part of the life cycle of a living thing, characterized by the cellular nuclei of the specimen containing a haploid (individual) set of chromosomes. In different organisms the haploid phase occurs at different stages in the life cycle. Most animals have greatly reduced haplophase, which is limited, practically speaking, to sexual cells. Many green algae go through their entire cycle, with the exception of the zygote, in haplophase. In flowering plants, haplophase is represented only by pollen grain growth with pollen tubes (male haplophase) and by seed sacs (female haplophase).