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In some of the species of Gill-bearing Fungi, especially
where the substance becomes tough and hard, there is a tendency
in the gills to run into each other by means of lateral
processes or veins, and so to make pores. The Fungi of this
first division are known under the general name of Affaricini,
or Mushroom-like Fungi. Almost all the species are of considerable
dimensions ,■ a very few only, as the pretty holly-leaf
Agaric, with its long bright bristles, require a common lens
to see their beauty.
In a very important group of Fungi, however, the pores are
the essential character, as the gills are in those we have just
described. These pores may he partially or entirely free, as
in the genus* Fistulina (Plate 17, fig. 1), with which most
are familiar under the form of the dark-red Fungus which is
so common on the trunks of old oaks, and which when divided
looks very like heet-root, the whole plant resembling
an ox-tongue. In general however they are closely packed
and more or less intimately united, sometimes separating
easily from each other, and sometimes inseparable. The
former condition occurs in the most characteristic genus of
the group. Boletus (Plate 15, fig. 4, 5, 6), which under a variety
of forms adorns our woods or the scanty herbage under old
trees, more rarely appearing on hedgesides, or in the open
fields. Under fir-trees a bright-yellow species is extremely
common, and one of a more sombre tint where larch is predominant.
Sometimes they grow in conspicuous rings, and
sometimes they attract notice from the instantaneous change
which they undergo, when broken and divided, from white or
yellow to deep blue. This change was long a source of perplexity
to those who examined it, but it is now known to depend
upon the action of ozone upon the juices.
* This genus is indeed sometimes associated, but wrongly, with the genera
o f the next division.
All the true species of Boletus are fleshy, but they are
closely connected with one of the largest genera of Fungi, the
Pohj'pori (Plate 16, fig. 1-6), which exhibit every gradation,
from great succulence to the hardness of wood, in their multitudinous
species. The scaly Polyporus (P. squamosus), so
common on ash; the hispid, ferruginous P. hispidus, which
abounds on apple-trees; the coriaceous P. versicolor, with its
velvety pileus and many-coloured zones, so common on stumps
and felled wood; and the hard, hoof-shaped P. igniarius, to he
found everywhere in plum-orchards,—are examples of different
conditions familiar to us all. Multitudes of other forms
occur, distinguished by the presence or absence of a stem,
the complete attachment of the pileus to the substance on
which it grows, so that the whole plant consists of resupi-
nate pores, by the clothing of the pileus, by the nature of the
pores, etc. Many of these are extremely common, and others
as rare, and some run so closely into each other that the species
are very difficult to distinguish. In a few foreign species
the pores are so large that tliey very closely resemble a honeycomb,
and in others, almost the whole plant is of a gelatinous
texture. Suoh also is the case in a rare British species of
the genus Merulius, which contains the well-known Dry-rot,
Merulius lacrymans (Plate 3, fig. 1), so destructive to our
ships and domestic buildings. The walls of the pores are here
mere veins, and there is a close connection with some of the
lower forms of the Gill-hearing Fungi. The Pore-bearing
Fungi are included under the common name of Polyporei.
Occasionally the walls of the tubes or pores are broken up ;
and as this takes place in an early stage of growth, the whole
surface of these processes is covered with the fructifying cells,
or, in other words, with the hymenium.
This paves the way to a third group of some importance.