DISEASES OF THE ORANGE IX FLORIDA. 155 



one point in Lake County. Dr. Martin found it in 

 1886 at Green Cove Spring. It does not seem to 

 be widespread nor at present of much importance, 

 but is recorded here that attention may be called 

 to it, so that its nature may be known and its prog- 

 ress watched. 



3. Cause. The cause of this disease is a parasitic 

 fungus (Collelotrichum adustum, Ellis) which draws 

 the nourishment from the leaf it inhabits. It be- 

 longs to a group of fungi that are known to be im- 

 perfect forms, and are supposed to be a phase of 

 growth in the life history of some mature form of 

 fungus. The particular form of which this species 

 is a phase of growth is not known nor even sus- 

 pected. Its connections are to be looked for among 

 some of the many species of ascomycetous fungi 

 which inhabit decaying vegetable matter, and for 

 this reason are supposed by the uninformed to be 

 of no economic interest. 



VI. SOOTY MOULD. 



1. Nature of the Disease. The leaves of certain 

 trees badly affected with some kind of scale insects 

 become covered with a sooty layer, which is of a 

 dark drab or dirt color early in its growth and 

 finally becomes sooty black. The layer thus 

 formed is only loosely attached to the smooth sur- 

 face of the orange leaf and frequently comes off in 

 patches. 



2. Distribution. This disease does not appear to 



