ECOLOGY OF WOODLAND PLANTS. 359 
within the last 70 years. They cut it into long splinters and 
made it serve for candles,” In Switzerland and elsewhere on the 
the continent, such pine splinters (or “ Kienspähne ”) are still 
frequently used for this purpose. The altitude of these moors 
ranges from 800 to 1100 feet. This succession of deposits is 
well seen in section at Wessenden Head and Deerhill, where the 
series has been cut through by moorland streams. At the base 
is a thick bed of bluish clay which is permeated by numerous 
root-fibres. Above this is the moor pan, a layer of only a few 
inches in thickness, which can be easily detected by the peculiar 
grating sound produced when the blade of a knife is pushed into 
it. Resting on this is a thick bed of peat from four to six feet 
in thickness, while in some parts it very greatly exceeds this. 
At the base of the peat, remains of birch are abundant, especially 
at Deerhill, where the overlying peat, having been denuded, a 
very large number of birch remains are to be seen. We have 
here just those conditions necessary for the accumulation of peat, 
as indicated by Hall (43), Livingstone (60), and others, viz., con- 
siderable rainfall and an impermeable stratum, which result in a 
waterlogged soil, cutting off access of air and so checking the 
process of oxidation and the development of aerobic bacteria. 
These conditions, together with the poverty of the soil in 
mineral salts, especially carbonate of lime, favour the accumu- 
lation of humus and of humic acid; this in turn affects the 
osmotic action of the roots, with the result that, even in perma- 
nently wet places, xerophytes only can exist, and these are also 
favoured by the general climatie conditions of this zone. A. 
general account of these peat-moors has recently been given by 
C. E. Moss (71). 
On the steep hill-slopes peat is either very thin or absent, the 
soils being formed by denudation of the grits, shales, and clays, 
and forms a transition region to the Heather Zone of the Mill- 
stone-Grit Plateau. 
These slopes are clothed with a very characteristic vegetation. 
Pteris is the dominant plant, and its associates are Bilberry 
(Vaccinium Myrtillus), Ling (Calluna), Deschampsia, Nardus 
stricta, and Festuca ovina, forming a Xero-pteridetum. These 
may be traced ascending the deep cloughs in gradually narrowing 
strands, the Bracken becoming reduced in size (sometimes not 
more than a few inches in height) until on the exposed summits 
it is practically absent. A map showing the distribution of 
