MISSOURI BOTANICAL GARDEN. 



walls radially to another yellow area at that height or longi- 

 tudinally to one above. Immediately around the yellow 

 areas it looks as if the hyphae were passing through this 

 wood as rapidly as possible. As the disease progresses the 

 mycelium can be found only sparingly in the yellow areas 

 and in the surrounding wood. Their former presence is 

 indicated by the numerous holes in the walls. 



From the facts presented, it seems that the growth of 

 the fungus is about as follows : The mycelium starts at 

 some point in the heart- wood where it flourishes in a limited 

 area for some time. Some of the threads then grow out 

 from this area (which is limited, for some reason or other), 

 and grow both transversely and longitudinally from the 

 original center. At points some distance from this center 

 new centers are established, which in time are limited 

 and form starting-points for further growth. One may 

 cut through a young branch and find the cut surface per- 

 fectly sound. On splitting both pieces of the branch, one 

 may find that at points several inches above the cut one or 

 more distinct yellow areas are present, and the same may 

 be true of the piece below the cut. In the wood between, 

 numerous hyphae occur, which, however, do not spread in 

 this wood. The areas where vigorous development has 

 taken place ultimately become holes, and the tree then 

 appears as already described, i. e., sound wood filled 

 with lens-shaped cavities. The original hyphae are gradu- 

 ally absorbed, so that after a time the figure-8 holes in the 

 walls are the only evidence of their former presence. 



The path of the mycelium is always the shortest distance 

 from hole to hole. This apparent avoidance of the wood 

 between holes an apparent preservation is very strik- 

 ing. It is suggested that this is probably due to chemical 

 influences which affect the hyphae in this manner. All 

 attempts to grow the mycelium have so far failed. Media 

 were prepared from decoctions of cypress wood and care- 

 fully titrated ; they were then inoculated with fresh myce- 

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