SYMPTOMS OF DISEASE IN PLANTS. 243 



this disease tlie fungus may gain an entrance into the bud at an early 

 stage of its development, and cause a complete rotting of the petals 

 before the calyx has opened. In other cases the rotting starts later 

 and the flower may be partially opened before its development is ar- 

 rested. In these affected flowers the claws of the petals will be brown 

 and soft, even though the exposed portions are normal in appearance. 

 A minute mite is constantly associated with this disease and the evidence 

 points to the fact that the mite acts as a carrier for the fungus, carrying 

 it from bud to bud. In this connection the black rot of the cabbage 

 may be mentioned, for the cabbage is really a large bud. This disease 

 is of bacterial origin, the organism entering at the leaf margins. They 

 make their way down through the veins to the central axis and fre- 

 quently cause a complete rotting of the fully or partially developed 

 heads. This disease is particularly destructive on low, heavy soils. 



The rotting of fruit is always caused by the inroads of bacteria or 

 fungi. In the majority of cases it is some filamentous fungus that 

 causes the trouble. The fruit-rotting fungi may gain an entrance through 

 wounds or bruises, or in other cases they may penetrate the uninjured 

 skin. In some cases the rotting may begin when the fruit is still im- 

 mature and hanging on the tree, and the work of destruction may be 

 continued after the crop is harvested. Many fruit-rotting fungi only 

 attack the ripe fruit, just at time of maturity or after it has been har- 

 vested or during storage. Soft fruits like strawberries suffer rapid decay 

 from fungi, while fruits like apples with a protective epidermis may be 

 preserved for a long time. 



The brown rot of peaches, plums and cherries is very destructive in 

 certain regions when conditions become favorable. Affected fruits show 

 brown patches of soft tissue. The patches spread rapidly in circum- 

 ference until the whole fruit is involved and if the weather is moist 

 these rotted areas will show conspicuous pale brown conidial tufts, which 

 produce myriads of spores that spread the rot to other fruits. It is 

 these rotting fruits that produce the "mummies" already mentioned. The 

 same fungus that causes the brown rot of peaches, plums and cherries 

 also affects the apple. It may work in the same way or it may trans- 

 form the apple into a black mummy, shiny and coal black, with no 

 external evidence of the fungus. This rot of the apple should not be 

 confused with the true black rot which works in a somewhat similar 

 way. In the true black rot the surface of the apple soon becomes 

 covered with minute black pustules, and the fruit becomes more or less 

 shrivelled and shrunken. In both the black rot and the brown rot the 

 pulp is colored a dark brown, the black coloration being due to changes 

 in the skin. The bitter rot shows brown circular areas with concentric 

 zones of pink spore pustules. This is one of the most destructive apple 

 diseases known for the central Mississippi Valley region, especially for 

 southern Illinois and Missouri and adjacent territory. Green mold is 

 one of the most destructive fungi for stored apples. Apples affected 



