Dicranum condensatum
Dicranum bonjeanii
condensed dicranum moss
bonjean's dicranum moss, crisped heron's-bill moss
1–9 cm, densely tomentose below with reddish brown rhizoids.
2–8 cm, scarcely tomentose with whitish 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.
erect-spreading, sometimes nearly appressed, flexuose, little changed when dry, undulate or rugose, (3.5–)4–5.5(–6) × 1–1.5 mm, flat to ± concave proximally, subtubulose above, from a lanceolate base to a short, broadly acute apex, distal part of stem often with ovate, short-subulate, blunt leaves;
margins serrate in the distal half;
laminae 1-stratose;
costa ending just before the apex, sometimes with two poorly developed toothed ridges above on abaxial surface, 1/13–1/8 the width of the leaves at base, row of guide cells, two thin stereid bands, adaxial epidermal layer of cells not differentiated, the abaxial layer with a few (usually 2) cells differentiated in distal part of the leaves;
cell walls between lamina cells not bulging;
leaf cells smooth;
alar cells 2-stratose, well-differentiated, sometimes extending to costa;
proximal laminal cells long, sinuose, pitted, (28–)47–71(–113) × (5–)9–11(–14) µm;
distal laminal cells short-linear, sinuose, pitted, (25–)36–51(–73) × (5–)8–14(–20) µm. Sexual condition pseudomonoicous;
dwarf males on rhizoids of female plants;
interior perichaetial leaves abruptly long-acuminate, convolute-sheathing.
1–4 cm, solitary, rarely 2 per perichaetium, yellowish.
2.5–3.5 cm, solitary, rarely two per perichaetium, yellowish brown 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.
2.5–3 mm, arcuate, inclined to horizontal, striate when dry, yellow-brown;
operculum 1.7–3 mm.
19–26 µm.
14–28 µm.
Dicranum condensatum
Dicranum bonjeanii
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 bonjeanii was recorded from Maine by B. H. Allen (1998b). It is difficult to distinguish from the myriad forms of the polymorphic D. scoparium. Indeed, few of the many herbarium collections from North America named D. bonjeanii are actually that species or at least what is known as that species. It has been noted before (R. R. Ireland 1982) that it may be merely an enviromental form growing in a calcareous, often hydric habitat. Most Europeans (e.g., A. J. E. Smith 1978; E. Nyholm 1986+, fasc. 1) recognize the species as it occurs in Europe, and some that come to North America to collect (e.g., R. K. Tuomikoski et al. 1973) find the species to be distinct on this continent. However, H. A. Crum and L. E. Anderson (1981) and other North American bryologists have synonymized the species with D. scoparium. D. Briggs (1965), who cultivated and studied British plants of both D. bonjeanii and D. scoparium under controlled environmental conditions, found that while they show wide intraspecific variation, especially in regard to the leaf habit and undulation, and thought that they should be kept as separate taxa because each maintains a distinctive array of gametophytic characters. Also, both species are distinctive ecologically: D. bonjeanii prefers eutrophic fens, whereas D. scoparium usually grows in decidedly dry to mesic woodlands, on soil, humus, humus over rock, stumps and logs, tree bases, etc.
Dicranum bonjeanii is best known by its glossy, mostly erect, nearly straight, undulate leaves with broadly acute apices, weakly developed marginal teeth and, what is most important, two poorly developed ridges present only near the leaf apex on the abaxial surface of the costa. The two ridges on the costa, best seen in cross section, will distinguish the species most of the time from D. scoparium which usually has four ridges on its costae. Its preference for eutrophic fens and other calcareous habitats, while avoiding acid substrates, is important from an ecological standpoint and helps give a clue to the identity of the species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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