II] WOODLAND ASSOCIATIONS 47 



Trees and Shrubs 



The sessile-fruited oak (Quercus sessiliftora) is undisput- 

 ably the prevailing tree of these woods. Because of the com- 

 paratively great amount of light which penetrates the oak 

 canopy, the ground is fully covered by vegetation ; and therefore 

 the tree may be spoken of as the dominant species, as it exercises 

 a controlling influence on the rest of the vegetation of the wood. 

 In the earlier accounts (op. cit.) of the vegetation of the Pennines, 

 the plant was referred to as " Quercus Robur Linn." It has, 

 however, been shown (Moss, 1910 a) that this name refers to 

 the peduncled oak alone, and that it is possible and desirable 

 to distinguish separate associations of the two British species 

 (Q. Robur and Q. sessiliftora) of oak. In this district, Quercus 

 sessiliftora grows well and forms moderately large trees up 

 to an altitude of about 800 feet (244 m.), particularly on the 

 shales : above this altitude, especially on soils over the massive 

 sandstone rocks, the trees are apt to be of short stature and 

 of small girth ; and near the present altitudinal limit of wood- 

 land, the trees are often little bigger than shrubs (see figure 3). 

 Seedlings are often met with in the damper woods, but are rare 

 in those with a peaty soil at the higher altitudes. 



The pedunculate oak (* Quercus Robur) is absent from the 

 great majority of the oak woods of the Pennine slopes. As has 

 been already stated, this species is found in a few of the western 

 woods situated on the glacial sands : elsewhere in the district it 

 only occurs as a planted tree, along with other aliens, such as 

 the sycamore, the beech, the larch, and the pine. It is present, 

 as might be expected, in most of the newer plantations and in 

 park-lands; but, even in such localities, it is not very abundant, 

 and it rarely grows to a large size. 



No conifers are indigenous in the woods of Quercus sessili- 

 flora of this district; but the Scots pine (*Pinus sylvestris) 

 and the larch (*Larix decidua) are frequently planted. Other 

 conifers occasionally or rarely met with in the woods are the 

 black or Austrian pine (*Pinus austriaca), the spruce fir (* Abies 

 excelsa), and the Douglas fir (*Pseudotsuga Douglasii). 



As sub-fossil timber, the Scots pine is occasionally found 

 buried under the peat of the southern Pennines; and it is 



