Vlll PREFACE. 



page 45 we have to thank Messrs. Macmillan, and 

 for the like courtesy in the case of the figures on 

 page 35 we are indebted to the author, Mr. A. W. 

 Hill, and to the proprietor of the ( New Phytologist.' 



Our best thanks are due to the many friends and 

 correspondents who have, in various ways, assisted us 

 with the work; to Professor Otto Nordstedt, the 

 greatest living authority on the group, and to Mr. 

 James Britten, Dr. Daydon Jackson, Mr. Robert 

 Paulson, and Dr. A. B. Rendle, for much valuable 

 advice ; to the other botanists too numerous to specify 

 individually (among whom however may be mentioned 

 Messrs. Arthur Bennett, Gr. C. Druce, E. S. Marshall, 

 R. Lloyd Praeger and C. E. Salmon), for the specimens 

 which they have communicated to us during many 

 years, and which in particular made it possible to 

 estimate the variation and to arrive at the distribution 

 of the several species ; to Mr. W. H. Pearsall for 

 ecological information, and to Mr. Cecil V. B. Mar- 

 quand for cytological notes; to the officers of the 

 Department of Botany of the British Museum and 

 of the Royal Herbarium at Kew for their extremely 

 courteous help in consulting books and specimens. 



The writers hope that the issue of these volumes 

 may result in a larger number of British botanists 

 being attracted to the study of this remarkable group 

 of Cryptogams, so problematical in regard to its 

 origin and affinities. 



In the second volume it is proposed to include some 

 account of the fossil remains of Charophyta which 

 have been found in this country. 



JAMES GROVES. 



G. R. BULLOCK-WEBSTER. 



February, 1920. 



