Dicranum condensatum
Dicranum howellii
condensed dicranum moss
Howell's broom moss, Howell's dicranum moss
1–9 cm, densely tomentose below with reddish brown rhizoids.
2–8 cm, densely tomentose with white to reddish brown rhizoids.
erect-spreading, flexuose, ± curled at the tips when dry, slightly undulate or rugose, (2–)3.5–4.5(–7) × 0.5–1 mm, concave below, strongly keeled above, oblong-lanceolate, with a broad lanceolate base gradually narrowing to a short-acuminate apex;
margins serrulate in the distal half, involute in central part;
laminae 1-stratose, with a few 2-stratose regions;
costa percurrent to shortly excurrent, 1/10–1/5 the width of the leaves at base, strong, smooth or papillose to toothed above on abaxial surface, abaxial ridges absent, with a row of guide cells, two thick stereid bands extending well into the apex, adaxial epidermal layer of cells not differentiated, the abaxial layer differentiated;
cell walls between lamina cells strongly bulging;
leaf cells papillose above on abaxial surface, sometimes nearly smooth;
alar cells 2-stratose, differentiated, not extending to costa;
proximal laminal cells elongate, pitted, (25–)41–56(–112) × (5–)6–7(–10) µm, abruptly shorter towards the apex;
distal laminal cells quadrate, irregularly angled, rounded or rectangular, not or indistinctly pitted, cell walls unequally thickened, (5–)7–8(–20) × (5–)7–8(–12) µm. Sexual condition pseudomonoicous;
dwarf males on stem rhizoids of female plants;
interior perichaetial leaves abruptly short-acuminate, convolute-sheathing.
falcate-secund to straight and erect, sometimes slightly crisped, smooth, (5–)8–10(–12) × 0.8–1.5 mm, concave proximally, keeled or tubulose above, lanceolate, apex acute;
margins strongly serrate in the distal part, entire proximally;
laminae 1-stratose;
costa ending before apex to shortly excurrent, 1/12–1/5 the width of the leaves at base, with 2, rarely 4, toothed ridges on the abaxial surface extending from about the leaf middle nearly to the apex, rarely almost smooth, with a row of guide cells, two thin stereid bands, adaxial epidermal layer of cells not differentiated, the abaxial layer interrupted by several enlarged cells that form part of the abaxial ridge, not extending to the apices;
cell walls between lamina cells not bulging;
leaf cells smooth;
alar cells 2-stratose, well-differentiated, sometimes extending to costa;
proximal laminal cells linear-rectangular, pitted, (52–)65–105(–120) × (10–)12–18(–22) µm;
distal laminal cells shorter, sinuose, pitted, (42–)54–90(–108) µm × (10–)12–14(–16) µm. Sexual condition pseudomonoicous or dioicous;
dwarf males on rhizoids of female plants or male plants as large as females and growing intermixed or in ± separate tufts;
perichaetial leaves gradually acuminate, not or partially convolute-sheathing.
1–4 cm, solitary, rarely 2 per perichaetium, yellowish.
1.5–4 cm, solitary, sometimes 2 per perichaetium, yellow to reddish brown.
1.5–3 mm, arcuate, inclined to horizontal, furrowed when dry, slightly contracted below the mouth, yellowish brown;
operculum 1.5–2.5 mm.
2–3.8 mm, arcuate, inclined to horizontal, smooth to striate when dry, yellow to dark reddish brown;
operculum 2–3.8 mm.
19–26 µm.
18–26 µm.
Dicranum condensatum
Dicranum howellii
Dicranum condensatum is a common species recognized in the field by its occurrence on sandy soil, by its light green to yellowish brown, dull plants in compact, dense tufts, its erect-spreading, oblong-lanceolate leaves, narrowing to a short-acuminate apex, keeled above, somewhat undulate or rugose, curled at tips when dry, and its solitary setae with an arcuate, inclined to horizontal capsule. The papillose leaf cells with strongly bulging walls between the cells and the irregularly angled median and distal cells with nonpitted walls are distinctive microscopic characters. Dicranum spurium is the species most commonly confused with D. condensatum. Both species occur on sandy soil with their ranges overlapping. The former occurs farther northward, where it is found in Newfoundland, while the latter occurs farther to the south, where its range extends to the tip of Florida. Dicranum spurium has broader leaves, the broadest point near the middle rather than near the base like D. condensatum, and leaves that are tubulose above (most noticeable when wet) rather than keeled. Rarely, D. condensatum can be mistaken for 9. D. ontariense as discussed under that species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Dicranum howellii occurrs only in the northwestern part of North America. It is closely related to the common and nearly ubiquitous D. scoparium. The shape of the interior perichaetial leaves is the most reliable way to distinguish the two. Gradually acuminate perichaetial leaves that loosely surround the seta are characteristic of D. howellii. Dicranum scoparium has abruptly acuminate exterior perichaetial leaves, interior ones that are abruptly acuminateto blunt at the apex and are convolute-sheathing around the seta. The interior perichaetial leaves of D. howellii are also longer and narrower than those of the D. scoparium. Other less significant features of D. howellii are the consistently glossy, long leaves, mostly 8–10 mm, with long distal cells, averaging 54–90 µm, and the common occurrence of only two, rarely four, serrated ridges on the abaxial surface of the costae. Dicranum scoparium by comparison has glossy to sometimes dull leaves that are often shorter, mostly 5–8.5 mm, with shorter distal cells, averaging 27–43 µm, and the costae usually have four, rarely two, serrated ridges on the abaxial surface. The perichaetial leaves are undoubtedly the most important feature separating the two species, as well as being the easiest to observe. Eastern North American plants of D. scoparium all have the abruptly acuminate perichaetial leaves that are characteristic of the species, as do plants elsewhere in the world. The perichaetial leaf character was one reason D. howellii was believed to be a distinct species by F. Renauld and J. Cardot (1889, plate 12B) who first illustrated that character and this remains the most significant reason for maintaining it as a distinct species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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