68 BRITISH MOSSES. 



But whilst there are instances of this wide dispersion, 

 there are instances too of the opposite kind. Amongst the 

 British Mosses and Hepatic (as we learn from Mr. Wallace 

 on the authority of Mr. Mitten) seventeen Mosses and 

 nine Hepaticae are said to be peculiar to the British Islands, 

 and of these, three genera of Mosses and three of 

 Hepaticae are also non-European (i.e., not known on the 

 Continent of Europe). The three non-European genera 

 of Mosses have their greatest development in the Andes ; 

 the three non-European genera of Hepaticae have their 

 greatest development in the temperate regions of the 

 southern hemisphere. Let me take one of the Mosses of 

 which the genus is non-European Streptopogon. This 

 genus is thus distributed : Seven species in the Andes ; 

 one in the Himalayas ; three in the south temperate zone ; 

 one in Sussex. Take, again, one of the Hepatic, Aero- 

 bolbus ; its species are confined to New Zealand and the 

 adjoining islands, with one species in Ireland. 



There are other noteworthy but isolated facts about the 

 distribution of Mosses to which I may here refer : one is, 

 that the great boulders of the plains of the centre of 

 Germany are found to bear alpine species of Moss as if 

 brought from some distant or elevated region ; is this due 

 to the actual transport of the boulders on which they live 

 or to the retreat of the northern flora in the tail of 

 the ice as it retreated northward as the glacial period 

 disappeared ? In any event it reminds one of the scattered 

 patches of alpine gentians, which are to be found in the 

 great stretch of moorland south of the Danube, and 

 between that river and the Tyrolese Alps. 



