11] WOODLAND ASSOCIATIONS 47 
Trees and Shrubs 
The sessile-fruited oak (Quercus sessiliflora) 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. sessiliflora) of oak. In this district, Quercus 
sessiliflora 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 sessilt- 
flora of this district; but the Scots pine (*Pinus sylvestris) 
and the larch (*Laria 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 
eacelsa), 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 
