26 
IOWA ACADEMY OF SCIENCE 
The sporophores are hoof-shaped, very hard, the upper surface a very dark 
brown, while the fruiting surface is a cinnamon brown. They are — 12 
inches long, 2 — 6 inches broad, by 1 — 6 inches thick and always occur singly. 
The hymenium is composed of rounded pores. The upper surface is marked 
by concentric ridges, which correspond to the annual growth. Thus the fungus 
is perennial, and attains to such an age that the upper surface may be covered 
with tiny moss plants, also deeply checked. If a sporophore is cut open, each 
year’s growth is definitely marked by a lighter band separating them. This 
is quite distinct to about half its age, when the remainder is made up of 
lighter mycelial threads. 
The condition favoring the entrance of the spores are through wounds, knot- 
holes, and cavities made by boring insects. It is from the location of the sporo- 
phore on the host, that we are led to determine the means of infection. There 
is also a greater diversity in the size of hosts of this fungus. It has been 
found frequently on red oaks of but three inches diameter; and not in connec- 
tion with a wound or knot, and in most cases the host has been dead. But in 
the case of the larger trees it has never failed to be located at some wound or 
knot. In making a cross section of a tree containing one of these sporophores, 
I found a cavity which had been formed by some boring insect. The fungus 
being located at this cavity leads us to conclude that it either entered or grew 
out through this opening. In the light of the paper by Hopkins (8) on the 
relation of fungi and insect burrows, we must conclude that this species is a 
wound parasite. Due to these exposed areas the spore gained access through 
the cambium layer, and germinated, penetrating the heart wood of the tree. 
After the mycelium had penetrated the host gathering nourishment, a sporo- 
phore was formed, which is the only outward sign of disease. The location of 
these punks on the host varies. It is found on small trees near the ground, 
while on the larger trees it is observed higher up near a broken limb or wound. 
It is very seldom there is more than one specimen found on a tree. 
A study of a cross section of an oak near one of these sporophores shows 
that the fungus has destroyed a definite portion of the entire heart wood, 
changing it to a light brown, pulpish mass. The light and dark wood is not 
separated by a darker area as in the former, but they are inter-mixed. One 
noticeable effect is that the medullary rays stand out very firm while the sur- 
rounding area is broken up. 
The greater abundance of this fungus was found on the red oak, but it is not 
as common as the former studied. Still I have noticed that it is found but 
very little among the healthy timber, while among the dwarfed, scrubby jack 
oaks and the stunted burr-oaks of wind swept hillsides, it is more numerous. 
From this might we not conclude that the vitality of the tree gave a means of 
infection. The proportion of trees diseased to those not is very small, in fact 
much less than in Pyropolyporus igniarius. 
The effect, economically, of this fungus is rather difficult to judge, as the 
extent of the disease is not very great. Although we find it scattered in different 
localities, yet there is no extensive tracts affected. But as its host is one of 
our most desirable kinds of woods, the result will be more noticeable later, if 
its spread is not checked. For each year a sporophore discharges myriads of 
spores, and some of these are sure of finding access in some tree, consequently 
the infected areas are increased each year. As no study has been made of a 
large diseased tree, we only form a conjecture as to its probable condition; 
