UNIVERSITY OF CALIFORNIA agricultural experiment station

COLLEGE OF AGRICULTURE THOMAS FORSYTH HUNT, DIRECTOR

BERKELEY, CALIFORNIA

CIRCULAR No. 84

Mushrooms and Toadstools.

By W. A. Setchell.

(January, 1913.)

What is a toadstool? The answer of the botanist is that a toad-
stool is any one of the fleshy umbrella-shaped fungi which commonly
are called by that name or by the name of ■ ' mushroom. ' • The popular
desire, however, seems to be to restrict the name "toadstool" to the
poisonous species and that of "mushroom" to the edible species. This
is, however, very unsatisfactory, since one cannot tell, except by trial,
whether a particular toadstool is poisonous or not. Edible, innocent,
and poisonous toadstools. A few toadstools are extremely poisonous,
a considerable number are probably slightly poisonous, most toadstools
are innocent, i. e., not poisonous, and some of the innocent species are
edible. Edibility implies that only those innocent species which are of
fair size, sufficiently delicate texture, and of agreeable flavor are to
be included in the list.

How may one tell an innocent from a poisonous toadstool? The
popular mind always seeks some test which may be applied. Such a
test should, of course, be decisive and of uniform result. Many
reputed tests pass current and are implicitly believed in by some. So
far as is known there is no single test, short possibly of chemical
analysis, which will give results of any value whatsoever! It may be
well to mention some alleged tests in order to emphasize their unreli-
ability and their danger.

UNRELIABLE TESTS.

1. The so-called "Silver Test" is one most prevalent. It is believed
that a silver spoon or coin placed with the toadstools while cooking
will demonstrate by blackening or failure to blacken whether the
toadstools are safe to eat or not. It need only be said in criticism that
there are both poisonous and innocent species which act alike on silver.
This test is therefore of no value.

2. Some say that if the outer (upper) skin of the top of the toad-
stool peels off readily, that such a species is edible. It may be said
that certain edible species will "peel" and other edible species will
not "peel." Some poisonous species also will "peel." So there is
no reliance to be placed on this "test."

3. It is alleged that edible toadstools while raw have an agreeable
flavor when tasted (in minute quantities as a rule) while poisonous
species are bitter or peppery, or even disagreeable in flavor. Some
disagreeably flavored toadstools are innocent and even of agreeable
flavor when cooked, while some others are looked upon with suspicion
and reputed poisonous. The most poisonous toadstools, however,
are, at least, not at all disagreeable as regards the flavor of the raw
flesh. Consequently, this test offers no certain way to distinguish
poisonous from innocent or edible toadstools.

— 2 —

4. When one breaks open a toadstool or bruises it, it ma}' change
color or it may not. Sometimes the change is to light or to dark blue,
sometimes to a reddish or brownish tint of darker or lighter hue.
This may or may not be significant, but it is no reliable test of a general
character. In general, any decided change of color should arouse sus-
picion, but the lack of it gives no indication whatsoever as to the nature
of the toadstool.

5. Some toadstools when broken open show a milky juice. This is
usually white but may be red, orange, or blue. Some such toadstools are
regarded as poisonous, others are well known to be innocent, and some
are delicious eating. On the other hand the lack of a milky juice is
no evidence of either non-poisoncus or of poisonous character.

6. Many, if not all, toadstools are liable to be infested by insects,
whose larvae are often so abundant within the plant (often without
any external evidence of it) that the toadstools are fairly honeycombed
by their ravages. Some take this as an indication of a non-poisonous
nature on the part of the toadstool. Experience has shown, however,
that this is not so, but that the insects attack both poisonous and non-
poisonous species.

MORE CERTAIN METHODS.

There are, then, no tests to be applied with any certainty and the
question still before us, is: How may one tell the poisonous from the
innocent species ? There are two methods :

I. By eating them! This is, however, a tedious process and one
attended with more or less danger. It is not to be recommended, espec-
ially to the beginner. If tried, the following process is usually recom-
mended. A very small bit of the raw toadstool is chewed but none of
the juice swallowed. If after 24 hours no disagreeable result is
experienced, a similar bit is chewed and some of the juice swallowed.
If after a similar interval, no disagreeable symptoms result, a small
piece may be chewed and swallowed. If nothing suspicious occurs after
24 or 36 hours, a fair quantity may be tested by cooking and eating. It
is proper to warn the novice that this may be done safely only after
learning to distinguish the most poisonous species (especially the
species of Amanita mentioned later on), since of some of these it needs
only a very small piece to produce serious poisonous effects.

II. By learning of the experience of others. There has been
accumulated a certain amount of knowledge concerning the innocent
or poisonous character of toadstools. While this body of knowledge
it not complete and while there are certain parts of it about which
there is lack of agreement, a considerable number of toadstools are
well known t<> be either poisonous or edible. How then is one to avail
himself of this knowledge .' By studying the toadstools and the various
books written on the subject. Much that is reliable and satisfactory
may be learned in this way. One must learn to know the various
kinds of toadstools as one learns to know the ordinary plants of hill
and forest and garden.

— 3 —

What are the distinguishing marks of difference among toadstools?

I. In general, each toadstool possesses an upper flattened horizontal
structure which is usually called the "cap," or botanically, the
"pileus," and a stalk, botanically called the ''stipe." In some cases,
the stalk or stipe fits into a swollen cup-like structure at the base
which is called the "volva." The presence or absence of a volva is a
matter of considerable importance; consequently in studying toad-
stools one should be careful to obtain the very base. Many toadstools
have a sort of ring or collar encircling the stipe somewhere between
the base and the pileus.

II. Structures of very great importance are those found on the under
side of the cap or pileus. This portion of the pileus is called the
"hymenium." By the difference in the structure of the hymenium,
toadstools may be divided into four classes, as follows :

1. Hymenium smooth. There are not many toadstools in this group and few
of them of a texture sufficiently soft to allow of eating. There are no poisonous
species known in this group.

2. Hymenium spiny. These are called "Hedgehog Toadstools or Mushrooms."
The species possible of being eaten are few and none of them, so far as is known,
is poisonous.

3. Hymenium porose. The hymenium in the toadstools of this group is made up
of closely crowded tubes, perpendicular to the horizontal diameter of the pileus,
as may be seen by breaking the pileus open. It is the mouths or openings of these
tubes which give the surface of the hymenium its porous or spongy appearance.
There are many species in this group ; some are innocent and some are poisonous.
They are all to be avoided by the beginner until he has learned to distinguish
them from the descriptions or pictures in the books or has had the distinguishing
characters pointed out by one who is acquainted with them.

4. Hymenium made up of "gills." "Gills" are flattened, knife-blade-like struc-
tures radiating out from the center of the lower side of the pileus or cap to the
circumference. Some extend from the place where the stipe joins the under side of
the pileus to the circumference, while shorter ones extend from some point farther
out to the circumference. By far the larger number of toadstools are of this
fourth class and are called "Agarics." The Agarics are divided into 5 subclasses
by the color of their spores. In order to determine the color of their spores it is
necessary to remove the pileus (which should be fairly young and fresh) from
the stipe and place it, hymenium-side down, on a piece of paper, preferably of a
light gray, brown, or blue. It is also advisable to cover the pileus with a tumbler
or dish so as to prevent too rapid drying. In from one hour to several, according
to the species, the spores, which are the minute bodies from wmich the toadstools
grow again, will be expelled from the surface of the gills onto the paper in such
quantity as to indicate the color. The colors are as follows :

(a) White. The majority of Agarics are in this subclass. Those of this sub-
class having a cup or swollen bulb at the base accompanied by a ring half to three-
quarters up the stipe are to be avoided, for these belong to the species of Amanita
and some of them are among Hie most poisonous of toadstools. Those of this
subclass having the solid portion of the pileus thin in proportion to the gills and in
which the gills are nearly all of equal length are to be avoided, especially if the
top of the pileus is bright colored. Avoid also all of this subclass having a milky
juice, unless the juice is reddish. Other white-spored Agarics may be eaten, at
least cautiously at first.

(b) Black. Black-spored Agarics are all innocent and especially those in which
the gills, when old, change into inky fluid. They are to be eaten, however, before the
gills turn black.

(c) Ochre. In these the spores are yellowish or rusty brown. None of the
species is reputed poisonous.

(d) Brown. The spores are dark brown or purplish brown. The common
mushroom, with gills which are pink changing to purplish black, and with a distinct
ring on the stipe, belongs here and is edible as are most of the species. Some,
however, are under suspicion.

(e) Rose or Red. Some of the pink-spored forms are under suspicion, but those
with deep red spores and a volva, but without a ring, are edible.

WHAT TO AVOID.

1. All toadstools in the young or "button" stage. At this time it
is impossible to determine, except after long experience, some poisonous
species from some edible species.

2. Avoid all those with pores on the under side of the cap until suffi-
cient acquaintance teaches the difference between edible and poisonous
varieties.

3. Avoid all species with gills, white spores, a ring, and a volva or
bulb-like base. The most poisonous species are in this group.

4. Avoid those having a milky juice unless the milk is red.

5. Avoid those having the cap thin in comparison with the gills,
especially if they are bright colored.

6. Avoid all toadstools which are not strictly fresh since decay
sometimes greatly increases poisonous substances. By following these
rules implicitly one may avoid the most poisonous kinds, but the novice
should experiment with the greatest caution.

Nature of Toadstool Poisons. Atkinson's account or that of Ches-
nut recommended in the list of books should be consulted for definite
information.

Nutritive Value of Toadstools. In general, it may be said that
even the most nutritious toadstools are of little nutritive value but
are valuable as food accessories or condiments, not, in any wise, as
substitutes for the meat or vegetable ordinarily consumed.

Cultivation of Toadstools. The details are to be learned from
special books and pamphlets. The accounts in the books by Atkinson,
Duggar, and Hard in the list given below are all excellent.

Books. In general, those interested should consult the various books
and pamphlets on the subject, which will lead to the knowledge of
other sources of information. Some to be found (or which ought to
be found) in many Public Libraries are the following:

* Atkinson, George F. Mushrooms Edible, Poisonous, etc. (Ithaca, N. Y. Andrus

& Church, 1901).
Chesnut, V. K. Thirty Poisonous Plants of the United States (U. S. Dept. of

Agriculture, Farmers' Bulletin, No. 86. Washington, 1898).
Clements, Frederic E. Minnesota Mushrooms (being IV of "Minnesota Plant

Studies," published by the University of Minnesota, Minneapolis, Minn.,

1910).
Duggar, B. M. The Principles of Mushroom Growing and Mushroom Spawn

Making. (U. S. Dept. Agriculture, Bureau of Plant Industry, Bulletin

No 85, Washington, 1905.)
*Farlow, W. G. Some Edible and Poisonous Fungi. (U. S. Dept. Agriculture,

Division of Vegetable Physiology and Pathology, Bulletin No. 15, Washington,

1898.)
Gibson, W. Hamilton. Our Edible Toadstools and Mushrooms and How to Dis-
tinguish Them (New York, Harper & Brothers, 1895).
♦Hard, M. E. The Mushroom Edible and Otherwise, its Habitat and its Time of

Growth. (Columbus, Ohio, The Ohio Library Co., 1908.)
Mcllvaine, Charles. One Thousand American Fungi. (Indianapolis, Ind., The

Bowen-Merrill Company, 1900.)

W. A. SETCHELL, Botanist.

♦These are especially recommended for first reading.