ECOLOGY OF WOODLAND PLANTS. 361 
conditions, favour the development of Xerophytes. It is a 
typical physiologically dry area. Although the unreclaimed 
heather moors are now small in extent and somewhat widely 
separated, the roadside vegetation often consists of the relies of 
the original moorland, and is of the heather moorland type, and 
this indicated on the large-scale maps shows the present moor- 
lands to be joined by a network of heath-plants. This primitive 
vegetation is only kept in check by heavy manuring, and if that 
is neglected the fields soon revert. Many acres which formerly 
produced rich crops have now “gone back” to moor. This 
type of vegetation extended formerly over the whole of the 
Gritstone area. The features thus brought out help us in great 
part to reconstruct the former vegetation of the Moss Moor and 
Millstone-Grit plateau. 
Although the rainfall in the latter area is considerable, the 
soils are so permeable and poor in humus that they retain little 
water. Heavy manuring in a great measure corrects this, but 
when this is discontinued the less resistant cultivated plants 
give way to xerophytes, which alone can withstand the drier 
conditions and the sudden changes of temperature to which 
such soils are liable. 
As Graebner has shown, the effect of rich nutrition on heath- 
plants, while it favours increased growth, renders them less 
able to withstand the extremes of drought and cold. 
Oak is the dominant tree, but prior to cultivation, as shown 
by Moorhouse (69) and in ancient records, it was much more 
extensive in this area. Along the edges of the plateau, Birch 
(Betula verrucosa, Ehrh.) is abundant and at Honley Moor are 
plantations of Pine, while Holly (Llev Aguifolium, Linn.) is 
common on the slopes of Honley Wood. The tendency in 
recent years has been to replace Oak with Sycamore, Elm, and 
Beech. Woodlands are developed chiefly along the valley-slopes, 
and on the map they give a general idea of the contour of the 
country, and appear much narrower than they really are. The 
eastern boundary of the Gritstone plateau is well marked by 
these woods, the woods on the plains being characterized by 
their broader (squarer) outlines. 
The prevailing west winds sweep across these plains, and a 
reference to the map will show that plants growing in the open 
oak-birch woods, along the edge of the plateau, are placed under 
conditions of drought and exposure (especially when we 
