on dead trunks, etc., and sometimes is found growing from the
wounds of living trees. It is very hard and woody. It has a hard crust,
much harder than that of the _Polyporus lucidus_. The surface is more or
less marked by concentric zones which mark off the different years'
growth, for this plant is perennial. At certain seasons of the year the
upper surface is covered with a powdery substance of a reddish brown
color, made up of numerous colored spores or conidia which are developed
on the upper surface of this plant in addition to the smaller spores
developed in the tubes on the under surface.

The plant varies in size from 5--20 cm. or more in diameter, and 1--10
cm. in thickness, according to the rapidity of growth and the age of the
fungus. The fruiting surface is white, and the tubes are very minute.
They scarcely can be seen with the unaided eye. Bruises of the tubes
turn brown, and certain "artists" often collect these plants and sketch
with a pointed instrument on the tube surface. For other peculiarities
of this plant see page 15. The age of the plant can usually be told by
counting the number of the broader zones on the upper surface, or by
making a section through the plant and counting the number of tube
strata on the lower surface of the cap at its base.

=Polyporus leucophaeus= Mont., is said to differ from this species in
being more strongly zonate, and in the crust being whitish instead of
reddish brown.

=Polyporus fomentarius= (L.) Fr. [_Fomes fomentarius_ (L.) Fr.,] is
hoof-shaped, smoky in color, or gray, and of various shades of dull
brown. It is strongly zoned and sulcate, marking off each year's growth.
The margin is thick and blunt, and the tube surface concave, the tubes
having quite large mouths so that they can be readily seen, the color
when mature being reddish brown. Sections of the plant show that the
tubes are very long, the different years' growth not being marked off so
distinctly as in _P. applanatus_ and _leucophaeus_. The plant grows on
birch, beech, maple, etc. The inner portion was once used as tinder.

=Polyporus pinicola= (Swartz.) Fr. [_Fomes pinicola_ (Swartz.) Fr.]
occurs on dead pine, spruce, balsam, hemlock spruce, and other conifers.
The cap is about the width of the _F. applanatus_, but it is stouter,
and does not have the same hard crust. The young growth at the margin,
which is very thick, is whitish yellow, while the old zones are reddish.
The tubes are yellowish, a