Violet crystalwort Riccia huebeneriana
A flat green liverwort.
Often shows violet or purplish tints (see image, right).
Nutrient-poor muds on the edges of ponds, lakes and reservoirs that are exposed when water levels fall. Trampling of mud by cattle seems to assist its growth.
Stabilisation of water levels for recreational or amenity purposes and water pollution by over-enrichment from farm fertilisers.