106 PLANT DISEASES 



Two other forms of summer fruit are also produced by 

 the fungus under certain conditions. 



Finally, a fourth and higher form of fruit appears on 

 diseased grapes that are lying on the ground during the 

 winter months ; in this form the spores are produced 

 in asci, and mature during the following spring. It is 

 supposed, but not yet definitely proved, that the spores of 

 this winter form of fruit start the disease afresh in the 

 spring. 



PREVENTIVE MEANS. All diseased fruit, whether hang- 

 ing on the vines or lying on the ground, should be collected 

 and burned: otherwise there is a danger, amounting almost 

 to a certainty, that the disease will appear during the 

 following season. In like manner all fruit showing the 

 least trace of ' spot ' or summer stage of the disease should 

 be promptly removed before the stylospores are ripe, so as 

 to check as much as possible the spread of the disease. 

 In those instances where the disease has previously existed, 

 the vines should be sprayed with Bordeaux mixture just 

 when the leaf-buds are expanding, and again at intervals. 

 After the fruit is half-grown, ammoniacal solution of copper 

 carbonate should be used for spraying instead of the 

 Bordeaux mixture, so as to avoid spotting the fruit. It 

 has been demonstrated in the United States that spraying 

 with Bordeaux mixture not only checks the disease, but also 

 keeps the vines healthier and more prolific than unsprayed 

 vines that have not suffered from the disease. 



Scribner, Bot. Gaz., vol. xi. p. 297 (contains the first 

 account of the ascigerous form of fruit). 

 Viala and Ravaz., Le Black Rot, 1886. 

 Massee, Gard. Chron., Jan. 26, 1895, figs. 



