Algae occur as surface crusts, as free living organisms in water bodies and in symbiotic association with fungi in lichens. Algae occurring in these forms have potential roles in physical improvement and protection of soils, in nitrogen fixation in paddy rice cultivation and arid agriculture, in primary biomass production and in secondary production for industrial uses. They also play useful roles in reclamation and purification of polluted waters. These potentials are discussed with special reference to Nigeria. It is argued that algae as plants may not be 'lost' to Nigeria but that their yet unexploited potentials need to be fully investigated.