242 
Journal of Agricultural Research 
Vol. I, No. 3 
brown areas, which become hazel in color when the wood is dried, 
appear on the surface of the sap wood and in its outer layers. At this 
stage a cross section of the root has a mottled appearance, and this 
discoloration gradually spreads till the root is affected to its center. 
The earliest discolored spots have by this time turned white. (PI. 
XXII, fig. 2.) Tater, as the rot ages, especially in the larger roots 
which lie near the surface of the ground, this white changes to a cream 
and finally to a straw color. The lower portion of the smaller diseased 
roots, those 2 inches or less in diameter, become completely rotted and 
white throughout before the advancing rot has reached the stool of the 
tree. On these small rotted roots the bark separates easily from the 
wood, since much of the living bark has been destroyed. The bast fibers, 
however, remain intact, which gives the inner bark a loose, shredded 
appearance. The rot gradually moves up the roots till the stool is 
reached. This is also attacked by the fungus, but the rotted area ends 
abruptly at the surface of the ground. 
A radial-longitudinal section of the rot in a fresh state has a sodden, 
watery appearance, with white longitudinal and transverse lines some¬ 
what like the rot produced by Polyporus hispidus in oaks. These white 
lines or bands are not cellulose, however, but are spaces filled with air 
and the mycelium of the fungus in the region of the large vessels. When 
the rotted wood is thoroughly dry, these white lines disappear, and the 
uniformly creamy-white rot is left. The rot in all the trees examined 
did not extend for any appreciable distance into the heartwood of the 
trunk proper above the collar of the tree, even when the large, completely 
buried roots, 6 to 12 inches in diameter, were rotted throughout. 
The thoroughly rotted wood when dry is very light in weight and, 
superficially, looks and feels like pith. If a freshly dug root in the 
advanced stage of the rot is twisted, it will split into concentric layers and 
also into longitudinal blocks, giving the broken end of the root a coarse, 
fibrous appearance. The lower ends of the diseased roots may be in a 
thoroughly rotted condition, easily splitting into these concentric layers 
and rough, fibrous masses, while that portion of the root next to the 
base of the tree remains comparatively sound. The roots of several of 
the trees overthrown by the wind were thus affected. The presence of 
this rot is often indicated by irregular white mycelial patches on the 
outside of the bark of the root or of the stool of the tree. 
In a radial-longitudinal section through the heartwood of a diseased 
root the advancing line of the rot first appears as a watery dark-brown 
zone 1 to 3 inches wide. This dark area terminates rather abruptly in 
the ultimate cream-colored rot on one side and in the sound heartwood 
on the other. A microscopic examination of the diseased wood shows 
that the starch and other cell contents of the roots are first extracted; 
then the walls of the wood elements are gradually destroyed, especially 
the walls of the tracheids and vessels adjacent to the large medullary 
