A floristic inventory of phanerogamic hydrophytes from the temporary swampy environments of coastal plains of northern of Rio de Janeiro State was made. The botanical vouchers were collected in 27 expeditions between September/1998 and July/2001. They were herborized and identified by the traditional methodology. The exsicatae were deposited in the UNIRIO herbarium (HUNI). One hundred and thirteen taxa, distributed among 40 families were found. The environment analyzed could be floristically characterized by the Cyperaceae, represented by 23 taxa (ca. 20%), followed by Fabaceae and Onagraceae (seven taxa), Poaceae (six taxa), Asteraceae and Scrophulariaceae (five taxa) and Apiaceae, Lentibulariaceae and Polygonaceae (four taxa). These environments have great phytophysionomic changes according to hydrogeology. Some species are annual, disappearing completely in the dry season; another species tolerates the dryness but the population reduce drastically, changing substantially the landscape. Some species regarded as strictly aquatic were found in humid soil, producing flowers. This shows the necessity to include amphibious species on the aquatic flora studies because sometimes the boundaries between the biological types were not well defined.
hydrophytes; floristics; temporary swamp; Rio de Janeiro; coastal plains
