Preface: The study of hayfever falls into two fiels--the clinical and the botanical--each so broad of scope and widely differing in character that for one to excel in one is almost to preclude the possibility of excelling in the other. The past twenty-five years--approximately the time since pollen has been generally recognized as the cause of hayfever--has seen the accomplishment of much excellent work in both fields, but that of the former greatly exceeds that of the latter, and the facts of the latter field still remain scattered and so mingled with fancies that one who is not a trained botanist could scarcely be expected to separate them. This book is intended, therefore, to interpret the botanical facts of hayfever in terms of their clinical significance. Here are described all of the plants known to cause hayfever, most of those reasonably suspected of doing so, and many which have been mentioned in heayfever literature, possibly wrongly. In the plant descriptions I have not attempted to define the species beyond pointing out a few of the salient features which may readily be used and most easily retained in memory. The plants are presented in the sequence of Engler and Prantle in their "Natuliche Pflanzenfamilien". In the Choice of botanical names usage and expediency have been my guides. Nor have I attempted to settle the questions of priority, nor even to make the names conform either to the "International Rules of Botanical Nomenclature", or to the "American Code of Botanical Nomenclature". For the names of the grasses I have followed principally Hitchcock; for those of trees principally Sargent; for those of cultivated plants Bailey; and for those of the ragweeds and their relatives Rydberg. Otherwise I have given primary choice to names of current usage especially in hayfever literature, except where these have appeared to be definitely wrong or misleading. Where more than one name is commonly used those of secondary choice are added as synonyms. For the capitalization of specific names, since these are all Latin or at least Latinized in form, it seems that one has no choice but to follow the Latin rules for capitalization. Consequently names of people and names of genera which are used as nouns, are always capitalized, while names of countries and places which are used as adjectives are not. Hence the capitalizaiton in such names as Populus Sargentii, Cynodon Dactylon, but lack of capitalization in such as Artemisia canadensis. English names are given as far as these are known to the author. In fact an attempt has been made to present all the vernacular names which have any use or value whatever, but some which are obvious translations of the Latin or otherwise useless have been rejected. Where more than one vernacular name is given, the name of preference is placed first. All of the illustrations are the work of the author, except where otherwise indicated. Those of plants were prepared from living or occasionally herbarium specimens especially for this volume. It is a pleasure to acknowledge my indebtedness and express sincerest appreciation of the generous help I have received from friends and colleagues. Especially am I indebted to Professor L.R. Abrams for reading the sections on the regional botany of the Southwest, and of southern California, and to Dr. John H. Barnhart for help in solving questions of nomenclature, and to Professor W.F. Wells for the description and figure of the Wells Air Centrifuge, to Dr. Ralph Bowen for reading the manuscript, and to Professor G. Erdtman for the description and figure of the Aerosol Collector. I am also indebted to the director and staff of the New York Botanical Garden, where much of the work was done, for the use of the herbarium and library and much incidental assistance.--The Author

Roger P Wodehouse

The Chronica botanica Company

New series of plant science books, vol. XV, Waltham, Mass, 1945