Vegetation of Limestone Pavements 161 



being little evaporation, the soil is almost always moist. 

 Many of the plants found are those of the ash-woods, such 

 as the dog's mercury (Mercurialis perennis), the wood 

 garlic (Allium ursinum), and the hartstongue fern 

 (PhylUtis 8colopendrium= Scolopendrium vulgar e); but in 

 addition to the woodland species, there are Bibes petrseum 

 Sm., the green spleenwort (Asplenium viride), Lastrea 

 rigida, and the holly fern (Polystichum Lonchitis). 

 The following is a more complete list : 



Sometimes, in more sheltered places, the limestone 

 pavement becomes completely overgrown with vegetation 

 and an ashwood may then take possession of the habitat 

 (Plate XIV b). 



The Sub-formation of the Chalk 

 By A. Gr. Tansley and W. M. Rankin 



The English chalk uplands^ called "downs" in the 



south and " wolds " in the north, have 



Characters of y^He extension in the south and east of 

 tne cnaJK. 



the country. Their well-known soft and 



rolling contours are very familiar to dwellers in and 



travellers through the country lying east and south-east 



of a line drawn from north Yorkshire southward to 



Buckinghamshire and thence south-westward to the 



Devonshire coast of the Channel. 



T. 11 



