Montana Field Guide

Plants: Acrocarpous (Vitt 1988), growing in open, frequently wide-spreading tufts (Crum and Anderson et al. 1981) or mats (Lawton 1971), green with yellow tones to deep green (Crum and Anderson et al. 1981). Fertile stems upright (Lawton 1971) and mostly 10-20 mm tall (seldom 35 mm); infertile stems sometimes reaching 70 mm (FNA 2014), spreading, creeping or arching and with radiculose tips (Crum and Anderson et al. 1981); rhizoids abundant at the stem bottom (Lawton 1971).

Leaves: Smaller and more distant below, wavy (Crum and Anderson et al. 1981), twisted, bent or curved when dry, plane (FNA 2014) and upright to spreading about 45 degrees when damp (Crum and Anderson et al. 1981), 3-5 mm in length (FNA 2014), 1-2 mm in width (Lawton 1971), obovate, occasionally elliptic (FNA 2014), ovate, or nearly circular (Lawton 1971), narrowing to an acumen or acute leaf tip with a long and occasionally-toothed cusp; base extending well down the stem and widely so; margins flat, sharply dentate in about the distal half; costa reaching or exceeding the leaf tip (FNA 2014).

Leaf Cells: Marginal teeth 1- or sometimes 2-celled; cells at the leaf edge arranged in 1 layer, long and thin, usually in 2-4 rows; medial laminal cells with length similar or longer than width, the cells smaller near the margins, occurring sometimes in up-and-down rows, seldom in oblique rows, nonporose (FNA 2014), the cell walls and angles thickened (Crum and Anderson et al. 1981).

Fruit ripens in the last part of spring (FNA 2014).

Plagiomnium drummondii also has obovate leaves that are sharply dentate above, but it often has multiple setae, unlike P. cuspidatum (FNA 2014).

Plagiomnium rostratum and P. ellipticum also have teeth only in the upper part of their leaves; their teeth, however, are usually dull and not as large as those of P. cuspidatum (FNA 2014).

The variation of characters within and among populations of Plagiomnium makes identification difficult without fertile plants (FNA 2014).

Damp soil, humus, stone, rotting wood, fissures in bark; in wet woods and wooded peatlands with high-mineral content (FNA 2014). Occurring from low elevations to about 9840 feet (Lawton 1971).

Archegonia and antheridia associating in the same bract cluster. Perigonial and perichaetial leaves to 6 mm (Lawton 1971). Seta solitary, 20-30 mm tall, occasionally reddish. Capsule 2-3.5 mm in length, drooping, with an obscure neck (FNA 2014), yellow to ochre; stomata sunken with guard cells only partially hidden; exostome teeth yellow with green tones, papillose; endostome segments more brownish, the keel widely perforate, with knobby cilia (Lawton 1971).