52 



fruits in particular this is of frequent occurrence. As the 

 fruit ripens the blotches, which are hard and brittle, sometimes 

 become considerably chequered and fissured similar to the 

 cracking of mud in dr} r ing. 



The spots, are to some extent formed on both surfaces of the 

 leaf, but are much more abundant on the upper surface. This 

 character is more particularly noticeable in the grape. fruit 

 than in other species of citrus. On grape fruit the spots are 

 almost wholly limited to the upper surface. In the common 

 sweet orange and sour orange they occur abundantly on the 

 lower surface, but are still more numerous on the upper sur- 

 face. On the different portions of the fruit and young stems 

 the spots are apparently uniformly abundant. This malady is 

 most severe on the lowei portions of the tree, but the charac- 

 teristic spots are also found on the leaves and twigs in the tops 

 of large trees, nearly 30 feet from the ground. 



The infection, it appears, usually takes places at an early 

 stage in the development of the leaves and stems, and if the 

 disease becomes severe the infected organs are considerably 

 modified in appearance. The leaves becomes greatly distorted 

 and wrinkled and remain much smaller and more pointed than 

 normally. Many of the leaves fall before reaching maturity, 

 only a scanty foliage remaining on badly affected branches. 

 The branches are also considerably contorted and stunted in 

 severe attacks. 



Cause. — From studies that have been made of this disease 

 it- seems very probable that it is caused by some vegetable 

 parasite, although the microscopic studies which have thus far 

 been carried on have failed to reveal the presence of any such 

 organism. The disease is apparently contagious, spreading 

 from definite centres. In some groves infected areas are plainly 

 seen. In the centres of these areas, where the disease first 

 started, the trees will be found to be very badly affected, 

 but towards the margins the malady becomes gradually less 

 apparent. 



Melanose appears to be of an entirely local nature. In its 

 growth and development each spot is entirely independent on 

 any other spot, probably being caused by a separate infection. 

 The tissue between the diseased spots is evidently perfectly 

 healthy outside of the general debility which results from the 

 infection of such a large portion of the leaf. The strict locali- 

 sation of the disease, so similar to what occurs in scab, again 

 strongly suggests that the disease is caused by some vegetable 

 parasite. Infection can take place apparently only when the 

 tissues are quite young. If the leaves and stems escape the 





