52 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- 
30 
