Dicranum polysetum
Dicranum elongatum
dicranum moss, wavy broom moss, wavy-leaf heron's-bill moss, wavy-leaf moss
dense heron's-bill moss, elongate dicranum moss
4–15 cm, densely tomentose with whitish or reddish rhizoids.
2–10 cm, tomentose throughout 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, erect-appressed to rarely spreading when dry, apex sometimes flexuose, smooth, (2.5–)3–4.5(–6) × 0.3–0.5 mm, from a lanceolate base to a long, fine, tubulose subula, apex usually acute, sometimes apical leaves of stems blunt, julaceous;
margins entire, rarely slightly denticulate at apex;
laminae 1-stratose;
costa percurrent or shortly excurrent, 1/6–1/4 the width of the leaves at base, smooth or weakly rough above on abaxial surface, abaxial ridges absent, with a row of guide cells, two stereid bands not extending to apex, adaxial and abaxial epidermal layers of cells usually not differentiated or sometimes a few cells in both layers enlarged;
cell walls between lamina cells slightly bulging;
leaf cells smooth;
alar cells 1-stratose or 2-stratose, well-differentiated, not extending to costa;
proximal laminal cells usually elongate, pitted, (14–)24–36(–49) × (2–)4–6(–9) µm;
distal laminal cells short-rectangular, quadrate, rounded, or sometimes irregularly shaped, incrassate, not pitted, (5–)12–17(–23) × (4–)6–8(–9) µm. Sexual condition dioicous;
male plants as large as females;
interior perichaetial leaves abruptly short-acuminate, convolute-sheathing.
1.5–4 cm, usually aggregate, 3–6 per perichaetium, brown or reddish brown.
1.5–2 cm., solitary, yellowish to yellowish brown or reddish yellow.
2–3.5 mm, arcuate, inclined to horizontal, furrowed when dry, yellowish brown or reddish brown;
operculum 2–4 mm.
1.2–1.8 mm, nearly straight and erect to slightly arcuate, striate when dry, yellowish brown;
operculum 1.2–1.8 mm.
12–24 µm.
17–22 µm.
Dicranum polysetum
Dicranum elongatum
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 elongatum is easy to recognize because the plants are relatively small, slender, glossy, and grow in dense, compact tufts. The leaves are short, narrow, usually less than 6 × 0.5 mm, ending in a long, fine, tubulose subula, acute at the apex, smooth or nearly so on the abaxial surface, and have entire margins or rarely some denticulations at the apex. Capsules, which are not uncommon on plants in some arctic localities, are short, less than 2 mm, straight and erect to slightly arcuate, smooth but striate when dry.
Dicranum elongatum can readily be confused with the closely related D. groenlandicum. They both are arctic-alpine species sharing nearly the same type of habitat with almost the same distribution. They can usually be readily distinguished in their typical form but there appear to be many intergradations that cause difficulty. Dicranum groenlandicum has narrowly obtuse leaf apices and cells that are pitted to well above the middle of the leaf in contrast to the acute leaf apices and cells that are pitted only up to the middle of the leaf in D. elongatum. E. Hegewald (1972) found that the pits in the leaf are the most reliable means of separating difficult specimens of Finnish plants. H. A. Crum and L. E. Anderson (1981) expressed doubt as to whether the two are genetically different. Both D. elongatum and D. groenlandicum often bear at the apex of some stems julaceous shoots with small, ovate, broad leaves with obtuse apices. This can lead to the misidentification of some plants of D. elongatum unless the leaves in the basal part of the stems are always used to determine the shape of the leaf apices.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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