VI PREFACE. 



tannica.' Professor Agardh lias published hia new arrange- 

 ment of Rhodospcrmecv, based on a more accurate exami- 

 nation of the conceptaeular fruit or " sporiferous nucleus " 

 and this mode of classification, which I should adopt in 

 any New Edition, would involve many changes of name 

 and transposition of place from one family to another. I 

 have however 'given in an Appendix the Agardhian ar- 

 rangement of Rhodospermecp, adopted by me in my more 

 recent publication, the ' Nereis Boreali- Americana,' so far 

 as the British Flora is concerned ; and also an inventory 

 of the species added to the British list since the ' Phyco- 

 logia Britannica' was completed. 



W. H. H. 



Trin. Coll. Dublin, 



July 21, 1857. 



