Ulothrix and Spirogyra belong to the class Chlorophyceae, commonly called green algae. Ulothrix, found in freshwater and marine water, is generally found attached to the bed of water bodies. The cells are very long and broad and favour low temperature for growth. They attach themselves to the bed by a modified holdfast cell. Spirogyra on the other hand a free-living and form mass floating on surface of water bodies. They are generally found in freshwater region and named so due to their spiral form of chloroplast.
Both these groups of organisms from filaments of chain of cells and are unbranched. Both show vegetative reproduction by fragmentation.