Micrasterias(mike-raz-tear-ee-ass) is a genus of unicellular algae in the family Desmidiaceae. The cells are flattened and disc-like. The cells of the genus Micrasterias are organized in two semi-cells that are mirror images of each other. The semicells have a distinctive shape with an intricate lobes and indentation. At the end of the lobes the cell wall may sometimes form notches or short spines. The nucleus is located in the centre between the semicells. Each semicell has a chloroplast with some pyrenoids. Usually found in oligotrophic, acid waters. This specimen of Micrasterias rotata collected in the Salzburger Land, Austria. Dark ground illumination.