In damp meadows all round Lough Neagh, in the North of Ireland, grows an Orchid, _Spiranthes Romanzoffiana_ (Fig. 30), whose greenish-white flowers possess a delicious fragrance resembling that of its ally, _S. spiralis_, the Autumnal Lady’s Tresses. _S. Romanzoffiana_ occurs also in Co. Cork, but we may search in vain for it throughout the rest of Europe. It is an American plant, widely spread throughout Canada and the northern States, and found on the Asiatic as well as the Alaskan side of Behring Sea. Again, in pools along the western Irish coast from Cork to Donegal, and also in the Hebrides, grows the Pipewort (_Eriocaulon articulatum_), a little aquatic with a tuft of grassy leaves from which a slender stem rises above the water, bearing a button-like head of small grey flowers. This plant also is absent from all the rest of Europe and from Asia, but widely spread in northern North America. The little Blue-eyed Grass of Canada (_Sisyrinchium angustifolium_), again, grows abundantly in many areas in the West of Ireland, where it would seem to be undoubtedly native, and is otherwise confined to North America. One or two other plants, of the same foreign distribution, have in Europe a less restricted range; they need not be mentioned individually, for enough has been said to show that along the western coasts of the British Isles [Illustration: FIG. 29.--STRAWBERRY-TREE (_ARBUTUS UNEDO_) AT THE LAKES OF KILLARNEY.] [Illustration: FIG. 30.--_SPIRANTHES ROMANZOFFIANA_ GROWING BY LOUGH NEAGH. [_To face p. 174._] there is a small but well-marked element in the flora which has its home in the northern portion of the New World; in our islands these species live side by side with the Pyrenean and Mediterranean plants lately dealt with. Here, then, is the problem set before us. How are we to account for the presence of these unexpected strangers in a flora derived in the main from a westward migration from the adjoining parts of the Continent, from which they are absent? And especially what are their relations to the Glacial Epoch, during which the Continental flora was forced far southward by the advance of the ice, while that of our own islands was probably greatly reduced, and the balance forced into limited refuges in the south-west, if it survived at all? It should at once be pointed out that these peculiar Pyrenean and American elements in our flora are matched by similar elements in the fauna. Into the zoological evidence we cannot go here, but one well-marked species of each geographical group may be mentioned. The Spotted Slug of Kerry (_Geomalacus maculosus_) is elsewhere confined to Portugal; while a little fresh-water Sponge, _Heteromeyenia ryderi_, widely spread in Irish lakes and rivers, and occurring also in Scotland, is otherwise exclusively American. In speculating, therefore, as to the origin of the plants, we must not leave out of account the question of the corresponding animals.