Links With the Past in the Plant World

by A. C. Seward

There would seem to be no insuperable objection to the conclusion that the Mediterranean plants in Ireland and in the south of England reached their present home after the retreat of the ice at the end of the Glacial period, and after Ireland became an island. A full consideration of the problem is beyond the scope of this book, but I have briefly stated the case, not with the authority of an expert but in order to draw attention to a particularly fascinating study in plant-migration.

Fig. 2. Eriocaulon septangulare With. West Connemara. (Photograph by Mr W. R. Welch.)

In a volume by W. Canton entitled A Child's book of Saints a story is told in which the presence in Ireland of Mediterranean species receives a more picturesque explanation. The Monk Bresal was sent to teach the brethren in a Spanish monastery the music of Irish choirs. In later years Bresal longed for a sight of his native land, though he loved his home and 'every rock, tree, and flower' in his adopted country. After returning to Ireland, his thoughts reverted to Spain; 'it appeared to him as though he was once again in a granite nook among the rocks beside the Priory'; he saw the ice-plant with its little stars of white flowers sprinkled with red (the London Pride) and a small evergreen tree from which he had often gathered the orange-scarlet berries (Arbutus). The Prior of the Spanish monastery 'with heavenly vision saw Bresal gazing at the evergreen tree and the ice-plant, and turning to the trees blessed them and commended them to go and make real his dream. As Bresal brushed away his tears he saw with amazement at his feet the ice-plant and hard by the evergreen tree.'

The plant represented in ([Fig. 2]) is another British species which tasks the ingenuity of students of plant-geography. This is the Pipe Wort (Eriocaulon septangulare), the sole representative in Europe of a certain family of Monocotyledons: it flourishes in the west of Ireland and in the western islands of Scotland but nowhere else in Europe; it is native on the other side of the Atlantic in Canada and the northern United States of America. Mr Praeger in describing the striking mixture of species in the west of Ireland writes, 'The pool from which we gather the American Pipe Wort is fringed with Pyrenean Heathers. The cracks which are filled with the delicate green foam of the maiden hair are set in Bearberry and Spring Gentian; Habenaria intacta, far from its Mediterranean home, sends up its flower-spikes through carpets of mountain Avens; and St Dabeoc's Heath and the dwarf Juniper straggle together over the rocky knolls'([25]).

The presence of Eriocaulon on the western edge of Europe may be attributed to migration in pre-Glacial days from North America by way of a land-connexion, of which Greenland and Iceland represent surviving portions. The opinion held by Forbes, and advocated by some later naturalists, that the southern companions of Eriocaulon in the west of Ireland are survivors from a Tertiary flora which have lived through the Ice Age, is consistently extended to the Pipe Wort. On the other hand, before yielding to the temptation to regard these American and Mediterranean species as links with the Tertiary period, we must be convinced that the possibilities of post-Glacial introduction, even without the aid of land-bridges, have been exhausted. The Pipe Wort is a botanical puzzle which affords a good example of the accession of interest to field-botany effected by a knowledge of the distribution of the component members of the British flora. The problem of its past history suggests an experimental enquiry into the adaptability of its seeds to dispersal, and emphasises the importance of the co-operation of botanists and geologists in a common endeavour to trace the origin of British plants.

In addition to the Pipe Wort, mention may be made of three other American flowering plants recognised in the Irish flora. Sisyrinchium angustifolium recorded from the west of Ireland is native in temperate North America; the orchid, Spiranthes romanzoffiana, met with in the south and north of Ireland, is widely spread in Canada and the northern States, while Sisyrinchium californicum, a native of California and Oregon, was discovered by Mr Marshall in marshy meadow-land near Wexford([26]). In the case of the more recently discovered American immigrants, the possibility of human introduction must be borne in mind, though there are no special reasons for doubting that some, as in the case of Eriocaulon, reached the Irish coast by natural agencies.