2 
MILDEWS, RUSTS AND SMUTS 
connexion between fungi and plant diseases, was practically 
unknown, as indeed, were the life histories of most of the 
fungi now dealt with. An extensive index of host-plants 
has been prepared, as I consider that such an index is of 
great value—if not abused. The time was when most 
of the fungi dealt with in this book were named from the 
host-plant on which they were parasitic, and it was assumed 
that each host-plant had its own particular parasitic fun¬ 
gus. This idea has not proved to be correct, and it has been 
shown, by means of infection experiments, that in many 
instances the same fungus is parasitic on different host- 
plants. Carefully conducted infection experiments, des¬ 
cribed later, will undoubtedly demonstrate that certain 
fungi supposed to be confined to one particular kind of 
host-plant, are capable of growing on different plants. 
To the microscopist in search of beautiful and interesting 
objects, requiring no very special skill in their preparation, 
the fungi here described can be recommended. 
