FUNGOUS AND PHYSIOLOGICAL DISEASES. 483 



it has been found in a number of different places, but 

 as yet has not caused sufficient damage to attract serious 

 attention. 



On the leaves, fruit and twigs of affected trees small 

 brownish-black spots are to be seen. These spots are 

 sometimes separate and sometimes confluent. Where 

 separate, the intervening tissue is apparently quite nor- 

 mal, but where confluent to any considerable extent, a 

 brownish tinge is given to the whole leaf. The spots are 

 somewhat elevated and are occasionally found to be 

 cracked or fissured at the apex. Under diseased trees 

 large numbers of leaves are found, showing to what ex- 

 tent the disease has been injurious. The disorder causes 

 damage to the trees by defoliating them, rendering the 

 leaves unable to carry out assimilative processes for quite 

 a time before they drop, and also in rendering the fruit 

 unsightly, because of the irregular dark-colored areas 

 which cover the surface. 



Careful microscopical examination has been made of 

 the diseased spots, but nothing has been found to which 

 the trouble might be attributed. It has been suggested that 

 it may be caused by some vegetable organism, but thus 

 far nothing has been found to establish this fact beyond 

 the observation that the disease seems to spread from 

 tree to tree, and the fact that it yields to applications 

 of fungicides. 



Dr. N. A. Cobb, of New South Wales, called atten- 

 tion to a disease of citrus fruit to which he applied the 

 same name, believing them to be identical. McAlpine,* 

 however, after carefully comparing Australian and Florida 

 specimens of diseased leaves, says, "For the present, at 

 any rate, the two diseases cannot be considered identical." 



* Fungus Diseases of Citrus Fruits in Australia. 16. N., 1899. 



