Plants medium-sized, pale or whitish green to yellow-green. Stems sparsely and irregularly branched; hyalodermis absent, central strand present; outer pseudoparaphyllia broad, triangular to irregular; rhizoids or rhizoid initials at various points on leaves, or on scattered points or in rows on stem; axillary hairs , distal cells 1 or 2, hyaline. Stem leaves ovate or narrowly ovate, abruptly narrowed to apex, straight, concave, not plicate; narrowly decurrent; margins entire; apex rounded; costa single, 3/5-9/10 leaf length; alar cells differentiated, quadrate or short- to long-rectangular, inflated, hyaline, brownish with age, walls thin or somewhat incrassate, region distinctly delimited, ovate or broadly ovate; medial laminal cell walls incrassate or thin, porose or not. Sexual condition dioicous; inner perichaetial leaves not plicate; vaginula naked. Capsule with annulus not separating; exostome external surface reticulate basally, margins dentate distally. Spores 12-23 µm.

Species 1: nearly worldwide.

Straminergon was earlier included in Calliergon; the single species of Straminergon differs from those of Calliergon in its mostly pale green to pale stramineous shoots and markedly smaller and sparsely branched shoots. Furthermore, S. stramineum has much smaller and more sparse axillary hairs, and its alar regions are ovate to broadly ovate along the basal leaf margin.

Lower Taxon

• Straminergon stramineum (Dickson ex Bridel) Hedenas