Dicranum polysetum
Dicranum acutifolium
dicranum moss, wavy broom moss, wavy-leaf heron's-bill moss, wavy-leaf moss
acuteleaf dicranum moss, sharp-leaf heron's-bill moss
4–15 cm, densely tomentose with whitish or reddish rhizoids.
1.5–7 cm, generally branched above, somewhat tomentose with reddish brown rhizoids.
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.
erect-spreading, slightly curled to ± straight when dry, usually with a few undulations in distal part, (3.5–)5–8(–10) mm × 0.5–1 mm, concave below, keeled above, sometimes margins ± involute, lanceolate, narrowly acute to acuminate;
margins serrulate to serrate above;
laminae 1-stratose or with few 2-stratose regions on or near the distal margins;
costa percurrent to shortly excurrent, 1/6–1/4 the width of the leaves at base, smooth to slightly papillose above on abaxial surface, abaxial ridges absent, with a row of guide cells, two stereid bands extending to the apex, adaxial epidermal layer of cells not differentiated, the abaxial layer differentiated;
cell walls between lamina cells not or slightly bulging;
leaf cells smooth to weakly papillose above on abaxial surface;
alar cells 2-stratose, differentiated, often extending to costa;
proximal laminal cells linear-rectangular, pitted, (22–)41–60(–90) × (5–)6–8(–12) µm;
distal laminal cells short-rectangular, irregularly angled or rounded, not pitted, (7–)12–20(–32) × (4–)8–9(–14) µm. Sexual condition pseudomonoicous;
dwarf males on stem rhizoids of female plants;
interior perichaetial leaves abruptly short-acuminate, convolute-sheathing.
1.5–4 cm, usually aggregate, 3–6 per perichaetium, brown or reddish brown.
1.2–2.5 cm, solitary, yellow to reddish yellow.
2–3.5 mm, arcuate, inclined to horizontal, furrowed when dry, yellowish brown or reddish brown;
operculum 2–4 mm.
2–2.7 mm, arcuate, inclined to horizontal, furrowed when dry, rarely slightly strumose, brown to reddish brown;
operculum 1.5–2.5 mm.
12–24 µm.
14–28 µm.
Dicranum polysetum
Dicranum acutifolium
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Dicranum acutifolium has been reported from Colorado by W. A. Weber (1973), but has been deleted from the flora (Weber, pers. comm.). It has also been reported from New Mexico, New York, and Wyoming by W. L. Peterson (1979). This arctic-alpine species is recognized by its erect-spreading leaves, slightly curled when dry, keeled and often weakly undulate above, lanceolate, narrowly acute to acuminate, by its percurrent to shortly excurrent costae, smooth to slightly papillose above, and by its leaf cross section that shows only the abaxial row of cells differentiated, a few 2-stratose marginal cells and the cell walls between lamina cells smooth to slightly bulging. Dicranum acutifolium has often been confused with D. fuscescens but the latter species has a longer, rougher subula that in leaf cross section in the distal half reveals very large and obvious papillae, compared to the smaller and less distinct ones in the former, and margins that are almost completely 2-stratose, while those of D. acutifolium are mostly 1-stratose. It has also been confused with 13. D. brevifolium and for distinctions see discussion thereunder.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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