Abstract: The study presents results of micromorphological studies of flood-plain ephemeral species of the Amur basin in their relation to specie’s ecology. The 7 species were examined: Coleanthus subtilis (Tratt.) Seidel (family Poaceae), Dichostylis micheliana (L.) Nees (family Cyperaceae), Gratiola japonica Miq., Limosella aquatica L., Lindernia procumbens (Krock.) Borb. (family Scrophulariaceae), Symphyllocarpus exilis Maxim. and Centipeda minima (L.) A. Br. et Aschers (family Asteraceae). All these species are mainly found at shoals throughout their habitat. A combination of typical hydromorphic and specific adaptive microscopic features is revealed. Adaptation of the species to the sandy and muddy habitats take place through histological transformations of the plant’s tissues. At the same time, narrow specialization of the species does not influence the typical organization of the plant organs and does not cause the simplification of their inner structure. The following microfeatures have adaptive significance: cortex suberization and epidermis cutinization; development of aerenchyma with schizogenic air cavities, separated by live intact parenchymal cells; sclerified solid stele. The examined species exhibit more terrestrial micromorphological features (sclerification, suberization and cutinization of tissues) than hydrophytic ones. It was suggested that specific shoal complex has been mostly formed by terrestrial species.