TIMBER PRODUCTION 53 
common oak flourishes in heavy soils of this character 
when of sufficient depth. On non-calcareous soils the 
common oak is restricted to the heavier and the durmast 
oak to the lighter soils. But the outstanding feature 
elicited by a study of the distribution is that deep soils 
are only necessary for the common oak, whilst the other 
species flourishes on relatively shallow soils where, 
moreover, it produces quite good timber. 
From an investigation upon which the writer is 
engaged at the present time, I believe it will also prove 
to be a fact that whereas Quercus robur requires a soil 
relatively rich in mineral salts, Quercus sessiliflora grows 
well in soils which are relatively deficient in this respect. 
It is by no means infrequent to find plantations of 
Quercus robur on light soils to which it is quite unsuited, 
as also on shallow soils where it grows for a time but 
afterwards becomes stunted. 
The question naturally arises as to whether there is 
any difference in the quality and properties of the 
timber produced. 
The sp. gr. of the wood of Q. sessiliflora is slightly 
higher than that of Q. robur, and, though the available 
data are somewhat conflicting (doubtless owing to 
confusion of the species), it seems evident that for 
durability and strength the wood of Q. sessiliflora is 
preferable to that of Q. robur. Moreover, the grain 
of the common oak is not so even and consequently 
harder to work than that of the durmast oak. 
A very important difference is that whereas Q. robur 
tends to produce a short bole with numerous strong 
branches, the durmast oak usually, even when grown 
in open canopy, forms‘a long straight bole with weak 
