LOWER VASCULAR PLANT

formerly pteridophyte, also called vascular cryptogam, any of the spore-bearing vascular plants, including the ferns, club mosses, spike mosses, quillworts, horsetails, and whisk ferns. Once considered of the same evolutionary line, these plants were formerly placed in the single group Pteridophyta and were known as the ferns and fern allies. Although modern studies have shown that the plants are not in fact related, these terms are still used in discussion of the lower vascular plants. Vascular plants are those that possess a specialized conducting system for the transport of water, minerals, and food materials, as opposed to the more primitive bryophytesmosses and liverwortswhich lack such a system. They include both the seed plantsangiosperms and gymnosperms, the dominant plants on Earth todayand plants that reproduce by sporesthe ferns and other so-called lower vascular plants. The pteridophytes represent the oldest of land plants. In their early evolution (during the Devonian and Carboniferous periods, 408 to 286 million years ago), there were many forms that are now extinct. The sphenophytes, for example, were once a large and diverse group of herbs, shrubs, vines, and trees but are now limited to only 15 species of horsetails; the woody lycophytes (club mosses) are entirely gone, leaving only a faint trail in their reduced modern representatives. Much of the fossil fern foliage of the Carboniferous Period is of the uncharacteristic seed ferns, which are the probable antecedents of the flowering plants. Modern ferns represent an explosion of evolution in Cretaceous times (144 to 66.4 million years ago). The pteridophytes are not an economically important group. Though they are used locally by peoples around the world for medicines and food, their greatest value today is in horticulture (ferns). Their remains, however, provide the bulk of the world's coal beds, and their relatively simple structure and life cycle make them extremely valuable to researchers in understanding the overall picture of plant structure and evolution. A discussion of all types of plants is found in the article plant. For a discussion of the other types of vascular plants, see gymnosperm and angiosperm. For a discussion of the nonvascular plants, see bryophyte. Additional reading F.O. Bower, The Ferns (Filicales): Treated Comparatively with a View to Their Natural Classification, vol. 1, Analytical Examination of the Criteria of Comparison, vol. 2, The Eusporangiatae and Other Relatively Primitive Ferns, and vol. 3, The Leptosporangiate Ferns (192328), is a classic work of comparative morphology and systematics that emphasizes the need, now being realized, for a broad spectrum of comparative data. A comprehensive summary of paleobotanical knowledge is provided in Thomas N. Taylor, Paleobotany: An Introduction to Fossil Plant Biology (1981). The American Fern Society and the British Pteridological Society assemble the record of current research in the field in their publications American Fern Journal (quarterly), Fiddlehead Forum (bimonthly), The Fern Gazette (annual), and Pteridologist (annual).The abundance and diversity of pteridophytes are the focus of Hermann Christ, Die Geographie der Farne (1910), still an important broad treatment of fern distribution; John T. Mickel, How to Know the Ferns and Fern Allies (1979), the first manual to cover all of North America, with keys, brief descriptions, and illustrations; Rolla M. Tryon and Alice F. Tryon, Ferns and Allied Plants (1982), a good summary of the genera of tropical American pteridophytes with descriptions, maps, discussions, and many illustrations; John T. Mickel and Joseph M. Beitel, Pteridophyte Flora of Oaxaca, Mexico (1988), the best illustrated and most comprehensive pteridophyte manual for Latin America; and R.E. Holttum, A Revised Flora of Malaya: An Illustrated Systematic Account of the Malayan Flora, Including Commonly Cultivated Plants, vol. 2, Ferns of Malaya (1954), a well-illustrated enumeration and description of ferns that presents many of the author's ideas of systematic relationship.Life cycle and habitats are discussed in A.F. Dyer, The Experimental Biology of Ferns (1979), a series of essays on ecology, cytogenetics, reproduction, chemistry, and development; A.F. Dyer and Christopher N. Page (eds.), Biology of Pteridophytes (1985), a collection of symposium papers on a broad range of topics; F. Gordon Foster, Ferns to Know and Grow, 3rd rev. ed. (1984), a well-known book of horticulture with many helpful tips on cultivation; Barbara Joe Hoshizaki, Fern Growers Manual (1975), a good introduction to horticulture with encyclopaedic information on the species in cultivation; and Christopher N. Page, Ferns: Their Habitats in the British and Irish Landscape (1988), with excellent illustrations of habitats and ecology.Studies of form and function include K.R. Sporne, The Morphology of Pteridophytes: The Structure of Ferns and Allied Plants, 4th ed. (1975), a concise summary of ideas on fern structure; B.K. Nayar and S. Kaur, Gametophytes of Homosporous Ferns, The Botanical Review 37:295396 (1971), a thorough summation of the knowledge of the haploid generation of ferns, with an extensive bibliography; John T. Mickel, The Home Gardener's Book of Ferns (1979), a useful compilation of information on fern morphology, diversity, and cultivation; and Lenore W. May, The Economic Uses and Associated Folklore of Ferns and Fern Allies, The Botanical Review 44:491528 (1978), a summary of the diverse uses to which ferns have been put.For the origin and evolution of ferns and fern allies, see I. Manton, Problems of Cytology and Evolution in the Pteridophyta (1950), a milestone in the biology of ferns containing, for the first time, accurate data on chromosomes in relation to evolution and systematics; Richard A. White (ed.), Taxonomic and Morphological Relationships of the Psilotaceae: A Symposium, Brittonia 29:168 (1977), a series of papers on structure, relationships, and fossil history; and J.D. Lovis, Evolutionary Patterns and Processes in Ferns, Advances in Botanical Research 4:229439 (1977), an outstanding summary of the knowledge of fern phylogeny and classification. Also see appropriate sections of Robert F. Scagel et al., An Evolutionary Survey of the Plant Kingdom (1965); Ernest M. Gifford and Adriance S. Foster, Morphology and Evolution of Vascular Plants, 3rd ed. (1989); and David W. Bierhorst, Morphology of Vascular Plants (1971), which provides detailed treatments of vascular plants together with theory and interpretation.Nomenclature for the taxonomy of pteridophytes is provided in Edwin Bingham Copeland, Genera Filicum: The Genera of Ferns (1947), a valuable treatment of the classification and characteristics of ferns, containing many of the author's original correlations. Other works on classification include R.L. Hauke, The Taxonomy of Equisetum: An Overview, New Botanist 1:8995 (1974); J.A. Crabbe, A.C. Jermy, and John T. Mickel, A New Generic Sequence for the Pteridophyte Herbarium, The Fern Gazette 11:141162 (1975), a list of pteridophyte genera in a phylogenetic sequence; and Benjamin llgaard, A Revised Classification of the Lycopodiaceae s. lat., Opera Botanica 92:153178 (1987), a clear, detailed discussion of the taxonomic characters, genera, and species groups of the family, and Index of the Lycopodiaceae (1989), a listing of all the names, references, and type (original) specimens. Warren H. Wagner, Jr. Ernest M. Gifford John T. Mickel