Preface. vli 



as well as of testing the accuracy of the statements of other 

 botanists. The results of my cultures have been from time 

 to time published in various botanical periodicals of this 

 and other countries, and in the Transactions of the Linnean 

 and Royal Societies. 



It was at one time hoped, when the aecidiospores and 

 uredospores were shown not to be distinct species, that con- 

 tinued biological investigation would materially lessen the 

 number of species of the Uredineae, I am convinced, 

 however, that modern botanists have erred in grouping 

 together forms on account of the similarity of the teleuto- 

 spores ; for instance, the Pucciniae on the Compositae, 

 Labiatae, Umbelliferae, etc. The proper limitation of 

 species of these parasites cannot be effected on purel}- 

 morphological grounds ; it can only be accomplished when 

 the morphological characters are supplemented by a know- 

 ledge of the life-history of each individual species. 



I am greatly indebted to my friend, Professor J, W. H. 

 Trail, of Aberdeen, for his kind assistance in the revision 

 of the proof-sheets. 



I have also to thank numerous friends and corre- 

 spondents, both in this country and abroad, for information 

 an-d material for experiment, amongst whom I must 

 mention Professor Farlow, of Harvard University ; Mr. 

 W. B. Grove ; Rev. Dr. Keith ; Dr. P. Magnus, of Berlin ; 

 Mr. W. Phillips, F.L.S. ; Mr. H. T. Soppitt ; Professor P. 

 Sorauer, of Proskau ; Rev. Dr. Stevenson ; Rev. J. E. 

 Vize ; the late Dr. Winter, and many others. 



