Brown : Timber Rot 
13 
fibers narrow, oblique, simple pits.*^ This is in strong contrast to 
the chestnut where all gradations between tracheids and fibers oc- 
cur, and the latter are characterized by bordered pits of the usual 
type. Further, the fibers in oak have thicker walls and are 
more strongly lignified. 
In tangential section (Fig. 13) the two types of pith rays are 
easil)' discernible. The multiseriate rays appear as broad fusi- 
form structures extending for several millimeters in a vertical di- 
rection, while interspersed between them and far surpassing them 
in number, are the small uniseriate rays. The latter are shorter 
than those in chestnut. 
Description of the Decay in Oak. — The decay of oak associated 
with Hymenochaete rnbiginosa is similar to that of chestnut. 
White areas of varying extent and irregular outline are formed 
(Figs. 13, 16 o), which extend a millimeter or less across the grain, 
but often a centimeter or more longitudinally. These subsequently 
give rise to cavities or pockets lined and partially occluded with 
white fibers. After this stage further disintegration ceases and 
the wood appears sound except for the presence of many pockets 
scattered quite regularly through it. The wood of chestnut and 
oak never becomes soft and badly disintegrated in this type of 
decay, but the fungus exhibits a remarkable similarity of action 
on these two hosts. 
The effect of the mycelium of Hymenochaete rnbiginosa on the 
wood of chestnut and oak is comparable in its grosser aspects to 
that of Trametes abietis Karst, on the red spruce,^ and the “part- 
ridge” wood of oak caused by Stereum frustulosum (Pers.) Fr.^® 
In each case the areas of disintegration are at first localized. The 
elements of the wood within the infected areas are wholly or in 
part dissolved and cavities arise which are lined with a layer of 
almost pure cellulose, and remains of delignified elements.®^ In 
12 It is held by some that all prosenchyma is equipped with bordered pits. 
The “ so called ” oblique simple pits in the fibers are interpreted as flattened 
bordered pits which have been spirally stretched. 
13 Described by R. HartigO as Telephora perdix. 
1* Weiri® has recently published a description of a new fungus, Fames 
pHtearius Weir, in which the decay is similar to that of T. Pini Fr. The 
lignin reduction, however, is on a much larger scale and the cellulose pockets 
are frequently two inches in length and vary in breadth according to the 
structure of the host. 
