Spirogyra is a free floating filamentous alga, occurring in still freshwater, say pool, ponds etc. Rarely, it grows on moist soil. The cells are uninucleate with 1-15 spiral chloroplast and many pyrenoids. The spiral band of chloroplast run in anticlockwise direction. All the chloroplasts in the cell may be loosely or tightly coiled and run spirally in parallel. The band shaped chloroplast is either narrow (having smooth margin) or broad (having serrated margin).