Haplontic life cycle is common among filamentous algae, such as Oedogonium, Spirogyra, Ulothrix, etc.
Here the plant is haploid which produces the gametes. These gemetes fuse to form zygote which is diploid. The zygote or zygospore divides reductionally and produces the haploid plant again. In this case the haploid phase is very elaborate while the diploid phase is insignificant.