CHAPTEE II 



THE PLANT-FORMATION OF CLAYS AND LOAMS 



These soils may be defined as hea^y or medium in 

 texture, containing a large proportion of fine particles 

 and a small proportion of coarse sand. Chemically they 

 are either very poor or comparatively poor in lime. On 

 one side they pass into the lighter sandy loams as the 

 proportion of coarse sand increases, and on the other into 

 the marls and calcareous clays with an increase in lime- 

 content. In places where the ground-water is stagnant, 

 as in hollows or on undrained flats, they become marshy 

 and tend to give an acid reaction. 



The distribution of such soils in England is very vnie 

 and extensive, particularly in the Midlands and the south- 

 east, where the Secondary and Tertiary geological forma- 

 tions are mainly developed. Some of the more extensive 

 clays are the Oxford and Kimeridge Clays of the Jurassic 

 formation, the Weald Clay, the G-auIt, the London Clay, 

 and the non-calcareous Boulder Clays of the north. The 

 Clay-with-flints overlying the Chalk varies from a heavy 

 clay to a light loam. The shales, wliich represent the clay- 

 formations of the older rocks, bear a vegetation which, 

 while resembHng that of the clays in many respects, differs 

 in important characters, and is considered as belonging 

 to a different plant-formation. 



The clays and loams, forming as they do many of the 



