ciiAr. XVI.] 



THE BRITISH ISLES. 



341 



14. Sjnranthes romanzoviana S. W. Ireland (North America). 



15. (Sisyrinchium hermudiaimm. W. Ireland? introduced; (North America.) 



16. Poiamogeton loiigifoUus {lucens. var.) W. Ireland, unique specimen ! 



17. „ Ic'irldi (nafans sub.-sp.). W. Ireland (Arctic Europe). 



18. Eriocaulon septangular e. W. Ireland, Skye, Hebrides (North America). 



19. Carex huxhaumii. N. E. Ireland, on an island in Lough Neagh (Arctic 



and Alpine Europe, North America). 



20. Calamagrostis stricta {var.IIooheri). On the sliores and islands of Lough 



Neagh. The species occurs at one locality in Cheshire (Germany, 

 Arctic Europe, and North America). 



We find here nine soutli-west European species wliicli 

 probably had a wider range in mild preglacial times, and have 

 been preserved in the south and west of Ireland owning to its 

 milder climate. It must be remembered that during the height 

 of the glacial epoch Ireland was continental, so that these plants 

 may have followed the retreating ice to their present stations and 

 survived the subsequent depression. This seems more probable 

 than that so many species should have reached Ireland for the 

 first time during the last union with the continent subsequent 

 to the glacial epoch. The Arctic, Alpine, and American plants 

 may all be examples of species wdiich once had a wdder range, 

 and which, owing to the more favourable conditions, have con- 

 tinued to exist in Ireland while becoming extinct in the adjacent 

 parts of Britain and Western Europe. 



As contrasted with the extreme scarcity of peculiar species 

 among the flowering plants, it is the more interesting and un- 

 expected to find a considerable number of peculiar mosses and 

 Hepaticse, some of which present us with phenomena of distri- 

 bution of a very remarkable character. For the following lists 

 and the information as to the distribution of the genera and 

 species I am indebted to Mr. William Mitten, one of the first 

 authorities on these beautiful little plants. 



List of the Species of Mosses and HErATioTE which are teculiar to 

 THE BraTisH Isles (or not found in Eurore). 

 {Those belonging to non-European genera in Italics.) 

 Mosses. 



1. Systegium multicapsulare Central and South England. 



2. „ mittenii South of England. ■ ^ 



3. Campylopus shawii North Britain. 



4. „ setifolius Ireland. 



