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

INTRODUCTION

5

In the boletes the spore deposit is colored-usually a yellow to
olive-brown, but olive, dark yellow-brown such as bister, or cinnamonbrown are not uncommon. In a few species the deposit is pale yellow or
rich yellow to ocher-yellow, rarely mustard-yellow. In two groups it is
vinaceous to vinaceous-brown or lilac-brown to chocolate-brown (dark or
light), and in a few it is blackish brown. The colors are those found to a
large extent in the gill fungi.
Unfortunately for those who wish to make field identifications, it
does take a little time to get a spore deposit, but this must be done if
one's work is to be accurate. The best way to standardize the sporedeposit color is to dry out the spores by placing the deposit on top of
activated silica gel in a tightly closed dish for about 15 to 30 minutes,
then recording the color, using a color chart if one is available or, if not,
by identifying the color as closely as possible in one of the previously
mentioned categories. The best way to keep the spore deposit is to fold
it so the spores face to the inside of the fold and staple this to the card
on which one has written the notes for that particular collection. The
spores should not be "fixed" to the paper; some will be wanted for later
study.
Spore size is usually the first feature ascertained with the aid of a
microscope. One should always use spores from a deposit because,
having been discharged from the basidia, they are considered mature.
Bolete spores are mostly long and narrow. Most of the Michigan species
have spores 9-25, in length and 4-9 j in width. One should measure at
least 10 spores selected to represent the smaller, larger, and the mean
size as hundreds are scanned in a mount. The usual ranges in size run
something like 7-9 X 2.5-3.5 g in some species of Suillus to
16-24 X 5.5-8.p in some Leccinum species. Rarely does one find
basidiospores up to 35 g long. In measuring spores one seeks to establish
the typical size range for the species, not the absolute range which
would include the smallest and largest spore found. It is one of the
marvels of nature that each species has a characteristic size range with
such a narrow span for spores-when one realizes that millions of spores
are produced. However, accidents do occur, and as extremes one finds a
few exceptionally small and a few exceptionally large spores in most
mounts. If these are numerous enough we sometimes indicate their
presence by using parentheses around the numbers indicating the extremes as follows: (6) 8-122 X (3) 4-5 (7),u.
In Tylopilus sordidus exceptional spores, though relatively few, are
characteristic of the species. These are much wider than spores falling