CHAP. XVI.] 
THE BRITISH ISLES. 
341 
14. Spiranthes romanzoviana S. W. Ireland (North America). 
15. ( Sisyrinchium bermudianum. W. Ireland? introduced; (North America.) 
16. Potamogeton longifolius ( lucena . var.) W. Ireland, unique specimen ! 
17. „ Jiirkii ( natans sub.-sp.). W. Ireland (Arctic Europe). 
18. Eriocaulon septangulare. W. Ireland, Skye, Hebrides (North America). 
19. Carex buxbaumii. N. E. Ireland, on an island in Lough Neagh (Arctic 
and Alpine Europe, North America). 
20. Calaniagrostis stricta ( var.Hoolceri ). On the shores and islands of Lough 
Neagh. The species occurs at one locality in Cheshire (Germany, 
Arctic Europe, and North America). 
We find here nine south-west European species which 
probably had a wider range in mild preglacial times, and have 
been preserved in the south and west of Ireland owing 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 which once had a wider 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 Hepatic^ which are peculiar to 
the British Isles (or not found in Europe). 
( 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. 
