Preface. vii 
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 zcidiospores and 
uredospores were shown not to be distinct species, that con- 
tinued biological investigation would materially lessen the 
number of species of the Uredinee. 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 Pucciniz on the Composite, 
Labiate, Umbellifere, etc. The proper limitation of 
species of these parasites cannot be effected on purely 
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 
and 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. 
