viii ZYGNEMATACEAE 



omitted because of faulty descriptions. Also some recent descrip- 

 tions have had to be passed over because they lacked important 

 details, or because of discrepancies between figures and descrip- 

 tions. I have no doubt that some of these species are valid, and 

 if additional information could have been obtained, they would 

 have been included. No attempt has been made to guess at the 

 synonomy of all previously published species names. Such guesses 

 can be found in the Sylloge Algarmn by G. B. de Toni (1889), in 

 the Siisswasserjiora Mitteleuropa, 9 (1932), and in Rabenhorst's 

 Kryptogamenfiora, 13 (1941-44), abt. II. In the absence of 

 complete descriptions, or of the actual specimens, such conjectures 

 seem gratuitous. Synonyms that are the result of different con- 

 cepts of generic or specific limits are usually given. A few species 

 with incomplete descriptions, but with conspicuous structures 

 that distinguish them from other somewhat similar species, have 

 been retained. 



Among the many friends and students who have contributed 

 collections containing Zygnemataceae, I am particularly indebted 

 to Alma Ackley, Wayne University; Charles C. Adams, New 

 York State Museum; D. B. Anderson, Agricultural and Technical 

 College of North Carolina; the late W. M. Barrows, The Ohio 

 State University; Glenn W. Blaydes, The Ohio State University; 

 E. T. Bodenberg, Wittenberg College; Harold C. Bold, Vander- 

 bilt University; Helen B. Bromley, Stamford, Connecticut; 

 Charles Bullard, late of Harvard University; C. Cedercreutz, 

 Helsingfors, Finland; Glenn Couch, University of Oklahoma; 

 Francis Drouet, Chicago Natural History Museum; R. B. Gordon, 

 Westchester Teachers College; Lawrence Hicks, Columbus, 

 Ohio; Elwyn Hughes, University of Oklahoma; G. J. Ikenberry, 

 Oklahoma Agricultural and Mechanical College; Chin-Chih Jao, 

 Chungking, China; Minnie M. Johnson, Stephens College; Ivey 

 Lewis, University of Virginia; Liang Ching Li, Fan Memorial 

 Institute of Peiping, China; Floyd A. McClure, Lingnan Uni- 

 versity; B. B. Mclnteer, University of Kentucky; George Nichols, 

 late of Yale University; Claude E. O'Neal, Ohio Wesleyan Uni- 

 versity; Gerald Prescott, Michigan State College; M. S. Rand- 

 hawa, Fyzabad, India; H. C. Sampson, The Ohio State University; 

 H. Skuja, Uppsala University, Sweden; Ben H. Smith, Indiana 

 State Teachers College; G. M. Smith, Stanford University; Edith 

 L. Stephens, University of South Africa; E. L. Stover, Eastern 



