Ditrichum Moss

Rhizoidal tubers, consisting of swollen rhizoidal cells and arising laterally from axial rhizoids, are known for Ditrichum lineare only from Asia (T. Matsui et al. 1985; Matsui and Z. Iwatsuki 1990). This species is very similar in appearance to D. pusillum but is distinguished by the rectangular cells of the sheathing leaf base. The leaf margins of North American specimens of D. lineare are entire and plane or rarely only weakly recurved, irregularly 2-stratose but not noticeably thickened, and the lamina cells are elongate rectangular to linear. The leaf margins in D. pusillum are irregularly thickened, serrulate, more strongly recurved, and the lamina cells generally subquadrate to short-rectangular. Ditrichum lineare also has a subula shorter than the sheathing base, which is unusual in the genus. This macroscopic feature is sometimes used to distinguish it from the closely related D. pusillum, which has a subula longer than the sheathing base, typical of many species in the genus (R. R. Ireland 1982).

Plants in loose to dense tufts, yellowish green. Stems to 1(-1.5) cm, simple or with few branches. Leaves to 2 mm, erect and ± ap-pressed to the stem, oblong-lanceolate, widest at or slightly just proximal to the middle, tapering gradually to a rather blunt apex, lamina 1-stratose except on margins; margins subentire, plane to narrowly recurved, ± erect near the apex, irregularly 2-stratose in the distal half of the leaf; costa percurrent, broad, occupying about ¹/3 width of the leaf base, in section with a weakly developed stereid band on abaxial side of guide cells; cells of proximal part of lamina rectangular, thin to moderately thick-walled, becoming slightly shorter and narrower towards the leaf apex. Specialized asexual reproduction by rhizoidal tubers. Sexual condition dioicous; perichaetial leaves with a sheathing base, abruptly narrowed to a short subula about as long as the base or shorter. Seta yellowish, brown to orange-brown with age, to 2.5 cm or sometimes longer, erect. Capsule erect and symmetric or slightly curved, brown to reddish brown, narrowly ellipsoid to cylindric, 1-2 mm, smooth or indistinctly furrowed when dry; operculum obliquely conic-rostrate, blunt, 0.3-0.7 mm; peristome divided by perforations into 2 ± adhering divisions, 200-220 µm, finely papillose. Spores 13-16 µm, appearing smooth or very finely verrucose, brown.

Didymodon linearis Swartz, Adnot. Bot., 100. 1829; Ditrichum vaginans (Sullivant) Hampe; Trichostomum vaginans Sullivant

Ditrichum lineare (Sw.) Lindb. Acta Soc. Sci Fenn. 10: 108. 1871.
Didymodon lineare Sw. Adnot. Bot. 100. 1829. Trichostomum vaginans Sull. Musci Allegh. 176. 1845. Leptotrichum vaginans Schimp. Syn. ed. 2. 140. 1876. Trichostomum nodulosum Aust. Bull. Torrey Club 6: 73. 1876.
Plants gregarious, 1-2 cm. high; stems erect, simple or branching by slender innovations 1-1.5 cm. long: leaves erect, appressed, particularly on the branches, lanceolate, blunt or cucullate; margins entire or serrulate, plane or very slightly revolute; costa stout, ending below the apex in the lower leaves, excurrent in the upper; perichaetial leaves sheathing, the apex subulate, or short-cuspidate, serrulate, the base broad, the cells linear, not hyaline nor quadrate. Dioicous: antheridia terminal in buds on slender plants: seta 1-3 cm. long, erect, twisted in two directions, rufous, slender: capsule erect, smooth, almost cylindric; lid short, blunt or conic-rostrate with a serrate edge, the cells straight; mouth small and bordered; annulus large, double, falling with the lid ; peristome deeply inserted; teeth divided unequally at the base into two slender, finely papillose, nodose segments, smooth when immature: spores 10-12 ;i in diameter, nearly smooth, maturing in the autumn.
Type locality: Lanca-ster. Pennsylvania.
Distribution: On clay soil, roadside?, rarely on rocks; Prince Edward Island; New Hampshire and Vermont to North Carolina and Missouri; also in Europe.

Ditrichum lineare là một loài rêu trong họ Ditrichaceae. Loài này được Sw. Lindb. mô tả khoa học đầu tiên năm 1871.