vi BEITISH PLANTS 



superior qualities, to win a habitation which they them- 

 selves could not retain. 



The book is divided into three parts. The first part 

 deals with fundamental ecological considerations — the 

 factors of the physical 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 ex- 

 pression 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 development, 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 weU known. It only 

 remains for the student to apply them to the inter- 

 pretation of the facts of the flora of his own neighbour- 

 hood. 



The book is designed as a companion to the elementary 

 text-book and the field flora. To aid the reader, the 

 subject-matter 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. 



In this new edition a rather large number of altera- 

 tions and additions have been made in order to keep 

 pace with the onward march of the subject. Some of 

 these, it is hoped, may be of considerable interest to the 

 reader in view of the present tendencies of economic 

 botany and agriculture; others, on the ecological side, 

 are due to the authors' desire to incorporate in their 

 book some of the most important features of the work 

 which has been done in various parts of the world since 

 the pubhcation of the first edition. 



August, 1920. 



