Montana Field Guide

Plants: Pleurocarpous (Vitt 1988). Growing in somewhat crowded mats, in shades of yellow to brown (FNA 2014), often shiny (Lawton 1971). Stems prostrate, to 8 cm in length, pinnate or erratically so; possessing a central strand. Branches straight or a little bowed, to 8 mm in length (FNA 2014).

Leaves: Stem leaves upright or spreading a little, overlapping slightly or a little more distantly spaced, 1.7-2.6 mm in length, 0.6-1 mm in width, lance-shaped, sometimes with ovate tendencies, narrowing to form a long acumen, somewhat cupped, pleated longitudinally, slightly curved (falcate), sometimes secund; margins finely saw-toothed (FNA 2014) to smooth, sometimes flat or curved back and down proximally (Lawton 1971); base slenderly extending down the stem slightly (FNA 2014) or not (Crum & Anderson et al. 1981); costa robust, extending to ca ¾ or a little less of the leaf length, with a dorsal spine above. Branch leaves smaller and more slender than the stem leaves (FNA 2014).

Leaf Cells: Stem leaves with alar cells nearly square or slightly lengthened, the walls somewhat thick, the alar area well-demarcated and small; basal cells similar in size or larger than the alar cells (FNA 2014), typically porose (Lawton 1971), in 1 or 2 series, not distinctly dissimilar to the laminal cells adjacent to and above them; laminal cells long and narrow (FNA 2014). Branch leaf cells with basal laminal cells swollen along the leaf bottom (FNA 2014).

The notable combination of features includes the pleated, curved and lance-shaped leaves with the fine saw-toothed edges, and the slender laminal cells extending nearly to the bottom margin of the leaf adjacent to the costa (FNA 2014).

Brachythecium acutum also has leaves that narrow gradually but are seldom falcate (or secund). Although infertile plants of B. campestre that are robust can be distinguished from B. salebrosum by characteristics of the supra-alar cell region, smaller infertile plants probably cannot (FNA 2014).

Open to shaded sites on stones, soil, also on decaying wood, tree bottoms (FNA 2014), and humus in coniferous forests (Elliott 2016), disturbed areas such as exposed hillocks in forests of hardwood or lawns (Crum & Anderson et al. 1981). Elevation: 3-4920 feet (FNA 2014).

Autoicous. Perichaetial leaves enveloping the stem somewhat, the apices spreading (Lawton 1971). Seta smooth, 1-2 cm tall, deep brown or brown with some orange tones (FNA 2014) to yellow (Crum & Anderson et al. 1981). Capsule 2 mm in length, deep brown, a little bowed and slightly stretched-looking (FNA 2014), level, the theca 1.8-2.4 mm in length; operculum tall and cone-shaped, ca 0.7 mm; cilia knobby, sometimes transversely ridged (Lawton 1971).