REVIEW 
39 
a formation as “ the whole of the vegetation which occurs on a definite 
and essentially uniform habitat” (p. 19). This implies of course that (1) the 
same formation cannot exist in two distinct geographical areas, and (2) while 
the species and even perhaps the growth-forms in a given locality may 
disappear and give place to new ones, yet the formation remains the 
same. On the continent there is rather a tendency to take another 
view of the connotation of the term “ formation.” In the opinion of 
E. Warming, for example, “a formation appears with a certain determined 
uniformity and physiognomy, even in different parts of the world and even 
when the constituent species are very different and possibly belong to 
different genera and families.” Warming, in agreement with a body of 
continental ecologists, does not include the succession of evolutionary 
stages in the idea of “ formation ” — i.e. the same definite and essentially 
uniform habitat may support a succession of different formations at successive 
periods. This divergence of opinion is considerable and there is much to 
be said in favour of either view. In the interests of ecology a general 
agreement on so fundamental a question is much to be desired. The greater 
the interest taken in the subject and the more widespread its study in the 
field, the sooner will this goal be reached. 
As the author points out, the Peak District possesses no definite 
geographical boundaries. For the purposes of this book the area considered 
measures approximately 400 square miles. In it there are recognised five 
of the fourteen British plant-formations, viz. those of (1) Calcareous soils, 
(2) Siliceous soils, (3) Acidic Peaty soils (Moor Formation), (4) Fresh 
waters, (5) Cultivated land. In the northern half of the area (i.e. the 
plateau known as the Peak), No. 3 is by far the most extensive; in the 
southern section, cultivated land predominates. The associations marked 
by the presence of Heaths and Vacciuium are of course characteristic of the 
moors (No. 3). 
To South African readers the remarks upon various retrogressive associa- 
tions will be of particular interest (see pp. 20, 21, 97, 98, 188). South Africa 
should be a fruitful field for the study of the deterioration and disappearance 
of stable communities from large areas over which their predominence was 
once unchallenged — a study of no little economic importance. 
The book is written in an interesting manner and is tree from that em- 
barrassing richness of formidable technical terms which has characterised many 
ecological treatises. The majority of the photographs used for illustration 
are excellent and well reproduced. The work may be confidently recommended 
to any intending to follow this fascinating branch of botanical study. 
