over the wood, and somewhat gelatinous, _Merulius_.
2--Mass (stratum) of tubes easily separating from the
cap when peeled off, cap not with coarse scales,
tubes in some species in radiating lines, _Boletus_.
Stratum of tubes separating, but not easily, cap
with coarse, prominent scales, _Strobilomyces_.
Stratum of tubes separating, but not easily, tubes
arranged in distinct radiating lines. In one
species (_B. porosus_) the tubes do not
separate from the cap, _Boletinus_.

This last genus is apt to be confused with certain species of Boletus
which have a distinct radiate arrangement of the tubes. It is
questionable whether it is clearly distinguished from the genus Boletus.

BOLETUS Dill.

Of the few genera in the _Polyporaceae_ which are fleshy and putrescent,
_Boletus_ contains by far the largest number of species. The entire
plant is soft and fleshy, and decays soon after maturity. The stratum of
tubes on the under side of the cap is easily peeled off and separates as
shown in the portion of a cap near the right hand side of Fig. 169. In
the genus _Polyporus_ the stratum of tubes cannot thus be separated. In
the genera _Strobilomyces_ and _Boletinus_, two other fleshy genera of
this family, the separation is said to be more difficult than in
_Boletus_, but it has many times seemed to me a "distinction without a
difference."

The larger number of the species of _Boletus_ grow on the ground. Some
change color when bruised or cut, so that it is important to note this
character when the plant is fresh, and the taste should be noted as
well.

=Boletus edulis= Bull. =Edible.= [_Ag. bulbosus_ Schaeff. Tab. 134,
1763. _Boletus bulbosus_ (Schaeff.) Schroeter. Cohn's Krypt, Flora.
Schlesien, p. 499, 1889].--This plant, which, as its name implies, is
edible, grows in open woods or their borders, in groves and in open
places, on the ground. It occurs in warm, wet weather, from July to
September. It is one of the largest of the Boleti, and varies from 5--12
cm. high, the cap from 8--25 cm. broad, and the stem 2--4 cm. in
thickness.

[Illustration: PLATE 56, FIGURE 164.--Boletus edulis. Cap light brown,
tubes greenish yellow or yellowish; stem in this specimen entirely
reticulate (natural size, often larger). Copyright.]

The =pileus= is convex to expanded, smooth, firm, quite hard when young
and bec