50 M. Martins on the Vegetable Colonisation of the 



sulated, England would have been less personal, and its ener- 

 getic races might perhaps have been confounded with one 

 of the great continental nations which peopled it. 



While Messrs Watson and Forbes proved the continental 

 origin of the plants and animals of England, I studied the 

 vegetable colonisation of Shetland, the Feroe Islands, and 

 Iceland. These islands form, as it were, a continuous chain, 

 which joins the northern extremity of Scotland to the eastern 

 side of Greenland. These are the only lands which unite 

 Europe to America. I visited the Feroe Islands in 1839 ; the 

 vegetation of this archipelago struck me. Although lost in 

 the midst of the North Sea, its flora is composed of very com- 

 mon plants, the greater part of them indigenous to the plains 

 of middle Europe, others to the Alps of Switzerland, some to 

 Scotland and Greenland. Extending my investigations to 

 Shetland and Iceland, I found, in like manner, that these 

 islands have no vegetation peculiar to themselves, but that 

 all their plants come from the mainland. This is the result 

 to which Mr Watson came in his researches into the British 

 Flora. But here a new problem presented itself; do these 

 vegetable colonies come from Europe or America % A great 

 number of plants being common to the northern parts of the 

 Old and New World, the question presented some difficul- 

 ties. I found more than a hundred species, exclusively 

 European, among the plants scattered over the islands which 

 I compared with each other ; all the rest were common to 

 Europe and America. Europe has therefore had the prin- 

 cipal part in the colonisation of these archipelagoes ; a great 

 vegetable migration has advanced across England, Scotland, 

 the Orkneys, Shetland, and the Feroe Islands, as far as Ice- 

 land. Some species have come directly from the coasts of 

 Norway. But, at the same time, the arctic plants originating 

 from Greenland followed an opposite progress, and propa- 

 gated themselves across Iceland, Feroe, and Shetland, as far 

 as the mountains of Scotland, where they found a second 

 country. This double migration manifests itself by the 

 numbers. If we calculate the relative proportion of the 

 plants, exclusively European, which enter into the fl.ora of 

 Shetland, we find that it is a fourth, in that of Feroe it is not 



