Pethybridge & Praegkr — Vegetation South of Dublin, 14'i 



We are not, however, absolutely convinced that this method of 

 giving the lists of plants composing our associations has any great 

 additional value. It is true that this method of vf^orking out the lists 

 was rather an afterthought when many of the lists had been made ; and, 

 doubtless, greater value would have accrued had we made a far larger 

 number of lists than we did, and if we had had some workable method 

 by which we could, with greater accuracy than by merely judging 

 by the eye, have estimated the relative abundance of the different 

 species. 



THE ZONES OF VEGETATION. 



Using the word " zone" to represent the successive bands of vege- 

 tation which one would traverse in going from sea-level to the tops 

 of the mountains, we find in our area the following four well-marked 

 zones : — 



1. The Littoral Zone, 



2. The Agraiian Zone, 



3. The Hill-Pasture Zone, 



4. The Moorland Zone. 



It must not be supposed, however, that the limits of these zones are 

 very sharply marked by contour lines of altitude. It may also be 

 remarked here that in no case have we taken any contour line and used 

 it as an arbitrary division between two zones or two associations, 

 preferring rather in each individual case to work out to the best of 

 our ability the actual limits of the vegetation. As regards the littoral 

 zone, it is not necessary to do more than mention it at this place. 

 The agrarian zone runs on an average up to about 900 feet above 

 the sea (in one case we have tilled land up to 1250 feet). The moor- 

 land zone, in the shape at any rate of a dense sheet of the pure Calluna 

 association, is seldom found descending much below 1250 feet; so that 

 between these two altitudes the zones of hill-pasture may be said to 

 come in. Above the 1750 feet contour, the moorland, where drainage 

 is fairly good, begins to take on a somewhat different character, a large 

 quantity of moss being mixed with the heather, producing in certain 

 cases (Prince William's Seat, Killakee Mountain, Kippure) somewhat 

 the aspect of a moss-tundra. The change, however, is not sufficiently 

 distinct or well-marked to warrant our adding a fifth zone to the 

 four above mentioned. 



