Montana Field Guide

Plants: Acrocarpous, growing in open tufts (Crum and Anderson et al. 1981) or mats (Lawton 1971), pale green or green with yellow tones (FNA 2014). Fertile stems upright (Lawton 1971), 10-40 mm tall, not tree-like (FNA 2014), with brown tomentum at the stem bottom (Lawton 1971); infertile stems sometimes reaching 70 mm (FNA 2014), spreading or arching, sometimes with radiculose tips (Crum and Anderson et al. 1981).

Leaves: Smaller and more distant below (Crum and Anderson et al. 1981), somewhat twisted, bent or curved when dry, plane (FNA 2014) and more-or-less upright to spreading about 45 degrees when damp (Crum and Anderson et al. 1981), 2-6 mm in length (FNA 2014), 1.5-2.5 mm in width (Lawton 1971), obovate or sometimes widest in the middle (FNA 2014) to ovate (Lawton 1971), narrowing to an acumen or acute leaf tip, or tip sometimes more widely-angled to curved, with a long-to-short, dentate cusp; base extending well down the stem; margins flat, sharply dentate from the apex to mid-leaf or to slightly lower; costa reaching or exceeding the leaf tip (FNA 2014).

Leaf Cells: Marginal teeth 1- to 2-celled, or seldom 3-celled; cells at the leaf edge arranged in 1 layer, long and thin, in 2-4 series; medial laminal cells with length about the same as or a little longer than the width (FNA 2014), the cells 6-sided (Lawton 1971) and smaller near the margins, occurring in up-and-down rows rather than obliquely-rowed, nonporose (FNA 2014), fine- to firmly-walled, the angles not thickened (Crum and Anderson et al. 1981).

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

The similar Plagiomnium cuspidatum also has obovate leaves that are sharply dentate above, but it never has multiple setae (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. drummondii (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, bark; in wet woods and swamps. Occurring at low altitudes (FNA 2014).

Archegonia and antheridia associating in the same bract cluster. Perigonial and perichaetial leaves to 6 mm (Lawton 1971). Seta 1 to multiple, rarely 4, per perichaetium, 12-30 mm tall (FNA 2014), ochre to brown (Lawton 1971), sometimes russet. Capsule 2-3 mm in length, drooping to level (FNA 2014), yellow to ochre (Lawton 1971), with an obscure neck (FNA 2014); stomata nearly to the surface with guard cells not at all hidden; exostome teeth yellow with green tones, papillose; endostome processes widely perforate with knobby cilia (Lawton 1971).