The Braclcen Fern in Siliceous Grassland 143 



bircli, as in the south, may also colonise, and even fomi 

 woods on, heathland, but it is almost certainly unable to 

 withstand the competition of pine on such soils, because 

 of the deep shade cast by the latter, if the two species 

 meet under equal conditions. 



Pteris aquilina is an abundant constituent of the more 

 open woods on siliceous soils except in the 

 FemTn"^^'* dampest places, and it very frequently per- 

 SUieeous ^^^^^ after the woodland has disappeared. 



grassland. -^^ enormous extent of siliceous grassland 



in the north and west of England, and in 

 Scotland, is covered with this fern, which rapidly spreads 

 and covers the ground as soon as the shade of the trees 

 is removed. Under its shelter several woodland species 

 often maintain themselves, e.g. 8ciUa nov^scripta, Anemone 

 nemorosa, Oxalis Acetosella. The bracken does not fully 

 expand its fronds till early June in the south and late 

 June in the north of Great Britain, so that during the 

 spring the grasses and other low-growing constituents of 

 the turf can vegetate. In the late summer and autumn 

 however the light is cut off from them by the dense 

 foliage of the bracken. Thus the area occupied by Pteris 

 is withdrawn from pasturage during a considerable part 

 of the year and it thus becomes quite a pestilent weed of 

 the semi-natural siliceous pastures. Enormous tracts of 

 land are greatly lowered in value from this cause. Deep 

 ploughing is the only method of eradicating the deeply 

 situated rhizomes of the fern, though repeated mowing 

 at the beginning of the growing season will in time starve 

 the plants. The bracken is often cut in the autumn for 

 use as litter. 



