These are a type of plant characterized by their small size and lack specialized vessels for transporting food within the plant. Therefore, they must grow in a moist environment to survive. Food and water are transported within the plant by osmosis and diffusion.

The Life Cycle of Non-Vascular Plants

Non-vascular plants exhibit 'alternation of generations,' as do all terrestrial plants. Haploid gametes, in which each cell contains a fixed number of single chromosomes, give rise to diploid sporophytes, in which each cell contains a fixed number of paired chromosomes. The gametes release sperm and lay eggs, which fuse and hatch, developing into sporophytes. The sporophytes, in turn, produce spores that develop into gametes.

Non-vascular plants are gametophyte dominant, meaning that the most widespread and longest-lived plants are haploid gametes. Diploid sporophytes appear only occasionally and remain perfectly attached, dependent on gametes for nutrition. They produce haploid sporophytes (spore-producing structures) and a complex membrane that often aids in spore dispersal. Liverworts, mosses, and hornworts spend most of their life as gametes. Archegonia and antheridia are produced on these gametes. They are often found at the tips of shoots, in leaf axils, or hidden beneath the thalli. Some non-vascular plants develop complex structures that bear gametes, called gametangiophores. A flagellum surrounds the sperm, which then swims from the antheridia to the archegonia. Arthropods may assist in sperm transport. The fertilized egg then develops into a zygote, which in the archegonia develops into a sporophyte. Mature sporophytes do not branch but remain attached to the gametes. They consist of a stalk called a seta and a sheath surrounding a single sporophyte. Within this sporophyte, sporophytes are produced by meiosis. These spores are likely dispersed by the wind, and upon landing in a suitable environment, they can develop into new gametes. In this way, non-vascular plants spread through a floating mixture of sperm and spores, in a manner similar to seedless vascular plants (lycophytes) and ferns.