Imbribryum muehlenbeckii

Plants small to medium-sized, dark red to red-green, rarely entirely green. Stems 0.5–2(–3) cm, julaceous, without metallic sheen, older stem sometimes densely radiculose. Leaves rigid, imbricate, crowded, dark red to red-green, sometimes dark green, ovate, distinctly concave, 1–2(–3) mm; base not or weakly decurrent; margins revolute proximally, plane distally, entire to finely serrulate distally, limbidium absent; apex rounded to broadly acute, not cucullate; costa reddish, not reaching apex or rarely percurrent, awn absent; basal laminal cells occasionally pigmented, in 1 row; proximal cells abruptly quadrate, with scattered short-rectangular cells, 1–2:1; medial and distal cells hexagonal, (40–)50–70 × (16–)18–24 µm, (2–)3–4:1, walls firm, parallel to costa. Specialized asexual reproduction rare, by rhizoidal tubers, on rhizoids arising from leaf axils, orange-red to red-brown, 100–200 µm. Seta ± straight, red, red-brown, or purple. Capsule nutant, dark red-brown, short-pyriform, 2–3 mm, neck short. Spores 14–18 µm, papillose, yellow-brown.

Phenology: Capsules mature Jun–Aug (summer).
Habitat: Damp shaded siliceous rock, soil in rock crevices, montane
Elevation: moderate to high elevations (500-3000 m)

Greenland, B.C., Nfld. and Labr., Ont., Calif., Idaho, Maine, Mich., Mont., Nev., N.H., N.Mex., N.Y., Oreg., Pa., Tenn., Wash., Wyo., w Europe, Asia (Caucasus), Atlantic Islands (Madeira).

Discussion

Imbribryum muehlenbeckii is similar to small forms of I. alpinum, but has strongly concave, ovate leaves, short distal laminal cells, and a weak costa. Most material from western North America can be referred to an undescribed species; see discussion under 1. I. alpinum.

Selected References

None.

Lower Taxa