Page:Journal of botany, British and foreign, Volume 34 (1896).djvu/83

 ON THE BOTANICAL SUBDIVISION OF IRELAND. 63 average area of these portions being 818 square miles. This size is almost identical with the average size of Watson's 112 vice- counties of Great Britain, which is 804 square miles. Next, as to the order in which the counties and vice-counties should be numbered. Watson numbered the British provinces I. to XVIII., commencint? with S.W. England and ending with the extreme north of Scotland. The vice-counties he numbered in the same order, those included in Province I. being numbered 1 to 6 ; those of Province II. 7 to 14, and so on. Babington proposed a similar method for Ireland, but the result is not satisfactory. The Irish " provinces " are not numbered regularly from south to north, but the numbering runs first up the east coast, and then drops back into the south-west ; and this absence of regular progression becomes accentuated if the vice-counties are numbered in the sequence of the provinces ; when, for instance, we suddenly pass from Louth (127) 120 miles south-westward to Limerick (128). It will be generally admitted that the best scheme, and the most natural, is one which will show a regular progression from south to north — from a higher temperature to a lower : with such a system, the largeness or smallness of the numbers in the list showing the county-distribution of a species, will themselves .be a key to the northward or southward range of the plant. Thus, if out of, say forty vice- counties, we find the range of a plant is from 1 to 20, we will immediately know that it is confined to the southern half of Ireland. It appears to me that the practical advantages of such a plan are much greater than those which arise from a consecutive numbering for the vice-counties of each "province"; and the scheme which I suggest therefore embodies this principle. A glance at the botanical map in Cybele Hihernica shows that the charac- teristic plants of Ireland are distributed according to lines which have a general trend north-west and south-east, rather than west and east ; this is also the course followed by the isothermal lines of winter and spring ; and I have adopted a system of numbering that follows these natural lines, and proceeds in a regular manner from the extreme south-west of the country to the extreme north-east. Such a plan does not prevent the vice-counties being grouped under the ** provinces " if for any reason this is desired. We would then have the following table ; for the " provinces " I give the numbers used by Moore and More in Cybele Hihernica : — (1. South Kerry. 2. North Kerry. 3. West Cork. { 4. Mid Cork. 5. East Cork. 6. Waterford. 7. South Tipperary. I'll. Kilkenny. 3. Barrow j 13. Car low. (l4. Queen's County., T- rx (12. Wexford. 4. Leinster Coast • • • • 20. Wicklow. 2. Blackwater