THE VEGETATION OF WOODLANDS. 23 



wood sanicle, several violets (including Viola hirta), and several 

 rather rare wood orchids. In ascending a chalk escarpment 

 or valley side, one frequently observes near the summit a 

 sharp change from beech-wood to oak-wood, while the plateau is 

 covered with typical oak-wood. This is due to a definite change of 

 soil, the " clay with flints " which forms sheets of varying thick- 

 ness over the chalk, being typically non-calcareous. Typical oak- 

 woods also occupy areas on the rolling chalk plateau of 

 Hampshire, but though these areas are geologically mapped as 

 "chalk," the woods are invariably found to be developed on 

 non-calcareous soils overlying the chalk. 



The notes on woods just given may gain clearness if we 

 reproduce here the following summary from the " Woodlands of 

 England " : — 



I. Alder-Willow Series : on very wet soils. 



II. Oak and Birch Series : on non-calcareous soils. 



(A) Oak-wood Associations : on non-peaty soils at low 



and moderate elevations. 

 {a) Damp Oak-woods: on clays, shales, loams, fine 



sands, and moist soils generally. 

 {b) Dry Oak-woods: on sandstones, grits, sands, and 



dry soils generally. 



(B) Oak-Birch-Heath Association : on dry, coarse, 



sandy, and dry peaty soils (low elevations). 



(C) Birch-wood Association : on non-calcareous soils 



at high elevations. 

 [The Pine-wood Association (of Scotland) : on non-calcareous 

 peaty soils at moderate and high elevations (up to 2000 feet).] 



III. Beech and Ash Series : on calcareous soils. 



(A) Ash-Oak-wood Association : on calcareous clays, 



marls, impure limestones, and calcareous sand- 

 stones. 



(B) Ash-wood Association : on limestones. 



(C) Beech-wood Association : on Chalk in the south- 



east of England, with a western extension on the 

 Oolites of the Cotswold Hills. 



{To he concluded.) 



