INTRODUCTION 13 



may prove to be phases in the life-cycle of species belong- 

 ing to the Ascomycetes. 



Our knowledge respecting the morphology, correlation 

 of hitherto isolated forms, germination of spores, and 

 general life-history of species included in every group of 

 fungi, has been greatly advanced by the untiring energy of 

 Brefeld, whose investigations are contained in eight volumes, 

 with numerous beautifully executed, if somewhat crowded 

 plates. 



No student of fungi can afford to ignore the many 

 investigations by Marshall Ward, which deal mainly with 

 biological and morphological aspects of the subject. Apart 

 from the flood of new light thrown on each subject in- 

 vestigated, these studies are masterly examples of careful 

 and detailed methods and sound reasoning, the outcome 

 of extensive experience. Among other studies by this 

 author may be enumerated : ' A Lily Disease,' dealing 

 with the life-history of a parasitic species of Botrytis\ 

 ' Disease in Plants ' ; the predisposition and immunity of 

 the host, and relations between host and parasite ; also the 

 biology of Puccinia dispersa and its peculiar parasitism on 

 various species of Bromus. 



Salmon has worked continuously at the Erysipheae 

 for a number of years, with the result that we now know 

 more of this group from a biological, morphological, and 

 systematic standpoint respectively, than of any other family 

 included in the Ascomycetes. 



The last-mentioned author has also devoted much atten- 

 tion to the origin and significance of ' biological forms,' or, 

 as they are sometimes termed, ' biological species.' These 

 terms are applied to certain parasitic fungi, when races of 

 a species are respectively confined to a single, or at most 



