94 The Plant-formation of Sandy Soil 



naturally characterised by absence of the great number 

 of woodland species which frequent damp soils. Societies 

 of Pteris aquilina, Holcus mollis (Plate Illb), and Scilla 

 non-scripta are characteristic. Potentilla erecta, Digitalis 

 'pwr'purea, Hypericum pulchrum, Galium saxatile and Soli- 

 dago Virgaurea are also specially characteristic. 



Changes in the level of the ground-water, owing to 

 the slope of the ground, sometimes lead to the alternation 

 of the damp and dry oakwood associations in the same 

 wood within very short distances. 



Subordinate Associations 



Just as in the case of the formation of clays and loams, 

 so here, there are retrogressive associations, consequent on 

 clearing of the woodland, and represented by scrub and 

 grassland. These are largely represented on the sandy 

 "commons" of southern England just as the neutral 

 pasture and corresponding scrub are represented on the 

 commons on clay soil. 



Scrub-association. This is dominated by the shrubs 

 of the dry oakwood whose spines protect them from 

 destruction by browsing cattle, i.e. Gratsegus monogyna, 

 Prunus spinosa, JJlex europseus and Rubus spp. The 

 association consequently closely resembles the corre- 

 sponding member of the plant-formation of clay and loam. 



The gorse (JJlex europseus) is perhaps the most abun- 

 dant and characteristic member of the scrub association. 

 It is frequently a pure dominant on the sandy commons 

 referred to, forming a close scrub under the shade of which 

 little can grow. The gorse actively spreads from seed 

 and forms a progressive society colonising the grass heath 

 association, where it flourishes much more vigorously 

 than under the partial shade of the dry oakwood. 



Grass heath association (Graminetum arenosum). 

 This association generally forms a close short turf, 



