DISEASES AND PESTS OF PLANTS. 



31 



fungus-cushions of a brownish colour on the affected areas. These cushions, or 

 tufts, are composed of spore-producing threads (conidiophores) of the causal fungus, 

 from which summer spores are produced in great numbers and scattered by the wind. 

 As the fruit approaches maturity it becomes more susceptible, and decay during 

 transportation is one of the most serious consequences of the presence of the disease. 

 Fruit apparently sound and free from injury of any kind when packed, but with the 

 spores adhering to the surface, may rot extensively in the course of two or three 

 days. Rotted fruits gradually shrivel up,- forming the so-called " mummies," and 

 these form the source of infection in the succeeding spring. The hybernating fungus 

 may behave in two ways, according to conditions. In the case of mummies left 

 hanging on the tree the fungus produces spore-bearing cushions similar to those 

 formed during the earlier stages of the rot. These spores may disseminate the 

 disease exactly as in the preceding summer. Where the mummies have fallen to 

 the ground and become lightly covered with earth, or kept moist amongst grass or 



Fig. 8. Brown-rot in plums. 



a cover-crop, the fungus may produce a totally different kind of spore-bearing struc- 

 ture. In this case a delicate fleshy cup of a brown colour, % to % inch in diameter, 

 is pushed above ground on a slender stalk. The inner surface of this cup is lined 

 with minute sacs, each of which when ripe contains eight spores. These spores are 

 liberated about blossoming-time. 



In addition to the fruit, the blossoms and twigs may be blighted, but in the 

 latter case the infection has in all probability come about through the previous 

 infection of the flower or fruit working back through the pedicels or flower-stalks. 



Control. Since the " mummies " form the means of carrying the fungus over 

 the winter, it is essential that these be knocked off the tree, if they have not fallen 

 naturally, collected and destroyed, unless they can be ploughed in deeply enough in 

 the spring to prevent them from becoming sources of infection. They would have 



