vi PREFACE 
history of strife with the elements, of invasions, of 
colonization, of the formation of communities and asso-— 
ciations. In the course of time they change ; some perish ; 
others give origin to new forms destined one day to dis- 
place them, and, through their superior qualities, to win 
a habitation which they themselves could not retain. 
The book is divided into three parts. The first part 
deals with fundamental ecological considerations—the 
factors of the environment—water, temperature, light, 
air, and soil. 
The second part comprises a general description of 
British plants examined in the light of these factors and 
considered as an outcome and expression of them. 
The third part is an attempt to present in an elementary 
manner the physiognomy of the British flora in its most 
conspicuous associations, to explain its origin and develop- 
ment, and to analyze its present distribution. 
The matter dealt with in the third part covers a wide 
field, and in the present state of our knowledge only a 
broad survey can be attempted. This department of the 
science is quite a recent one, but the principles of eco- 
logical botany are now fairly well known. It only remains 
for the student to apply them to the interpretation of the 
facts of the flora of his own neighbourhood. 
The book is designed as a companion to the elementary 
text-book and the field flora. Most examination-papers 
now contain questions on ecology, but they are seldom 
attempted with success. Special attention has been 
given to the claims of the general reader as well as to 
the needs of students and teachers of Nature Study. 
The subject-matter, therefore, has been treated wherever 
possible in a suggestive manner, so that interest may be 
awakened and inquiry stimulated. With this end in 
view, we have been sparing of technical terms, and care 
has been taken to explain their meaning and to give their 
derivation where necessity or convenience has compelled 
their use. 
