Dicranum Moss

This species is easily recognized by its strongly undulate leaves and aggregated setae.

W. L. Peterson (1979) recorded Dicranum polysetum from Nunavut. It is one of the largest, most conspicuous, and most easily recognized species in the genus in North America. The species is immediately recognized by the large stems, 4-15 cm, with a dense mat of whitish or reddish tomentum, giving the stems a thickened appearance, by the shiny, strongly undulate, wide-spreading leaves with margins strongly toothed in the distal half and by the clustered sporophytes (3-6 per perichaetium). Microscopically, the species is readily distinguished by the elongate, abundantly pitted cells throughout the leaf and by the toothed ridges on the abaxial surface of the costa in the distal part of the leaf. Dicranum polysetum is one of the few species in North America that has no apparent intergradations with any other species of the genus. It is common in southeastern Canada, northeastern United States, and the Canadian Rocky Mountains, where it extends south to Wyoming and Colorado, occurring in both states in a small number of localities. It is rare west of the Rockies, where it is known from only a few localities in northwestern Montana, southern Idaho and northeastern Washington and Oregon.

Plants medium-sized to large, 2–10(–15) cm high, green to yellowish green or golden brown, shiny, in dense tufts. Stems erect or ascending, often branched, densely tomentose nearly throughout. Leaves not much altered or somewhat flexuose when dry, erect-spreading or sometimes irregularly falcate-secund when moist, lanceolate, up to 10 mm long, gradually narrowed from an oblong base to a slender, keeled, usually undulate acumen, apex narrowly acute; margins plane, or slightly recurved on one side below the middle, serrate in the upper half; costa narrow, subpercurrent to percurrent, ridged or lamellate in 2 serruate rows at back above the middle; upper cells short-rectangular, ca. 50 µm × 9 µm, thick-walled, somewhat porose, sometimes mammillose at back; basal cells elongate, linear-rectangular, thick-walled, somewhat porose; alar cells quadrate or hexagonal, inflated, bistratose, thin-walled. Dioicous. Male plants dwarfed, located at lower part of the females. Setae straight, often aggregate, 2–5 per perichaetium, 2.5–4.0 cm long, yellowish, becoming reddish with age, twisted when dry; capsules cylindric, 3–4 mm long, strongly curved, inclined to horizontal, asymmetric, furrowed when dry and empty, not strumose; opercula long-rostrate, 2.5–4.0 mm long; annuli none; stomata present; peristome teeth lanceolate, ca. 0.6 mm long, unequally divided to the middle, brownish or reddish brown, papillose above, vertically striolate below. Spores 19–26 µm in diameter, minutely papillose.

Plants in loose tufts, light green, glossy. Stems 4-15 cm, densely tomentose with whitish or red-dish rhizoids. Leaves erect to spreading, ± flexuose, little changed when dry, strongly undulate, (5.5-)7-9.5(-10.5) × 1-2 mm, lanceolate, concave proximally, keeled above, acute; margins strongly toothed in the distal half; laminae 1-stratose; costa ending before apex, occupying ca. ¹/16-¹/8 of leaf base, strong, with two toothed ridges distally on abaxial surface, with one row of guide cells, two stereid bands, adaxial epidermal layer of cells not differentiated, abaxial layer with a few cells enlarged; cell walls between lamina cells not bulging; leaf cells smooth; alar cells 2-stratose, well-differentiated, not extending to costa; proximal laminal cells elongate, pitted, (45-)78-129(-156) × (5-)9-10(-14) µm; distal laminal cells shorter, sinuose, pitted, (42-)64-68(-115) × (4-)9-10(-13)µm. Sexual condition pseudomonoicous; dwarf male plants on stem rhizoids of female plants; interior perichaetial leaves abruptly long-acuminate, convolute-sheathing. Seta 1.5-4 cm, usually aggregate, 3-6 per perichaetium, brown or reddish brown. Capsule 2-3.5 mm, arcuate, inclined to horizontal, furrowed when dry, yellowish brown or reddish brown; operculum 2-4 mm. Spores 12-24 µm.

Distribution: China, Korea, Japan, Russia, Europe, North Ameica.

Habitat: on humic soil in bogs, rocks, or rotten wood.

Dicranum undulatum Ehrh. ex Web. & Mohr, Index Mus. Pl. Crypt. 2. 1803, hom. illeg.

Dicranum rugosum (Funck) Bridel