Water-clover ferns, Marsilea, in the Southeastern United States

Abstract

A surge in the collection of exotic Marsilea , M. mutica , M. minuta and M. hirsuta in the southeastern United States has prompted the need for updated identification aids. This study provides an annotated key to all water-clover ferns occurring in the region. It describes and illustrates recently documented exotic species and a previously misidentified western introduction. It details the rediscovery of M. ancylopoda , presumed extinct, and confirms its identification as the western species M. oligospora . Finally it clarifies the status and distribution of two additional western North American species introduced to the southeast, M. vestita and M. macropoda .