Dec. io, 1913 
Polyporus Dryadeus 
245 
When sporophores are developed at the collar of trees growing in sandy 
land, the soil for 4 to 6 inches wide and 2 to 3 inches deep immediately 
at the base of the sporophore is often cemented into a hard, compact, 
bricklike mass, apparently by hyphae, as many colorless fungous threads 
were found ramifying through it. 
Polyporus dryadeus has been found attacking the roots of Quercus 
texana Buckl. and Q. nigra L. in eastern Texas. Some of the diseased 
trees were dying, while others were evidently in poor health. It has 
been found on Q. alba L. and Q. veluiina Lam. in the Ozark National 
Forest, of Arkansas. The majority of the trees in the Ozarks affected 
with the disease caused by P. dryadeus were growing on sandy ridges and 
southern slopes where the soil was thin and conditions were unfavorable 
to rapid, vigorous growth. Two trees of Q. minor (Marsh) Sarg. were 
found with this disease in Oklahoma; one was dead and the other in 
apparently fair health. 
Polyporus dryadeus also occurs in Q. alba L., Q. rubra L., and Q. prinus 
L. in Virginia, where seven trees were found with this rot; five were grow¬ 
ing in crowded, unfavorable conditions, while one was standing at some 
distance from other trees and was apparently in good health. Yet at 
least two large roots of this lone tree—a white oak—were thoroughly 
rotted, while sporophores were found on three sides of the tree, one 
growing from the top of an exposed root. This sporophore was over 1 
foot tall and at least as wide, judging from the old weathered remains. 
It was from this root that figure 5 of Plate XXII was taken. Of the 
five crowded trees one was much suppressed and would probably have died 
in a year or two. This tree was dug up, and studies were made of its 
roots, stool, and trunk. All of its roots, except three large lateral ones 
which ran near the surface of the ground, were completely rotted by P. 
dryadeus . The three living roots were partially rotted on the lower side 
and at the ends, but were still alive and strong enough to hold the tree 
in the ground. Old sporophores were found on all sides of this tree at 
the ground line. 
The trees of Quercus prinus which were attacked by this root rot were 
found by Mr. G. F. Gravatt, of the Office of Investigations in Forest Path¬ 
ology, who made the following statement concerning the diseased trees: 
Early in July at Bluemont, Va., three small trees of Quercus prinus were found which 
had been killed while in full leaf and which from a distance were mistaken for chest¬ 
nut trees that had been girdled by the chestnut bark disease (Endothia parasitica ). 
Whitish spots of mycelium were found on the bark of nearly every root, while the lower 
portions of the roots were so thoroughly rotted that the two smaller trees were easily 
pulled up by hand. The two small trees were somewhat suppressed, but the largest 
(sH inches in diameter) was situated in an open space in the woods. These three 
trees were about 100 yards distant from each other. 
The writer examined the rot from the roots of these diseased trees and 
found that it was caused by Polyporus dryadeus . 
