Vlil PREFACE. 



as distinguished for his indefatigable and successful micro- 

 scopic observations as for his constant readiness to encourage 

 his fellow-labourers in Natural History, I owe the patronage 

 of many of tlie eminent naturalists whose names adorn the 

 list of my Subscribers ; and, to render this Monograph more 

 complete and deserving of such support, he has taken the 

 trouble of measuring all the species. Tedious and uninviting 

 as the task must have been, these accurate measurements 

 will show how much his love of science has contributed to 

 enrich a work of which I regard them as one of the most 

 important features. 



It gives me sincere pleasure to acknowledge how much I 

 am indebted to the kindness of M. de Brebisson, who has so 

 long studied these Algae, and who is deservedly esteemed 

 the highest authority on the subject. By his valuable aid 

 my nomenclature has been rendered far more perfect than it 

 could otherwise have been. He has most liberally supplied 

 me with sjDecimens and drawings of almost every species ; 

 has copied, for my use, figures contained in works which I 

 had no opportunity of consulting, and has at all times readily 

 furnished me with such information as I required. To the 

 extent indeed of my obligations in these respects every page 

 of this work bears frequent but inadequate testimony. 



Professors Kiitzing and Bailey have also afforded me 

 important assistance, by supplying me with drawings of 

 many species and by the communication of interesting 

 facts. 



My friends, the Rev. M. J. Berkeley, Dr. Dickie, Mr. 

 Sidebotham, and Mr. Thwaites, have materially aided me in 

 the execution of this Monograph by sending me their obser- 

 vations and specimens. Dr. Williams of Swansea has obli- 



