4. Plagiomnium drummondii (Bruch & Schimper) T. J. Koponen, Ann. Bot. Fenn. 5: 146. 1968.
Mnium drummondii Bruch & Schimper, London J. Bot. 2: 669. 1843 (as drummondi)
Erect stems 1-4 cm, not dendroid; sterile stems to 7 cm. Leaves light green or yellow-green, moderately contorted when dry, flat when moist, obovate or sometimes elliptic, 2-6 mm; base long-decurrent; margins toothed from about mid leaf to apex, sometimes to just below mid leaf, teeth sharp, of 1-2(-3) cells; apex acuminate or acute, occasionally obtuse or rounded, short- to long-cuspidate, cusp toothed; costa percurrent, excurrent, or rarely subpercurrent; medial laminal cells ± isodiametric or short-elongate, 30-50(-60) µm, much smaller near margins, often less than 1/2 size, in longitudinal, not diagonal rows, not or weakly collenchymatous, walls not pitted; marginal cells linear, in 2-4 rows. Sexual condition synoicous. Seta 1-3(-4), yellow to reddish brown, 1.2-3 cm. Capsule horizontal to pendent, ovoid or obovoid, 2-3 mm, neck not distinct; operculum conic-apiculate. Spores 18-25µm.
Capsules mature late spring. Humus, soil, logs, rock, stumps or tree bases in fire-dependent forests/woodlands, mesic hardwood forests, swamps, wet forests; low elevations; Alta., B.C., Man., N.B., N.W.T., N.S., Ont., Que., Sask.; Idaho, Md., Mich., Minn., Mont., Nebr., N.Y., N.C., Ohio, Pa., Wash., W.Va.; Europe; Asia.
See discussion for this species under 3. Plagiomnium cuspidatum.