214 BRITISH PLANTS 
limestone cliffs in Sligo; Simethis bicolor, Kerry and Devon; 
and Inula salicina, found only on the shores of Lough 
Derg, in Galway. 
More remarkable still, a few plants are found in the 
west of Ireland and not elsewhere on the continent of 
Europe. They occur, however, in North America, and 
it has been suggested that they may have travelled over 
that lost continent, Atlantis, which some people have 
supposed once stretched across the Atlantic between 
Europe and America. It is pretty certain, however, that 
in pre-glacial times land did extend in that direction, 
running from the north of Scotland to Iceland and Green- 
land, and from Greenland to the mainland of America. 
Along this highway the horse possibly travelled into 
Europe, for this animal is American in origin, and with 
it might have come plants, of which three only still 
remain to tell the tale. These American plants are: 
Spiranthes Romanzoviana, west of Ireland ; Hriocaulon 
septangulare, Connemara and the Hebrides; and Sisy- 
rinchium angustifolium, a plant allied to the iris, found 
in the west of Ireland. 
Last of all we have that rare and extremely beautiful 
filmy fern, T'richomanes radicans, the Killarney fern, 
which occurs in a few places in the wet, shady recesses of 
rocks near the Lakes of Killarney, in North Wales, and 
in the Isle of Arran. Elsewhere it is found only in the 
Azores, the Canary Islands, and the island of Madeira. 
English Plants absent from the Irish Flora.—While 
some plants are found in Ireland, and nowhere else in 
Great Britain, there are others unknown in Ireland which 
are quite common in England. Among them are the’ 
following : 
Black bryony (T’amus communis), white bryony (Bryonia 
dioica), herb-paris (Paris quadrifolia), snowdrop, lily-of- 
the-valley, butcher’s-broom, hop, wayfaring-tree (Vibur- 
num Lantana), mistletoe, wild service-tree (Pyrus tor- 
minalis), Ulex minor, traveller’s-joy (Clematis Vitalba), 
and Myosurus minimus, the mousetail. 
The absence of these plants from Ireland is, in most 
cases, due to the fact that Ireland was separated from 
Great Britain before the latter was separated from the 
Continent, so that many species must have arrived in 
England too late to cross over into Ireland. For this 
