THE MONTHLY BULLETIX. 



529 



Description of Affected Oranges. 



Oranges, in which the fungus has developed considerably, become 

 exceptionally highly colored while other fruit on the same tree may 

 still be green. Directly over the affected parts there is often found a 

 light colored spot, though all do not show this. Affected oranges from 

 the various districts show the same general characteristics. "When an 

 infected orange is cut in half longitudinally (through the navel to the 

 stem end), the rot is revealed as a black area in the cells of the pulp 

 sack, almost invariably near the navel and extending more or less 

 deeply towards the heart of the fruit. (Figs. 324 and 325.) The affected 

 area is usually comparatively small, generally one quarter to one half 

 inch deep, but occasionally extending through the bulk of the pulp. 

 The pulp and juice in close proximity to the affected area has a bitter 

 taste, while the balance is more or less sweet and pleasant. 



Fig. 32 5. — Opening in the navel tissue of this 

 orange made infection an easy matter. (Original.) 



Effect of the Fungus on the Fruit. 



The fungus evidently exerts a stimulating influence upon the phj'si- 

 ologieal processes of the fruit and even though the area affected is small. 

 the whole orange is influenced and a high color produced. The black 

 color of the affected tissues may be due to the action of a secretion by 

 the fungus upon the cell tissue, or to the oxidation of a product of the 

 fungus. The fungus seems to be able to make but a very weak attack 

 upon the tissues and has very limited power of penetration. Unless the 

 cell walls are very thin or there is an opening, the spread of the infec- 

 tion from cell to cell is very slow. After an orange is cut through the 

 affected area the mycelium rapidly extends over the surface, finally 

 covering the peel and causing the half orange to appear as a black, 

 smutty mass. (Fig. 328.) 



