X PREFACE TO THE ENGLISH EDITION. 



the records of economic interest are selected chiefly from Farlow 

 and Seymour's Host-Index, which contains the complete list. 



I here take the opportunity of expressing my thanks to 

 Professor I. Bayley Balfour for valuable aid and advice; to 

 Professor J. W. H. Trail for kindly revising important parts of 

 the proofs; to my brother, Eobert Smith, for assistance in proof- 

 reading, and to other friends who have aided me. 



The difficulties of translation are well known ; in the present 

 case they have been increased by the technical nature of the 

 subject, and by the modification which the original has under- 

 gone. Faults there must be; for those I ask the indulgence of 

 the reader. 



W. G. SMITH. 



Royal Botanic Garden, 



Edinburgh, October, 1896. 



