A detailed study of the New Forest Ranunculus known as R. lutarius (Revel) Bouvet is furnished and comparison made with closely allied species. It is usually annual most frequently bearing flowers with three petals, three stamens and nine carpels. Found to be a stable taxon it is best regarded as var. terrestris of R. tripartitus from which species the foliar characters are the chief distinction. The suggested hybrid origin is shown to be, at least, doubtful.