Rhizomnium nudum
Rhizomnium
naked rhizomnium moss
rhizomnium moss
dark red or reddish brown when old;
micronemata absent.
red or reddish brown, becoming darker, sometimes black when old, usually erect, rarely sinuate at maturity or sterile stems sometimes arching, usually simple, not dendroid;
rhizoids brown, macronemata often matted proximally, mainly restricted to stem bases distally, not in longitudinal rows, micronemata present or absent.
green to dark green, weakly contorted when dry, broadly obovate, elliptic, or often ± orbicular, (3.8–)4–6(–9) mm;
margins green or sometimes pale reddish, 1–4-stratose;
apex rounded, occasionally retuse, rarely short-apiculate;
costa ending well before apex to 7/8 leaf length or rarely subpercurrent;
medial laminal cells elongate or short-elongate, (60–)70–130(–170) µm, rarely collenchymatous, walls with broad central pits;
marginal cells linear or short-linear, in (1–)2(–3) rows.
green, dark green, or occasionally reddish, reddish brown, or yellow-green, somewhat contorted when dry, erect-spreading and flat, sometimes undulate when moist, obovate, elliptic, or rarely ± orbicular, 1–7(–13) mm;
base narrowly short- to long-decurrent;
margins plane, green, reddish, or brown, rarely blackish with age, 1–4-stratose, entire;
apex usually rounded, occasionally retuse or emarginate, sometimes apiculate;
costa ending well below apex (to about 7/8 leaf length and often 2-fid distally), subpercurrent, or percurrent, distal abaxial surface smooth;
medial laminal cells elongate, sometimes short-elongate or ± isodiametric, 35–180 µm, sometimes in weakly developed diagonal rows, usually collenchymatous, walls pitted or not;
marginal cells differentiated, linear, rhomboidal, or rectangular, in (1–)2–3(–6) rows.
1–2.5 cm.
single, reddish brown, occasionally orange, often pale, 1–5 cm, straight to somewhat flexuose.
dioicous.
dioicous or synoicous.
ovate, 2.5–3.5 mm;
operculum conic-apiculate;
exostome yellow, lamellae 18+.
horizontal to pendent, yellow or yellowish brown, elliptic, ovate, subglobose, oblong, or cylindric, 1–4.5 mm;
operculum conic, conic-apiculate, or conic-rostrate;
exostome yellow or brown when mature;
endostome yellow or yellowish brown, segments free.
25–35 µm.
25–50 µm.
asexual reproduction absent (sometimes by green protonematous rhizoids in R. punctatum).
Rhizomnium nudum
Rhizomnium
Rhizomnium nudum is one of the most easily recognized species of the genus. The plants are characterized by the absence of micronemata, by their broad, weakly contorted, and nearly flat leaves when dry, and by having thin central laminal cell walls (broad pits), the bar bell appearance of the walls observed in leaf sections. The leaves are only weakly undulate when moist.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species 13 (8 in the flora).
The presence or absence of micronemata along mature stems is essential when separating species in Rhizomnium (micronemata are smaller, less branched and paler than macronemata, mainly restricted to leaf or branch bases distally). In most instances, micronemata are easy to observe, but growing stems often lack them, particularly in plants of R. magnifolium, so this character should be assessed using older stems, which are sometimes buried in the litter. Occasionally, patches of weakly developed plants of R. gracile have nearly naked stems requiring close inspection of a number of stems in order to observe the micronemata or micronemata initials. Five species of Rhizomnium are circumtemperate or circumboreal, one species is circumarctic, and two are endemic to the flora area.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Micronemata present on mature stems | → 2 |
1. Micronemata absent from mature stems | → 5 |
2. Plants (2-)3-8(-12) cm; leaves 4-9(-13) mm; medial laminal cells (50-)80-180(-210)µm; marginal cells linear; margins usually 2-stratose | → 3 |
2. Plants 1-6(-9) cm; leaves 1.5-6(-7) mm; medial laminal cells 35-90(-100) µm; marginal cells mainly rhomboidal or ± rectangular; margins 1-stratose | → 4 |
3. Medial laminal cells (50-)100-180(-210) µm, not or weakly collenchymatous; costae percurrent, rarely subpercurrent or ending well before apex; margins reddish, brown, rarely green, or blackish with age; apices bluntly apiculate. | R. appalachianum |
3. Medial laminal cells (55-)80-100(-130) µm, weakly collenchymatous; costae ending well before apex, subpercurrent, or percurrent; margins green or sometimes reddish; apices rarely weakly apiculate. | R. magnifolium |
4. Plants 1-3(-5) cm; leaves 1.5-3(-4) mm, obovate or orbicular; sexual condition dioicous. | R. gracile |
4. Plants (2-)3-6(-9) cm; leaves 3-6(-7) mm, broadly obovate, elliptic, or rarely orbicular; sexual condition synoicous. | R. pseudopunctatum |
5. Leaf margins 1-stratose; leaves (1-)1.8-2.4(-3.8) mm, usually reddish to reddish brown; arctic-alpine. | R. andrewsianum |
5. Leaf margins (1-)2-4-stratose; leaves (2-)3-6(-9) mm, light to dark green, occasionally reddish at margins; more temperate regions | → 6 |
6. Plants (1-)2-5 cm; leaves often ± orbicular; apices rarely short-apiculate; medial laminal cell walls with broad central pits. | R. nudum |
6. Plants 1-3(-5) cm; leaves obovate or elliptic; apices short-mucronate or apiculate; medial laminal cell walls lacking broad central pits | → 7 |
7. Leaves obovate or elliptic, (2.5-)4.5-6 mm; medial laminal cells short-elongate, sometimes elongate or ± isodiametric, (35-)45-60(-70) µm; setae (2-)3-5 cm; w North America. | R. glabrescens |
7. Leaves broadly obovate or elliptic, (2-)3-5(-7) mm; medial laminal cells short-elongate or elongate, (50-)65-100(-120) µm; setae 1.5-3.5 cm; widespread. | R. punctatum |
BC
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WildflowerSearch
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USDA Plants Database
