The non-vascular plants are members of three phyla, the mosses, liverworts, and hornworts. The three phyla are traditionally called bryophytes. In these plants the gametophyte is the dominant portion of the life cycle. The plants appear leafy but lack true stems, roots or leaves. Because they lack vascular tissue they are all limited in size, most are no larger than 20 cm tall. The lack of vascular tissue also means that they are generally found in moist habitats. Moist habitats are also needed to allow the flagellated sperm to swim to the egg. Although these 3 groups of plants are all non-vascular, they are not actually closely related.