Ricciocarpos natans
Marchantiophyta
Ricciocarpos natans (Ricciaceae)
Fringed heartwort
Floating Heart Thalloid Liverwort
Infrequent
Distinguishing Features
An occasional aquatic or semi-aquatic liverwort from stagnant waters, Ricciocarpos natans forms tight and large (1cm or larger) rosettes that are grooved and green above and black below. When lifted from the water or surface sediments, the dark underside is laden with long, black, root-like tangles, and the upper surface is marked by faint polygons. As the margin of a water body recedes, this species can live out its days on wet mud, often growing upwards of 2-3 cm wide.
Similar species
Unmistakeable while floating in open water, it is likely to cause a little confusion if found living on sediments or soils where water has stranded it. Riccia sorocarpa is furrowed, too, but lacks the black bottoms and polygonal patterning of the upper surface that is found in Ricciocarpos. Other thalloid liverworts found in similar habitats, such as Marchantia polymorpha and Conocephalum species have more clearly delimited polygons and lack the large black root-like structures on their undersides.
Habitat
Floating on the surface of nutrient- and mineral-rich water in marshes, ponds, ditches, lakeshores, and slow-moving streams, or stranded on shoreline mud, in the lowland, steppe, and montane zones; infrequent east of the Coast-Cascade Mts. and in sw BC.
Associated species
Riccia frostii, Riccia cavernosa, Physcomitrium patens, Ephemerum serrulatum