Lemnoideae (Araceae) are extremely reduced floating aquatic herbs. Subcosmopolite often found in lentic environments of tropical regions. In Brazil occurs 15 species. Based on field and herbarium work, this study unraveled the Lemnoideae subfamily in Rio de Janeiro state. Eleven species were recorded: Landoltia punctata occurs in restinga, rain forest, secondary vegetation and urban zone. Lemna aequinoctialis is widely distributed on the state, occur in restinga, rain forest, secondary vegetation and urban zone. Lemna minuta and Lemna valdiviana occurs in restinga and rain forest. Spirodela intermedia and Wolffia arrhiza occurs only in restinga. Wolffia brasiliensis occur in restinga and rain forests. Wolffia cylindracea was found in secondary vegetation. Wolffia globosa occurs in rain forest. Wolffiella neotropica and Wolffiella lingulata occur only in restinga. This study presents morphological descriptions, identification key, illustrations and other information on Lemnoideae species in Rio de Janeiro state. The fieldwork and specimen analysis revealed three new occurrences to the state and two for the country.
Southeast Brazilian Flora; Lemna; Lemnaceae; duckweed; new occurrence