In higher plants, germ cells form on the gametophyte, a haploid generation that develops from spores. In mosses (sphagnum, cuckoo flax), the gametophyte is represented by a leaf-stem plant, in ferns and seed plants, the gametophyte is poorly developed and short-lived. So, in ferns, a sprout grows out of a spore. The growth is not dissected into organs, has a rhizoid (primitive root hairs), later germ cells form on it. In bryophytes and ferns, sexual reproduction is closely related to water: only in the presence of water do spermatozoa advance to the ovum. In seed gametophytes, it is strongly reduced, for example, seed plants, have dioecious gametophytes, which develop from different spores. Microspores give rise to the male gametophyte, megaspores – to the female. In flowering plants, the male gametophyte is represented by pollen grains ripening in the anther of the stamen and are formed from microspores. When ripening in pollen grain, two cells are formed – generative and vegetative. The female gametophyte, developing from the megaspore, is an embryonic sac located inside the ovum. A number of divisions occur in it – as a result, six haploid cells are formed, including an egg and one double central nucleus.