Mainly temperate and subarctic.

Plants mainly trailing on ground. Roots emerging from point of origin on underside of main stems. Horizontal stems on substrate surface or subterranean, long-creeping. Upright shoots scattered along horizontal stem, 5-16 mm diam., round or flat in cross section, unbranched or with 1-4 lateral branchlets. Leaves not imbricate, linear to linear-lanceolate; leaves on horizontal stems scattered, appressed, membranous; leaves on lateral branchlets mostly 6-ranked or more, monomorphic with few exceptions, appressed, ascending to spreading, margins entire to dentate. Gemmiferous branchlets and gemmae absent. Strobili single and sessile or multiple and pedunculate, apex blunt to acute; peduncle, when present, conspicuously leafy; sporophylls extremely reduced, much shorter than peduncle or stem leaves. Sporangia reniform. Spores reticulate, sides at equator convex, angles acute. Gametophytes nonphotosynthetic, mycorrhizal, subterranean, flat and irregularly button-shaped, with ring meristem around circumference. x = 34.
(Flora of North America)