CYCADOPHYTE

any member of a diverse collection of mostly extinct primitive gymnospermous plants. They probably had their origins among the progymnosperms of the Devonian period (408 to 360 million years ago), possibly among a primitive, long-extinct group of non-seed-bearing plants, the Aneurophytaceae, in which disposition of fertile structures and patterns of branching bear some resemblance to those of seed ferns. Although some botanists prefer to restrict the term cycadophyte to the members of the division Cycadophyta, three groups of primitive seed plants are discussed here, of which the seed ferns (division Pteridospermophyta) and cycadeoids (division Cycadeoidophyta) are represented only by extinct forms. A third group, the order Cycadophyta (cycads), is today represented by 10 or 11 living genera and some 130160 species. Additional reading A survey of cycadophytes is found in Harold C. Bold, Constantine J. Alexopoulos, and Theodore Delevoryas, Morphology of Plants and Fungi, 5th ed. (1987). Other works include Charles Joseph Chamberlain, The Living Cycads (1919, reprinted 1965), the best comprehensive work on the cycads; Cynthia Giddy, Cycads of South Africa, 2nd rev. ed. (1984), an excellent introduction to cycad morphology, noted for its beautiful colour illustrations of Encephalartos species in natural habitats; Divya Darshan Pant, Cycas and the Cycadales, 2nd ed. (1973), a fine presentation of all aspects of the life of Cycas and a valuable general reference to their anatomy and morphology; and Pl Greguss, Xylotomy of the Living Cycads, with a Description of Their Leaves and Epidermis, trans. from Hungarian (1968), which emphasizes the structure of cycad xylem and includes important information on the habits and leaf morphology of cycads.