782 



In order to show some of the most important causes of errors, 

 I shall point out, that several of the species, which have heen found on 

 the coasts of Greenland, the Faeroes and Iceland, according to papers 

 published during the latest years, e.g. Rosenvinge's on the marine 

 algae of Greenland, my own paper on the Faeroese marine algae, and 

 lastly Jonsson's on the marine algae of Iceland, also will be found 

 m the surrounding countries on renew^ed investigations. In Batter's 

 recently published list of the marine algae of Great Britain we thus fmd 

 many of Rosenvinge's new Greenlandic species mentioned. Another 

 source of error is naturally the different authors' varying opinions of 

 species; and even if w^e try ever so conscientiously to make out the 

 different synonyms, there are still, according to our present know- 

 ledge, a great many genera — I need only mention promiscuously 

 Lithothamnion, Sphacelaria, Myrionema, Acrosiphonia, Spongomorpha, 

 Cladophora, Enter omorpha, Ulothrix — of which it is almost impos- 

 sible to make any statement with certainty. On the whole, it is espe- 

 cially the classification of the Chlorophycece which causes the greatest 

 difficulties; and as the plants of this group thrive in very extreme 

 conditions, which quality they have in common with the Cyano- 

 phycece, for instance they are w^ell fitted for standing a mixture 

 with fresh w^ater, it w^ould perhaps be most correct to side w^ith 

 Kuckuck wdio says (56, p. 10): »Bei pflanzengeographischstati- 

 stischen Zusammenstellungen scheinen mir daher die Chlorophy- 

 ceen und Cyanophyceen eher geeignet, das Resultat zu truben als 

 zu klaren, und aus diesem Grunde will ich auch hier von einer 

 Berucksichtigung jener Pflanzengruppe absehen.« But as it cannot 

 be denied, however, that there are several species, even among the 

 Chlorophycece and Cyanophycece, which are of no small importance 

 from a phyto-geographical point of view% I have used them here 

 as far as possible for the sake of comparison. 



Further, it is naturally of great importance in a comparison of 

 this nature, to exclude the species which by mistake have been in- 

 cluded previously in the flora of a country, wiien closer investiga- 

 tions have show^n that it is only by erroneous determination or for 

 some other reason, that they have been included, and thus do not 

 belong to the flora at all. As to Greenland, so many species had 

 been incorrectly admitted, according to Rosenvinge (71, p. 154) 

 that the phyto-geographical character of the algae -flora has been 

 essentially altered by their omission; also, with regard to the 

 Faeroes we have been obliged to exclude several of the species 



