Pethybrtdge & Praeger — Vegetation 8onfh of BnhJin. 177 



Mucli of tlio low-lying land in our area is drift-covered, but we 

 have inserted in the form of dotted lines the boundaries of the 

 geological formations obtained from the " solid " geology maps of the 

 Geological Survey, the names of these being inserted on the map in 

 capital letters. , 



In selecting colours for differentiating the associations, we have 

 endeavoured, as far as possible, to represent the higher associations by 

 somewhat darker tints, so that, on the ivhole, decrease in deptli of tone, 

 of whatever colour, represents decrease in altitude, and vice versa. The 

 colour of the woods, however, and of Kippure does not fall in with this 

 scheme. The colours were also selected, as far as possible, with a view 

 to their easy differentiation by artificial light as well as by daylight. 

 A considerable amount of detail which could be put on the six-inch 

 map has necessarily been omitted on reduction. This applies with 

 considerable force to the use of letters. On the six-inch maps we are 

 able in most cases to trace the gradual passage of one association into 

 another, and to indicate the phases of transition by suitable lettering 

 at the overlaps. We had hoped to be able to do this on the present 

 map ; but on reduction it was found to be not feasible, as the attempt 

 to insert too much detail tends to obscure the usefulness of the map 

 as a broad general survey. 



Taking a broad view of the map as a whole, the distinction between 

 the green land of the great central plain of Ireland to the north and 

 the variously-coloured mountain land of the south is sufficiently con- 

 spicuous. The following notes will help to elucidate the map by 

 describing the general features and vegetation of a few of the more 

 prominent and remarkable areas. 



The Two-rock Mountain group. 



This group of hills, including Two-rock, Three-rock, Tibradden, 

 and Kilmashogue, and rising to 1699 feet in Two-rock, is characterized 

 by a general absence of peat of any depth ; and, in consequence, an 

 absence of the Scirpus association and other wet-vegetation types of 

 the high moors. Here, on the other hand, the Ulex Gallii association 

 attains a large development, forming in places a fringe of great breadth 

 and considerable altitudinal range. This gives way at length to a 

 poor Calluna association. Thus, on the Three-rock Mountain, at 

 1300 feet, a rather abrupt change is noticeable from a friable earthy 

 soil covered with a grassy sward dotted with rounded bushes U. Gallii, 

 among which Calluna, Erica cinerea, and Agrostis vulgaris flourish, 



