viii PREFACE 



for valuable help and criticism in the more purely physical 

 and mathematical parts of the research. Of the photographs here 

 published ten were kindly made for me by Mr. J. E. Titley of 

 Four Oaks, Warwickshire, three each by Mr. J. H. Pickard and 

 Mr. P. Grafton of Birmingham, and two by Mr. C. W. Lowe of 

 Winnipeg. They are all acknowledged in the text. In the final 

 revision of the proofs, Mr. W. B. Grove has been good enough to 

 give me the benefit of his wide mycological knowledge and experi- 

 ence. Lastly, my gratitude is due to the Birmingham Natural 

 History and Philosophical Society for defraying the cost of three 

 of the Plates. 



A. H. REGINALD BULLER. 



WINNIPEG, July 1909. 



