PREFACE vii 



TiUyard, Prof. A. Wall, Dr J. E. B. Wanning, Prof. D M S 

 Watson, and many others. That I have been able to carry out 

 this work at all I owe to the labours of generations of systematists, 

 botanical and zoological, foremost among whom, inasmuch as 

 the hypothesis of Age and Area was originally founded upon 

 their work, I must place my predecessors in Ceylon, G. H. K. 

 Thwaites and Henry Trimen. I must also specially mention 

 Sir Joseph Hooker, as this work forms a continuation of his 

 labours of the fifties. Last, but not least, I am deeply grateful 

 to my wife, and to my relatives, Mrs and Miss Steel, Vo^'r much 

 help ungrudgingly given. 



For illustrations I am much indebted for loan of blocks to the 

 Royal Society, and to the Editors of the Annals of Botany, Nature, 

 and Nezv Plnjtologist: also to my daughter Margaret, who made 

 the drawings from which all, except those on pp. 125, 153, 173, 

 241 and 242, were jDrepared. 



J. C. WILLIS. 



Cambridge, 



4 April, 1922. 



