6 Origin of the British Flora. 



dispersal of the various species which constitute our flora, 

 with special reference to the present and past distribution 

 of the plants. Finally, I propose to give an historical 

 account of each species as far back as geological evidence 

 will yet allow it to be traced. 



It may be considered presumptuous to attempt such a 

 task ; but, though the following Chapters are most imper- 

 fect, yet they may do good by directing attention to lines 

 and methods of research which are as yet little appreciated. 

 The section on the geological history of our flora, being a 

 record of the actual distribution in space and time of our 

 plants from direct observation, will perhaps be the one to 

 which botanists will most readily turn. It may be sug- 

 gested, however, that the section on means of dispersal is 

 equally important, and that the connexion between the 

 different Chapters is so close that it is impossible properly 

 to appreciate the relationship of the living plants to their 

 fossil representatives without a study of the subject from 

 various points. 



Though the present volume is professedly occupied with 

 a discussion of the origin of the British flora, it should not 

 be forgotten that in questions of geographical distribution 

 it is impossible to separate animals from plants, for many 

 plants are directly dependent on certain animals for means 

 of dispersal. Moreover, certain animals are dispersed by 

 the same means as flowering plants, have the same difficul- 

 ties to contend with, are no less dependent on climatic 

 conditions, and are almost equally tied to a single spot 

 during the lifetime of the individual. The land mollusca 

 in particular are in these respects so like the more sedentary 

 species of flowering plants that I have not hesitated to 

 speak of them where they help to illustrate the subject 

 under consideration. Beetles, I believe, would also be of 

 use ; but of this order I have unfortunately no knowledge, 



