Spirogyra is commonest green alga and is found in bright green free-floating mosses in the still water of freshwater ponds, pools, lakes and ditches and also in slow flowing streams called Nadees. The united protoplasmic moss of the two gametes is called a zygospore. Zygospores are liberated by the destruction or decay of cell walls of the female cells. Prior to germination the diploid zygospore nucleus undergoes meiosis. It comprises of two successive divisions. Ist is reduction division and IInd mitotic. At the end of meiosis the zygospore protoplast contains 4 haploid nuclei, of these three are non-functional and one is functional, which germinate to give rise to a single filament.