Notes and Conuiiciits. 319 



harbour several woody species characteristic of chalky and 

 limestone soils, such as Rhamnus caihayticiis and Viburnum 

 Lantana, while in the Alder-wilknv thickets occurring on soils 

 fed with neutral or acidic waters, calcicole species are absent. 

 From this lowland type two great systems occur, the distribu- 

 tion of which follows, in the main, two chief classes of soil, 

 siliceous and calcareous. 



(11.) OAK AND BIRCH SERIES. 



The woods in this series occur on all the ' siliceous ' [i.e., 

 non-calcareous) soils, ranging from the stiffest clays to sand 

 and gravel, and derived from rocks of various ages. \\'iLhin 

 this series three associations occur, but more or less merging 

 into one another. 



(.4) An Oakwood Association, by far the most widely 

 distributed of British Woodlands. The dominant 

 tree is Quercus Robur { = Q. pednnculata). Owing 

 to the great variety of soils on which the oak is 

 dominant, the associated trees and especially the 

 ground vegetation, show a wide range, and two 

 groups of associations are distinguished — {a) Damp 

 Oakiaoods on clays and loams of the London Clay, 

 the Gault, the Weald Clay, etc., in the south of 

 England ; these are connected by every gradation 

 wiih [b) \he Dry Oakvvoods, found on coarsely- 

 grained, siliceous, shallow soils of the Palaeozoic 

 and igneous rocks of the west and north of Eng- 

 land. In these woods Q. sessiliflora is usually 

 dominant, but with a varying admixture of 

 Q. Robur. 



(B) The Oak-birch-heath association is a type charac- 

 terised by the presence in the ground vegetation of 

 bilberry, hair grass and ling. Such woods cover 

 wide areas in Kent, Surrey, Sussex, and locally 

 as far north as Cheshire and Nottingham. This 

 wood is probably a stage in the degeneration of 

 oak forest to heath land, similar to that described 

 by Graebner in the great heaths of the north-west 

 German plain. In the hilly districts of the north 

 of England, the woods on non-calcareous soils are 

 dominated by Q. i>essiliflora, but this tree becomes 



1910 Sept. I. 



