Montana Field Guide

Plants: Pleurocarpous (Vitt 1988). Growing in uncrowded clumps or interwoven into mats (Lawton 1971), pink to brown or yellow (FNA 2014) or deep green distally, reddish-brown proximally. Stems 8-20 cm, frequently pinnately and abundantly branched (Lawton 1971); terminal cell of axillary hair long and quadrangular to short and very narrow; possessing a central strand and without a hyalodermis; exterior pseudoparaphyllia wide (FNA 2014).

Leaves: Stem leaves dense and overlapping near the top of the stem, loosely spaced below, spreading ca 45 degrees or more, 1.8-4 mm in length, 1.4-2 mm in width (Lawton 1971), widely heart-shaped with ovate tendencies, not pleated longitudinally (FNA 2014), slightly cupped, a little curved or twisted when dry; apex widely angled or slightly rounded; margins smooth, flat or rolled up and inward (Lawton 1971), often hood-like around the leaf tip (Crum & Anderson et al. 1981); base widely extending down the stem (FNA 2014); costa percurrent (Lawton 1971). Branch leaves egg-shaped and conspicuously more slender than the stem leaves (FNA 2014).

Leaf Cells: Alar cells long and quadrangular, swollen and fine-walled, transparent, the alar area deltoid and well-defined, extending from the leaf edges to the costa or close to it (FNA 2014); laminal cells fine-walled, occasionally porose near the bottom of the leaf; median laminal cells longer and narrower than the apical cells; apical cells adjacent to costa occasionally transparent (Lawton 1971).

The branches are typically crowded, longer near the base and becoming shorter toward the apex, with branching all around the stem and leaves more or less spreading, thereby resembling tiny Spruce trees (FNA 2014).

Calliergon cordifolium leaves are similar to the branch leaves of C. giganteum and the two species may be confused when C. giganteum plants do not develop the distinctive Spruce-like form. However, the alar region’s boundary in C. cordifolium is gradually transitioned rather than well-defined, and C. cordifolium plants are never light pink. C. cordifolium also grows in habitats higher in nutrients and slightly lower in mineral content than C. giganteum (FNA 2014).

Mineral-rich wetlands and shallow water (Elliott 2016), underwater, drifting on lakes (FNA 2014), emergent (Vitt 1988), lake shores. Elevation to ca 9840 feet (Lawton 1971).

Dioicous (FNA 2014). Seta brown with orange tones (Crum & Anderson et al. 1981), 7-8 cm tall. Theca 3-3.5 mm in length (Lawton 1971), level to greatly inclined, long and bowed, the neck narrowing (Crum & Anderson et al. 1981); exostome with an external network of lines below and toothed above (FNA 2014); cilia of the endostome knobby (Crum & Anderson et al. 1981).