9 22 Proceedings of the Royal Irish Academy. 



few indigenous species can be found until undulating or hilly ground occurs, 

 and then hollows, valleys, and eastern slopes alone show trees of normal 

 shape or development. 



How far the effect of the salt wind extends inland it is difficult to say, 

 but probably no part of Ireland is quite free from it. On high ground and 

 poor soils, the salinity of the air, however, may be obscured by the ordinary 

 desiccation caused by evaporation and a reduced temperature surrounding 

 the branches. The evaporation effect of wind in drying up branches to a 

 fatal degree is usually confined to trees with low vegetative vigour, as those 

 growing at or near the vertical tree-limit, or on poor, acid soils, while it is 

 a common occurrence in old trees, and forms the early stage of that con- 

 dition to which the term " stag-headed" is applied. The cause of desiccation 

 in all these cases is practically the same, namely, evaporation from the 

 surface of the branch or leaf at a more rapid rate than the loss can be made 

 good by water absorbed by the roots. In young and vigorous trees, or those 

 growing on good soils, fatal desiccation seldom, if ever, occurs at elevations 

 below 1000 feet in inland districts ; but all freely exposed trees show a 

 shorter growth of twigs and branches on the windward side, and the same 

 tendency to produce a flat-topped crown. The further east, or the greater 

 the shelter afforded to the westward, the less marked does this habit of 

 growth become. But at high altitudes the reduction in osmotic pressure 

 throughout the cellular system of the tree, brought about by the low 

 temperatures of soil and air, may often cause the death of the ends of the 

 branches by excessive evaporation, and produce results similar to those 

 found near the sea. Trees growing on poor, peaty, or water-logged soils 

 are also affected in the same way, owing to the slow rate at which the roots 

 take in water, and their reduced functional activity. 



The precise cause of the effect of sea-wind upon tree-growth is difficult to 

 determine, but probably both chemical and physical action is responsible. 

 That the salinity or low temperature of the air, and not merely the drying 

 action of the wind, is the cause of injury may be inferred from the condition 

 of trees growing near sea-level on north and east coast-lines, where the winds 

 off the sea are comparatively rare in occurrence and light in force during the 

 summer months. Trees and hedges within two hundred yards of the sea 

 show the same effect from sea-wind on these coasts as those on the west, 

 although the low elevation and good soil on which many of them are growing 

 are able to produce a vigorous growth a few yards further inland. 



In connexion with this point, a few observations made on the Old Head 

 plantation near Louisburgh may be cited. Old Head rises sharply from the 

 sea to a height of 340 feet, and is clothed with forest growth down to within 



