Introductory Mycology [3 ed.] 0471522295, 9780471522294

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THIRD EDITION

Introductory Mycology

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2010

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Introductory Mycology THIRD EDITION

Constantine

J.

Alexopoulos

Professor Emeritus of Botany

University of Texas

Charles

at

Austin

W. Mims

Associate Professor of Biology

Stephen F. Austin State University

Artwork by Dr. Sung-Huang Sun

and Dr.

Raymond W.

Scheetz

JOHN WILEY & SONS New

Yorlc

Chichester

Brisbane

Toronto

2

Copyright

© 1952,

1962, 1979, by John Wiley

& Sons,

All rights reserved. Published simultaneously in Canada.

Reproduction or translation of any part of

work beyond

this

that permitted

by Sections

107 and 108 of the 1976 United States Copyright

Act without the permission of the copyright

owner

is

unlawful. Requests for permission

or further information should be addressed to the Permissions Department. John Wiley

&

Sons.

Library of Congress Cataloging in Publication Data:

Alexopoulos, Constantine John, 1907Introductory mycology. 1.

II.

Mycology.

1.

Minis, Charies

W,

joint author.

Title.

QK603.A55 1979

589'.

79 12514

Wl-02214-4

Printed

in the L'niled Stales

10 9 8 7 6 5 4

.^

of America

Inc.

To

Juliet

and Sanch

Preface

An

informal survey of a number of teachers of mycology in the United States, some young, and some more experienced, revealed that the morphology/taxonomy approach is still widely used in introductory mycology courses for graduate and un-

other flagellate fungi into the Subdivision Diplo-

dergraduate biology, botany, microbiology, and

erable detail,

plant pathology majors for

been used

in the

which

two previous

proach coincides with our

book has

this

editions. This ap-

own views and

will con-

tinue to be the basis of this book. Although

we

mastigomycotina.

We have completely

rewritten and updated most

modern taxonomic Myxomycetes in consid-

chapters in accordance with proposals. In treating the

we have been

influenced by their ne-

glect in all other textbooks of

mycology

in

English

and we cannot conceive of an introductory mycol-

ogy course

omits them. Besides, our

that

terest in these

organisms

is

well

own

We

known!

in-

have

some physiological,

considered discussing the lichenized fungi together

biochemical, genetic, and ecological data in a few

with the nonlichenized, which they resemble, but

found

places, to

desirable to introduce

it

we have

minimum

kept these to a

expand the book unduly and

remain introductory. needs

to

know how

We

so as not

to allow the text to feel

still

We

how

claim

morphological/taxonomic discussion of the

becomes,

fungi, the system of classification used

of course, of paramount importance. Since the sec-

ond edition of this book was published,

a

number of

systems have been proposed, but none has been universally accepted. ogists

seem

to

hold

The one view many mycolis

the removal of the fungi

from the Kingdom Plantae

kingdom of their own. We call this kingdom Myceteae and subdivide it into the more or less traditional Divisions, Subdivisions,

Classes,

into a

from

viation

such

—

is

tradition

—

if

them separately, as more detail.

have kept phylogeny out of

As long

about

the

as

in the

little

book.

this

mycology remains

fungi

new become

alive,

continually

will

To

would be

fungi are related

available and our present phylogenetic ideas will

become

own

obsolete.

Why

burden the student with our

conjectures about fungal relationships? Indi-

vidual instructors can teach their

own views

with-

out interference from us.

On

the matter of illustrations

most of the

when

life

we have

retained

cycle drawings, updating them

necessary, because students found them so

useful in

previous editions.

We

have added some

we

new drawings, Raymond W.

Our only major

de-

graphs and electron micrographs, both scanning

regarded

as

and Subclasses

discuss in the usual sequence.

treat

but in a

we know how

foolish.

data

and ecology.

decided to

last edition,

that a student

fungi are constmcted and

they reproduce before studying their biochemistry

In a

finally

it

the separation of the

be

that

Oomycetes from

ably executed for this book by Dr.

Scheetz, and a

and transmission,

We

to illustrate

express gratitude to

all

number of photo-

important structures'. colleagues

who have

critically read portions

we

of the manuscript and

have incorporated many of

their suggestions.

We

alone, however, are solely and jointly responsible for

any errors of

fact or

judgment

Austin and Nacogdoches. Texas

March

I.

1979

that

appear

this

book.

We

shall

always welcome suggestions

from both teachers and students for the improvement of possible subsequent editions.

in

CONSTANTINE J. ALEXOPOULOS CHARLES W. MIMS

Acknowledgments

We

want to thank

lishers of

authors, editors, and pub-

all

books and journals who permitted us

to

quote passages and use illustrations from published

works

as credited.

who

thanks to those illustrations,

the

first

ledge

time.

also

We

wish

to

extend our

provided glossy prints of

some of which

help

the

We

are published here for

are especially pleased to

of Dr.

Raymond W.

Szaniszlo and Mr. R. Slocum.

son, P.

greatly indebted to Mrs.

Austin, without this

whose help

Scheetz,

cologists

who

L. R. Batra, R. K.

crographs, and scanning electron micrographs he

Carroll, O. R. Collins,

produced especially for

mill. R.

work of Dr. Sung-Huang Sun. are also due to a large number of mycol-

ogists

who

helped with the literature and

made important particularly to

merous drich,

to S.

Benjamin.

S.

mention, the help of Drs. Henry AlBartnicki-Garcia, L.

Meredith

Batra, R.

S.

Blackwell,

H.

J.

L.

Kramer. E.

S. Luttrell,

loch, K. B. Raper, D. R. Reynolds,

Seymour, Martha Sherwood,

J.

W.

K.

Brodie, J.

W.

D. MalD. Rog-

G. Soren-

S. Fuller, T.

W.

C

M. Ham E

Lichtwardt, C.

Moss, K. B. Raper, D. R. Reynolds

Trappe, and Mr. R. Slocum. we thank our wives Juliet Alexopoulos

Finally,

and Sandy

acknowledge, among others too nu-

Kimbrough, C.

J.

M.

D. Rogers, Roland Seymour, Paul L. Szaniszlo

we want

G. C. Carroll, G. T. Cole. Y. Hiratsuka.

ers, R.

who

J.

Benjamin, G. L. Benny, G.

A. Humber, R.

Miller. S. T.

my-

manu

was prepared: Drs

before the final draft

suggestions for the treatment of

certain fungal groups. In this connection,

for pub-

read critically portions of the

script

Thanks

at

locating literature,

are especially grateful to the following

Department of Biology, University of Southern many fine drawings, photomi-

the art

in

book could not have been completed

We

supplement

are

lication as scheduled.

acknow-

Mississippi, for the

this edition, to

We

Betty White, Librarian

of the Science Library, University of Texas

Mims

for offering

many

the clarification of the writing

suggestions for

and for

their pa-

tience and understanding during the years required to

complete

this

new

edition.

This book was edited by Rosemary Wellner. her

we

To

express our gratitude for her very careful

editing, and for putting

up with our idiosyncrasies

with unusual understanding.

Preface

To The Second Edition

Progress

mycology has been so pronounced in and the first edition of this book

in

the last ten years,

been so kindly received by

has

teachers throughout the world, that

compelled

and

students

have

I

felt

revise the text in accordance with

to

mycetes; and to document the text

In

an

is

no different from the

first in

morphological-taxonomic

essentially

book, the system of classification adopted

is,

of

The phylum no longer recognized. The

course, of considerable importance.

Myxomycophyta

newer findings. The new edition

much more

thoroughly.

Acrasiales

and

is

Labyrinthulales

are

treated

as

general approach to the study of fungi. Morphol-

orders of uncertain affinity and are not included in

ogy and taxonomy continue to form the basis of discussion. However, significant physiological and

any class or division. The Myxomycetes and the

genetic knowledge

vision Mycota.

its

logical and

is

interwoven with the morpho-

taxonomic wherever

on an introductory

it

can be discussed

sary to eliminate

bacteria

maries

was

at the

some of

first

made

neces-

it

the features that

edition.

regretfully

For many years mycologists have recognized

Phycomycetes are a heterogeneous group 1958 Sparrow pointed out that the

that the

level.

Rising costs of production have

desirable in the

Plasmodiophorales are treated as classes of the Di-

seemed

Thus, the chapter on

omitted, and the

sum-

ends of the chapters were eliminated.

of fungi. In

aquatic Phycomycetes consisted of several distinct "galaxies'" to which he gave

names with

class

endings. These galaxies are here recognized as classes,

and the concept

is

expanded

to include the

For the same reason, the number of references has

non-aquatic groups. Sparrow used the term Phyco-

been

mycetes for one of these galaxies.

kept relatively small.

Two

features of the

first

edition

which students

Oomycetes

as a class

name

I

am

particularly praised: the inclusion of derivations of

mycetes has been so well established

mycological terms

sense that to give

life

in the text,

and the

illustrated

cycles, are retained.

Although

this

book was

originally written to

serve an undergraduate course,

adopted as a

text in

fact influenced

my

it

has been widely

graduate courses as well. This

decision to deal with

some

sub-

ject matter at a higher level than in the first edition; to introduce les.

the

new groups, such

as the Labyrinthula-

Hyphochytridiomycetes, and the Tricho-

new

substituting

for this group. in

Phyco-

its

wider

restricted

meaning would

be inadvisable. Furthermore, those

who agree with who prefer may

it

a

the principle of this classification, but

not to discard the Phycomycetes as a group, treat the classes in this

the class

In treating the

as sub-classes

Ascomycetes

followed Martin's lioiuiry

book

under

Phycomycetes.

new key

in

I

have essentially

Ainsworth's Dic-

of the Fungi, deviating from

it

in certain

Preface to the Second Edition

places.

have

I

adopted

LuttrelPs

sub-classes:

Hemiascomycetidae, Euascomycetidae, and Locu-

mended by

name endings

using

loascomycetidae,

recom-

the code, and have retained his conve-

Euascomycetidae

of the

subdivision

nient

into

four series: Plectomycetes, Pyrenomycetes, Dis-

comycetes, and Laboulbeniomycetes. viated the

from both

name

ales

and

Luttrell

and Martin

have de-

I

in retaining

Sphaeriales for the order they call Xylariin

the

was

fortunate in securing once again the

pared the drawings for both editions. express

my

leagues

who

Deuteromycetes has been

tal-

who I

pre-

wish

to

appreciation to her and to those col-

furnished

me

with glossy prints of

photographs or electron micrographs of fungi. 1

owe

of the

special thanks to Professors Jules Brunei

University

of Montreal

Rogers of the University of reading the

recognizing the Clavicipitales.

The chapter on

I

ented services of Dr. Sung-Huang Sun,

first

me

nished

and

Illinois,

Donald P. who, after

edition from cover to cover, fur-

with long

lists

of comments, correc-

and suggestions, and to Professor Ralph

considerably expandfed to include a discussion of

tions,

the parasexual cycle, to inform the student of the

Emerson of

new and

of suggestions regarding the treatment of the lower

rapidly spreading ideas on the classifica-

tion of the

more

Hyphomycetes, and

to give

attention to the medical fungi than

somewhat was given

In

my

fungi.

treatment of the Basidiomycetes

I

have

I

am

particularly grateful to Professor G.

on

mycetaceae

me

of

in this class

instead of in the

Deu-

colleagues will again regret the ab-

sence of phylogenetic diagrams and the very limited

phylogenetic discussions. The more

the fungi the relationships.

special

fungi.

my

more uncertain I

I

I

become about

study their

prefer, therefore, not to share

burden with students

who

my

are just beginning the

dealing

erobasidiomycetidae and take time on

Some

section

the

followed Martin but have included the Sporobolo-

teromycetes.

for

his

July. 1962

with

W.

Het-

the

willingness

to

numerous occasions to discuss with

problems on the classification of the

From both teachers and students shall conwelcome suggestions which may help imI

tinue to

prove subsequent editions.

Once again my wife has been

of the greatest

help in judging the clarity of presentation. For her help, her encouragement, and her patience crateful.

study of fungi.

Austin, Te.\

list

Martin of the University of Iowa for his suggestions

in the first edition.

the University of California for his

CONSTANTINE

J.

AlEXOPOULOS

I

am

To

Ever since cades ago,

book

my I

student days,

more than two

have recognized the need for a

Mycology

in

Preface The First Edition

written for the student

knows nothing about

the fungi and

who

de-

the kindergarten to the university, and function

text-

has replaced structure as the raison d'etre of bio-

who

logical teaching. This, of course,

is

as

it

should be

needs an

except for the undisputed fact that a beginning stu-

orderly presentation of certain fundamental facts

dent understands function only through the struc-

on the structure and

tural features associated

nisms

in the

classification of these orga-

form of broad concepts and patterns,

with function.

see photosynthesis; he sees leaves,

without the innumerable details and exceptions

bles, and, eventually, chloroplasts: he

which make the study of fungi so fascinating for

parasitism; he sees hyphae

the specialist, but so bewildering for the beginner.

toria

With the discovery of

antibiotics, with the re-

cent strides in the genetics and the biochemistry of the fungi, and with the realization of the role

which

fungi play in the causation of allergies and parasitic

ten

diseases of

man,

become greater some knowledge of mycology

on the elementary

rather than less, for is

the need for a textbook writ-

now

level has

not only necessary to the biologist in gen-

eral, but

is

becoming

a part of the cultural back-

ground of every educated and well-informed vidual.

It

indi-

should be possible then to give the

among

which have invaded the

in the

form of

lesions,

of

Physarum polycephciluin and

A

a, but rather the

spora. In order for function to have any concrete

meaning

—and remember, we speaking of — knowledge of general are

beginning student

a

science,

therefore,

tainly

no agreement as

to the general

is

cer-

approach

which such a text should take. This, of course, the age of biochemistry.

ecological approach

is in

is

The physiological and vogue all the way from

the

struc-

and probable relationships, and a working

sification of the fungi in general without "telling

for an elementary text in this field, there

Plasmodium

Fiiligo septicu: he

two colgrow together and form the zygospores of Phycomyces or the ascocarps of Neuroand

onies which

all."

believe, the need

and symptoms

rather the fascinating streaming of the

does not see genes

knowledge of terminology,

I

cells,

oxygen, nitrogen, phosphorus, and carbon, but

ture

Although few people dispute,

does not see

host cells, haus-

leaf spots, twig cankers, or skin

student an insight into the importance of fungi to

and clas-

not

and sores; he does not see percentages of

man and

into the structure, life history,

He does

oxygen bub-

it

seems I

to

me, are

the language of the

essential. In this

book,

have discussed the structure of the

fungi with stress on the

life

histories of various

representative organisms and have given the basis

of what to

me

appears to be the most acceptable

system of classification, with some general

re-

marks concerning the probable relationships of the major fungal groups. The purpose of this book

Preface to the First Edition

then

answer

to

is

ble the question: affect

us?"

and concisely as possi-

as simply

"What

are fungi and

how do

they

for the student in agriculture, bacteriol-

ogy, or other general

no time and.

who

of knowledge

field

has

stage of his training at least, no

at this

desire to enter into the intricate details of Mycol-

ogy.

hope

I

that

book also

this

background, such as can be given troductory course for which student

who wishes

and their a

to

make

treatise

in a

one-term

in-

designed, for the

the study of the fungi

work. This book

activities his life's

complete

is

it

provide a

will

on the fungi, and

is

not

not in-

is

So much undertake

for the reasons

this task.

Now a

which prompted few words

the organization of this book. teria,

in

me

to

defense of

The chapter on bac-

which may seem out of place in a book of was included at the express request of a

this type,

number of my students who think that a brief survey of our knowledge of the structure of bacteria would be at least as useful and as fully justified in a text on Introductory Mycology, as are the chapters on molds and yeasts invariably included ductory Bacteriology texts. Certainly brief discussion of the in

feel that a

I

Actinomycetes

in Intro-

is

essential,

view of the great role which these organisms ap-

pear to play

in the

view of the

and

without a perfect stage

economy of

nature and of

man.

if

the

—

are discussed

immediately afterward.

The terms

inclusion of the derivations of mycological in the text at the

time such terms are

troduced and defined rather than alone

in the

first in-

glossary

admittedly experimental. However, the

is

opinion of a number of students consulted

is

that

the advantage of such inclusions as aids in under-

standing the meaning of the terms far outweighs the possible disadvantage of temporary breaks in

may

thought which parenthetical intrusions

A

tended as a reference book.

Deuteromycetes themselves

studied,

— those

book which

feature of the

cially helpful to the

beginner

is

lustrated life cycles for a great

hope

I

cause.

will be espe-

the inclusion of

many

il-

of the species

discussed. Although such arrangement of figures

more space and

requires

therefore necessitates a

greater reduction in size of the individual drawings

than other arrangements, the advantage gained by the presentation of the entire

more than compensates

On

life

cycle

at

a glance

for the sacrifice in size.

the subject of classification,

conservative as possible

when

I

aim

to be as

insufficient

knowl-

edge of structure and relationships does not warrant acceptance of

but as

has

modem

made

it

newer systems of classification, where newer knowledge

as possible

advisable to discard older concepts

even though such concepts may be well established

and

in

link

between the bacteria and the fungi upon which

in the literature.

Thus,

interesting to speculate.

discarded

Archimycete-Oomycete-Zygomy-

it

is

fact that they provide a possible

The chapter on slime molds

is

included because

these organisms are traditionally studied in

ogy and particularly because ture

Mycol-

their intricate struc-

and great beauty are always sources of

interest

to the student.

are discussed immediately

Ascomycetes instead of at the very end of the book as has been customary in other books on Mycology. The dual naming and classification of after the

the

Ascomycetes

is

a difficult concept to teach to

beginners and can be taught ification of the

flagellation, as

Karling. cete this

The Deuteromycetes

much

Deuteromycetes

the imperfect stages of the

better

is

if

the class-

discussed while

Ascomycetes

are being

the

in the

Phycomycetes,

I

have

cete concept in favor of the classification based on

It is

my

specialists

adopted by Sparrow, Bessey, and understanding that most Phycomyin

this

country

have

adopted

system. The choice of a classification system

for the

Ascomycetes was

a

more

difficult task.

I

have recognized the old and convenient subdivision of the class into

two subclasses,

the Protoas-

comycetes and the Euascomycetes, and the subdivision of the latter into Plectomycetes, Pyreno-

mycetes,

and Discomycetes.

I

have placed the

Erysiphales in the Pyrenomycetes because of the

arrangement of their asci

in

the cleistothecium;

Preface to the First Edition

include them in the Plectomy-

many mycologists

In treating the

cetes.

lowed conservative

Pyrenomycetes,

lines.

I

have

fol-

The main deviations from

references

cluded.

languages have been

foreign

in

should be the

I

in-

person to deny the

last

value of a knowledge of as

many

foreign languages

system are represented by the inclu-

as possible in the training of a scientist; but the

sion of the Mycosphaerellaceae and the Pleospora-

value of foreign languages and the importance of

the traditional

ceae

the Pseudosphaeriales rather than in the

in

Sphaeriales, and by the transfer of the Phyliachora-

ceae

— following Miller—

to the Sphaeriales.

Nann-

reading foreign journals do not alter the fact that

American undergraduate who can read a

the

guage other than English

been adopted for the Dis-

same

is

comycetes except for the inclusion of the family

dents

who have

feldt's classification has

Sclerotiniaceae gists

now

which most American mycolo-

recognize.

The

the Basidiomycetes into

traditional subdivision of

most of our graduate schools.

mycetes are treated rather

The Holobasidio-

To

briefly.

discuss

them more thoroughly would necessitate the feel,

in-

should be

for the

left

more

ad-

vanced student of Mycology. times

at

in

is

in-

order to point out to the stu-

dent that there are other views on classification besides those

material

have

I

who

new

have adopted, but controversial

minimum

tried to

will use this

with a difficult,

of

I

kept at a

is

confusion. student

which

facts,

book

order to avoid

in

keep

mind

in

will

be struggling

new terminology and

and

that the

with a mass

that, at this stage of his training,

he will not be ready to shoulder the burdens of the intended specialist. For this reason, phylogenetic discussion also has been kept

enough

some

minimum, but we do have

at a

introduced to indicate that

is

definite, if not

always agreed upon, ideas on

On

the matter of references,

to include:

my

policy has been

(1) all those cited in the text: (2) all

those from which illustrations have been taken;

and

(3) a

few of the most recent

to the subject matter in

they

may

articles pertaining

—even though

each chapter

not have been mentioned in the text

give the interested student a good liographical

wish to express

I

aided

grateful to

my

start

—

to

toward bib-

work on any given phase. Very few

my

me

in

sincere appreciation to

any way.

who

wife,

I

all

am especially me so many

has given

hours, which she would normally devote to her

own

profession, studying and criticizing the

script for clarity of statement

manu-

and logic of presenta-

She has been of the greatest possible help and

inspiration throughout the entire task of writing this

book.

I

am

thankful to Professor Benjamin

Hickok of Michigan entire manuscript rial

suggestions for

who read the who made numerous edito-

State College,

and

its

My

clarification.

sincere

thanks go to Dr. E. D. Devereux of Michigan State College,

who

read the chapter on bacteria; to Dr.

Leland Shanor of the University of read the chapters on

Illinois,

who

Myxomycophyta and Phyco-

mycetes; and to Dr. Lewis Wehmeyer of the University of Michigan, who read the chapters on Ascomycetes and Deuteromycetes. I alone, however,

am

responsible for the errors which

in this

may

be found

book, and for the views expressed on con-

troversial

the origin and evolution of the fungi.

still

who have

tion.

Controversial material on classification

troduced

not reached the stage of passing

required for the Ph.D. degree by

Hemibasidiomycetes and

troduction of very detailed and difficult material I

unfortunately true of most graduate stu-

nately, are

are discussed under four orders.

lan-

indeed unusual. The

the dreaded language examinations which, fortu-

Holobasidiomycetes has been followed. The former

which,

is

material.

My

thanks also go to Mr.

Nicholas Mizeres, formerly Assistant

in

Michigan State College, who read the of the manuscript while he was enrolled at

troductory Mycology course, and

who

Zoology first

in

draft

my

In-

criticized

it

from the student's viewpoint. Professors F.

C. Strong, E.

A.

Bessey. and

E. S. Beneke of Michigan State College, and Professor

J.

Arthur Herrick of Kent State University,

Preface to the First Edition

have generously contributed a number of excellent color transparencies from which black and white

Coleman has

negatives were made. Mr. Philip G.

taken a

book.

number of photographs

To all

who have tions

given

from

ticularly

all

am

320, respectively. Individual credit lines for these quotations appear as footnotes on the pages on

me

I

express

respective

to those

who have

—

my

gratitude.

permission to copy

their

glossy prints

tanical Club,

authors of mycological articles

the above

grateful also to

especially for this

W. B. Saunders Co., Torrey BoMcGraw-Hill Book Co., Inc., and The Macmillan Co. for pemiission to use the quotations which appear on pages 50. 50. 75, 124, Science Press,

illustra-

publications

furnished

I

—

me

par-

with

as well as to the managers, editors,

which the quotations are used. Finally

I

my

wish to express

who

who

or publishers of the journals or books in which

original drawings and

such illustrations have appeared. In order to avoid

from published drawings, and

lengthy and tract

cumbersome legends which would

from the value of the

ductory text,

all

been assembled of the book.

I

under the section

my

have

"Acknowl-

the Glossary at the

wish to extend

Michigan State College 14. 1952

Januarx

illustrations in an intro-

credit lines for illustrations

edgments" which follows

de-

end

appreciation to

Mrs. Sung-Huang Sun. formerly Assistant any, Michigan State College,

Bessey,

Distinguished

Michigan State College,

also

in

prepared

made

all

Bot-

all

the

copies

to thank Dr. E. A.

Professor for the

of

many

Botany,

stimulating

informal mycological discussions which

we have

had during the past four years and which have been of great help to

me

in

formulating certain concepts.

thanks to The

Const.

J.

Alexopoulos

Contents

Part Chapter

1

INTRODUCTION

1

Kingdom Myceteae: the major taxa.

Part 2

1

Introduction to the fungi and outline of

3

Introductory Mycology

Part

1

INTRODUCTION

Kingdom Myceteae

—Introduction

to the

Fungi and Outline of the Major Taxa MOLDS, MILDEWS, YEASTS,

MUSHROOMS, AND PUFFBALLS

mushrooms

Three and one-half millennia ago, so the legend

began

in

goes, the Greek hero Perseus, in fulfillment of an

among

the largest fungi and attracted the attention

oracle, accidentally killed his grandfather Acri-

of naturalists before microscopes or even simple

sius,

whom

he was to succeed on the throne of

"When

Argos. Then, according to Pausanias,'

Perseus returned to Argos, ashamed of the no-

homicide, he persuaded Mega-

toriety of the

the

dim

past,

for the

lenses had been thought of. With the invention of the microscope

by van Leeuwenhoek

in the

and the

man who

deserves the honor of being

Pier"

mycology who,

called the founder of the science of

him. So when he received the kingdom of Proetus

Antonio Micheli, the

he founded Mycenae, because there the cap

1729, published

(mykes) of

which

his scabbard

had fallen city.

off, I

and he

seven-

teenth century the systematic study of fungi began,

penthes, son of Proetus, to change kingdoms with

regarded this as a sign to found a

are

have also

Italian botanist

Nova Plantarum Genera,

his researches

is

in in

on fungi were included.

To define

But what are fungi?

the exact limits of

more we

heard that being thirsty he chanced to take up a

the group

mushroom (mykes) and

study living organisms the more meaningless our

that water flowing

from

it

he drank, and being pleased gave the place the

name of Mycenae. "-

—

—

the Mycenean may have been named mushroom. Derived from the same Greek word, mycology (Gr. mykes = mushroom for a legendary

+

logos

=

discourse), etymologically,

of mushrooms.'

And

virtually impossible, for the

become

to delimit

any particular group.

At present, biologists use the term fungus

Thus, one of the greatest civilizations ever developed

attempts

is

indeed that

is

is

the study

how mycology

fungi; L. fungus

=

= mushroom from

(pi.

Gr. sphongos

sponge) to include eukaryotic, spore-bearing,

achlorophyllous organisms that generally repro-

duce sexually and asexually, and whose usually filamentous, branched somatic structures are typically

surrounded by

cell walls containing chitin

or cellulose, or both of these substances, together with many other complex organic molecules (Table 'See Frazer's translation (1898) of Pausanias (Ramsbottom,

1-1,

page

11).

1953).

^Quoted by permission of Macmillan and Co., Lxjndon. 'Actually, the word mycology

The

correct

word

is

is

an improperly coined term.

mycetology, inasmuch as the combining

form of mykes

is

Greek grammar.

;

in

accordance with the principles of

Introductory Mycology

means

In simpler words, this

that fungi

have

typical true nuclei in their cells, that they repro-

duce by means of spores, and chlorophyll.

some

It

that they have no means that most fungi possess mechanism, that they have

also

sort of sexual

certain

mushrooms such

imiscaria) lightning.

as the fly agaric (Amanita

somehow correlated with thunder and The role that mushrooms play in the

is

religion and

mythology of Mexican and Gua-

temalan Indian tribes (Figure

I- 1)

is

well docu-

thread-like bodies that usually branch, and that

mented by Lowy (1971, 1974, 1977) and the

these tubular threads have cell walls that character-

ligious rights of

istically

contain chitin or cellulose or both these

substances. This

any, but, like

Some

perhaps as good a definition as

is

all

definitions,

true fungi, for

it

is

not watertight.

example, are not filamentous,

and the filaments of a few others have no walls. to

Some

have

true algae, because they are

lost their

such ceremonies.

world, a world in which the nucleus of the atom

fit

become

has

Then

the fungi.

some organisms mycologists have more or less by default, but which are

there are

It

tants of the

study mainly the molds and the truffles, the

few people

realize

can be said truthfully that scarcely a

day passes during which

modial slime molds.

and the smuts, the mushrooms, and the puff-

a household word,

intimately our lives are linked with those of

or

we

in

Nevertheless, even in today's science-conscious

probably not fungi. They are the cellular and plasIn this book,

mushrooms

cell

presumed

chlorophyll through evolution,

mildews, the yeasts, the cup fungi, the

the Indians of

thors (1974) in various writings about the use of

hallucinogenic

how

rusts

re-

Mexico have been interestingly described by Wasson and by Heim and, most recently, by Wasson and coau-

the above definition rather well but are not fungi.

studied,

some of

harmed

all

of us are not benefited

directly or indirectly

by these inhabi-

microcosm. Mycologists are indeed

poor propagandists. Fungi play such an important role

in the

slow

but constant changes taking place around us be-

we usually include in the fungi. We also devote some time to the slime molds, which in many ways resemble the fungi, balls,

and

all

the other groups

and which mycologists usually study.

Importance of Fungi. is only 250 years

fungi

The systematic study of old, but the manifestations

of this group of organisms have been

thousands of years

proposed over a

—ever

shell full

since the

known

first

toast

of wine, and the

first

for

was loaf

of leavened bread was baked. Indeed, ancient peoples were well aware of biological fermentation.

The Egyptians considered it the gift of the great God Osiris to mankind. The ancient Greeks and

Romans worshipped Dionysus and Bacchus and celebrated the Dionysia and the Bacchanalia, great festivals

Romans and

in

which

wine

flowed

truffles to lightning hurled

The mushrooms

freely.

attributed the appearance of

by Jupiter

to the

Figure

1-1

.

Two mushroom

stones, possibly used in

religious ceremonies or simply as art objects

the Middle Preclassic (± 1000-300 B.C.).

from

Human

ef-

earth.

32 cm, cap diam. 15 cm. Both at the Museo de Antropologia, Guatemala. Courtesy

ico

B. Lowy.

Even in modem times, the Indians of Mexand Guatemala believe that the appearance of

figy (left): height

— Kingdom Myceteae

— Introduction

to the

Fungi and Outline of

Major Taxa

tlie

cause of their ubiquity (Cooke, 1975) and their as-

the mycologists. Cytologists, geneticists, and bio-

tonishingly large numbers. Specifically, fungi are

chemists have found that fungi can be important

the agents responsible for tion of organic matter

much

of the disintegra-

and as such they affect us

di-

terials subject to

known

Because of the rapidity with which

ma-

fungal attack; they cause the ma-

of fungi than of plants or animals. Furthermore,

other consumer goods manufactured from raw

jority of

cal processes.

some fungi grow and reproduce, a much shorter time is required to obtain a number of generations

by destroying food, fabrics, leather, and

rectly

research tools in the study of fundamental biologi-

many

plant diseases, and

diseases

because fungal spores produced by meiosis will

of animals and of humans; they are the basis of a

grow

number of industrial processes involving fermentation, such as the making of bread, wines, beers,

an opportunity for direct and rapid tetrad analysis.

the fermentation of the cacao bean, and the prepa-

tubes, require less space, less care, and less expen-

ration of certain cheeses; they are

employed

in the

In addition, fungi,

sive

commercial production of many organic acids, of

some drugs such of some vitamin

as ergometrine and cortisone and

preparations, and are responsible

for the manufacture of a

number of

antibiotics, no-

tably penicillin and griseofulvin.

On

the

one hand they are responsible

damage

millions of dollars" worth of

—together with

sible

many

red bread

mold Newospora

is

one example.

can mycologists of the U.S. Department of Agriculture, discovered this fungus in 1927

make

it

and pointed

an almost ideal orga-

nism for the study of the laws of heredity. In a

Dodge then step-by-step laid the new branch of science that has known as haploid genetics. Geneticists

series of papers.

foundations of a

come

to be

—have been respon-

and biochemists, alerted by Dodge's discoveries,

began using Neurospora as an experimental

would remain forever locked up

dead plant and animal bodies. ticularly important in the

The

by

important chemical elements that, without

their activity,

test

for the recycling of

bacteria

for millions of years

in

C. L. Shear and B. O. Dodge, two eminent Ameri-

for

to crops

causing plant disease, yet in their role as saprobes, fungi

which can be grown

equipment than most plants and animals.

out the properties that

Fungi are both destructive and beneficial to agriculture.

into haploid individuals this gives geneticists

Many

in

fungi are par-

decomposition of plant

A

manner

in

elucidated the in

tool.

series of researches followed that brought out

the

which genes control enzymes, and biochemical pathways that operate

living organisms, winning, incidentally, the

debris because of their ability to utilize cellulose.

Nobel Prize for geneticist G. Beadle and bio-

Plant nutrients are thus released into the soil in a

chemist E. Tatum. The recent book by Brodie

form available

to

growing plants and COj

in large

(\91S). Fungi

—Delight of Curiosity,

explores the

in

subject of the importance and the fascination of

photosynthesis. Finally, to introduce an epicurean

fungi in a delightful, short account. All students

quantities

is

added

we must

theme,

to the

not overlook the delights of a

thick, juicy steak

would have brunnesens, 1976).''

it

atmosphere to be used

—with

"smothered"

is

as the chefs

the sporophores of Agaricus

the cultivated

More

—

mushroom (Malloch, mushrooms in

said about edible

Chapters 17, 21, 24, and 27.

The

fungi are no longer the private concern of

studying mycology

In

the

more recent years and up to 1976, most mycologists used Tame Agaricus bisporus for the cultivated mushroom.

many who

are not

The sline molds

are also being widely used in

many

years, they were the property

research.

' ,

-

of mycologists alone. Then cytologists, biochemists,

and biophysicists found Physarum polycepha-

luin to

be an excellent experimental organism for

the study of *

—and

should read this book.

DNA

synthesis, the mitotic cycle,

morphogenesis, and of the causes and the mecha-

nism of protoplasmic streaming and of synchro-

Introductory Mycology

Figure 1-2 Successive stages of growth of a hyphal half-hour intervals (Gelasinospora autosteira).

nous mitosis as explained

in

Undoubtedly, many more fungi have contribu-

make

to the

the welfare of

knowledge and, consequently, are already known;

humans. Some

others await discovery. will find

It

the mycologists

is

who

them!

at

filaments constituting the body (soma)

The

They resemble simple

plants in that, with

few ex-

ceptions, they have definite cell walls, they are

usually nonmotile, although they

may have

spore (Gr.

uals of the

part of the fungus

in the

spoici

=

seed, spore)

same

production of

species.

new

is

a

individ-

Fungi do not possess

stems, roots, or leaves, nor have they developed a

of a

organism are potentially capable

is

point and to start a

which we

new growing

able to produce a

new

individual. Reproductive

from somatic

classify the fungi.

Few

struc-

on the basis of fungi can be

identified if their reproductive stages are not available.

motile

minute, simple propagating unit without an em-

"^

1-2), but

of growth, and a minute fragment from almost any

With

parts of

reproductive cells, and they reproduce by means of

A

parts of an

tures and exhibit a variety of forms,

fungi constitute a

group of living organisms devoid of chlorophyll.

bryo that serves

most

structures are differentiated

General Characteristics.

spores.

drawn

fungus elongate by apical growth (Figure

1968).

tions to

The

Chapter 4 (Rusch,

tip,

relatively

few exceptions, the somatic

any fungus resemble those of many other

fungi.

Ultrastructure." 1954)

we have

In the last

learned

two decades (since

much about

the ultrastruc-

ture of fungi through the use of the electron micro-

scope (Bracker. 1967). Thus,

knowledge

it

is

now common

that the fungal protoplast has the

same

vascular system, as plants have. Fungi are usually

filamentous and multicellular; their nuclei can be

demonstrated with relative ease; their somatic structures, with few exceptions, exhibit little differentiation

and practically no division of labor.

^

The terms soma and somatic

(Gr.

soma, somatos

=

body) are

equivalent to the term "vegetative" in plants. '

We are assuming

ogy of

that the student

ultrastructure. If not,

ommended

is

familiar with the terminol-

some reading on the subject is recBrown and Bertke, 1974).

(Jensen and Park, 1967;

Kingdom Myceteae

— Introduction

to the

Fungi and Outline of the Major Taxa

general structure as the protoplast of other eukaryotes.

The nucleus

is

bounded by a nuclear en-

velope consisting of two membranes with characteristic

pores.

It

during

toplasm, which

fungi, however, see Bracker (1967) and Beckett,

Heath, and McLaughlin

(

1974).

contains usually one nucleolus

consisting mostly of

appears

additional information on the ultrastructure of

RNA,

nuclear is

which sometimes

bounded by

the

dis-

Somatic Structures.

The fungal

thallus typi-

cy-

cally consists of microscpic threads or filaments

plasma mem-

directions, spreading over or

division.

In

the

that

branch

in

all

brane, the usual organelles and inclusions are

within the substratum utilized for food. Each of

found; mitochondria, vacuoles, vesicles, endoplas-

these filaments

mic reticulum, ribosomes, microbodies, microtubules, crystals, glycogen, and so on. Loma-

Gr. hyphe

somes (Figure

1-3),

membranous

structures lying

between the plasma membrane and the are

more commonly found

in fungi

cell wall,

than in most

=

is

known

web).

A

as a

hypha

hypha (pi. hyphae; is made of a thin,

transparent, tubular wall filled or lined with a layer

of protoplasm varying in thickness.

The protoplasm tous fungi

is

in the

hyphae of most filamen-

other organisms. Golgi bodies or dictyosomes

partitions or cross-walls that divide each

(Figure 1-4). on the other hand, are not always

into

present in fungi, at least in what has

come

to

be

regarded as their typical form. Inasmuch as ultra-

compartments or

called septa (sing, partition) (Figure

The cross-walls

cells.

septum; L. septum

=

are

hedge,

I-5B). In the simpler filamen-

groups of fungi,

tous fungi septa are always formed at the base of

best to relegate further discussion of this topic

reproductive organs but are confined to those loca-

structural details differ in different it is

by hypha

interrupted at irregular intervals

to the discussion of particular fungal groups.

Figure 1-3.

For

tions so that the vigorously

growing hyphae are

Transmission electron micrograph of a lomasome (plasin Pythium. Courtesy S. Grove and C. E. Bracker.

malemmasome)

Introductory Mycology

Figure 1-4. Transmission electron micrograpli illustrating a Golgi apparatus (dictyosome). From 1. B. Heath (1975). Protoplasma 85:147-176.

coenocytic(Gr. ^o/noj (Figure 1-5 A) that here, however,

is

= common + koite = couch)

non-septate (aseptate). Even

when

the

hyphae age, septa are

often formed at various places.

hypha die and the protoplasm

is

As

portions of a

withdrawn toward

the

growing

tip, a

septum

portion from the living

We

Figure 1-5. Somatic hyphae. A. Portion of hypha. B. Portion of a septate hypha.

that separates the

dead

generally formed,

recognize two general types of septa: pri-

mary and formed

is

adventitious. The primary septa are

in association

with nuclear division and are

coenocytic (nonseptate)

Kingdom Myceteae

— Introduction

Fungi and Outline of the Major Taxa

to the

,^-^— ^^^^l^^^fMf^ -

Figure

I

Transmission electron micrograph of a median longitudinal section through a septum with a central

-6.

pore. Courtesy C. E. Bracker.

down between

laid

tious septa are

daughter nuclei. The adventi-

formed independently of nuclear

refer

when we

discuss the fungi in which they

At the moment we should

occur.

stress that

in

division and are especially associated with changes

fungi possessing perforated septa, the protoplasts

moves

on each side of the septum are connected by living

to another (Talbot,

strands that pass through the pore or pores and con-

in the concentration

of the protoplasm as

from one part of the hypha

it

nect adjacent cells. These pores are usually large

1971).

Septa vary in their construction. ple, others

more complex.

Some

are sim-

All types appear to be

formed by centripetal growth from the hyphal wall inward. In some septa growth continues until the septum

is

a solid plate; in others the septum re-

mains incomplete, leaving a pore

may the

in the center that

often be plugged or occluded (Figure 1-6). In

most complex fungi the septa have a special

central apparatus in the

inflation

form of a barrel-shaped

surrounded typically by a perforated

membrane (see Figure 20-2). This is the so-called dolipore septum (L. dolium = a large jar or cask, i.e., barrel) (Moore and McAlear, 1962). We

enough sarily

the Basidiomycetes (Chapter 20) in which

it

most

frequently occurs. There are several other types of structures associated with septal pores to

which we

is

and other not neces-

inhibited in regularly septate fungi.

Plas-

modesmata (Figure 1-7) have also been demonstrated in a few fungi (see Powell, 1974). They are probably of more common occurrence than observations to date indicate. The individual cells of septate

hyphae may contain one, two, or many

nuclei. Uninucleate cells are characteristic of

some

fungi, binucleate cells of others, whereas multinucleate cells

'

discuss this interesting structure in connection with

to permit the passage of nuclei

organelles so that nuclear migration

may occur

in

most.^

Regardless of the number of nuclei they contain, hyphal seg-

ments between septa are usually called

however, a

cell

cells. Strictly

speaking,

contains only a single nucleus and the term

coenocyte would describe more accurately a compartment with

more than one nucleus.

Introductory Mycology

Transmission electron micrograph illustrating piasmodesmata septum of Endomyces geotrichum. Courtesy C. E. Bracker.

Figure 1-7. in a

Cell Wall Composition. in the

Vr

The

cell

wall (at least

fungi that have been studied in this regard)

is

multilaminate. with the lamellae consisting of variously oriented

fibrils

(Aronson,

1965).

The

some Oomycetes, from which group

it

had long

been thought to be absent.

The composition of the cell wall of many fungal is not the same under all circumstances. On

species

may

principal chemical constituents of the fungal cell

the contrary, substances that

wall are various polysaccharides, but proteins,

young hyphae may disappear almost completely as the hyphae grow older, or other materials may be deposited and mask the presence of the earlier constituents, making their detection very difficult. Furthermore, it has been shown definitely that ex-

li-

and other substances are also included. The

pids,

chemical composition of the

same

cell wall

is

not the

As more data accumulate certain become evident that make cell wall com-

in all fungi.

patterns

position appear to be an important criterion of

ternal

fungal relationships. Table 1-1, modified slightly

media,

from Bartnicki-Garcia's 1970 review, this

illustrates

tendency. This table will be more meaningful

when you become familiar with the fungal groups mentioned and we refer to it again several times when discussing various fungi. What you should note

now

is

in the cell

found

that chitin is characteristically present

walls of most fungi.

in recent years (Lin

Sicher, and Aronson.

It

has even been

and Aronson, 1970; Lin,

1976) in the cell walls of

factors

pH

— such

be present in the

as the composition of the

values, and temperature

—profoundly

influence the composition of the fungal walls (Foster.

1949).

Nuclear Division.

Fungi possess organized,

demonstrable nuclei each with a nuclear envelope, a nucleolus,

and chromatin strands

that

become

organized into chromosomes during division (Figure

1-8).

The

nuclei in the somatic portions of

most fungi are extremely minute, and

their study

TABLE

1-1.

Cell Wall Composition in the Fungi. (Modified sliglitly 1970).

Cell Wall Category

from Bartnicki-Garcia,

Introductory Mycology

with the in

light

microscope

general in the fungi

is

very

difficult.

may be simply

Mitosis

described as

found

are characteristically

in

close association

with the nuclear envelope and are associated with

follows. If

those fungi producing flagellate cells, centrioles

we

disregard

cetes, mitosis in

some stages of the Myxomymost fungi is typically in-

tranuclear (closed) and

material controlling the formation of the spindle

apparatus. Nuclear divisions involving centrioles

characterized by the

are said to be centric as opposed to noncentric

presence of centrioles or small electron-dense struc-

divisions that lack them. Fungal centrioles typi-

is

tures called spindle pole bodies 9)

By

or

nucleus

associated

(SPBs) (Figure

organelles

1-

(NAO).

we mean that the nuclear envelope break down during prophase, as is the

intranuclear

does not

cally exist in pairs

eukaryotes.**

Each

and are similar is

to those

a short cylinder

of other

composed of

nine triplet sets of microtubules arranged in a ring. In the

more complex,

nonflagellate fungal groups

case in most plants and animals you have probably studied, but instead remains

throughout

Figure

19

much

more or

less intact

of the division (Figure 1-10). In

*

Centrioles

may

also function as kinetosomes or basal bodies in

motile cells (see page 27).

Transmission electron micrograph showing a spindle pole body (SPBl appressed to the surface of The Insert at the upper right shows duplicate SPBs on the surM. A. Rogers.

the nuclear envelope of an interphase nucleus (N). face of a prophase nucleus. Courtesy

Kingdom Myceteae

— Introduction

to the

Fungi and Outline of the Major Taxa

Figure 110 Transmission electron micrograph of an intranuclear, centric mitotic division. Note the paired centrioles (C) at the opposite ends of the nucleus. From R. Mc Nitt (1973). Can. J. Bot. 51:2065-2074. By permission of the National Research Council of Canada.

centrioles are absent.

instead a

SPB

Each prophase nucleus has

that characteristically is associated

clear division the

SPB

resulting daughter

divides (Figure 1-9) and the

SPBs migrate to the opposite much the same fashion as

with the nuclear envelope. This structure lacks the

poles of the nucleus in

microtubular components of a centriole and

centrioles do.

usually appears as an electron-dense, dumbbell-

shaped, rod-like or spherical structure. During nu-

Although there regarding the

way

is still

in

no unanimity of opinion

which fungal somatic nuclei

Introductory Mycology

we

Lu (1974) has summarized "The current consensus is mitosis occurs more or less normally in fungal

divide,

think that

the situation admirably: that

may

groups of fungi

be found in

Robinow and

Bakerspiegel (1965), Aist and Williams (1972),

McNitt 1973), and Lu ( 1974). (

Two recent reviews

nuclei with interphase, prophase, metaphase, ana-

of the subject are those by Heath (1978) and Fuller

phase and telophase as described for higher

(1976).

cell

types.""' Heath (1978), however, should also be

There

are, of course,

some

different groups of fungi.

pointed out

more

Meiotic divisions are also intranuclear but other-

wise typical. Because fungal chromosomes are so

consulted.

in

differences

Some

the groups in

among

of these will be

which they occur.

A

detailed account of mitosis in different

small,

it

is

sometimes

curately and be sure

takes place.

As

difficult to

when

count them ac-

a reduction division

a result, the electron microscope

has been used extensively for demonstrating the

occurrence of synaptonemal complexes (Figure 'Reproduced by permission of

the National Research Council

11),

which

are considered

now

1-

to be strong evi-

of Canada from the Canadian Journal of Botany, 52:299-305.

dence of meiosis

1974.

meiosis would normally occur. These structures

or. at least, of the place

where

'f^

Figure 111. A. Transmission electron micrograph of a meiotic prophase nucleus containing a synaptonemal complex (arrow). B. Higher magnification of a synaptonemal complex. A and B, courtesy W. J. Sundberg.

Kingdom Myceteae

Figure

112

(1969).

4m.

— Introduction

to the

Fungi and Outline of the Major Taxa

Light micrograph of a median longitudinal section through a rhizomorph. 56:610-619.

From

J. J.

Motta

J. Bol.

are thought to be

formed by synapsed meiotic

chromosomes.

The mycelium of parasitic fungi grows on the more often within) the host, either

surface of (or

spreading between the cells or penetrating into

The Mycelium

The mass of hyphae constituting is called the mycelium (pi. mycelia; Gr. inykes = mushroom). The mycelium of some fungi forms thick strands. In certain types of such strands the rhizomorphs (Gr. rhiza = .

the thallus of a fungus

—

root

+

inorphe

=

their individuality

shape)

—

the unit

hyphae lose

and form complex tissues

exhibit a division of labor (Figure

1-12).

that

The

them.

If the

mycelium

is

sorbed through the host the

walls

come

intercellular,

cell

mycelium penetrates

food

is

ab-

wall or membrane.

If

into the cells, the hyphal

into direct contact with the host pro-

toplasm. Intercellular hyphae of

many

fungi, espe-

cially of obligate parasites of plants, obtain

nourishment through haustoria (sing, haustorium; L. haustor = drinker). Haustoria, which

string-like

mass has a thick, hard cortex, and a growing tip whose structure reminds us of that of a

the fungus sinks into the plant host cells through a

Rhizomorphs are resistant to adverse conditions and remain dormant until favorable conditions return. Growth is then resumed, and the rhizomorph attains great length. Rhizomorphs are

growths of the somatic hyphae. They are regarded

root tip.

usually produced by the most complex fungi, the

minute pore punctured

in the cell

wall, are out-

as specialized absorbing organs. Haustoria

may be

knob-like in shape, elongated, or branched like a miniature root system (Figure 1-13).

As evidenced by

a

number of

ultrastructural

Basidiomycetes, but are also found in other groups

studies in several fungi (see, for instance. Little-

(Goos, 1962).

field

and Bracker,

1972; Coffey, Palevitz, and

Introductory Mycology

Figure 113 Three types of haustoria. B. redrawn from Smith (1900). Bot. Gaz. 29:15^184. C, redrawn from De Bary (1863). Ann. Sci. Nat. Bot. 4 ser., 20:5-148.

Allen, 1972; Coffey, 1975), penetrates a host cell

it

when

a

haustorium

does not puncture the host

plasma membrane but simply invaginates

it.

The

fungal wall around the haustorium remains intact

and

is

completely enveloped by an encapsulating

through which the haustorium has penetrated (Figure 1-14).

It

appears, therefore, that the chief func-

tion of haustoria

is

to increase the absorptive area

of a parasitic fungus.

Dickinson (1949) has shown

zone or sheath possibly of host origin but which

ligate

parasites will

composition from the host

tificial

membranes

differs

in

cell

wall

that certain

send haustoria through

obar-

substituted for the epidermis of

rust fungus Transmission electron micrograph illustrating a haustorium ot the within the body of the haustorium. lini with a host cell. Two nuclei (N) are visible of the haustorium. and the (NR) region neck the (HMC), cell mother haustorial the Also note Allen (1972). Can. J.Bol. host cytoplasm (HC). From M. D. Coffey, B. A. Palevitz, and P. J. Council of Can50:231-240. Courtesy M. D. Coffey. By permission of the National Research

Figure 114 Mdampsora

Introductory Mycology

the host in

which the fungus

duction of haustoria

is

growing. The pro-

is

probably a response to the

contact stimulus as well as to the stimulus of nutrients.

Haustorium-like branches of the mycelium

are also produced by the black stem rust fungus

gmminis

(Piicciiua

=

nically (Gr. a

tritici)

not

when growing axe-

xenos

-I-

=

stranger, i.e..

pure) on agar under conditions unfavorable for sa-

probic growth (Williams,

1969). Until relatively

was considered to be an obligate parasite but a number of isolates have now been grown axenically on artificial media. recent times, this fungus

The hyphae of saprobic

fungi

come

in intimate

contact with the substratum and obtain food by direct diffusion through the hyphal walls, causing

disintegration of the organic matter that they utilize.

The

older hyphae die as the

mycelium grows

and branches, and they themselves disintegrate

Fungal tissues (plectenchyma).

Figure 1-15

B. Pseudoparenchyma.

A. Prosenchyma.

in

nature because of the activities of other microorga-

nisms

life

history of

most

mycelium becomes organized into woven tissues, as distin-

fungi, the

many

tures that

prey on their dead bodies.

that

During certain stages of the

ma =

=

Gr. skleros

guished from the loose hyphae ordinarily compos-

matic structure

We

ing a thallus.

infusion,

use the general term plec-

(Gr. plekein a

i.e.,

=

woven

to

weave

-I-

enchymu =

tissue) to designate all

We recognize two genprosenchyma (Gr. emhynui = infusion, i.e., ap-

organized fungal tissues. eral

pros

types of plectenchyma:

=

toward

-I-

proaching a tissue)

is

a rather loosely

woven

tissue

stroma

Two

such somatic

stromata; Gr. stro-

(pi.

mattress) and the sclerotium (pi. sclerotia;

loosely or compactly

tenchyma

fungi form.

structures are the

on which or

hard).

A

much

like a mattress or a cushion,

stroma

which

in

16C,D

)

is

a hard resting

may

it

a compact, so-

fructifications are usually

formed (Figure 1-16/4,5). able conditions:

is

A

sclerotium (Figure

body

periods of time and germinate on the return of fa-

vorable conditions.

Growth.

Most fungi

will

grow between 0° and

which the component hyphae lie more or less parallel to one another, and their typically

35°C, but the optimum temperature range

elongated cells are easily distinguishable as such;

thermos

in

pseudoparenchyma parenchyma

=

closely packed cells

=

false

-l-

,

more or

less isodiametric or oval

resembling the parenchyma cells of vascular

plants.

have

(Gr. pseudo

a type of plant tissue) consists of

In this type of fungal tissue, the

lost

their

hyphae

1-

resistant to unfavor-

remain dormant for long

is

20° to

30°C. There are a number of thermophilic (Gr.

=

hot

-I-

philein

=

ever, that, as defined by (

1964), have a

at

'"

The

to love) species, howCooney and Emerson

temperature for growth

50°C and a minimum

or above

20°C.

maximum

at

ability of fungi to withstand

low temperatures,

in a

dormant

or

above

extremely

state, is utilized in

individuality and are not distin-

guishable as such (Figure 1-15).

Prosenchyma and pseudoparenchyma compose various types of somatic and reproductive struc-

'"Tansey and Brock (1972) have reported

60°C

is

that

approximately

the upper temperature limit for the growth of eukaryotes

including fungi.

Kingdom Myceteae

— Introduction

to the

Fungi and Outline of the Major Taxa

Reproductive body

Stromatic tissue

Sclerotium Figure 1-16.

Cross section of sclerotium

Stroma and sclerotium. A,B. Daldinia

the long term storing of fungal cultures in liquid ni-

trogen

at a

temperature of

-

In contrast to bacteria, fungi prefer an acid

dium for growth, with a pH of 6 being near timum for most species investigated Although

light is not required for the

me-

the op-

growth of

C,D. Claviceps purpurea.

some

fungi,

many

196°C.

sp.

light

is

essential for sporulation in

species (Cochrane, 1958).

teresting that the effect of light

pears to be localized and the

mycelium

thallus

is

However,

it

is in-

on some species ap-

not transferred through

to nonilluminated

portions of the

(Koehn, 1971). The phenomenon of zona

Introductory Mycology

from alternating zones of sporulatwas said to be

tion, resulting

ing and nonsporulating mycelium,

caused by diurnal periodicity of alternating light

and darkness (Hawker, 1966). Sagromsky (1976),

however, denied

how

actly

that require

that zonation

is

due to

light.

Ex-

light triggers sporulation in the fungi it

has not been determined. Cochrane

(1958) stated that the weight of the evidence favors the hypothesis that light checks growth, thus initiating a chain of events that leads to sporulation.

Light plays an important part

in

since the spore-bearing organs of

spore dispersal

many

fungi are

positively phototropic and discharge their spores

toward the

light.

The

on the relationship of fascinating reading.

classic researches of Buller light to spore dispersal

They may be found

make

in his

Re-

searches on Fungi, published between 1909 and 1950.

Fungal hyphae are capable of indefinite growth

under favorable conditions. In nature, fungal colonies

have been known to continue growing for 400

years or more.

It

is

probable that some mycelia,

but not individual cells, are thousands of years old.

The mycelium of a fungus generally begins as a germ tube emerging from a germinating spore (Figure 1-17). The mycelium has a tendency to grow more or less equally in all directions from short

a central point, and to develop a spherical colony.

You can observe tory

this ideal situation in the labora-

by growing certain fungi

in liquid

media; a

spherical, fluffy colony then develops around a

Figure 1-17. Two stages in the germination of a spore. A. Approximately IVi hours after the beginning of germination. B. Approximately 10 hours after germination.

phal tip growth.

The

results

tions indicate that the hyphal

of various investiga-

apex

is

more

or less

devoid of most cellular inclusions except for large

numbers of cytoplasmic

vesicles (Figure 1-19) that

are thought to function in hyphal tip growth. In

fungi having regularly

septate hyphae.

densely staining or refractive body

a

small

known

as the

seed, placed in the water or other

Spitzenkorper has also been found near the hyphal apex. The principal forms of apical arrange-

liquid

media employed. An actual sphere is seldom formed in nature, however, because of the effect of

ment of protoplasmic components within hyphae have been described by Grove and Bracker 1970)

external factors, such as the type of substratum,

and are shown

particle of food, such as a grain of

tion of a

light,

hemp

and chemicals,

to

wheat or a por-

which fungi readily

spond. Fungal colonies tend to be circular

re-

A

on

diagrammatic fashion

in

Figure

1-20.

Electron microscopic studies of the apices of ac-

in out-

solid media (Figure 1-18). hypha grows only at its tip. In view of this, both light and electron microscopic techniques have been used to examine hyphal tips in an attempt to elucidate the mechanisms involved in hyline

(

in

tively

growing hyphae have lead

to

what may be

described as the "vesicular hypothesis of hyphal tip

growth"" (Grove and Bracker,

Bracker, and Morre, 1973). This hypothesis

1970; Grove,

1970; Bartnicki-Garcia, is

stated very well

by

Figure 1-18. Mycelial fragmentation as employed in the laboratory for the propagation of fungi. A. Agar disc with fungus mycelium growing through it. cut from a colony and transferred to the surface of sterile agar. B. Resulting fungal colony 7 days after a disc similar to that in A was placed in the dish. Photograph by R. W.

Scheetz.

"^rw^-.

% \

Figure 1-19. Transmission electron micrograph of a median longitudinal section through the tip of an actively growing hypha. Note the numerous apical vesicles. From S. N. Grove and C. E. Bracker (1970). J. Bad. 104:989-1009. By permission o{ Journal of Bacteriology.

Introductory Mycology

elongation.

A

diagramatic representation of the

process described above

is

shown

Figure 1-21.

in

Before leaving the topic of hyphal growth should be noted that an exciting discovery has cently been

made

in this area

it

re-

by Bracker, Ruiz-

Herrera, and Bartnicki-Garcia (1976). These investigators have isolated a small microvesicular

much

structure

smaller than the vesicles described

above, which they have named the chitosome (Figure 1-22). According to these workers, the chi-

tosome is "the cytoplasmic container and conveyor of chitin synthetase en route to its destination at the cell surface."'- You will recall from our earlier discussion that chitin

is

an important

component of most fungal cell walls. Chitin synthetase is an enzyme capable of forming chitin microfibrils.

Diagramatic comparisons of the principal forms of apical organization in hyphae. A. Oomycetes. B. Zygomycetes. C. Septate fungi. Redrawn by R. W. Scheetz from S. N. Grove and C. E. Bracker"(1970). y. Bad. 104:989-1009. By permission of Journal of Bacteriology. Figure 1-20

•"Membrane material from the endoplasmic ticulum

is

transferred to dictyosome cistemae by

membranes

blebbing; cisternal

from ER-like

to

are transformed

plasma membrane-like during

ternal maturation: secretory vesicles released

dictyosomes migrate the plasma

to the

membrane, and at

cis-

from

hyphal apex, fuse with liberate their contents

into the wall region. This allows a

brane increase

membrane

re-

the hyphal

plasma mem-

apex equal to the

surface of the incorporated vesicles as

well as a contribution of the vesicle contents to

surface

expansion."" Apparently such

parashos

(Gr.

food

ei-

infecting living organisms as parasites

ther by

=

eating beside another) or by at-

tacking dead organic matter as saprobes (Gr.

supros

=

rotten

-I-

bios

—

life).

Many

symbiotic relationships with plants as

and

Grove, Bracker, and Morre (1970) as follows:

In nature fungi obtain their

Nutrition.

in mycorrhizae,'"*

said

form

about which more will be

subsequent chapters. The majority of

in

known

also

in lichens'-^

fungi, whether normally parasitic or not,

are capable of living

on dead organic material, as

shown by their ability to grow artificially on synthetic media." Fungi that live on dead matter and are incapable of infecting living organisms

we

call

obligate saprobes; those capable of causing disease or of living on dead organic matter, according to circumstances, facultative parasites (or facul-

tative saprobes); and those that cannot live except

on living protoplasm, obligate parasites. organism infected by

a parasite

is

A

known

living

as the

apical

vesicles contain material utilized in hyphal wall

formation as well as possibly enzymes involved in wall synthesis or the softening of pre-existing wall

'-Quoted by permission of the National Academy of Science.

"See

Chapters 17. 27, 28.

'"See Chapters 17, 22.

material. In any event, the overall result

is

hyphal

"

Substrata on which

liquid

" Quoted by permission of

the

American Journal of Botany.

and

.solid

we

culture fungi artificially.

media, the

agent, generally agar.

latter

containing

We

some

use both

solidifying

u.

si:

3 c

CO

2

— 24

Introductory Mycology

^ X ^¥-

3^

/

\,

1^.

J

^

22 A. Transmission electron micrograph of a thin section Ihrougli a sample of isolated chitosomes. B. Negatively stained preparation of isolated chitosomes (C) after incubation with substrate. Chitin microfibrils (arrows) have been synthesized in vitro. From C. E. Bracker, J. Ruiz-Herrera, and S. Bartnicki-Garcia (1976). Proc. Natl. Acad. Sci. 73:4570-4574. Courtesy C. E. Bracker. Figure

host.

1

It is

probable

that,

when we we

the physiology of the fungi,

learn

more about

shall be able to

devise synthetic media on which to grow called obligate parasites.

made As

Much

all

progress

is

the so-

being

in this area.

previously stated, fungi require already elab-

own. But

if

given carbohydrates

preferably glucose or maltose synthesize their

own

in

some form

— most

fungi can

proteins by utilizing inorganic

or organic sources of nitrogen and various mineral

elements essential for their growth. Laboratory studies have established that C,

orated food in order to live because, lacking chlo-

Mg,

rophyll, they are incapable of manufacturing their

by many fungi, probably by

S, B,

Mn, Cu, Mo.

Fe, and all.

O, H, N,

Zn

P,

K,

are required

Other elements.

Kingdom Myceteae

— Introduction

Fungi and Outline of the Major Taxa

to the

such as Ca, are required by some. Whether Ca also essential for

established but eral

rule,

organic

appears highly probable. As

glucose

a gen-

the best source of C, and

is

N compounds

In the formation of reproductive organs, either

is

fungi has not been definitely

all

the best source of N, with

sexual or asexual, the entire thallus verted into one or

more reproductive

this pattern

pounds which function as vitamins for other organisms. Some, however, are deficient in thiamine or

however, the reproductive organs

and must obtain these or

their pre-

cursors from the substratum. Fungi usually store

excess food

the form of glycogen or

in

lipids.

ments.

Some

omnivorous and can

are

subsist

green mold (Pemcillium sp.) and the

black mold (Aspergillus sp.), given a

common

little

-I-

=

are called holocarpic (Gr. holes

karpos

=

fruit).

In the majority of fungi, arise

from only a

portion of the thallus, while the remainder continues

normal somatic

its

activities.

The fungi in = good

category are called eucarpic (Gr. eu

this

karpos

=

fruit).

The holocarpic forms

are,

therefore, less differentiated than the eucarpic.

on

anything that contains organic matter. The com-

mon

whole

-t-

Different fungi have different food require-

con-

together in the same individual. Fungi that follow

ammonium compounds and nitrates next in line. Many fungi are capable of synthesizing com-

biotin, or both,

may be

structures, so

somatic and reproductive phases do not occur

that

mois-

Asexual Reproduction. Typically, fungi reproduce both asexually and sexually. In general asexual reproduction is more important for the propa,

grow on anything from cheddar cheese to shoe leather. Other fungi are more restricted in their diet; a few obligate parasites not only require

gation of the species because

living protoplasm for food, but also are highly spe-

several times during the season, whereas the sex-

ture, will

cialized as to the species and

even the variety of

host they parasitize. Inasmuch as fungi obtain their

food

in solution, the

through

the cell

walls and membranes. Thus, a

down

fungus must break smaller ones before

it

larger molecules into

can absorb them.

by secreting extracellular enzymes

It

does

that act

this

on the

substratum digesting the food outside the fungal

body. The enzymes a fungus

capable of produc-

is

ing govern to a large extent

its

ability to utilize

certain substances as food.

larly

since the asexual cycle

ual stage of

Reproduction.

new

individuals having

cal of the species.

Two

all

is

the formation of

the characteristics typi-

general types of reproduc-

tion are recognized: sexual and asexual. Asexual

reproduction, sometimes called somatic or vegetative,

in

the

many

fungi

is

is

usually repeated

produced only once a

year.

We

sometimes define asexual reproduction as

the nonsexual production of specialized reproduc-

such as spores. A broader definition, however, also includes any method of propagation tive cells

new

of

individuals, such as simple division of an

unicellular organism into daughter cells, or of a

multicellular thallus into a

each of which grows into a

number of fragments

new

individual.

It

is

this

broader concept of asexual reproduction that

we

are using here. In accordance with this concept

methods of reproduction commonly may be summarized as follows: (1)

the asexual

Reproduction

results

production of numerous individuals, and particu-

food molecules must be of

small enough size to be capable of passing freely

it

found

in fungi

fragmentation of the soma, each fragment growing into a

new

individual; (2) fission of somatic cells

budding of somatic cells or bud producing a new individual; and

into daughter cells; (3)

spores, each

does not involve the union of nuclei, sex