118 



N. H. AGR. EXPERIMENT STATION 



[Bulletin 144 



Thick walled spores known as chlamydospores are common (Fig. 

 11). These probably assist in carrying the disease over the win- 

 ter. The mycelium of the fungus probably plays a part in this 



connection also, as it has been found that 



it is not killed by a prolonged exposure at 



very low temperatures. 

 The fungus grows 



well on various media 



in laboratory cultures. 



The manner of spore 



production in these 



cultures is shown in Fig. 



12. Small knobs are 



produced on the side of 



the hyphae, and from 

 Fig. 10.— Spores of cyi- these ouc spore after an- 

 ZnZtTJZl • other is developed and 



cut off. These spores 

 germinate readily when placed on fresh media (Fig. 13). By 

 means of the application of spores from laboratory cultures 

 spots have been produced both on stored apples and on those 



Fig. 11.— Chlamydos- 

 pores from a fruit spot. 



Fig. 12.— Spore formation of Cylindrospo- 

 rium Pomi in artificial cultures. 



Fig. 13.— Germination of spores. 



7. Spores, if. After twenty-one hours. 



3. After forty-two hours. 



still on the tree. Infections were obtained in the orchard most 

 readily in the month of July. That natural infection does 

 not usually occur earlier than this is indicated by the fact that 

 sprayings made the first week in July are as effective as those 

 made earlier in the year. 



