Geranium pusillum L. (Geraniaceae): a newly naturalized plant in Taiwan.

Geranium pusillum L., an annual or biennial herb mainly native to Europe, northern Africa, and western Asia, has recently become naturalized in mountain regions of central Taiwan at about 1,800-2,300 m in elevation. This species is very similar to G. molle, which was also recently found to have become naturalized in Taiwan; however, the former has smaller flowers and scabrous fruits. In the present work, we provide a taxonomic description, an illustration, photographs, and scanning electron micrographs to facilitate identification. Furthermore, a key to the taxa of the genus Geranium in Taiwan is also provided.