28 
IOWA ACADEMY OP SCIENCE 
This fungus is of the bracket form with sporophores varying in size from 
2 — 14 inches long, 1 — 8 inches wide, by % — 2 inches thick; it is somewhat hoof- 
shaped or elongated, very hard, the upper surface dark colored and encrusted, 
while the fruiting surface is nearly white. The under surface is marked along 
the edge by an encrusted ridge, and the upper surface is marked by concentric 
ridges showing that it is perennial. In the popular mind it is associated with 
etching, because its hymenium changes to a darker color when bruised. 
As a parasitic fungus on the red oak its sporophore is found near the 
ground. The means of infection is not very easily determined, as no wounds 
have been observed; but as the sporophores are located so near the ground 
we may conclude that infection is brought about through the roots, or at the 
base of the trunk near the ground line. This seems quite probable as sufficient 
moisture is one of the requisites for germination. The fact that it does not 
attack young trees, but becomes parasitic upon older trees in which the vitality 
has been lowered leads us to conclude that lack of vitality may be a means of 
infection. The mycelium spreads upward through the entire wood, and the 
trunk becomes thoroughly infested before the fungus attains sufficient vigor 
to produce its external fruiting bodies. The wood is rendered very brittle, 
and the tree is poorly fitted to withstand the force of wind in severe storms. 
The trees affected have always been large, probably more than thirty years old. 
The only evidence of the disease is the presence of a sporophore. 
As a parasitic fungus this one is the least numerous of any yet studied. 
Only two specimens have been found on living trees. But as a saprophyte it 
is very common, being found on any dead tree, log or stump. But I believe 
that the log or stump of maple was more infected by it than any other. Dr. 
Heald (7) says, “Any logs or woods affected with this fungus should be burned 
as the fungus continues its growth. It seems quite probable that the vegetative 
mycelium is often the means of infection, rather than the spore direct.” 
BIBLIOGRAPHY. 
1. Atkinson, G. P. Some wood destroying Fungi. Rep. Louisiana Geol. Surv., 1899: 332- 
338. pi. 56-62. F. 1900. 
2. Atkinson, G. F. Studies of some shade tree and timber destroying Fungi. Bull. 
Cornell Agr. Exp. Sta. 193: 199-235. F. 56-94. Te. 1901. 
3. Atkinson, G. F, Studies of some tree destroying Fungi. Trans, Mass. Hort. Soc. 
109-130. 1902. 
4. D’Allemand, B. R. A. The disease of the cottonwood and the lombardy poplar. Ann. 
Rep. Nebr. Hort. Soc. 190^: 189-193. 1904. 
5. Galloway, B. T., & Woods, A. F. Disease of shade and ornamental trees. Year- 
book U. S. Dept. Agric. 1896: 237-254. F. 53-57. 1897. 
6. Hard, M. E. Mushrooms, edible and otherwise, p. xi & 609, F. SOlf.. 1908. 
7. Heald, F. D. A disease of the cottonwood due to Elfvingia megaloma. Ann. Rep., 
Nebraska Agric. Exp. Sta. 19: 92-100. pi. l-J/. 1906. 
8. Hopkins, A. D. Insect in.1uries to hard wood forest trees. Yearbook U. S. Dept. 
Agric. 1903: 313-328. pi. 39 t£ F. 27-J,3. 1904. 
9. Marshall, N. L. The mushroom book, xxviii & 170. illust. 1905. 
10. Metcalf, H. Disease of ornamental trees. Yearbook. U. S. Dept. Agric. 1907: 483- 
494. pi. 58-60 d Fig. 52. 1908. 
11. Murrill, W. A. Polyporacea. N. Am. Flora 9: 1-131. 1907-08. 
12. Orton, W. A. & Ames, A, Plant diseases in 1907. Yearbook U, S, Dept. Agric. 
1907: 577-589. 1908. 
13. Schrenk, H. von. Two diseases of red cedar, caused by Polyporus juniperinus n. sp. 
and Polyporus carneus Nees. Bull. U. S. Dept. Agric. Veg, Path. 21: 1-22. pi. 1-7 & 
Fig. 1-3.. 1900. 
