72 THE STORY OF PLANT LIFE 



the Palaeozoic rocks, and a newer series or the Meso- 

 zoic, and later Cainozoic rocks, the Jurassic and 

 Tertiary series being confined to the east and south 

 of England, and except in the case of the Oolite 

 and chalk-forming being usually lowland areas. 



The Palaeozoic rocks lie to the west of England 

 and are found throughout Ireland, covering large 

 parts of Scotland, especially on the west coast. 

 These older rocks coincide more or less with the 

 regions of highest altitude, and to a nearly similar 

 extent those of greatest rainfall. On the contrary 

 the newer formations are dry and lie east of the 

 older rocks, uninfluenced by the effect of the Gulf- 

 stream which is so marked on the west coast, and 

 thus escape those humid conditions to which the 

 older rocks are exposed. The older rocks again are 

 harder, and though subjected to a much longer 

 period of denudation have resisted such forces far 

 better than the newer rocks, which are loose and 

 friable, or being calcareous easily decomposed by 

 the carbonic acid in rain-water (see Fig. 12). 



We may split up the various types of geological 

 formations and the different rock-soils they aiford 

 into half a dozen types. These are clay and loam, 

 sand, siliceous soils such as those derived from slate, 

 which are close-grained and sticky, etc., limey soil, 

 humus, or peat, saline soil. 



Primarily plants may be said to be either fond of 

 a limey soil and calciphile, or not, when they are 

 calcifuge. The same sort of relationship exists 



