The boletes of Michigan, by Alexander H. Smith and Harry D. Thiers.

INTRODUCTION

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full of colored beads (fig. 12). In some the same effect is produced by
KOH. Viscidity of the pileus surface (whether it is sticky or slimy to the
touch) for a given species may be caused by the breakdown of the
hyphal walls or the actual secretion of slime by the hyphae-in the latter
case the walls of the hypha remain clearly defined under the microscope.
The context of the pileus is typically composed of interwoven
rather wide thin-walled hyaline hyphae, but in some, as mounted in
Melzer's, the content is seen to stand out boldly and become bright
yellowish orange to cinnabar-red or bright orange-brown. As yet we do
not know the significance of this feature or the identity of the compound which colors when iodine is added; it may be glycogen.
Clamp connections (fig. 21a) are present in some boletes, such as
Suillus cavipes, but are absent in many others. In some species they
appear to be very rare, and the taxonomic importance of their presence
or absence is to be doubted in such cases.
In a few species of boletes, such as B. calopus, some hyphal fragments or special walls such as transverse septa appear to be truly amyloid (blue in Melzer's), a feature characteristic of Chroogomphus, a
group of gill fungi apparently derived from the boletes and which, possibly, should be included in this family.
HABITAT RELATIONSHIPS OF BOLETES
This topic is of great interest to all collectors regardless of their
intent. The various facets of the subject will be taken up in the order of
importance to the collector. First are associations with specific woody
plants.
This subject has been rather well explored because it is important
to foresters. It is well known that boletes are forest fungi and that a
very large number are found only near certain kinds of trees. Fuscoboletinus ochraceoroseus is always near Larix occidentalis (western
larch), Leccinum atrostipitatum has always been found with species of
Betula (birch), and Suillus americanus with Pinus strobus (white pine),
etc. The reason for this close association is that the mycelium of the
fungus is living on the rootlets of the tree, where it forms small structures with the tree rootlet. The combination of fungous mycelium and
tree rootlet is termed a mycorrhiza. It is thought that both the tree and
the fungus benefit from this association. At least the fungus does not
infect the whole root system of the tree-killing it as might happen, for