nt (No. 1930, C. U. herbarium) collected in
Cascadilla woods, Ithaca.

=Polyporus sulphureus= (Bull.) Fr. =Edible.= (_Boletus caudicinus_
Schaeff. T. 131, 132: _Polyporus caudicinus_ Schroeter, Cohn's Krypt.
Flora, Schlesien, p. 471, 1899).--The sulphur polyporus is so-called
because of the bright sulphur color of the entire plant. It is one of
the widely distributed species, and grows on dead oak, birch, and other
trunks, and is also often found growing from wounds or knot-holes of
living trees of the oak, apple, walnut, etc. The mycelium enters at
wounds where limbs are broken off, and grows for years in the heart
wood, disorganizing it and causing it to decay. In time the mycelium has
spread over a considerable area, from which nutriment enough is supplied
for the formation of the fruiting condition. The caps then appear from
an open wound when such an exit is present.

The color of the plant is quite constant, but varies of course in shades
of yellow to some extent. In form, however, it varies greatly. The caps
are usually clustered and imbricated, that is, they overlap. They may
all arise separately from the wood, and yet be overlapping, though
oftener several of them are closely joined or united at the base, so
that the mass of caps arises from a common outgrowth from the wood as
shown in Fig. 184. The individual caps are flattened, elongate, and more
or less fan-shaped. When mature there are radiating furrows and ridges
which often increase the fan-like appearance of the upper surface of the
cap. Sometimes also there are more or less marked concentric furrows.
The caps may be convex, or the margin may be more or less upturned so
that the central portion is depressed. When young the margin is thick
and blunt and of course lighter in color, but as the plant matures the
edge is usually thinner.

In some forms of the plant the caps are so closely united as to form a
large rounded or tubercular mass, only the blunt tips of the individual
caps being free. This is well represented in Fig. 185, from a photograph
of a large specimen growing from a wound in a butter-nut tree in Central
New York. The plant was 30 cm. in diameter. The plants represented in
Plate 69 grew on an oak stump. The tree was affected by the fungus while
it was alive, and the heart wood became so weakened that the tree broke,
and later the fruit form of the fungus appeared from the dead stump.

[Illustration: PLATE 69, FIGURE 184.--Polyporus sulphu