xiv PREFACE 



ferences; these result in most cases from different points of view, 

 different estimates or emphasis of characteristics in these ever elusive 

 objects. 



To Professor Torrend, formerly of Lisbon, the writer is indebted 

 for a set of European types, and to Professor Bethel, pathologist of 

 Denver, for rich material from the fertile mountains of Colorado 

 and California. To Professor Morton Peck, of Oregon, we are in- 

 debted for many notes of the color of plasmodia and for collections 

 of Pacific coast forms. Mr. Bilgram, of Philadelphia, read the manu- 

 script of the genus Physarum and has contributed many rare species. 

 To Dr. Sturgis, of Massachusetts, we are indebted for material from 

 both east and west. 



The present volume is intended especially for American readers 

 and is accordingly particularly devoted to a discussion of species so 

 far reported on the western continent; nevertheless it has seemed 

 wise to include a brief description of some other forms as well, and 

 reference to many extra-limital species now generally recognized will 

 be found here and there in connection with the more extended treat- 

 ment of related American forms. 



February twenty-eight, 1921. 



At the last moment, nearly all plates and drawings of the first edition 

 disappeared ! necessitating a quick renewal of drawings and plates. This 

 may in part explain lack of uniformity, and various minor irregularities sure 

 to grieve the intelligent student. 



