202 



the Nordreoer. For if no Arclic algæ occurred in the Færoes we 

 might wonder why birds only in spring would bring algæ along 

 with them from the south and west and not also in autumn from 

 the north. I quite agree with Wille in thinking that the flights of 

 birds which yearly take up their abode in the Færoes or pass the 

 islands on their way northwards could very easily have conveyed 

 to the islands the freshwater algæ-flora — and perhaps the whole 

 of the flora — which is found there, and in that case they will 

 doubtless keep on conveying new forms to the islands. 



But as maintained by Ostenfeld (see above p. 113) it is pos- 

 sible that there has existed a post-glacial land-bridge, and the flora 

 has consequently migrated across it. Adolf Jensen 's^ interesting 

 paper seems to favour this tlieory, but it is as yet far from proved. 

 Therefore the conclusion that the flora of the Færoes have migrated 

 by means or ways which are still in existence commends itself to 

 me as far more satisfactory. I shall here relative to this shortly 

 allude to Warming's exhaustive and interesting treatise on this 

 subject in his well-known work: »Om Grønlands Vegetation^«. In 

 this work he quite abandons the theory of a post-glacial land-bridge 

 as being necessary to account for the European character of the 

 flora of South and South-East Greenland. As means of immigration, 

 he mentions the three different factors already pointed out: birds, 

 wind and ocean currents, and also in connection with the regions 

 of the High-North: ice and floating timber. In speaking of these 

 factors he gives instances of the manner in which the immigration 

 of the flora has been affected by them. Among other cases in point 

 Warming also mentions Jan Mayen and writes: »surrounded by 

 vast ocean depths (1000 — 2000 fathoms) and being of vulcanic origin 

 this island must have emerged from the ocean (its rocks are more 

 recent than those of the Færoes and Iceland) without ever having 

 been connected with any land; it lies far from Greenland, about 

 60 geographical miles, from Iceland about 75, from Spitzbergen and 

 Norway about 120; yet in spite of the extremely unfavourable 

 conditions for all vegetation existing on it, it has obtained a flora 

 consisting of at least 20 flowering plants^«. 



^ A d o 1 f J e n s e 11 : > Om Levninger af Grundtvandsdyr paa store Havdyb mellem 

 Jan Mayen og Island . (Vidensk. Medd. fra den naturh. Foren, i Kbhvn. 1900). 



^ E. Warming: Om Grønlands Vegetation . (Medd. om Grønland, XII, 1888). 



^ Ostenfeld- H ansen in his »Contributio n å la flore de Tile Jan 

 Mayen« mentions altogether 178 species of piants from this island, of which, 

 however, 21 are marine algæ, and on the Amdrup Expedition of 1900, N. Hartz 



