ECOLOGY OF WOODLAND PLANTS. 347 
b. A typical Mixed Deciduous Wood of the Plateau and Slopes 
of the Millstone-Grit Area. 
Figs. 7 and 8 (pp. 348, 349) of Armitage Bridge Woods 
ilustrate the characteristic features of the woods skirting the 
edge of the Gritstone Plateau. 
The three portions of this woodland are known by distinctive 
names, as is common in the woods of the district generally. 
They surround that portion of the plateau known as Netherton 
Moor, cut off from the main tableland by the stream in Dean 
Clough to the north, by Mag Brook to the south, this stream 
joining the River Holme, which forms the eastern boundary. 
The plateau is under cultivation, but skirting the margin and 
covering the slopes are the relics of the primitive vegetation. 
As shown by the contour-lines, the altitude at the edge of the 
plateau is 550 feet. It then suddenly drops to 375 ft., or about 
2in 5. The upper portion has a very shallow sandy soil covered 
with a thin layer of peat, and succeeded below by shales and 
clays overlaid with deeper moister soils. The distribution of 
trees is shown in fig. 7. In Old Spring Wood and Spring Wood 
the dominant tree is Oak, with an admixture of Birch and Pine, 
and while Oak is the dominant tree in Mag Wood, areas to the 
north and east are occupied by shade-trees, Sycamore (Acer 
Pseudo-platanus, Linn.), Elm (Ulmus montana, Stokes), and 
Beech (Fagus sylvatica, Linn.) The characteristic plants of 
the undergrowth are shown in fig. 8, and they are Deschampsia 
Jiexuosa, Pteris aquilina, Calluna Erica, Vaccinium Myrtillus, 
and Holcus mollis. A reference to this map will show clearly 
the effect on the vegetation of the changed conditions in a very 
short distance. While the distribution of Bracken seems to be 
limited to a large extent by the shade-trees, obviously other 
factors come into play to limit its distribution in the Oak areas. 
In the higher parts of the wood, where the soil is shallow, 
sandy, and covered with a thin layer of peat, Bracken oceurs in 
patches and is in competition with Ling and Bilberry; their 
rhizomes must of necessity occupy practically the same layer, 
and frequently we find them interlacing. Here we have a Xero- 
pteridetum, the elements of which are not complementary ; they 
form what we may term a competitive association, sometimes 
one, sometimes the other species dominating. Below this is a 
transition region, from the sandstones to the shales and clays ; 
