Vlll BE HIM I J >E SMIDIAr I-:.]-!. 



have been issued concerning- British Desmids. Several 

 have appeared by Bennett, Roy, and Turner, and also 

 a very good and comprehensive account of ' The Scot- 

 tish Desmidieae ' by Roy and Bisset. The latter paper 

 includes all the published information on Scottish 

 Desmids np to 1894. 



During the last fifteen years many papers have been 

 published by continental botanists on Desmids from 

 various parts of the world. The principal contributors 

 to Desmid-literature have been Wille in Norway, 

 Wittrock, Nordstedt, Borge, and Lagerheim in Sweden; 

 Borgesen in Denmark; Schmidle and Leminermann 

 in Germany ; Liitkemiiller in Austria ; Gutwinski in 

 Poland ; Gay in France ; and Johnson in Xorth 

 America. Many of the works of these authors have 

 been up to the present absolutely indispensable to 

 students of British Desmids, and some of them will 

 always remain so. 



In the present monograph we have endeavoured to 

 bring together all the published information concerning 

 British Desmids that we have already mentioned, also 

 much work which we have ourselves published con- 

 cerning these plants, as well as a large number of 

 hitherto unpublished investigations. 



The number of species described and figured in the 

 present work will lie approximately 690, and the 

 number of varieties about 400. This is an increase of 

 400 species and 402 varieties over those enumerated 

 in the last monograph of British Desmids, by Cooke, 

 the majority of which have been added by our own 

 researches. 



Although many months have been spent by us from 

 year to year, investigating districts in almost all parts 

 of the British Islands, large areas yet remain practi- 



