Montana Field Guide

Plants: Acrocarpous (Vitt 1988), growing in open clumps of erect shoots. Stems unbranched (Crum and Anderson et al. 1981), reddish to russet, mostly 2-3 cm tall, rarely to 6 cm (FNA 2014), possessing a central strand (Lawton 1971); macronemata mostly below (FNA 2014).

Leaves: Moderate to deep green, twisted, bent or curved when dry (FNA 2014), spreading when wet, 1-1.5 mm in width (Lawton 1971), 2-4 mm in length, seldom reaching 5 mm, the upper leaves much larger (FNA 2014) and more crowded than those below (Crum and Anderson et al. 1981), elliptic, sometimes with ovate tendencies, to ovate with the leaf edges occasionally running somewhat parallel, seldom slender, ending in an acute or seldom obtuse to curved leaf tip, sometimes forming an acumen, but rarely developing an apiculus or cusp; base extending well-down the stem; margins flat, russet, dentate in the distal half to sometimes a little further down the margin, the teeth varying in size and sharpness, mostly in pairs; costa nearly reaching to extending beyond the leaf tip, seldom with several, dull teeth on the upper part of the dorsal surface (FNA 2014).

Leaf Cells: Margins mostly of 2 cell-layers, seldom more, the cells long and narrow in 2 to seldom 4 rows (FNA 2014), forming a border, the marginal teeth of 1 cell (Lawton 1971); medial cells of the lamina about as wide as long or slightly elongated, a little larger toward the center than near the margins, obliquely- or longitudinally-rowed (FNA 2014), with wall-angles thickened (Lawton 1971).

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

M. marginatum occasionally has leaves as slender as those of the similar M. lycopodioides, making the two species difficult to distinguish, particularly when sterile. M. lycopodioides has a shorter beak on the calyptra and is dioicous; M. marginatum is seldom dioicous (FNA 2014).

Damp soil and humus in forests and near watercourses (Lawton 1971), protected bluffs (FNA 2014), and seldom decomposing wood (Crum and Anderson et al. 1981), frequently inhabiting calcareous areas. Occurring from lowlands to about 9840 feet (Lawton 1971).

Archegonia and antheridia mostly mingling in the same cluster, seldom dioicous. Seta solitary (FNA 2014), 20-30 mm tall (Lawton 1971). Capsule sometimes reaching 4 mm in length, ochre (FNA 2014), with a short neck; stomata sunken with guard cells visible (Lawton 1971), occurring in the neck (Crum and Anderson et al. 1981); exostome russet or sometimes more yellow (FNA 2014), papillose; endostome segments with wide perforations on the keel and groups of 2-3 knobby cilia. Calyptra draping like a hood (Lawton 1971).