THE VEGETATION OF WOODLANDS. 21 



higher altitudes the bearberry i^Arctostaphylos) and crowberry 

 {Empeirum) form large cushions. Humus is everywhere present, 

 varying from a few inches to deep peat. In the undergrowth 

 of these woods several small plants occur which are rare in 

 most places, except in these old pine-woods, such as the winter- 

 greens {Pvrola), chickweed wintergreen {Trientalis), and several 

 small orchids {Goody era repens, Listera cordata, etc.). The 

 natural habitat of the pine-wood is in a zone above the oak-wood, 

 and it competes with birch-wood for the higher ground up to 

 about 2000 feet. It is well known that remains of birch and 

 Scots pine occur extensively in the peat of the higher moorlands, 

 which are now treeless. It is probable that many of these 

 moors could again be afforested with Scots pine, spruce and 

 larch, but one rarely sees any attempt to establish hardwoods 

 in the natural area of the Highland birch and pine. 



(3) Beech and Ash Series. — These constitute the third great 

 group of the woodlands of England. During the earlier 

 botanical surveys in Yorkshire, it was found that ash was the 

 dominant tree in woods on limestone soils. This was confirmed 

 later in the surveys of Somerset and Derby by C. E. Moss. 

 Beech-woods are also known to be the natural woodland on the 

 calcareous soils of the chalk. 



The typical ash-wood is best developed on the massive 

 exposures of the mountain limestone in England, which are 

 highly calcareous. Oak is rare on this limestone, and the 

 experience of foresters is that it does not grow well when planted, 

 except in the more alluvial soils of the valley-bottoms. As 

 regards moisture, the ash may be found on wet soils, through 

 all degrees of moisture to a rocky knoll with a shallow soil. 

 There is, however, a general belief that the ash prefers moisture, 

 and it is possible that, in what appear to be dry soils, its deeper 

 roots may find in the limestone fissures a constant supply of 

 moisture. 



Wych elm and hawthorn are common associates of the ash, 

 and in some districts yew and whitebeam {Fyrta Aria). The 

 ground-vegetation varies according to the water-content of the 

 soil. In wetter parts wood-garlic {Allium ursinum), red campion 

 and valerian are generally present ; in slightly drier parts dog's 

 mercury often forms continuous unbroken sheets ; in dry parts 

 ground ivy {Nepeta glechoma) frequently forms a carpet. These 

 ash-woods are full of interest to the botanist, because there a 



