134 C. E. Moss, W. M. Rankin and A. G. Tansley. 
is no doubt largely due to the abundance of the seed, and to its 
efficient dispersal by wind, partly to the well known fact that the 
birch succeeds better on poorer soil than the oak. Partly owing 
to this cause, and partly, perhaps, because birch yields timber of 
much less value, and was therefore largely left during the period of 
great demand on oak for the navy, the native woodland of sandy 
soils is now very largely, and over some tracts almost exclusively, 
birch. This is the case for instance in Worth Forest, on the 
Hastings Sand of Sussex. 
A new factor in the vegetation of these sandy soils was 
introduced by the extensive planting of Scots pine (Pinus sylvestris ), 
which, according to most authorities, is not native in southern 
England. 1 This tree is said to have been introduced into the New 
Forest about 1770, but some of the southern planting probably 
dates back a good deal earlier than that. On all the dry sandy 
and gravelly soils, Scots pine flourishes exceedingly and reproduces 
itself freely from self-sown seed. In the neighbourhood of old pine 
plantations or of mature self-sown woods, thousands of pine 
seedlings in all stages of growth may be found colonising the 
heathlands, and, to a somewhat less extent, the open oak-birch 
woodlands. In this way, many of the south English heaths are 
being rapidly converted into pine woods, the pine easily beating the 
oak and beech in facility of seed-distribution, while the deeper shade 
which it casts enables it to conquer the birch in the later stages of 
competition. The process is only checked by the frequent heath 
and forest fires which occur in this part of the country in dry 
summers. On the wetter soils of the lulls of the north and west of 
England, pine does not now spread naturally to any appreciable 
extent, 3 though in the region of the Pennines, there is evidence 
from the wood found beneath the peat that pine formerly occurred 
as an occasional constituent of the ancient woods. 
Thus we see that much of the oak-birch-heath woodland is 
almost certainly derived from the dry type of oakwood and repre- 
1 It is, however, at least possible that the Scots pine is a native 
constituent of our southern woods. There are several records 
of the occurrence of pine wood in the southern peat, and it 
may be that the tree has remained as a subordinate constituent 
of the dry oakwoods till extensive clearing afforded the 
conditions for rapid colonisation of the sandy soils. 
2 On the Cleveland moors of north-east Yorkshire, however, 
where the rainfall is relatively low, the Scots pine spreads 
freely from seed. 
