48 VEGETATION OF THE PEAK DISTRICT [CH. 



rather remarkable therefore that the plant is not indigenous in 

 the Pennine woods at the present time. Still, judging from 

 the paucity of the number of the records of buried pine 

 timber, the species does not appear to have been more than 

 an occasional or, at most, a locally abundant integer even 

 in the prehistoric woods of the Pennines; and it probably 

 became extinct at a very remote date. At the present time, 

 seedling pines are not abundant on the Pennines even in and 

 around pine plantations ; and the tree does not flourish nearly 

 so well on these hills as on the dry and sandy heaths in the 

 south of England. 



The only species of poplar which is indigenous in this 

 district is the aspen (Populus tremula); and even this species 

 appears to be quite rare in the oak and birch woods. Other 

 poplars (e.g., *P. canadensis and *P. candicans) are planted 

 occasionally, though more frequently on the outskirts of the 

 woods than inside the woods themselves. 



Several indigenous species of willow occur. Salix cinerea 

 is common, and ascends to nearly 1200 feet (366 m.) in some of 

 the cloughs. 8. caprea is occasional ; but both S. cinerea and 

 S. caprea are absent from the driest woods. 8. aurita is local, 

 but occasionally forms thickets in damp spots in the cloughs. 

 S. pentandra is also rare. Hybrids of S. caprea, S. cinerea, 

 and S. aurita are not uncommon. S. repens occurs, but is 

 rare. S. fragilis, 8. viminalis, 8. caprea x viminalis occur 

 locally by the stream sides, at altitudes below 600 feet 

 (183 m.). Although 8. alba, S. purpurea, and x S. rubra 

 (=8. purpurea x viminalis) are recorded (Linton, 1903), they 

 are perhaps not indigenous in the Peak District. 



The hazel (Corylus Avellana) is rather abundant in the 

 damper woods, but much rarer in the drier ones. 



The common birch (Betula pubescens) is, on the whole, the 

 most constant and the most abundant associate of the sessile 

 oak. Forms or varieties with glabrous or sub-glabrous twigs 

 (B. pubescens forma denudata) are not uncommon: B. pubescens 

 var. parvifolia is rare, but has been observed. In some of the 

 woods, however, the birch is rare or absent. Not infrequently, 

 the birch becomes locally dominant in places where extensive 

 felling of the oak and no subsequent planting, have taken 

 place ; and its small, light, and winged fruits are evidently of 



