Differential interference contrast (DIC) light micrograph of Encyonema sp. freshwater diatoms. Encyonema cells build tubes of polysaccharides in which the cells can move freely. The sheaths provide a certain protection against feeding for the single cells. The single cells contain wall-bound chloroplasts whose brown colour is caused by the dye fucoxanthin. Here most of the cells are seen in shell view, only at top left and bottom right can one cell each be seen in girdle view. Magnification: x600 at a print width of 10 centimetres.