Dicranum fulvum
Dicranum fragilifolium
boulder broom moss, dicranum moss
fragile leaf dicranum moss
1.5–3.5 cm, sparsely tomentose with light- to reddish brown rhizoids.
1.5–6 cm, densely tomentose with dark brown to red rhizoids.
erect-spreading, some weakly falcate-secund, crisped when dry, smooth, (3–)4–5(–7) × 0.5–0.8 mm, some leaf tips broken off, concave below, subtubulose above, narrowly lanceolate to a long, narrow subula occupied mainly by the excurrent costa, apex acute;
margins serrate to serrulate in distal half;
laminae 1- or 2-stratose above, sometimes 2-stratose in patches;
costa excurrent, 1/4–1/3 the width of the leaves at base, abaxially toothed or papillose in distal half, abaxial ridges absent, with a row of guide cells, two stereid bands not extending above the leaf middle, adaxial and abaxial epidermal layers of cells somewhat differentiated or with a few cells enlarged in both layers, cell walls between lamina cells strongly bulging in distal part of leaf lamina;
leaf cells smooth or abaxially prorate above;
alar cells mostly 1-stratose or sometimes with a few 2-stratose cells, distinctly differentiated, often extending to costa;
proximal laminal cells elongate-rectangular, not pitted or with few pits, (19–)24–33(–42) × (4)5–6(9) µm;
distal laminal cells regularly quadrate to short-rectangular, not pitted, (5–)10–11(–16) × (4)5–6(9) µm. Sexual condition dioicous;
male plants as tall as female plants but usually more slender;
interior perichaetial leaves abruptly long-acuminate, convolute-sheathing.
straight, erect-spreading, rigid, appressed when dry, smooth, (5–)6–7(–7.5) × 0.4–0.6 mm, most of the leaf tips deciduous and absent, concave proximally, canaliculate distally, from a lanceolate base to a long subula formed by the excurrent costa, apex acute;
margins entire to somewhat serrulate above;
laminae 1-stratose or some 2-stratose regions near costa;
costa excurrent, 1/4–1/3 the width of the leaves at base, smooth or slightly rough above on abaxial surface, abaxial ridges absent, with a row of guide cells, two thin stereid bands (2–3 cells thick), adaxial and abaxial epidermal layers not differentiated or sometimes with a few cells in both layers enlarged;
cell walls between lamina cells slightly bulging;
leaf cells smooth;
alar cells 1-stratose, sometimes with some 2-stratose regions, well-differentiated, sometimes extending to costa;
proximal laminal cells elongate-rectangular, usually pitted or indistinctly pitted, (25–)39–55(–84) × (5–)7–8(–10) µm;
median laminal cells rectangular, not pitted, (11–)21–22(–37) × (4–)7–8(–10) µm;
distal laminal cells nearly elliptic, incrassate.
1–2 cm., solitary, brown or reddish brown.
1.5–2.5 cm, solitary, yellowish to brown.
dioicous;
male plants as tall as females, usually more slender;
interior perichaetial leaves abruptly long-acuminate, convolute-sheathing.
1.5–3 mm, straight and erect, smooth, slightly furrowed when dry, reddish brown;
operculum 1.5–2 mm.
1.8–2 mm, arcuate to nearly straight, ± erect, smooth, sometimes striate when dry, yellowish brown;
operculum 1–2 mm.
14–28 µm.
16–28 µm.
Dicranum fulvum
Dicranum fragilifolium
Dicranum fulvum has dull, blackish green plants, especially evident from the leaves on the basal part of the stems, leaves crisped when dry, broad costae that cover 1/4–1/3 the width of the leaves at base, laminae that are mostly 2-stratose in the distal half of the leaf, and erect, cylindrical capsules that are slightly furrowed when dry. It is sometimes confused with D. fuscescens but that species has keeled leaves in the distal half, with 2-stratose regions restricted to the margins, and horizontal capsules, whereas D. fulvum has subtubulose leaves, with almost entirely 2-stratose laminae above, and erect capsules. When D. fulvum has some of its leaf apices broken off, which is not uncommon, it can be confused with D. viride, which has the majority of its leaf tips absent. The usual occurrence on rock of plants of D. fulvum as opposed to the usual occurrence on bases of tree trunks of D. viride often gives some clue to their identity. Morphologically, the proximal leaf cells of the two differ: D. fulvum has shorter cells, averaging 24–33 µm, compared to the longer cells of D. viride, averaging 33–42 µm.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Dicranum fragilifolium is a rare boreal species with shiny, light green to yellowish brown, erect-spreading leaves. The distal portion of the leaves is fragile and often broken off, thereby giving the plants a distinctive appearance. The deciduous leaf apices presumably serve as a type of asexual reproduction by regenerating to produce new plants. The species is often confused with D. tauricum, another species with deciduous leaf tips, but the latter occurs only in western North America. Where their ranges overlap they frequently are difficult to tell apart. When sporophytes are present the straight capsules of D. tauricum are distinctive from the usually arcuate ones of D. fragilifolium, which unfortunately rarely produces them. When sterile, the best way to separate the two is by the costa cross section in the proximal half of the leaf: D. fragilifolium has stereid cells in two thin bands while D. tauricum has none. Also, in D. fragilifolium there are 2–3 layers of cells above and below the guide cells, while in D. tauricum there are 1 or rarely 2 layers of cells. One other species with deciduous leaf tips that has sometimes been confused with D. fragilifolium is D. viride of eastern North America. It has a straight capsule like D. tauricum but as in D. fragilifolium capsules are rarely produced. The broad costa of D. viride, covering 1/3 or more of the leaf base, will distinguish it from D. fragilifolium, the costa of which covers 1/4 or less of the leaf base.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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