J. J. Griffith 371 



cases contamination of the soil leads to a very considerable change in 

 the type of vegetation. Speaking generally, bent-grass (Agrostis vul- 

 garis) predominates and where the harmful effect is very pronounced 

 the herbage may consist entirely of bent. Where the situation is some- 

 what damp there is a tendency for Yorkshire fog {Holciis lanalus) to 

 take the place of bent to some extent, and even Molinia coerulea may 

 flourish in some comparatively wet situations although it does not 

 appear on the adjoining unaffected land. Another peculiarity of these 

 affected pasture lands is the almost universal absence of clovers even 

 in areas where contamination is but comparatively slight. It appears 

 that clovers are less resistant to the evil influences of mine refuse than 

 almost any plant entering into the composition of the herbage on normal 

 soils. Sheep's fescue (Festuca ovina) flourishes relatively well on soils 

 which are only slightly affected. The presence of certain weeds, e.g. 

 Viola lutea and sea campion (Silene maritima), also frequently serves 

 to distinguish the affected areas. 



The general appearance of affected pasture land is such as to enable 

 one to draw the line of demarcation between it and the non-affected 

 land with comparative ease, the herbage of the former being scanty, of 

 poor quality, and, towards the autumn, showing proportionately much 

 more withered inflorescence. 



In order to illustrate the results of my observations with reference 

 to the effects upon grass land, Mr R. G. Stapledon kindly carried out a 

 botanical analysis of the herbage on a field which is quite typical of the 

 affected land. In Table I, A represents the herbage on unaffected land, 

 while B and C show the composition of the herbage on affected land in 

 the same field. 



Table I. 



