CERCOSPORA 



485 



saturated with moisture, and a temperature ranging between 

 7 5 and 90 degrees F. The disease first appeared in a corner 

 of a house, and within four days every plant in the house, 

 which was 100 ft. long, was killed. At this time I visited the 

 house, obtained material, and suggested preventive methods. 

 Within three months of this occurrence, the disease was 

 reported from various other localities, and the season follow- 

 ing it was generally distributed in the London district. This 

 rapid extension of the disease was at first inexplicable, until 



FIG. 146. i, Cercospora melonis, a leaf of cucumber showing early stage ot 

 disease ; 2, sporophores emerging from a stoma, and bearing spores, mag. ; 

 3, spore, highly mag. 



it suddenly appeared in the houses of a grower located at 

 some distance from the nearest known infected area. The 

 explanation was as follows. This grower had sent a consign- 

 ment of cucumbers to Covent Garden, and by some mistake 

 his own empty packing-cases or ' flats ' were not returned, 

 bu,t instead, those belonging to another grower whose plants 

 were diseased. Spores of the fungus had been conveyed 

 from one district to another, adhering to the empty cases. 

 I obtained a case that had contained diseased plants, and 



