350 Edwin F. Hopkins 



by mycelium can begin only at an injured place'. Again, there are plants 

 such as the hyacinth, on which the conidia will germinate and cause 

 local injury, without actually invading the plant. Finally, there is the 

 tulip, in the case of which infections take place easily on uninjured plants. 

 While this series is too incomplete to be conclusive, the tendency shown 

 is clear, and further experiments in this direction would probably furnish 

 additional evidence of the very limited range of the parasitism of B. 

 Tulipae. 



Life history 



Primary inoculation and infection 



The fungus survives the dormant period of the bulb as mycelium or 

 sclerotia and is planted with it in the fall. When the bulb starts into 

 activity in the spring, the fungus starts also and sometimes spreads 

 throughout the entire outer scale of the bulb. If the original infection 

 is near the apex of the bulb, the shoot also is involved in the lesion and 

 the mycelium growing from the bulb tissue infects the leaf tissue. This 

 condition was frequently encountered in studying the disease and is 

 well illustrated in figure 27. Usually it is only the outer, sheathing leaf 

 that is diseased, although sometimes the whole shoot may be affected 

 and fail to emerge from the soil. After growing in the leaf for a time, 

 the mycelium emerges from the dead tissue and, if favorable conditions 

 prevail, conidiophores and conidia are produced. These are formed 

 on the aerial mycelium and also arise directly from the mycelium in the 

 leaf. The unspecialized hyphae and the conidiophores which arise from 

 the leaf emerge through the stomata, and in the specimens observed, only 

 one came from each stoma. 



Secondary inoculations and infections 



The conidia, produced in great abundance on these first-infected leaves, 

 furnish abundant inoculum for secondary inoculations. Although it is 

 not improbable that they are also transported by such other agencies 

 as insects, spattering rain, animals, and man, the conidia are for the 

 most part scattered to the infection courts by means of the wind. 



The infection courts may be any part of the tulip plant except the roots. 

 Conidia falling on these parts germinate very quickly under proper con- 

 ditions. Experiments with conidia in tulip juice and in distilled water 



