PREFACE 



Some thirty years ago, a pupil of the strictest school of natural 

 selection, and enthusiastic in my belief in its principles, I set 

 out upon a course of independent observation of nature. Ten 

 years of such work convinced me that a simpler explanation of 

 phenomena was always to be found, and one that seemed more 

 in accordance with the facts; and I endeavoured — with what 

 success this book will show — to free myself from the trammels of 

 the natural selection theory, and to work as if I had found myself 

 in another planet where scientific investigation was just begin- 

 ning. Stationed in one of the best centres in the tropics (where 

 the phenomena of distribution are more impressive than in 

 Europe), badly handicapped in laboratory work by a serious 

 accident, and finding my chief pleasure in travelling about the 

 world to see its vegetation — I took up the study of distribution, 

 in which I had always taken much interest. 



Here, as elsewhere, it was soon evident that the current 

 theories pro^'ided an explanation that was not only unnecessarily 

 complex, but one that did not explain. As one of my critics 

 words it, "for some reason the plant has advantages which 

 enable it to spread"; and beyond that point we cannot go. 

 Gradually it became clear to me that plants spread very slowly, 

 but at an average rate determined by the various causes acting 

 upon them, so that age forms a measure of dispersal when one 

 is dealing with allied and similar forms. 



Age as an explanation of spread is enormously simpler than 

 natural selection, and that it is probably valid is shown by the 

 way in which it can be used for prediction. An opponent re- 

 marks that "it is too simple to be true," but this very simplicity 

 seems to me a strong reason in favour of its adoption, at any 

 rate as a preliminary hypothesis. Of two explanations take the 

 simpler, is an old rule, and as Hooker has said, "no speculation 

 is idle or friiitless, that is not opposed to truth or to probability, 

 and which, while it coordinates a body of well-established facts, 

 does so without violence to nature, and with a due regard to the 



