9 8 Proceedings of the Royal Irish Academy. 



conclude, therefore, that either the Pine does not occur in the bog remains 

 on this part of the island, or that it is confined to the deeper layers which 

 have not yet been reached in peat-cutting. 



If the tree remains in the Clare Island peat can be accepted as evidence of 

 a succession in the forest flora due to climatic changes, it would appear that 

 when the Pine and Birch found in the lower parts of the bogs flourished, many 

 parts of the island subsequently covered with marsh were dry, and some of the 

 existing marshes and swamps were without definite outlets. An increase in 

 rainfall raised the level of these swamps at some period before the arrival of 

 the Oak, and this rainfall either reached a stationary point or again diminished, 

 allowing the peat to rise above the water-level, or bringing the latter down 

 sufficiently to allow a fresh growth of Pines to spread over the peat. After 

 or during this period, the Oak found its way in, and was probably accompanied 

 by Hazel, Alder, Holly, and other species now established throughout the 

 British Isles. Another rise in the water-table appears to have followed, 

 covering the Pine and Oak on the margins of the bogs, and killing off the 

 growth of Pines, in which Oak occasionally occurs, on the bog surface. 

 Somewhere about this period it is probable mountain peat began to form 

 on the poorer soils, and Sphagnum peat on the marsh bogs ; but while the 

 evidence for the latter theory is fairly conclusive, it is difficult to determine 

 whether mountain peat in the west of Ireland is due to soil or climatic 

 conditions, although both have probably something to do with it. There 

 is little doubt that the mild winters, and cool, moist summers of Ireland 

 favour the leaching out of lime from the surface soil, and bring about 

 an acid condition of shallow soils more rapidly than would occur with a 

 Continental climate. 



If the scanty remains of tree stumps in the peat of Clare Island formed 

 the only evidence of succession in a former forest flora, the above conclusions 

 might be regarded as premature. But it is a striking fact that mountain and 

 lowland bogs throughout Ireland yield certain evidence of a distinct and well- 

 marked change in the flora during the last few thousands of years, and a 

 succession similar to that found on the island. If a typical lowland bog is 

 examined from the outer edge to the centre, so far as this can be done in the 

 tew cases in which the peat has been sufficiently cut out, tree-stumps are 

 found to occur singly or in groups to a distance of 200 to 300 yards inwards. 

 At the outer edge, where the turf has usually been cut away to the natural 

 soil, stumps of Oak, Alder, Birch, Yew, Willow, and Pine occur more or less 

 universally— not necessarily in one section, or in any one individual bog, but 

 generally throughout the country, Oak being most frequently represented 

 near the edges, with an occasional Yew or Alder, and sometimes Pine and 



