viii PREFACE 



of its anatomical and morphological detail. Important fruit 

 crops have been omitted because a second volume is contemplated 

 which will deal more especially with them. 



ACKNOWLEDGMENTS 



The preparation of this work has been greatly aided through 

 the generous assistance of fellow workers in the fields of botany 

 and agriculture. Many have contributed the results of their 

 researches and illustrative material, and the author expresses his 

 deep appreciation of this cooperative spirit which has made 

 possible the inclusion of valuable data. Individual acknowledg- 

 ment accompanies the text and illustrations in each case. Thanks 

 are due The University of Chicago Press for permission to use 

 illustrations from the Botanical Gazette. Acknowledgment to 

 other journals, publications, and publishing houses appears at the 

 point of insertion of the material used. 



The preparation of the original plates was aided in part by a 

 grant to the University of Chicago from the Rockefeller Founda- 

 tion. The original line drawings and photomicrographs were 

 prepared by the author and associated students, especially Miss 

 Jean Port, who also aided in the preparation of the manuscript. 

 The author is deeply indebted to Professor E. J. Kraus, who read 

 the entire manuscript, for valuable suggestions and encouragement 

 from the inception of the idea of the book to its final completion. 



Herman E. Hayward 

 Chicago, Illinois 

 September, 1938 



