126 Plant-formation of Siliceous Soils 



taken place. The white birch {B. alba = B. verrucosa) 

 is probably not indigenous in these woods; and the 

 pendulous form {B. alba forma pendula = B. pendula 

 Roth.) is extremely rare even as a planted tree. 



The wych elm (Ulmus glabra Huds. non Mill.; U. 

 montana) is indigenous, and occurs up to about 1000 feet 

 (305 m.). Above this altitude, it occurs in plantations up 

 to 1500 feet (457 m.). It is a constant and sometimes an 

 abundant constituent of the damper woods, but is rare in 

 the drier ones. In favourable localities, seedlings are very 

 common. 



The rowan or mountain ash (Pyrus Aucwparia) occurs 

 in most of the woods ; and, in rocky, upland, and heathery 

 situations, it is often very abundant. 



The holly {Ilex Aquifolium) also is found in almost 

 every oakwood on the Pennines ; but, although it some- 

 times produces flowers, it rarely fruits. 



The ash (Fraxinus excelsior) and the alder (Alnus 

 rotundifolia) are almost limited to stream sides and 

 marshy places, where, however, they are often very 

 abundant. 



Of rarer trees, the aspen (Populus tremula) and the 

 small-leaved lime (Tilia cordata ; T. ulmifolia ; T. parvi- 

 folia) are very rarely met with; and possibly they are 

 not indigenous on the siliceous soils of the Pennines. 

 The cherry {Prwnus Cerasus and P. Avium) also occurs 

 in the woods, and is locally not uncommon. 



A number of shrubby species are fairly abundant and 

 snruDs characteristic on the damper soils, but there 



is no species which is generally dominant. 

 Brambles are exceedingly abundant and very many 

 species are recorded by batologists. Rubus Selmeri and 

 B. dasyphyllus ascend higher than any of the other forms. 

 R. csesius is rather rare and confined to the lower levels. 

 Of the roses, R. canina is fairly abundant and R. arvensis 

 locally so at the lower altitudes ; among the less common 



