Preface and Acknowledgments
Individuals who work with the vascular plants of Iowaresearchers, conservationists, teachers, agricultural specialists, horticulturists, gardeners, etc.-and those who are simply interested in knowing more about the state's plants have long felt a need for a comprehensive flora of Iowa. This annotated checklist is designed to be a first step toward such a flora. It consists of a summary of the natural and vegetational history of the vascular plants of Iowa, including a description of the state's natural regions, a discussion of the origins of the Iowa flora by Dean M. Roosa, and an annotated checklist of the vascular plants of the state by Lawrence J. Eilers. The data were collected by both authors with the assistance of many other field botanists.
Previous Work
A more complete discussion of the history of field botanizing in Iowa can be found in Eilers (1975). Examples of early Euro-American explorations into Iowa are the Lewis and Clark expedition of 1804-1805, the Long expedition of 1819, and the Nicollet expedition of 1839. These exploratory expeditions usually included one or more naturalists whose duties were to observe and record what they could of the biological and physical features of the regions they passed through. Eilers summarizes this early work:
Unfortunately, most of the records of Iowa plants in the reports of these travels were in the form of notes with indefinite localities, with the exception of a list of 11 plants from the Spirit Lake vicinity in the report of the Nicollet Expedition. (See Shimek [1915] for a more detailed account.) Although Zebulon Pike led an expedition up the Mississippi in 1805 (Pike, 1810), there are no specific references to Iowa plants in his report. Other botanists undoubtedly visited Iowa at an early time, e.g., Nuttall, Watson, and Gray, but, to my knowledge, they left no significant records of Iowa Plants.
The earliest significant record of Iowa vascular plants appears to be the listing of 205 species from Iowa by Dr. C. C. Parry (1852) as a part of the report ofD. D. Owens' geological survey of Wisconsin, Iowa, and Minnesota. The first effort toward a flora of Iowa was a partial checklist of vascular plants by Bessey (1871). Arthur published a catalogue of the phanerogamous plants in 1876 and a series of additions in 1877, 1878, 1882, and 1884. This was followed by an extensive series of papers on the vascular flora of Iowa by T. J. and M. F. L. Fitzpatrick beginning in 1897. Greene (1907) edited the only attempt at a flora of the entire plant kingdom native to Iowa. This was a joint effort by a number of prominent Iowa botanists, and included synoptic keys. Of the more than 3,000 species listed, 1,585 were vascular plants.
The last attempt to publish a comprehensive vascular flora of the state was the annotated list of Cratty (1933) based on the collections in the Iowa State University herbarium. He listed 1,608 species, 1,315 of which are native. Goodman (1939, 1942) and Hayden (1940, 1945) added 75 additional species in supplementary lists. The keys in Conard's useful Plants ofIowa (1951) were based on Cratty's flora, with the addition of a number of cultivated plants and the elimination of the rare species. (Eilers 1975: 59-60)
In addition, a number of local checklists, county floras, and small and large revisions of plant groups are found in the literature from the early part of the century (see Eilers 1975 for a summary of these works). Other important early naturalists were L. H. Pammel, B. Shimek, T. H. Macbride, and H. S. Conard.
Present Status
In 1947 Gilly wrote that "no adequate flora of the state of Iowa can be prepared in the near future." Since that time, numerous specimens have been collected and stored in Iowa herbaria, and many articles have been published about Iowa's vascular flora. Much credit must be given to R. F. Thorne, taxonomist at the University of Iowa during the 1950s and early 1960s, for restimulating floristic study in Iowa. Thorne was an avid student of the Iowa flora (Thorne 1953, 1954, 1955, 1956, 1964). Also, seven of his Ph.D. students completed most of the floristic work in Iowa indicated by the shaded areas in map 1. In addition, P. H. Monson, a student of R. W. Pohl's at Iowa State University, completed a study of the Des Moines Lobe in northcentral Iowa in 1959.
Map 1. Floristic surveys completed in Iowa. The various shaded areas indicate the regions studied by each author. The stars indicate additional county surveys (floras) conducted. 
= County flora completed before 1950. 
= County flora completed between 1960 and the present.
That this floristic momentum has continued since is illustrated by the county floras undertaken by master's students, county forays sponsored by the Department of Natural Resources (DNR), the field activities of Bureau of Preserves and Ecological Services personnel of the DNR, research instigated by the Nature Conservancy, and the individual studies of a number of dedicated field botanists. Map 1 summarizes the regional and county floras that have been completed in Iowa. Manuals, revisions of previous studies, and monographs based wholly or partly on Iowa taxa have also greatly expanded our knowledge of Iowa plants. In addition, the recently published state and regional checklists, floras, and manuals of this region have been most helpful. These include Flora of the Great Plains (Great Plains Flora Association 1986), Guide to the Vascular Flora of Illinois (Mohlenbrock 1986), The Vascular Plants of South Dakota (Van Bruggen 1985), the several parts of Michigan Flora (Voss 1972, 1985), Vascular Plants ofMinnesota (Ownbey and Morley 1991), A Synonymized Checklist of the Vascular Flora of the United States, Canada, and Greenland (Kartesz and Kartesz 1980), and National List ofScientific Plant Names (United States Department of Agriculture 1982a, 1982b).
Acknowledgments
Many individuals have contributed directly or indirectly to the development of this publication. To each, we offer our sincere thanks. We cannot thank each one of you here, of course, but that does not mean that we are not grateful for your assistance. Several have made significant contributions, beginning with James Peck, Carol Jacobs, and Margaret Oard, who spent much time pulling plant data together. We are grateful to John Pearson of the Bureau of Preserves and Ecological Services, Iowa Department of Natural Resources, and Mark Leoschke, formerly of that office, for a number of suggested additions, deletions, and modifications. William Pusateri of the Iowa Department of Transportation, Paul Christiansen of Cornell College, and William Watson also made significant contributions to this work. Jeffrey Nekola located several new species in Iowa and searched out a number of interesting habitats. We wish to thank Diana Horton of the Botany Department, the University of Iowa, for offering both corrections and encouragement. Her sharp-eyed assistant, Jennifer Bell, spotted several errors, and we appreciate her help. We owe a great debt to James Peck of the University of Arkansas and to Donald Farrar of Iowa State University for their reviews of the pteridophytes and to Duane Isely of Iowa State University for reviewing the legumes. They added significantly to the quality of the treatment of these taxa. Richard Baker of the University of Iowa reviewed the physical setting section and made important suggestions and corrections, for which we are grateful. We also want to express our gratitude to Douglas Ladd of the Nature Conservancy Office in Missouri, who carefully critiqued the checklist and offered a number of worthwhile suggestions for improving it.
John Downey, former head of the Biology Department at the University of Northern Iowa, suggested to the senior author that this work should be computerized. Because of this, the work has been greatly improved, but at the cost of countless hours learning how to do it! The curators of the herbaria at Iowa State University, Deborah Lewis, and the University of Iowa, Diana Horton, were most helpful with our herbarium research, for which we offer our sincere thanks. Much of this work was completed during summers spent at Iowa Lakeside Laboratory. Thanks are tendered to the successive directors of Lakeside Lab, Richard Bovbjerg and Robert Cruden, for their support and to Mark and Judy Wehrspahn, who made us comfortable while there. The senior author is grateful to John Downey, Daryl Smith, and George Hoffman, successive heads of the Biology Department at the University of Northern Iowa, for continued support of this work. He is thankful for the unfailing encouragement of his wife, Charlotte. Also, we are grateful to all those, especially Lois Tiffany of Iowa State University, who gave us their support all along the way.
Financial Support
The senior author wishes to express his gratitude to the University of Northern Iowa for granting him a Professional Development Leave during the fall semester of 1983, for support for research during the summer of 1982, and for Faculty Research Awards for 1977-1978 and 1978-1979. He is also grateful for a research grant from the Iowa Science Foundation in 1985 and for grants from the Brenton Bank Foundation and Pioneer Hy-Bred International, Inc., to support a research leave during the spring of 1984. Finally, he wishes to thank the Department of Biology at the University of Northern Iowa for providing space, time, and assistance during the long course of this research.