Dicranum polysetum
Dicranum muehlenbeckii
dicranum moss, wavy broom moss, wavy-leaf heron's-bill moss, wavy-leaf moss
muehlenbeck's dicranum moss
4–15 cm, densely tomentose with whitish or reddish rhizoids.
3–7 cm, densely 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, strongly cirrate to crisped when dry, smooth, (4–)5–6.5(–8) × 0.5–1 mm, concave below, tubulose above, lanceolate, acute;
margins entire below, slightly serrate to entire above;
laminae 1-stratose;
costa excurrent, 1/6–1/4 the width of the leaves at base, smooth or weakly toothed above on abaxial surface, abaxial ridges absent, with a row of guide cells, two stereid bands extending to the apex, adaxial and abaxial epidermal layers of cells differentiated;
cell walls between lamina cells slightly bulging;
leaf cells smooth to slightly rough above on abaxial surface;
alar cells 2-stratose, differentiated, sometimes extending to costa;
proximal laminal cells rectangular, pitted, (19–)37–55(–73) × (5–)9–12(–14) µm;
distal laminal cells short, irregularly quadrate-rectangular, not pitted, (7–)11–12(–23) × (6–)8–9(–13) 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.
1.3–3 cm, solitary, yellowish to yellowish brown.
2–3.5 mm, arcuate, inclined to horizontal, furrowed when dry, yellowish brown or reddish brown;
operculum 2–4 mm.
2–4 mm, long-cylindric, arcuate and inclined to ± straight and nearly erect, smooth, striate when dry, yellowish brown;
operculum 1.5–2.5 mm.
12–24 µm.
14–24 µm.
Dicranum polysetum
Dicranum muehlenbeckii
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 muehlenbeckii is a somewhat rare species throughout North America, where it is often misidentified as other species of the genus. There should be no reason for its misidentification if its important characters are utilized for recognition. Smooth, erect-spreading leaves, cirrate to crisped when dry and tubulose above, smooth leaf cells, 1-stratose laminae, and cross section of the costa showing the abaxial and adaxial rows of cells differentiated, all combine to make the gametophytes different from all other North American species of the genus. Sporophytes are rarely produced but the 2–4 mm, solitary, long-cylindric, slightly strumose capsules, which are suberect to slightly arcuate and weakly striate when dry, are distinctive.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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