IV] GRASSLAND ASSOCIATIONS 121 



the ecological relations show scarcely any perceptible alteration ; 

 and the soi-disant ' formations ' everywhere pass imperceptibly 

 one into another " (Gradmann, 1909 : 92). This criticism of a 

 method of classifying plant communities goes to the root of 

 the matter ; and the point of view which Gradmann here states 

 with lucidity and vigour is precisely the point of view which 

 the British school of plant geographers has definitely adopted. 



On bare slopes, where the soil is very dry, shallow, and 

 calcareous, the dominant grass (Festuca ovina) tends to become 

 much less abundant; and small plant societies, dominated by 

 such species as Brachypodium gracile, Lotus corniculatus, and 

 Thymus Serpyllum become numerous and abundant. 



The vegetation of the marshy places of the limestone slopes 

 is described in Chapter VI. 



Mixed Calcareous Grassland 



On ascending a steep slope of calcareous pasture in one of 

 the^ limestone dales, it is found that, at an elevation of about 

 1000 feet (305 m.), it opens out on to a plateau of upland 

 cultivation. From this plateau, rounded hill-summits rise, the 

 highest of which, on Bradwell moor, reaches an altitude of 

 1550 feet (472 m.). On the lower portions of the limestone 

 plateau, calcareous pasture may occur; but this is here fre- 

 quently fenced by characteristic white walls of loose blocks of 

 limestone. The walls indicate that some attempt has been 

 made to reclaim the land, and that regular grazing takes place. 

 Where the land has been ploughed at least once, and cultivation 

 continued, either permanent pasture or arable land still occurs 

 (see Chapter VIII) ; but if the land has never been ploughed or 

 if it has lapsed from cultivation, a type of grassland occurs 

 which is related to the primitive calcareous grassland. Sheep, 

 cattle, and horses may be frequently grazed over it ; and thus 

 those plants of the calcareous grassland which cannot endure 

 a high nitrogen content of the soil die off, while the rest remain. 

 A few other plants which tolerate the manuring of the soil 

 invade the pasture ; and thus a type of grassland occurs which 

 is, in a general way, related to the " Fettwiesen " of the Swiss 

 plant geographers (cf. Brockmann, 1907 : 332; Riibel, 1911 : 

 143). 



