H 7 
The Woodlands of England. 
observed correlation of the second and third woodland series with 
lime-content is sufficiently close to afford a satisfactory basis for 
classification, hut we have advisedly abstained from committing 
ourselves to the view that the lime-content is the cause of the 
observed distribution of woods. In any case we are convinced that 
this class of criteria furnishes a more natural basis for the primary 
classification of English vegetation than water-content alone, or 
even than so-called “physiological water-content.” 
We might, however, construct a classification of oakwoods on 
the basis of the dominant species of oak, rather than on water- 
content of the soil, and for such a classification there is much 
to be said. Quercus sessiliflora is certainly the characteristic oak 
of the north and west of England, just as Q. Robur is of the 
south and of the midlands. The vast majority of observed oak- 
woods are pure woods either of Q. Robur or of Q. sessiliflora ; 
comparatively few have the two mixed. It has even been suggested 
that where a mixture of the two species obtains it always indicates 
planting of Q. Robur, which in the vast majority of cases, at any 
rate, is the species planted. 1 But we have satisfied ourselves that 
the mixture of the two species is too general an occurrence on 
certain types of soil, particularly on sands and sandy limestones, to 
allow of this hypothesis being entertained. 
The factors which lead to the observed distribution of the two 
oaks are not yet clear; the two species certainly can and do flourish 
side by side on the same soil. Climate has been suggested as the 
differentiating factor, and the general distribution of the two species 
might seem to support such a suggestion ; but it is not borne out 
when we consider the fact that natural or semi-natural woods of 
the two species occur in the same region. The most probable 
hypothesis is that the main determining factor is depth of soil, for 
Q. Robur is certainly pre-eminently characteristic of the deep-soiled 
clays, loams and fine sands, which are mainly found in the south, 
in the east and in the Midlands, while Q. sessiliflora is equally 
characteristic of the shallow-soiled paleozoic sandstones, grits and 
mudstones of the north and west. 
If the dominant trees alone were concerned, a primary classifi¬ 
cation of oakwoods according to the dominant species would be the 
1 Mr. Lascelles, Deputy-Surveyor of the New Forest, however, 
in a letter to one of us, states his opinion that the plantations 
of 1700 and thereabouts, now the finest woods of the Forest, 
were in many cases purposely planted with Q. sessiliflora. 
