CHESTNUT BARK DISEASE. 7 



trates the bark to the wood of the chestnut tree, killing the 

 invaded tissues, but does not enter into the wood to any appre- 

 ciable extent nor does it affect directly any part of the tree 

 other than that with which it comes in contact. The tree or 

 branch is killed only when the disease goes completely around 

 it, thus girdling it and stopping the flow of sap to the parts 

 above the infected area. 



The mycelium or vegetative part of the fungous plant grows, 

 as has been stated before, in and beneath the bark and the spores 

 are borne in characteristic red-brown or orange-colored pus- 

 tules. These are seen dotting the surface of the cankers on 

 smooth bark and thickly clustered in the crevices of rough bark. 

 The spores are the bodies by which the organism perpetuates 

 itself and are borne on the fruiting pustules in countless num- 

 bers. There are two forms of these spores, one of which is 

 borne in the summer and the other in late fall and winter, both 

 being capable of infecting chestnut trees under the proper con- 

 dition. So small are the summer spores that 8,000 of them placed 

 end to end equal an inch in length. The chestnut blight fungus 

 does not so far as known injure any other kind of tree nor does 

 it usually attack a tree unless the bark has been injured or the 

 tree is in a weakened condition. It has, however, been found to 

 a very limited extent on a few oaks, but never doing any appre- 

 ciable injury. 



- REMEDIES TRIED. 



At present there are no sure remedies known for this dis- 

 ease, because the fungus grows- wholly within the tree, only 

 its fruiting pustules appearing on the surface, thus making it 

 very difficult to control the disease by spraying even if it were 

 practicable to do spraying in a chestnut forest. Other methods 

 of control have also proved unsuccessful. 



Spraying. It has been claimed that spraying with Bordeaux 

 mixture will prevent trees from becoming infected, which it 

 doubtless would if the tree had no wounds in the bark and 

 could be covered completely with the mixture at all seasons of 

 the year. But this is nearly impossible and surely impracti- 



