Montana Field Guide

Plants: Pleurocarpous (Vitt 1988), growing in slender to thick mats, deep green to somewhat yellow, shiny or not. Stems usually creeping, seldom upright, to 5 cm, typically with leaves somewhat flattened into one plane or occasionally appressed and overlapping, giving the stem a catkin-like appearance; pseudoparaphyllia wanting (FNA 2014).

Leaves: Typically closely spaced and overlapping (Crum and Anderson et al. 1981), similar in wet and dry conditions, spreading, seldom noticeably turned to one side with tips directed toward the substratum, and not symmetrical, not pleated, cupped or not, 1.5-4 mm in length, to 2 mm in width, egg-shaped and somewhat oblong to lance-shaped with ovate tendencies, gradually narrowing to the acumen or acute leaf tip (seldom slightly obtuse), the tip seldom curving back and downward; base extending down the stem widely (FNA 2014), the decurrencies oval and occasionally bulging or ear-like (Crum and Anderson et al. 1981); leaf edges generally curved widely back and downward much of the leaf length (not quite to the apex) but occasionally flat, and finely saw-toothed at the very end of the apex or seldom smooth; costa paired with one branch occasionally about half as long as the leaf, or costa absent. Branch leaves akin to stem leaves (FNA 2014).

Leaf Cells: Cells of the lamina smooth; basal cells of the lamina with walls scarcely pitted, wider and not as long as the medial cells; medial and upper laminal cells linear or linear and very narrowly diamond-shaped, sometimes slightly bent, usually longer than the apical cells, containing a lot of chlorophyll; alar cells circular, oval, square, or oblong, arranged in 3 to 8 longitudinal rows and ending in a few of the more rounded cells near the bottom, or cells all quadrate to oblong and ending with only 1 cell at the bottom (FNA 2014).

Fruit ripens in summer (FNA 2014).

Particularly in its western range in North America, this variable species displays its less common characteristics: stems catkin-like in appearance with very cupped and symmetrical leaves with slightly obtuse leaf tips, and capsules upright or nearly so and practically straight.

P. denticulatum is generally larger than the similar Plagiothecium laetum. P. laetum has leaves from 0.7-2.6 mm in length rather than 1.5-4 mm, narrower medial cells, and decurrencies deltoid and consisting of oblong cells rather than decurrencies often oval in shape and usually containing some oval-shaped cells; also the capsules of P. laetum plants are smooth rather than ridged when dry (FNA 2014).

In the woods on tree bottoms, decaying wood, soil and humus on top of boulders and shelves of bluffs (FNA 2014), in wet areas such as at the edge of bogs amongst dense sedges, favoring somewhat acidic habitats (Crum and Anderson et al. 1981). Occurring from lowlands to about 8860 feet elevation (FNA 2014).

Autoicous, occasionally dioicous, typically producing sporophytes. Perigonia and perichaetia numerous at stem bottoms. Seta 15-35 mm tall, spiraled, smooth, pale brown or sometimes red. Capsule usually nodding, seldom upright or simply tilting, usually bowed, in a range of brown shades when well-developed, to 3.5 mm in length, usually finely ridged or creased when dry, seldom smooth (FNA 2014), conspicuously shrunken below the opening when dry, and the neck very creased (Lawton 1971); operculum to 1 mm (FNA 2014), not as long as the urn (Lawton 1971); exostome teeth with fine, transverse ridges below on the outer surface and papillae above; endostome processes keeled (FNA 2014); cilia grouped in 2s or 3s (Lawton 1971), knobby (Crum and Anderson et al. 1981). Calyptra draping hood-like, hairless, falling away easily (FNA 2014).

Specialized vegetative reproduction frequently occurring via 3- to 7-celled gemmae at the leaf junctures (FNA 2014).