The many species of organisms in the plant kingdom are divided into several phyla, or divisions, totaling about 260,000 species. The bryophytes are a diverse assemblage of three phyla of nonvascular plants, with about 16,000 species, that includes the mosses, liverworts, and hornworts. Bryophytes lack a well-developed vascular system for the internal conduction of water and nutrients and have been called nonvascular plants. The familiar leafy plant of bryophytes is the sexual, or gamete -producing, generation of the life cycle of these organisms. The other phyla are collectively termed vascular plants, or tracheophytes .
Vascular tissue is internal conducting tissue for the movement of water, minerals, and food.
Besides the presence of vascular tissue, tracheophytes contrast with bryophytes in that tracheophyte leafy plants are the asexual, or spore-producing, generation of their life cycle. This ability to evolve into larger and more diverse sporophytes, together with the ability of the vascular system to elevate water, freed tracheophytes from direct dependence on surface water. They were thus able to dominate all the terrestrial habitats of the Earth, except the higher Arctic zones, and to provide food and shelter for its diverse animal inhabitants. Page 1 of 5 See an outline for this article. How to cite this article Learn about Encarta's editorial process.