Montana Field Guide

Plants: Acrocarpous (Vitt 1988), in open tufts or solitary (Flowers 1973), commonly conspicuously rosulate, pale to deep green, becoming brown below with age (FNA 2007). Stems simple, seldom branched (Flowers 1973), 1-4 cm (FNA 2007), upright, possessing a central strand (Lawton 1971).

Leaves: Contorted when dry, spreading and flat to slightly concave when moist, lanceolate or tongue-shaped, frequently with rows of teeth, their bases fused, arising from diagonal ripples on the back of the leaf surface, 2.5-8.5 mm in length, 1-2 mm in width; apex acute or occasionally obtuse; margins often 2-layered, differentiated with 1 or 2 rows of long narrow cells, congested with erratically-spaced teeth distally to mid-leaf or below, mostly double-toothed, occasionally single- or rarely triple-toothed; costa ending at or a few cells shy of the apex, smooth or toothed on back side near apex, seldom extending below mid-leaf, bearing lamellae on front surface; lamellae 2-6, each usually 8-12(-14) cells high, occasionally fewer (2-5) (FNA 2007).

Leaf Cells: Lamina of 1 layer of cells (except for margins) (Lawton 1971); basal cells usually oblong and clear (Flowers 1973), median laminal cells 6-sided, occasionally oddly-angled or rounded, usually thin-walled, sometimes thickened at the corners (FNA 2007).

Capsules ripen March-September (FNA 2007).

Young plants lacking sex organs may be hard to tell apart from A. undulatum (Lawton 1971). The latter is the largest species of the genus and tends to have longer, narrower leaves than A. selwynii (Vitt 1988).

Bare soil on disturbed sites, often root masses of overturned trees (Elliott 2016), from exposed to shaded areas. Low to high elevations (FNA 2007).

Dioicous; male plants same size or larger than female plants, ovate or nearly round, frequently each plant with more than one bud (FNA 20007).

Seta 1-3(-8) arising from each perichaetium, 5 cm or less in height, upright or a little wavy. Capsule cylindric, a little rounded and slightly tilted, occasionally straight and upright; 2-7.5 mm in length, 0.5-1 mm in width (FNA 2007), the neck short; operculum a long slender beak, frequently almost as long as the urn (Flowers 1973).