Longleaf Paraleucobryum Moss

Paraleucobryum longifolium is best distinguished by its 4-8 mm, whitish green to grayish green, glossy leaves that are falcate-secund, particularly at stem tips, slenderly subulate with margins usually serrulate in distal half. The costa has conspicuous fine striations or ridges, formed by small teeth when viewed at high magnifications, that are especially noticeable in the distal half even at low magnifications with a dissecting microscope. The capsules are common, 1.5-3 mm, erect, cylindric, straight, smooth, with a 1-2 mm long-rostrate operculum. This species and the next somewhat resemble a Dicranum because of the falcate-secund leaves. The species was reported from Alabama and Ohio by P. Müller and J.-P. Frahm (1987).

Paraleucobryum sauteri (Bruch & Schimper) Loeske has been considered a synonym by some bryologists (e.g., C. Barnes 1958; E. Lawton 1971). Gametophytically, it is distinguished by the costa (R. S. Williams 1913, as Dicranum sauteri Bruch & Schimper; P. Müller and J.-P. Frahm 1987) that is less than ¹/3 the width of the leaf base compared to the costa that is more than ¹/2 the width of the leaf base in P. longifolium, which also means more rows of laminal cells in P. sauteri than in P. longifolium. Müller and Frahm further distinguished P. sauteri by its leaf cross section which has large median cells compared to the smaller adaxial and abaxial layers of cells. Paraleucobryum longifolium, in contrast, according to them, has small median cells in comparison to the larger adaxial and abaxial layers of cells. They also found that the peristome teeth of P. longifolium are divided only to the middle and inserted at the mouth, whereas in P. sauteri the teeth are divided nearly to the base and inserted below the mouth of the capsule. Williams also used a peristome difference to distinguish the two taxa. He found that in P. sauteri the peristome teeth are punctate or nearly smooth on the exterior surface, whereas they are obliquely striate in P. longifolium. Müller and Frahm reported specimens of P. sauteri only for western North America through the Rocky Mountains from British Columbia to Colorado, South Dakota, Arizona and New Mexico. I have found the costa width in P. longifolium, however, to be quite variable in plants in eastern North America but some of the western North American plants do have a narrow costa that fits the description of P. sauteri. I also could not confirm the cross section difference between the two taxa in the few North American specimens that could be referred to P. sauteri. I have decided not to recognize P. sauteri for this flora because I believe that a detailed study of the P. longifolium-P. sauteri complex is necessary, especially in regard to the plants from the western part of the continent.

Plants medium-sized to large, up to 5(–8) cm high, green or yellowish green, with a grayish sheen when dry, in compact tufts. Stems erect or ascending, simple or branched, somewhat radiculose at base. Leaves 4–8 mm long, usually strongly falcate-secund, sometimes stiffly erect or fragile, linear-lanceolate, gradually narrowed to a subtubulose apex; margins plane below, slightly involute and serrulate above; costa broad, occupying ½ or more the leaf base width, filling nearly all of the subula, excurrent, 2–4 layers of thick-walled cells in transverse section, with the dorsal rows of green cells interspreading among the hyaline cells, forming longitudinal striations; laminal cells at the shoulder, elongate-rectangular to linear, sometimes porose; alar cells inflated, hyaline or brownish, usually extending close to the costa; asexual reproduction sometimes by means of fragile leaves. Setae straight, up to 1.5 cm long, reddish brown, twisted clockwise when dry; capsules erect, oblong-cylindric, 1–3 mm long, reddish brown to dark brown, irregularly furrowed when dry or empty; opercula long-rostrate, nearly as long as or slightly shorter than the urns; annuli none; stomata present; peristome teeth divided, ca. halfway down, reddish or brownish, usually perforate below, obliquely to vertically striolate to the apex. Spores 25–34 µm in diameter, finely papillose.

Plants whitish green to grayish green, sometimes yellowish, lighter in color at leaf bases. Stems 1-4(-7) cm. Leaves spreading, usually falcate-secund, 4-8 × 0.2-0.8 mm, margins usually serrulate in distal half; costa covering ¹/2-²/3 of leaf base, with longitudinal striations (ridges), appearing as rows of teeth at high magnifications, on abaxial surface, especially conspicuous in distal half, in cross section with adaxial hyalocysts, median chlorocysts and abaxial hyalocysts with scattered chlorocysts in some abaxial cells. Seta 8-20 mm. Capsule 1.5-3 mm; operculum 1-2 mm. Spores 22-35 µm.

Distribution: China, India, Japan, Russia, Europe, and North America.

Habitat: on rotten logs, tree bases or rocks, rarely on soil.

Dicranum longifolium Ehrhart ex Hedwig, Sp. Musc. Frond., 130. 1801; Campylopus canadensis Kindberg; D. serratum Kindberg