10 PREFACE 



lized many of the ideas incorporated in this book. Most of 

 all, I owe a debt of gratitude to my teacher and friend, the 

 late Hugh Hamshaw Thomas, sc.d., f.r.s., who guided my 

 first thoughts on the evolution of plants and who was a 

 constant source of inspiration for more than twenty-five 

 years. It was he who first demonstrated to me that the study 

 of Hving plants is inseparable from that of fossils, a fact 

 which forms the basis for the arrangement of this book, in 

 which hving and fossil plants are given equal importance. 



Finally, my grateful thanks are due to my wife for her 

 helpful criticisms during the preparation of the manuscript. 



Jv. rv. S. 



Cambridge 



