This study was performed in order to define some anatomical characteristics of Ammannia auriculata Willd. var. arenaria (Kunth) Koehne (Lythraceae) to ensure a proper identification of the species and prevent confusion with other plants. Roots, leaves and stems of the plants were fixed in Formalin-Aceto-Alcohol (FAA), stained with various dyes, examined under a microscope and their photos were taken. The microscopic investigations of the plant parts revealed that 1) the leaf anatomy showed partly mezophyte character, the stem and roots beared aquatic characters with a wide aeranchymatic cortex and 2) thick lignified secondary xylem tissue in the roots and stems were located outwards of the stele. The results were compared with those of similar studies.