Flora of North America species comparison

Platygyrium repens is one of the most ubiquitous pleurocarpous mosses in eastern North America. The species fruits infrequently in the northern reaches of its range and not at all in the southern portions. Brood branches are usually present and are rarely elongate and in such abundance that the plants dissolve into seemingly amorphous masses of slender branchlets. Although most specimens of P. repens can be identified easily, occasional sterile specimens lacking brood branchlets may defy certain identification. Homomallium adnatum sometimes has brood branchlets at its branch apices, and some sterile specimens may not be confidently distinguished from sterile specimens of P. repens. However, in H. adnatum the medial laminal cells are generally much shorter (rhombic or to 3–5:1) than those of P. repens, and foliose paraphyllia are sometimes present in the former but absent in P. repens. Erect branches bearing brood branchlets at their apices are also common in Leskeella nervosa, a more slender, dull, brownish, plant with narrow costate leaves, which co-occurs with P. repens in the northern reaches of its range.

(Discussion copyrighted by Flora of North America; reprinted with permission.)