IX 



done by Mr. Seymour, and to his persistence under difficulties, his 

 care and his interest in the subject, those who use the Index 

 will be indebted. During the considerable number of years when 

 there appeared no immediate prospect that the Index could be 

 printed the accumulation of material went on until it was estimated 

 that about 150,000 references had been brought together. When 

 in 1903 the Carnegie Institution expressed to the writer its will- 

 ingness under certain conditions to undertake the publication, it 

 was necessary to revise the large mass of data and put it in form for 

 printing since, owing to the numerous cross references, the cards 

 could not be printed directly. Mr. Seymour then brought together 

 the various cards of synonyms and Arranged them critically in 

 chronological order, or segregated them, as the case required. 

 They were then revised by the writer to conform to the general 

 plan adopted, and, in cases of disputed or confused synonymy, 

 examinations of authentic specimens were made, and, where it 

 seemed to be of interest, the results of the examinations taken in 

 connection with collateral reading were embodied in the form of 

 notes under different genera and species. Unless otherwise stated, 

 the notes are all by the undersigned, and in cases where Mr. Sey- 

 mour had made a critical examination the notes were written by him 

 and are signed with his initials. For the arrangement and relations 

 of the aecidia of Gymnosporangia, the Laboulbeniacece, Entomoph- 

 thoracece and certain genera of other orders specially studied by him, 

 we are indebted to Prof. R. Thaxter as well as for advice on gen- 

 eral questions. We are indebted to Mr. A. P. D. Piguet for valuable 

 suggestions made during the proof-reading. We also wish to 

 acknowledge with thanks critical information furnished by the fol- 

 lowing mycologists : Prof. J. C. Arthur, Prof. G. F. Atkinson, Prof. 

 E. A. Burt, Mr. J. B. Ellis, Prof. E. W. D. Holway, Prof. W. A. 

 Kellerman, and Prof. C. H. Peck. 



W. G. FARLOW. 

 CAMBRIDGE, Aug. 15, 1905. 



