vi PRETACB. 



themselves a special study. As I have paid no attention to these plants, they are 

 of course not included in this memoir. 



In the synonymy I have generally followed Prof. Eabenhorst. The original de- 

 scriptions of the forms, especially those of the older authorities, are very frequently 

 so meagre and obscure, that the species cannot be recognized by them with any cer- 

 tainty. Prof. Eabenhorst has gone over the ground most carefully, with access to 

 the whole literature of the subject and probably to all extant type specimens, and his 

 decisions are, no doubt, as accurate as the circumstances will allow. To attempt to 

 differ from them, to go behind his work to the original sources and make fresh 

 interpretations, would cause endless confusion. I have, therefore, nearly always 

 contented myself with his dictum, and have referred to him as the authority for the 

 names used. 



The following references were omitted through a misunderstanding from the first 

 portion of the text. 



Page 14. Gselosphmrium duhium, Grunnow. Rabenhorst, Flora Europ. Algarum, Sect. I. p. 55. 



" 15. Merismopedia convoluta,'BB.iiBis?,on. Rabenhorst, Flora Europ. Algarum, Sect. I. p. 58. 



" 18. Oscillaria chlorina, Kutzing. Rabeivhorst, Flora Europ. Algarum, Sect. I. p. 97. 



" 18. 0. Frohlichii, Kutzing. Rabenhorst, Flora Europ. Algarum, Sect. I. p. 109. 



" 19. 0. nigra, Vatjcher. Rabenhorst, Flora Europ. Algarum, Sect. I. p. lOT. 



" 19. 0. limosa, Agardh. Rabenhorst, Flora Europ. Algarum, Sect. I. p. 104. 



" 21. Ohthonoblasstus repens, Kutzing. Rabenhorst, Flora Europ. Algarum, Sect. I. p. 132. 



" 22. Lynghyq, muralis, Agaedh. Harvey, Nereis Boreali-Americana, pt. III. p. 104. 



In the text after the " Habitat" a name is quoted as the authority therefor ; if 

 such a name be in brackets, it signifies that the specimens were simply collected by 

 such individual, but that the identification was made by some one else ; when there 

 is not a name uninclosed in brackets, it is meant that the identification was made by 

 the author of this memoir. 



Since the present memoir has gone to press, I have received from the author a 

 copy of " Algae Rhodiacese. A list of Ehode Island Algae, collected and prepared 

 by Stephen T. Olney, in the years 1846-1848, now distributed from his own her- 

 barium." 



In the introduction to this list, Mr. Olney says: "Of the fresh-water species, I 

 have few for distribution. These were obtained mainly in the environs of this 

 city, and were placed in twenty-seven small vials in Goadsby's solution, and sent 

 to Prof. Harvey, who submitted them to the judgment of the most learned Eng- 

 lish botanist in this particular department, G. H. K. Thwaites, Esq., then of Bris- 

 tol, England. The large number of specites found in this collection, in so limited 

 a range, and collected within a very short period, is surprising, and shows what 

 raoie persistent collections will develop. I have not time to collate the numerous 

 publications of the lamented Prof. Bailey, or I might have made the list of this 

 portion of Ehode Island plants more complete." 

 The chlorosperms of this list are as follows: — 



Porphyra vulgaris, Ag.-Harv. Ner Bor. Am. 3. 53. Newport. 



Bangia fuscopurpurea, Lyngb.-Harv. Ner. Bor. Am. 3. 54. Soutliern Rhode Island. 



