NOTES ON THE ZYGNEMALES.* 



Edgar Nelson Transeau. 



The following notes principally concerning North American 

 Zygnemales are based on a study of the specimens accumulated 

 in the course of eight years collecting in central Illinois; a 

 collection made by Mr. Charles Bullard, of Cambridge, Mass., 

 in Massachusetts and New Hampshire; the specimens dis- 

 tributed in the Phycotheca Boreali-Americana by Collins, 

 Holden and Setchell; the specimens distributed in American 

 Algae, by Miss Josephine E. Tilden; the specimens in the U. S. 

 National Herbarium ; and small collections sent me by Professor 

 Farlow, Miss Tilden, Professor A. B. Klugh, Professor D. S. 

 Johnson and Miss Grace Stone. They have been compared 

 with the species distributed by Wittrock and Nordstedt in their 

 "Algae Aquae dulcis exsiccatae, " and other valuable European 

 and South American specimens sent me by Professors O. 

 Borge and O. Nordstedt. 



In determining almost any species of the Zygnemales it is 

 absolutely essential that the specimens show both the vegetative 

 cells and the mature spores. With the exception of a few 

 species of Mougeotia the spores are colored either yellow, 

 brown, or blue when they are mature. The characteristic 

 markings of the median spore wall do not develop usually until 

 this color appears. Consequently it is useless to attach names 

 to vegetative specimens based on dimensions and number of 

 chromatophores. Keys based on such characters are not only 

 useless, but misleading. 



Judging from my experience in Illinois it is highly probable 

 that the list of North American forms will be considerably 

 augmented, when intensive studies have been made at localities 

 in the Southern United States. The most satisfactory method 

 of collecting these forms is to take samples from the various 

 ponds and streams at regular intervals of ten days, or two weeks, 

 throughout the growing season. Many of the species show local 

 variations and considerable experience is needed before many 



*Contribution from the Botanical Laboratory of the Ohio State University. 

 No. 91. 



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