NOTE TO THE FOURTH EDITION. 



THE present edition has been revised and brought up to 

 date where necessary. The most important change is 

 under Type XXL, the Lichens, the description of which 

 has been considerably extended, so as to include an 

 account of the sexual reproduction, the evidence for 

 sexuality in Lichens having been materially strengthened 

 of late years. The author is greatly indebted to Dr. 

 O. V. Darbishire for various valuable suggestions re- 

 garding this group, and especially for the opportunity of 

 making use of the three new Figures (Figs. 102104), 

 which are taken from Dr. Darbishire's introduction to 

 Dr. v. Fischer-Benzon's work on the Lichens of Schleswig- 

 Holstein. 



D. H. SCOTT. 

 September 9, 1903. 



189769 



