389] H. 8. Fawcett 191 



An interesting example of an old, well-known disease with 

 a rather limited distribution is melanose, which is due to 

 Phomopsis citri. The fungus produces small, brown pus- 

 tules on the surface of rapidly growing leaves, twigs and 

 fruit. It was discovered in 1892 and was first definitely 

 described, by Webber, in 1897. At that time melanose was 

 already a rather serious disease in the middle portion of the 

 peninsula of Florida. During the past 20 years, citrus 

 nursery stock has been freely interchanged between different 

 parts of Florida, and thousands of acres in Cuba have been 

 brought into citrus culture for the first time, the stock for 

 planting being derived from Florida, and yet the area over 

 which the disease is now of serious commercial importance 

 is confined roughly between the parallels of 27% and 

 291/2 N. latitude in Florida. 



Southward from this area melanose gradually becomes 

 less and less severe and it finally disappears entirely, so that 

 the southernmost citrus districts of the state are free from 

 it. In Cuba, if the disease occurs at all, it is of no commer- 

 cial importance; I was unable to find any evidence of it in 

 the island in January, 1914. North of the Florida area of 

 most serious injury, melanose occurs in a less severe form, 

 and a mild form of the same disease has been reported for 

 southern Alabama and Louisiana, but it is apparently not 

 serious in these regions. No trace of this disease has ever 

 been found in California. 



The same Phomopsis that produces melanose also plays a 

 part in the so-called stem-end rot of mature or nearly mature 

 citrus fruits, and it is an interesting fact that this fruit rot 

 has never been known to be serious outside of the areas 

 where melanose is also of commercial importance. Like 

 melanose, stem-end rot has not been reported as occurring 

 either in Cuba or in California. 



The reasons for the peculiar distribution of Phomopsis 

 citri, as above described, are not at all understood, and we 

 cannot regard our knowledge of melanose and stem-end rot 

 as at all nearly complete until a properly substantiated ex- 



