Distribution: Occurring on both sides of the Cascades in Washington; British Columbia to California, east to Idaho and western Montana.
Habitat: Ponds, backwaters, slow-moving streams.
Conservation Status: Not of concern
Floating aquatic perennials, green to yellow-green to dark red, with 2 growth stages and only fertile in mature stage; stems prostrate and 1-3 cm when immature, nearly erect and 3-5 cm at maturity when crowded, lacking hairs; roots 3-5 cm.
Leaves sessile, and alternate, overlapping, 0.6-2 mm broad, 2-lobed, with 1-celled hairs on adaxial surface of upper lobe; emersed lobe greenish to reddish with narrow colorless margin, immersed lobe slightly larger than emersed lobe and often lacking color.
Sporocarps in pairs at base of lateral branches, megasporocarps each containing 1 megasporangium that produces 1 spheric megaspore 0.2-0.6 mm with a warty surface and tangled filaments; microsporocarps globose, apex with a rounded protuberance, 10-27 micrometers in diameter, containing up to 130 microsporangia, microsporangia each containing 32 or 64 microspores 3 micrometers in diameter.