STRUCTURE OF SPORES IN RELATION TO FERN PHYLOGENY' \VARREN H. WAGNER, Jn.2 Only in the past quarter of a century have the spores of ferns been used extensively in elucidating systematic relationships. Surprisingly, F. O. Bower (1923-28) made but little use of spores. In his volume I, "Criteria of Com-parison," there was no chapter on spores per se, and he devoted only a few pages to the subject (pp. 258-272). The trend toward utilizing spore structure was illustrated by Copeland (1947) who used them in characterizing the taxa in Genera Filicum. Since then there has been a veritable explosion in the interest in fern spores. The advent of more critical optical equipment, especially the scanning electron microscope, has provided a strong boost to palynological studies in general, especially at the level of species, varieties, and hybrids. For the investigation of spores taken from dried plants on herbarium sheets, the technique of using gummed tape, as described by Martin and Drew (1969), has proved to be especially valuable. Fern spores have actually been objects of study for well over a century, but many of the earlier papers are overlooked or ignored. Of course some represent only minor contributions, but one of them, the important article by E. Hannig (1911), pioneered the research on the development of the perispore and on the systematic significance of this, somewhat controversial, structure. (Alston's later  application of data from the perispore to classification was long presaged by Hannig.) Arnong other notable early workers were Fischer (1892), Fischer von Waldheim (1864), and Tchistiakoff (1874), each of whom gave contributions to the knowledge of the morphology and development of fern spores. Studies of spores of ferns of given localities have been popular for many years. C. B. Weaver in 1895 made one of the earliest of such investigations, "A Comparative Study of the Spores of North American Ferns," in which he illustrated 59 species. In 1935, McVaugh made a similar study of ferns of northeastern United States. Reed's 1953 book on the species of Maryland and Delaware is notable for illustrating not only the plants but their spores as well. More recently, Oliver (1968) described the spores of ferns of Indiana, and Maloney (1961a, 19611)) those of Minnesota. In other parts of the world we have the works, for example, of Knox (1951)involving British ferns, Sladkov (1959a, 1959b, 1959c, 1961, 1968) on Russianferns, and Sorsa (1964) on Scandinavian ferns. Especially valuable for thegeneral systematist are the investigations of Selling in Hawaii (1944, 1946),Tschudy and Tschudy in Venezuela (1965), and in particular Harris's book 'This paper was written under National Science Foundation Grant GB-30918X, "TheEvolutionary Characters of Ferns." I wish to thank the many individuals who have contributedin varions ways to this study, especially my collaborator, Florence S. Wagner, iny student,Royce W. Hill, and my two assistants, Randall Stoddard and Janice G. Lacy. Mr. P. Dayanadanvery kindly assisted me in making the scanning electron micrographs. SDepartment of Botany, University of Michigan, Ann Arbor, Michigan 48104.ANN. MIss>URI BOT. GAIU. 61: 332-353. 1974.