PREFACE ix 



We stand at a new point of departure in our theories of the 

 evolution of the higher plants. Arber was one of the first to 

 realise this, and his memoir represents a bold and vigorous 

 effort to grapple with the problems as they presented them- 

 selves to him, at the dawn of a new epoch. 



It is fair to mention that the last chapter, "On the Origin of 

 the Stele in the Earlier Cormophyta," was regarded by the 

 author himself as quite unfinished; it could hardly have been 

 otherwise with the data at his disposal. 



It has been a pleasure to me to write these few lines of appre- 

 ciation of mj^ old friend's latest work, 



D. H. SCOTT. 

 October 2, 1920. 



