VI PREFACE. 



To Mr. Jenner, one of the most untiring and successful 

 of Ciyptogamic botanists, and Avhose excellent Flora of 

 Tunbridge Wells is I believe the only one which contains 

 any thing like a complete list of the freshwater AIc/cb, I am 

 likewise greatly indebted for numberless recent specimens of 

 AlffcB, Avhich otherwise I had never seen, as W' ell as for many 

 original and accurate remarks. 



To Dr. G. J. Allman, my highly valued friend, and the 

 talented Professor of Botany in the Dublin University; to 

 Dr. Johnston, of wdiose valuable instructions in zoophy- 

 tology I entertain a grateful remembrance, and to be the 

 pupil of such a master any man might be proud ; to MM. 

 Montaigne, Areschoug, Decaisne, and Mr. Shuttleworth, 

 whose residence in foreign lands precluded unfortunately 

 frequent communication, and from whom therefore I regret 

 that I have not been able to obtain more of that information 

 of which they are so largely possessed ; to INIr. Thwaites, 

 of Bristol, Mr. Sidebotham, of Manchester, Dr. Dickie, of 

 Aberdeen, Mr. M'Colla, of Ireland, and Mr. Thompson, of 

 Belfast, my warmest thanks are due. 



I must not forget also to acknowledge the literary assist- 

 ance which I have derived from Mr. Coj^pin, of Trinity 

 College, Cambridge, nor omit to mention the deep obliga- 

 tion I am under to a lady for the devotion of much time to 

 the shading of many of the plates. 



To Mr. Ross, the eminent optician, with one of whose in- 

 struments most of the nicer observations were made, my 

 acknoTvledgments are likewise due. 



To the Subscribers also to this work I feel much indebted ; 

 their generous patronage has relieved my mind of consider- 

 able anxiety, for it has removed all pecuniary risk to myself, 

 if it has not insured a reward of the same nature. 



Norland Villa, Addison Eoad North, Netting Hill. 

 Julv, 1845. 



