The major difference between bryophytes and vascular plants is the lack of specialized structures to carry water and nutrients in bryophytes. This means that water and nutrients must be dispersed via diffusion to the tissues of bryophytes, which requires them to remain small. Bryophytes also vary in terms of their life stages and dominant forms from higher, vascular plants.
Bryophytes include mosses, liverworts and hornworts. All these groups require abundant water to live. Every plant alternates between what is known as a gametophyte stage, with only one set of chromosomes, and a sporophyte stage, with two matched sets of chromosomes. In higher plants such as ferns and angiosperms, the sporophyte is the large, leafy form. In bryophytes, this situation is reversed, with the gametophytes being the photosynthetic, more visible stage.
The most common type of bryophytes are the mosses. There are more than 15,000 known species of mosses. The life cycle of mosses begins when a sporophyte releases a spore. These spores are carried on air currents until they land in a suitable, moist location. The spore then sends out a network of tendrils across the surface. Multiple leafy gametophytes spring from these tendrils so that one spore can produce a whole patch of separate moss plants.