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

INTRODUCTION

15

such as New England, when that flora is studied on the basis of hyphal
characters. However, it is possible that in all areas cut over at the time
the virgin timber was harvested, then burned over repeatedly, and that
finally "came back" with a cover of such weed trees as aspen and birch
that these areas (as far as Leccinum is concerned) furnished an invasion
site offering many variants a chance to survive that they would not have
had under other circumstances. These variants undoubtedly came from
areas in which aspen and birch had escaped the devastation of American-type logging and subsequent treatment of the land, such as swamps
and stream borders, and which in a few years produced enough spores
to invade the burned-over sites as these were reoccupied by trees. But
few fungi are homozygous; this means that the invaders were for the
most part all slightly different genetically. These mycelia became established and are still producing basidiocarps, and since they are not all
genetically alike, the basidiocarps present differences confusing to the
taxonomist. We have located certain mycelia and find that each year the
basidiocarps from them are constant in the characters we are using to
distinguish them, but before we can recognize these variants as species
we must demonstrate that there is a population of mycelia all of which
produces similar basidiocarps, and there should be evidence from collections studied that this population occupies a considerable area. This may
take years to accomplish and is the reason we make no claim that this
publication is "complete" for the genus in the state. Obviously, new
variants are arising continuously, and species from other areas always
possess the potential of migrating into the state, especially if a temporary weather cycle of 5 to 10-year duration favors this process. Since on
occasion mushroom books are published, or republished, and their publishers make the claim that theirs is the only complete one, it is worth
mentioning that there is no complete technical monograph for any
group of higher fungi in North America, and one is not likely for a long
time, and none of the popular mushroom books was designed to be
"complete."
GENERAL COMMENTS ON DISTRIBUTION
If the boletes of the state are reviewed from the standpoint of
their occurrence in other areas, as one would expect, most are New
England species described by Peck and by Frost. Suillus is a typical
example (see S. acidus, S. americanus, S. subaureus, S. subluteus, S.
unicolor, S. brevipes, etc.). European species in the aggregate are in the