PREFACE 



THREE motives run through this book : An at- 

 tempt to expound the progress of evolution in objects 

 which are familiar and which have not yet been 

 greatly modified by man ; an effort to make a simple 

 historical record from unexplored fields ; a desire to 

 suggest the treasures of experience and narrative 

 which are a part of the development of agriculture, 

 and from which the explorer must one day bring ma- 

 terial for history and inspiration for story. 



It is now more than ten years since these studies 

 were begun. Some of the material has been published 

 in bulletins and journals, as indicated at intervals in 

 the text; but the continuity of the effort and the full 

 historical retrospect are first apparent in this book. 

 The prosecution of the studies has demanded the con- 

 sultation of original sources of information, when 

 such have been accessible, and it has required much 

 travel, including a visit to European herbaria in which 

 the types of certain species of plants are deposited ; 

 and the necessity of these verifications has delayed 

 the publication of the work two years after the com- 

 pletion of the manuscript. Yet, the book is only a 

 sketch. The subject has little continuity or homo- 



(vii) 



