Hello, Eugen.This plant I bought in Japan. The man who sold me this plant is not spoken in English and did not know its Latin name. But there was written Hydrocotyle sp "south".
Nata
The pic in Cavan's link looks more like it than what I've seen for H. ranunculoides. And since the seller called it H. "South" I would think that would rule out H. ranun. as it is a North American species, althought it is found in Florida and Texas.