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There are three major groups of bryophytes: the liverworts, the mosses, and the hornworts. The life cycles of these plants, like those of all land plants, exhibit a regular alternation between two morphologically and physiologically distinct generations, the haploid gametophyte and the diploid sporophyte with double the haploid number of chromosomes. However, bryophytes differ from all other plants in three important ways:
1. The bryophyte gametophyte, rather than the sporophyte, is the larger, long-lived or dominant generation.
2. The bryophyte sporophyte, unlike that of other plants, does not become a free-living and independent plant; instead, it remains permanently attached to the gametophyte.
3. The bryophytes lack xylem and phloem, the specialized tissues used by all other plants for the transport of water and food materials (primarily sugar).
Raven, P.H., R.F. Evert and S.E. Eichhorn. 1992. Biology of Plants, 5th ed., Worth Publishers, Inc., New York. Note: Chapter 15, pp. 298-316.
For a more detailed treatment of the bryophytes see:
Schofield, W.B. 1985. Introduction to Bryology. Macmillan Publishing Co., New York.
Watson, E.V. 1964. The Structure and Life of the Bryophytes, Hutchinson & Co.
(Publishers) LTD, London.