INTRODUCTION. XIX 



complete rearrangement. It is important to understand the life- 

 history of not only a few, but of all the generic forms. 



Much as has been accomplished in the past few years by the 

 studies of such men of prominence as Borzi, Cienkowski, Hans- 

 girg, Richter, Rostafinski, Sachs, Schaarschmidt, Sirodot, 

 Wittrock, "Woronin and others, there remains much more to be 

 done, and years may pass before the life-history of all the generic 

 forms shall be fully understood. 



To the names adopted for the plants described in this work, 

 we have added the synonymous names, with the names 

 of their authors, but have not every time quoted the titles of 

 the works in which the names occur ; this plan to economize 

 space, and because of secondary importance. The titles of the 

 papers or works of the various authors referred to, may be 

 found immediately preceding this Introduction. 



As this volume is complemental to our Desmids of the United 

 States and the first eight of the series of 150 plates represent 

 additional Desmids, have made the numbering of them a succes- 

 sion of those of the first volume, commencing with number LIY. 



