12 
Mycologia 
eral decay is always restricted, however, and does not seem to be 
important. 
Condition of the Wood Betzveen the Pockets.— As previously 
noted, the wood between the infected areas remains unaltered 
chemically and still responds to the various lignin tests. Here 
and there in a cross section a fungal filament maj' be seen extend- 
ing from cell to cell, but the tissue is usually quite free of ramify- 
ing hyphae. In general, delignification occurs only in those tissues 
where the hyphae extend vertically. 
It is obvious that mycelial connection exists between the pockets 
in the wood. This is brought about in some cases by isolated 
hyphae which extend horizontally through the tissues. More 
commonly, however, connecting strands of mycelium (Fig. 24) 
are formed for this purpose. These, as noted in the figure, con- 
sist of a number of filaments closely intertwined and forming a 
horizontal bridge between the pockets. The strands thus arising 
extend both radially and tangentially. They cause no chemical 
alteration in the wood other than that correlated with their pen- 
etration, but appear to be a means of spreading the areas of in- 
fection horizontally. 
Character of Normal Oak Wood . — While closely related botani- 
cally to chestnut, oak departs decidedly from the former in the 
anatomy of its wood. Both possess ring-porous wood with rows 
of smaller vessels which branch in the outer portion of the ring. 
■The transition from large to small vessels may or may not be de- 
cidedly abrupt. Annual ring formation is as pronounced as in 
chestnut. The chief difference between tbe two woods consists 
in the presence of large multiseriate pith rays (Fig. 16) in oak 
wood accompanying the smaller uniseriate rays. Contrasting 
the two genera, oak has two kinds of pith rays, chestnut one. 
When examined microscopically, the wood of oak is found to 
consist of the same elements as those of chestnut. There are 
several anatomical differences worth noting, however. The ves- 
sels have thicker walls. The parenchyma in oak is more abundant 
and makes up a greater proportion of the wood. There is an 
abrupt transition from tracheids to wood fibers, and fibrous 
tracheids do not occur. The tracheids possess bordered pits ; the 
Abrupt in white oak, gradual in live oaks and red oaks. 
