Hydrocotyle, also called floating pennywort,[5] water pennywort,[6] Indian pennywort, dollar weed, marsh penny, thick-leaved pennywort and even white rot[7] is a genus of prostrate, perennial[8] aquatic or semi-aquatic plants formerly classified in the family Apiaceae, now in the family Araliaceae.[3]
Water pennyworts, Hydrocotyles, are very common.[clarification needed] They have long creeping stems that often form dense mats, often in and near ponds, lakes, rivers, and marshes,[6] and some species in coastal areas by the sea.[9][10]
The genus Hydrocotyle has between 75 and 100 species[12] that grow in tropical and temperate regions worldwide.[8] A few species have entered the world of cultivated ornamental aquatics.[13] A list of selected species:[1][2][3][12][14][15][16]
One fossil fruit of a Hydrocotyle sp. has been extracted from borehole samples of the Middle Miocene fresh water deposits in Nowy Sacz Basin, West Carpathians, Poland.[18]