<Li> Musci L . </Li> <Li> Muscineae Bisch . </Li> <P> Mosses are small flowerless plants that typically grow in dense green clumps or mats, often in damp or shady locations . The individual plants are usually composed of simple leaves that are generally only one cell thick, attached to a stem that may be branched or unbranched and has only a limited role in conducting water and nutrients . Although some species have conducting tissues, these are generally poorly developed and structurally different from similar tissue found in vascular plants . Mosses do not have seeds and after fertilisation develop sporophytes with unbranched stalks topped with single capsules containing spores . They are typically 0.2--10 cm (0.1--3.9 in) tall, though some species are much larger . Dawsonia, the tallest moss in the world, can grow to 50 cm (20 in) in height . </P> <P> Mosses are commonly confused with lichens, hornworts, and liverworts . Lichens may superficially look like mosses, and have common names that include the word "moss" (e.g., "reindeer moss" or "iceland moss"), but are not related to mosses . Mosses used to be grouped together with the hornworts and liverworts as "non-vascular" plants in the former division "bryophytes", all of them having the haploid gametophyte generation as the dominant phase of the life cycle . This contrasts with the pattern in all vascular plants (seed plants and pteridophytes), where the diploid sporophyte generation is dominant . </P>

Moss plants are small but ferns can grow as tall as small trees. explain why this is so