240 
Journal of Agricultural Research 
Vol. I, No. 3 
tree, as it usually does, the shape is tuberous, ungulate, or even sub- 
globular (PI. XXI, figs. 2 and 3), with the bulk of the sporophore com¬ 
posed of a hard, granular core. This core usually has white mycelial 
strands. (PI. XXI, fig. 3.) The sporophore of P. dryophilus , therefore, 
has normally three distinct kinds of structures: (1) The hard, granular 
core, (2) the fibrous layer which surrounds this core except at the rear, 
and (3) the layer of tubes on the lower surface. Specimens are often 
found, however, especially from the western part of the United States, 
in which this fibrous layer may be entirely absent between the tubes 
and the granular core. (PI. XXI, fig. 3.) 
The sporophore of Poly poms dryadeus never has this granular core, but 
its context is fairly homogeneous and of a fibrous-corky structure. (PI. 
XXI, fig. 4.) Another very important difference between the two spe¬ 
cies is the location of the sporophores on the host tree. In P, dryadeus 
the sporophores are always on the exposed roots or on the trunks at or 
very close to the ground. The reason for this is explained later in this 
article. In P. dryophilus the sporophores are higher on the trunk of the 
tree, and in some cases are on the branches. 
The rot described and figured by Hartig is identical with the rot pro¬ 
duced by P. dryophilus , but does not resemble in the least the rot pro¬ 
duced by the real P. dryadeus . Since Hartig’s time European mycolo¬ 
gists have followed him in descriptions of the rot wrongly ascribed to P. 
dryadeus , but most of them have described the sporophores of the true 
P. dryadeus both as to its character and location on the tree—i. e., at the 
base of oaks. For instance, Von Tubeuf, in his Disease of Plants (1897), 
describes fairly well the sporophore of P. dryadeus , while his photograph 
of the rot is that of P. dryophilus . Massee, in his Diseases of Cultivated 
Plants and Trees (1910), states that “the largest specimens usually occur 
near the ground line, but it also springs from points where branches have 
died or been broken off.” The latter statement, so far as can be ascer¬ 
tained by the writer, is incorrect as to the location of the sporophores of 
P. dryadeus , but is correct for P. dryophilus. Massee also quotes Hartig 
as to the character of the rot produced. 
Polyporus dryophilus is known in Europe under at least three different 
names: Polyporus fulvus Fries (PI. XXI, fig. 5), P. friesii Bresadola, and P. 
vulpinus Fries. (Pl.XXI,fig. 6.) According to Eloyd (1913), not only are 
P. fulvus Fries and P. friesii Bresadola synonyms for P. dryophilus , but the 
P. corruscans of Fries is also the same plant. 1 Polyphorus vulpinus is the 
name given to the form of P. dryophilus found on species of Populus, 
authentic specimens of which were seen by the writer at the New York 
Botanical Garden in collections from Finland and Sweden and also from 
1 Since this article was written, the writer, through the courtesy of Mr. C. G. Lloyd, has examined the 
specimens of Polyporus corruscans and of P. rheades deposited in the Lloyd Herbarium at Cincinnati, Ohio. 
Both of these plants as represented in this herbarium are Polyporus dryophilus. the former being the usual 
form found on oak and the latter the one occurring on poplar. According to Mr. Lloyd, the type of P. 
rheades , found by him in Persoon’s Herbarium, is undoubtedly the plant called “P. vulpinus ” by Pries. 
