ACKNOWLEDGMENTS. 

In attempting a complete report of a group as large as the 
Oedogoniacez, one encounters numerous difficulties. The liter- 
ature is bulky and in many languages. Type specimens are 
unavailable in some cases. Thanks, however, to the very 
careful work of Hirn (1900), many forms are perpetuated by 
extremely accurate and representative drawings. Some of the 
difficulties are matched, on the other hand, by the relative 
constancy of the characteristics of the species as they occur in 
aquatic habitats the world over. Many species appear in the 
writer’s own collections. 
It is almost impossible to give full acknowledgment to all 
who have assisted in making this monographic report possible. 
The writer has examined the material distributed in the Phy- 
cotheca Borealis-Americana and important collections generous- 
ly supplied by the following: Prof. E. N. Transeau, Ohio State 
University; the late Prof. O. Nordstedt; Prof. R. B. Wylie, 
Iowa State University; Prof. G. E. Nichols, Yale University; 
Prof. F. E. Lambert, Tufts College; Prof. W. R. Taylor, Uni- 
versity of Pennsylvania; Prof. C. J. Chamberlain, University 
of Chicago; Prof. I. F. Lewis, University of Virginia; Mr. G. H. 
Wailes, British Columbia; Prof. Alma B. Acklev, College of 
the City of Detroit; Prof. B. B. MclInteer, University of 
"Kentucky. 
Data on distribution of the genus outside of the United 
States other than that secured from the literature have been 
supplied by Mr. G. H. Wailes, British Columbia; Prof. O. Borge, 
Srocknolar: ror Kk. M.“Strom, Oslo; Prof. H: Skuja, Riga; 
Prof. N. N. Woronichin, Leningrad. 
The section on Bulbochaete in this report has previously 
appeared, in substance, in the TRANSACTIONS OF THE AMERICAN 
MICROSCOPICAL SOCIETY (Tiffany 1928). The text and plates 
dealing with that genus are incorporated herewith with the 
permission of the Society, kindly extended through its Secretary, 
Professor H. J. Van Cleave. My thanks are due Professor I. F. 
Lewis, University of Virginia, for the loan of his unpublished 
manuscript on the genus Oedocladium. Professor Lewis is 
9 
