FusARiA OF Potatoes 119 



poor production of, spores; other forms normally present in the culture 

 may also be absent. This state of culture may sometimes exist when a 

 fungus is transferred from a mycelial growth, especially when it is taken 

 directly from host tissues. 



2. A culture is considered to be a normal one (Normkultur) when all 

 forms typical to the fungus — and especially the most important form, 

 the macroconidia — are abundant, comparatively uniform in size and 

 shape, smooth in outline, and so forth. 



3. After a long cultivation on artificial media, a fungus may lose certain 

 characters, such as ability to produce certain color and also its virulence 

 as a parasite. Such a state of culture is that of degeneration (Ahkultur), 

 and it may be accompanied also by smaller size and abnormal septation 

 of the conidia. (Only loss of color was observed by the writer; the other 

 observations are those of Appel and Wollenweber, 1910:22.) 



4. In the first period of growth of any one of the Fusai-ia, the first 

 conidia produced usually soon begin to produce new conidia, sometimes on 

 minute papillae located directly on the conidial walls, and sometimes on 

 more or less well-differentiated and well-developed conidiophores, the process 

 often much resembling the budding process in yeasts. In such young 

 cultures the conidia are more or less swollen, their contents are com- 

 monly densely granular, and septation is not clear. This period (Jung- 

 kultur) may last from one to five or more days. 



5. After the period just described, the fungus, when in normal con- 

 dition, produces conidia which remain for a greater or a less length of 

 time, of perfectly smooth outline and with clear septation. At this 

 state of maturity (HochkuUur) the conidia are also of most uniform and 

 typical shape and size, and it is the important stage for taxonomic study 

 of these organisms. 



6. Finally there comes a period (Altkultur) in which the conidia begin 

 to disintegrate through the process of self-digestion, or at least become 

 of less uniform and perfect type, and after a period of time the culture 

 begins to lose its vitality. 



These variations in character of the cultures show that only normal 

 and mature cultures must be considered, though the character of other 

 conditions may also give some help in identification. Another point which 

 must be clear from the account given above is that in the study of these 

 fungi they must be grown for a long period of time, under different cultural 

 conditions and from different kinds of material for inocula. Then, after 



