Riccia cavernosa
Distinguishing Features
Another ephemeral and rare species of fine, seasonally saturated mineral-rich soils, R. caverosa appears tiny (<<1cm) but tall thallus segments that are very tall relative to their length. In surface view, you should be able to make out the porous and bubbly surface texture. The body of the plant tends to ruputure dramatically into an amorphous mass akin to green caviar or algae, revealing the black spore-bearing capsules within.
Similar species
In its early growth stages, it could be mistaken for Riccia frostii, which can grow in the same habitat on the seasonally receeding margins of lakes, ponds and rivers. R. frostii, however, is not nearly as tall and tends to show hints of red colouration.
Habitat
Moist to wet mineral soil of seeps, shorelines and pond margins from low elevation to steppe and montane zones; infrequent in sw, sc and se BC, rare in ne BC [Peace River lowlands].
Associated species
Phascum cuspidatum, Riccia frostii, Ricciacarpos natans, Ephemerum serrulatum, Physcomitrella patens