Stonewort

Stoneworts, genus Chara, are large, multicellular green algae that grow rooted to the bottom of freshwater lakes and ponds, often encrusted with a rough coating of calcium carbonate that gives them a gritty texture and their common name. Molecular and structural evidence places stoneworts and their relatives among the closest living algal relatives of land plants, making them an important reference point for scientists studying how the ancestors of mosses, ferns and flowering plants first made the transition from water to land.