The ancestors of land plants evolved in water. An algal scum formed on the land , but it was not until the Ordovician, around , that the first land plants appeared, with a level of organisation like that of bryophytes. However, fossils of organisms with a flattened thallus in Precambrian rocks suggest that multicellular freshwater eukaryotes existed over 1000 million years ago.

Primitive land plants began to diversify in the late