vi DESMIDS OF THE I'MTKIi STATES. 



time, in this country and in Europe, upon the Alga of the United 

 States. His list of Alga includes about one hundred and sixty species 

 of Desmids. 



In a collection made by Stephen J. Olney, near Providence, R. I., 

 during the years 1846-48, there were about fifty Bpeciee of Desmids. 



My first contribution to the Literature of the fresh-water Algce, 

 appeared in the " Torrey Botanical Bulletin of N< w York," in 1877, 

 wherein are described thirty Desmids nol heretofore found in the 

 United States. Every succeed in <: year up to 1883, I have recorded in 

 the same journal, the results of my observations upon this interesting 

 class of American flora; what my success has been, may be inferred 

 from the fact that I have in my herbarium Dearly five hundred well 

 authenticated species and varieties of American Desmids. 



Only the great pleasure I derived from collecting, and studying the 

 life-history of this heretofore neglected class of plant-, enabled me to 

 make light of, and to overcome, the serious obstacles I met with at tin- 

 outset of my labors. There were oo borne correspondents with whom 

 to co-operate and do accessible good works t" guide me in m\ 

 searches over this alnm-t wholly nnexplored field. My first encour- 

 agement came from abroad. The late I >r. L Rabenhorst, of Meissen, 

 Prussia, and the late Alexander Braun, of Berlin, senl me many 

 valuable communications, and to the former particularly, I furnished 

 many sets of mounted specimens of our Alga for bis serial of decades 

 of Alga Exsiccata. 1 am particularly indebted, however, to Dr. Otto 

 Nordstedt, of the University of Lund, Sweden, for hi- kindness in 

 determining the identity of certain American species discovered by 

 me with those already known in Europe; ami also in confirming my 

 impressions concerning tin- restriction of others Bolely to the I oited 

 ^tates. 



My grateful acknowledgments are also due for valuable note- ami 

 [tapers, to Dr. V. B. Wittrock, of tie Scientific Academy of Stock- 

 holm; N. Wille, of Christiana, Norway; I". Bauck, Trieste ; Dr. .1. 

 Rostafinski, Cracow ; <;. Lagerheim, Stockholm, and others 



Meanwhile, the subject had awaken., I iutereel in various parte 

 the I nited States, and specimens began to come in from places it would 

 have been impossible for me to have visited. Among those t" whom 

 I am particularly indebted for favors oj thi- kiml. are : Mr. II W 



