Montana Field Guide

Plants: Pleurocarpous (Vitt 1988), growing in widely-spreading mats (Lawton 1971), not in clumps of erect shoots, light green with yellow to golden tones. Stems prostrate, pinnately and somewhat densely branched, 2-10 cm, somewhat yellow to light green; branches 2-15 mm in length; hyalodermis in attendance and central strand faint or wanting; pseudoparaphyllia leafy (FNA 2014); cortical stem cells big and with fine walls (Lawton 1971).

Stem Leaves: Curved in sickle-like fashion and strongly hooked to rolled nearly into a circle at the leaf apex and turned in one direction, 1.5-2.8 mm in length, to 0.6 mm in width, lance-shaped with ovate tendencies, slowly tapering to a slender acumen (FNA 2014), the base cupped (Lawton 1971), not extending down the stem; leaf edges flat, a little wavy below (FNA 2014), smooth or frequently finely saw-toothed distally (Lawton 1971); costa paired and short, faint; branch leaves akin to stem leaves (FNA 2014).

Leaf Cells: Laminal cells not papillose; medial laminal cells longer and narrower than the basal cells; basal laminal cells only slightly colored, the walls porose; alar cells a little swollen, somewhat transparent, with fine walls, the alar area somewhat distinct, with several cells in the far bottom corner by the margin (FNA 2014).

Fruit ripens in mid- to late-spring or early summer (FNA 2014).

The similar Hypnum lindbergii has leaves curved in sickle-like fashion (or only slightly so to straight) whereas the leaf apices of H. subimponens are coiled nearly into a circle or strongly hooked (FNA 2014).

Bottoms of trees, bluffs, perpendicular stone faces, and rotting wood. Occurring from lowlands to about 4920 feet elevation (FNA 2014).

Dioicous. Exterior perichaetial bracts bent back and downward; interior perichaetial bracts upright, faintly pleated or not, with a thin, smoothly-edged or somewhat dentate acumen. Seta 25-30 mm tall, russet, smooth. Capsule 3-5 mm in length, pale brown, upright or nearly so (FNA 2014), bowed close to the mouth (Lawton 1971); operculum cone-shaped or beaked; exostome teeth 16, with a zigzag line on the outer face, fine lines or ridges below, and papillae above; endostome processes 16, similar in height as the teeth, keeled, cilia not known to occur. Calyptra hairless and draping hood-like (FNA 2014).