1300 m; B.C.; Calif., Ida., w Mont., Ore., Wash.