JUNIPER DISEASES 207 



hollow. At first the decayed areas are a few inches in length 

 and pure white and are separated from one another by several 

 inches of sound wood which appears normal except that it is 

 somewhat brownish. Soon the white areas become holes with 

 their inner surfaces lined with white fibers mixed with a reddish 

 yellow felt of mycelium. The wood around the holes is brown- 

 ish and shades off gradually to the deep red jiormal wood. The 

 amount of soft white fibers around the edges of the large hole is 

 considerable and very striking in appearance when compared 

 with the normal red wood. When the holes become large, they 

 often fuse and cause hollow trunks. In very large trees there 

 may be several holes parallel to each other. 



The fruiting-bodies of the causal fungus are very rare and 

 appear at branch wounds. They are woody and usually hoof- 

 shaped. The upper surface is at first yellowish orange and later 

 turns to black with a yellowish margin. When young the top 

 is smooth but with age it becomes fissured. The lower surface 

 is yellowish brown. The inner substance of the fruiting-body 

 is reddish orange. A new layer of tubes is formed each year. 



Cause. 



White pocket heartwood-rot or white rot of junipers is caused 

 by Fomes juniperinus. The fruiting-bodies described above 

 are very rarely found. Infection is initiated by spores which 

 lodge on a broken stub of a branch. The mycelium penetrates 

 into the center of the heartwood of the trunk where the first evi- 

 dence of decay is the turning white of the normally red wood. 

 Later new areas of decay originate a few inches above and below. 

 The lignin is abstracted from the cell-walls and the primary 

 layers of the walls are dissolved. These two actions leave the 

 remainder of the walls pure white and unattached to one an- 

 other, so that they fall apart leaving a hole in the wood. The 

 life history and control of the wood-rot fungi are more fully 

 discussed on page 64. 



