vi PREFACE 



Acknowledgments 



In a study of this scope, the best can be achieved only with the 

 generous assistance of others. Institutions and individuals have been 

 most helpful in these studies through loans, gifts, and exchanges of 

 collections. 



Invaluable beyond estimation has been the loan of type collec- 

 tions. We have been privileged to borrow and to examine fully the 

 types of all available North American Hygrophorus species. We ac- 

 knowledge with thanks these loans from the several institutions and 

 persons listed herewith: The University of Florida, Gainesville (Mur- 

 rill's Florida types), Dr. Erdman West; Iowa State College, Ames; The 

 University of Massachusetts, Amherst, Dr. Howard E. Bigelow; The 

 New York Botanical Garden, New York City (MurriU's types), Dr. 

 Clark T. Rogerson; The New York State Museum, Albany (Peck's 

 types), Dr. E. C. Ogden and Mr. Stanley Jay Smith; The University of 

 North Carolina, Chapel Hill (Coker's types), Dr. John N. Couch. 



Our desire to study Friesian and other European species of Hy- 

 grophorus has been satisfied to some extent by the gift, loan, or ex- 

 change of collections from abroad. Material has thus been made availa- 

 ble to us by Dr. Meinhard Moser, Bodenbiologisches Institut, Imst, 

 Austria; Dr. P. Heinemann, Institut Agronomique, Gembloux, Belgium; 

 Dr. Morten Lange, The University of Copenhagen, and Mr. J. P. Jen- 

 sen, Copenhagen, Denmark; Dr. G. Taylor, Dr. R. W. G. Dennis, and 

 Dr. Derek A. Reid, Royal Botanic Garden, Kew, England; Dr. Marcel 

 Josserand, Lyon, and Dr. G. Metrod, Champagnole, France; Dr. M. A. 

 Donk, Dr. R. A. Maas Geesteranus, and Dr. C. Bas, The University of 

 Leiden, Netherlands; Dr. H. S. C. Huijsman, Cernier, Switzerland. 



In addition to loans and gifts of authentic exsiccati, we are deeply 

 indebted to the National Science Foundation for generous grants in 

 support of our field and laboratory studies; and especially to the Office 

 of Science Information Service, Support of Scientific Publications, for a 

 special grant covering the cost of composition, printing, and binding 

 of this volume. 



Finally, the entire manuscript has been read with great care by 

 Dr. A. J. Sharp, Professor of Botany, University of Tennessee. Without 

 his sharp-eyed professional criticisms many deficiencies in writing 

 would have been unsparingly imposed on the reader. The original 

 drawings were prepared by the senior author, and the plates were then 

 traced for reproduction by Mrs. Romance Carrier. The photographs 

 were made by us, with a few exceptions noted. To these individuals, 



