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THE    FUNGI 


•»■  *  f*  _    - 


^ 


The  father  of  American  mycology. 


THE    FUNGI 


IN  TWO  VOLUMES 
Volume  II 


By  Frederick  A.  Wolf  and  Frederick  T.  Wolf 

DEPARTMENT  OF  BOTANY  DEPARTMENT   OF  BIOLOGY 

DUKE    UNIVERSITY  VANDERBILT    UNIVERSITY 


New  York:   JOHN  WILEY  &  SONS,  Inc. 

Chapman  &-  Hall,  Limited 
London 


Copyright,  1947 

BY 

John  Wiley  &  Sons,  Inc. 


All  Rights  Reserved 

This  book,  or  any  part  thereof,  must  not 
be  reproduced  in  any  form  without 
the  written  permission  of  the  publishers. 


PRINTED    IN    THE    UNITED    STATES    OF    AMERICA 


PREFACE 

This  treatise  on  fungi  is  intended  as  a  reference  and  textbook. 
Its  content  falls  naturally  into  two  portions.  The  first  portion, 
included  in  Volume  I,  is  a  consideration  of  the  developmental 
morphology  and  taxonomy  of  fungi  and  is  basic  to  any  compre- 
hensive study  of  the  fungi.  The  second  portion,  included  in 
Volume  II,  deals  more  specifically  with  the  activities  of  fungi. 
It  must  be  borne  in  mind,  however,  that  we  have  attempted 
throughout  the  treatise  to  stress  the  need  for  more  emphasis  on 
problems  relating  to  fungus  activities. 

The  content  of  Volume  II  is  concerned  with  metabolic  and 
reproductive  activities,  the  modification  of  these  activities  by 
environment,  and  the  relationship  of  fungi  to  the  welfare  of 
man.  Consideration  is  also  given  to  certain  fungi  for  which 
habitat  is  largely  the  basis  of  grouping.  This  volume  may  be 
spoken  of  as  physiological  and  ecological  in  its  emphasis.  It  does 
not  purport,  however,  to  constitute  a  well-rounded  "physiology 
and  ecology  of  fungi"  for  the  reason  that  experimental  data  are 
still  too  meager  to  permit  the  preparation  of  such  a  textbook. 
This  explanation  is  made  at  the  outset  to  guard  the  reader  against 
eventual  disappointment.  The  need  for  a  volume  on  the  physi- 
ology of  fungi  is  keenly  felt  by  all  who  seek  such  information  in 
textbooks  on  plant  physiology,  only  to  find  that  such  books  are 
limited  to  consideration  of  the  physiology  of  seed  plants. 

Teachers  may  at  first  regard  our  departure  from  the  tradi- 
tional emphasis  on  taxonomy  and  classification  as  too  radical  to 
put  into  practice.  It  should  be  remembered,  however,  that  last- 
ing impressions  come  from  contact  with  living,  functioning  or- 
ganisms. From  experience  we  know  that  we  remember  with 
facility  where  and  under  what  circumstances  we  first  encoun- 
tered many  different  fungi  in  their  natural  habitats,  and  we  re- 
call how  intent  we  became  as  we  watched  their  development 
and  the  changes  which  they  induced.  If,  on  the  other  hand,  we 
had  been  presented  with  an  herbarium  specimen,  as  is  common 

v 


vi  PREFACE 

laboratory  practice,  and  had  been  asked  to  perform  an  "autopsy" 
in  order  to  arrive  at  an  understanding  of  the  structure  and  pos- 
sible functioning  of  the  victim,  long  dead  and  mummified,  little 
stimulation  of  thought  or  interest  would  have  resulted. 

The  further  objection  may  be  raised  that  knowledge  of  fungus 
activities  is  still  too  meager  to  be  presented  in  an  organized  man- 
ner to  students.  All  that  need  be  said  in  rejoinder  is  that  the 
seven-league  boots  of  physics,  physical  chemistry,  biochemistry, 
physiological  chemistry,  and  colloid  chemistry  will  enable  the 
teacher  and  the  student  alike  to  wade  far  out  into  the  depths  of 
the  vast  mvcologic  unknown.    Beginnings  must  be  made. 

Opinions  have  a  limited  value  in  the  field  of  science.  At  times, 
ours  are  expressed.  .Mycologists  may  not  find  themselves  in 
accord  with  some  of  these  opinions.  Be  that  as  it  may,  data  will 
some  day  exist  upon  which  ultimate  truth  will  become  securely 
established,  and  then,  of  course,  opinions  now  expressed  will  lose 
all  value. 

Our  efforts  have  been  concentrated  on  helping  the  student  to 
understand  fundamentals.  We  have  chosen %to  include  data  and 
conclusions  from  certain  reports  of  researches  and  have  omitted, 
without  apparent  reason  for  so  doing,  to  mention  others  that  are 
equally  good  and  pertinent.  No  intentional  discredit  or  lack  of 
merit  is  implied  in  these  omissions.  In  a  volume  of  this  scope  it 
is  simply  impossible  to  consider  each  subject  monographically. 
The  relative  importance  of  subjects  is  not  reflected  by  the  amount 
of  space  devoted  to  them.  References  to  reports  are  given  at  the 
end  of  each  chapter;  these  papers  contain  additional  pertinent 
references  to  other  researches,  so  that  interested  persons  can  gain 
a  more  comprehensive  grasp  of  a  particular  subject. 

Most  of  the  illustrations  are  adapted  from  those  of  others.  If 
in  any  instance  the  author  of  the  original  drawing  or  graph  has 
not  been  mentioned,  the  omission  is  unintentional.  We  herewith 
acknowledge  again,  with  gratitude,  the  kindness  of  those  who 
supplied  us  with  certain  illustrative  materials,  and  of  Mary  H. 
Wolf  for  her  assistance  in  the  preparation  of  illustrations. 

Since  the  legends  are  intended  to  explain  the  illustrations  ade- 
quately, mention  of  illustrations  is  omitted  from  the  text. 

We  are  indebted  also  to  Dr.  L.  E.  Wehmeyer,  who  carefully 
read  the  entire  manuscript,  for  his  criticisms  and  suggestions  and 
to  Mrs.  Fred  T.  Wolf  for  her  help  in  reading  proof  and  in  the 


PREFACE  vii 

preparation  of  the  indices.  Also  we  are  keenly  appreciative  of 
the  gift  of  a  wood-cut  picture  of  Louis  David  de  Schweinitz,  to 
whom  these  volumes  are  dedicated,  from  his  great-granddaughter, 
Dr.  Adelaide  L.  Fries. 

F.  A.  Wolf 
F.  T.  Wolf 
March,  1947 


CONTENTS 

1.  NUTRITION   OF   FUNGI 1 

Mineral  nutrition  of  fungi,  2.  Organic  nutrients  of  fungi, 
16.  Growth  factors,  24.  Influence  of  osmotic  pressure, 
29.    Implications,  29. 

2.  ENZYMES  AND  ENZYM1C  ACTIVITIES  OF  FUNGI    .       .      37 

3.  RESPIRATION 53 

Historical  material,  53.  Types  of  respiration,  56.  The 
respiratory  ratio,  62.  Respiratory  systems,  63.  Respiro- 
metry,  64.  Inhibition  of  respiration,  65.  Stimulation  of 
respiration,  66.    Implications,  66. 

4.  BIOCHEMISTRY  OF  FUNGI 69 

Organic  acids  and  other  products  having  six  or  fewer 
carbon  atoms,  70.  Polysaccharides,  79.  Fats,  79.  Sterols 
and  vitamins,  81.     Amino  acids,  83.     Pigments  of  fungi, 

83.    Other  metabolic  products,  86.    Implications,  88. 

5.  EFFECTS  OF  TEMPERATURE  ON  FUNGI 96 

Cardinal  temperatures,  97.  Resistance  to  low  temperatures 
and  high  temperatures,  103.  Influence  of  temperature  on 
infection,    109.      Temperature    and    reproduction,    111. 

Temperature  and  zonation,  114.  Temperature  coeffi- 
cients, 114.  Temperature  and  oxygen  tension,  117.  Im- 
plications, 119. 

6.  EFFECTS  OF  RADIATION  ON  FUNGI 123 

Morphogenic  reactions,  125.  Phototropism,  129.  Lumines- 
cence, 137.  Inhibitory  effects,  138.  Stimulatory  effects, 
143.  Effect  on  sporulation,  144.  Effect  of  X-rays,  145. 
Induction  of  saltations,  145.  Mode  of  action  of  short 
radiations,  147.    Implications,  147. 

7.  EFFECTS  OF  REACTION  OF  SUBSTRATE  ON  FUNGI      .     151 


x  CONTENTS 

8.  SPORE   DISSEMINATION 166 

Distribution  of  spores,  167.  Structural  adaptations  for 
expulsion  of  spores,  179.  Hygroscopic  mechanism  in 
Myxomycetes,  179.  Spore  expulsion  among  Phycomv- 
cetes,  180.  Spore  discharge  among  Ascomycetes,  186. 
Spore  discharge  among  Basidiomvcetes,  194.  Implica- 
tions, 205. 

9.  GERMINATION  OF  SPORES 210 

Germination  types,  210.  Methods  of  testing  spore  ger- 
mination, 212.  Hereditary  factors  and  germination,  214. 
Water  relations  affecting  germination,  218.  Effects  of 
temperature  on  germination,  221.  Influence  of  reaction 
on  (termination,  229.  Influence  of  oxygen  on  germina- 
tion,  230.  Influence  of  carbon  dioxide  on  germination, 
231.  Influence  of  light  on  germination,  231.  Influence 
of  nutrition  on  germination,  232.     Resume,  232. 

10.  HOST   PENETRATION 236 

Direct  penetration,  237.  Stomatal  penetration,  248.  Pene- 
tration through  wounds,  251.  Haustoria  and  their  sig- 
nificance,  252.  Penetration  by  ectoparasites,  253.  Im- 
plications, 254. 

11.  PHYSIOLOGIC      SPECIALIZATION      AND      VARIATION 

AMONG    FUNGI 257 

12.  ASSOCIATIVE  EFFECTS  AMONG  FUNGI 279 

Antagonism,  280.  Stimulation  by  associative  interaction, 
287.    General  considerations,  292. 

13.  MYCORRHIZAE  AND  MYCOTROPHY 297 

14.  GENETICS  OF  FUNGI 317 

Sexual  and  asexual  stages  of  fungi,  317.  Homothallism 
and  heterothallism,  319.  Dominance  and  lethal  factors, 
335.    Resume,  336. 

15.  POISONOUS  AND  EDIBLE  FUNGI 339 

Poisonous  fleshy  fungi,  339.  Food  value  of  fleshy  fungi, 
351.     Ergot  and  ergotism,  354.     Toxicity  of  Gibber ella 


CONTENTS  xi 

sanbinettii  (G.  zeae)  and  Fusarium  spp.,  359.  Implica- 
tions, 361. 

16.  MEDICAL  MYCOLOGY 364 

Historical  material,  366.  Coccidioides  hmnitis,  367. 
Cryptococcus  histolyticns,  368.  Histoplasma  capsulatum, 
369.  Fhialophora  verrucosa,  370.  Malassezia  ovalis,  372. 
Actinomyces  bovis,  373.  Sporotrichwn  schenckii,  375. 
Monilia  (Candida)  spp.,  377.  Aspergillus  fumigatus,  379. 
The  Trichophytoneae  or  ringworm  fungi,  379.  Implica- 
tions, 390. 

17.  GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI  ....     395 

Distribution  of  Myxomycetes,  397.  Distribution  of  Phy- 
comycetes,  399.  Distribution  of  Ascomycetes,  402.  Dis- 
tribution of  Basidiomycetes,  405.  Distribution  of  Deu- 
teromycetes,  410.     Implications,  412. 

18.  MYCOLOGY  IN  RELATION  TO  PLANT  PATHOLOGY     .     416 

Early  concepts  of  disease  in  plants,  417.  Contributory 
advances  in  bacteriology,  418.  Signposts  along  the  phyto- 
pathological  path,  419.  Developments  in  terminology, 
421.  Fungi  as  antigens  and  plant  pathology,  423.  Pres- 
ent trends  in  mycologic  and  phytopathologic  work,  424. 
Implications,  427. 

19.  SOIL  FUNGI 429 

Taxonomic  studies,  429.  Biochemical  activities  of  soil 
fungi,  434.    Soil-borne  pathogens,  437.    Implications,  437. 

20.  FUNGUS-INSECT  INTERRELATIONSHIPS        ....     442 

Insects  as  vectors  of  plant-pathogenic  fungi,  442.  Fungi 
occurring  on  or  within  insects,  444.  Biological  control 
of  insects,  448.  Insects  in  relation  to  reproduction  of 
fungi,  450.  Fungi  cultivated  by  insects,  451.  Implica- 
tions, 455. 

21.  MARINE   FUNGI 458 

Historical  background,  459.  Marine  Phycomycetes,  460. 
Marine  Ascomycetes,  466.  Marine  Fungi  Imperfecti,  468. 
Marine  slime  molds,  470.     Implications,  470. 


xii  CONTENTS 

22.  FOSSIL   FUNGI 474 

Geological  time,  474.  Age  of  fossil  fungi,  477.  The 
nature  of  fossilized  fungi,  478.  Preparation  of  fossils  for 
study,  479.  Classification  of  fossil  fungi,  479.  Fossil 
mycorrhizae,  487.    Implications,  488. 

AUTHOR   INDEX 491 

SUBJECT  INDEX 502 


Chapter  1 
NUTRITION  OF  FUNGI 

Fungi  are  commonly  regarded  as  unable  to  synthesize  their  own 
food;  that  is  to  sav,  they  are  not  autotrophic.  It  is  customary 
therefore  to  consider  them  parasites  and  saprophytes;  these  group- 
ings are  based  upon  whether  they  secure  their  food  from  living 
organisms  or  from  dead  and  decaying  plant  or  animal  tissues. 
Parasitic  fungi  may  better  be  spoken  of  as  paratrophic,  and 
saprophytic  fungi  as  saprotrophic.  A  moment's  contemplation 
will  reveal,  however,  that  these  terms  too  are  quite  arbitrary  and 
inadequate.  For  instance,  experience  has  shown  that  certain  fungi, 
such  as  the  Peronosporaceae,  Erysiphaceae,  and  Uredinales,  are 
strictly  paratrophic.  Others— for  instance,  the  Lycoperdales  and 
Phallales— are  strictly  saprotrophic,  and  between  these  extremes 
all  degrees  of  intergradation  exist.  In  fact,  such  terminology  be- 
comes confusing,  because  many  plant  pathogens  are  paratrophic 
during  part  of  their  annual  cycle  and  saprotrophic  during  the 
remainder. 

Concepts  regarding  the  nutritional  relationships  of  fungi  that 
underlie  such  terminology  emphasize  the  fact  that  fungi  lack 
chlorophyll,  and  thereby  the  impression  is  inferentially  fostered 
that  neither  parasites  nor  saprophytes  perform  syntheses.  As  a 
consequence  the  metabolic  changes  they  induce  are  not  properly 
appreciated,  and  too  little  consideration  is  given  to  the  determi- 
nation of  how  both  parasites  and  saprophytes  effect  not  only 
analyses  (katabolism)  but  also  syntheses  (anabolism). 

In  this  discussion  the  term  food  is  used  herein  in  the  broadest 
sense.  Any  substance  is  regarded  as  food  which  serves  as  a 
source  of  energy  or  is  used  for  growth  and  repair  or  for  the 
various  metabolic  processes  of  the  fungus.  This  usage  implies 
that  both  inorganic  and  organic  materials  play  a  role  in  the  nutri- 
tional requirements  of  fungi  and  in  this  sense  constitute  food.  The 
inherent  implications  in  this  usage  of  the  term  food  permit  dis- 

1 


2  NUTRITION  OF  FUNGI 

cussion  of  this  subject  under  two  headings:    (a)   inorganic  or 
mineral  nutrition  of  fungi,  and  (b)  organic  nutrition  of  fungi. 

MINERAL  NUTRITION  OF  FUNGI 

Problems  relating  to  the  mineral  nutrition  of  fungi  appear  at 
first  to  have  been  approached  wholly  by  empirical  methods.  The 
experiences  and  techniques  of  bacteriologists  constituted  the 
foundation  for  these  early  studies.  The  investigators  seem  to 
have  employed  such  chemical  compounds  and  in  such  proportions 
as  had  been  found  to  promote  the  growth  of  bacteria.  The  proper 
kind  and  amount  of  mineral  elements  were  not  sought  by  ex- 
tended series  of  experiments  in  which  ash  analyses  were  correlated 
with  rate  of  growth  or  with  amount  of  mycelial  mat. 

Not  only  were  these  procedures  employed  with  liquid  media 
but  also  mycologists  followed  the  bacteriologist  in  quite  the  same 
way  in  the  use  of  the  numerous  kinds  of  semisolid  media.  It  is 
not  unusual  to  find  now  that  a  particular  medium,  compounded 
according  to  a  certain  formula,  is  a  favorite  with  a  given  mycolo- 
gist and  that  he  attempts  to  cultivate  all  species  in  which  he  may 
be  interested  on  this  particular  medium.  It  will  become  apparent 
in  the  discussion  which  follows  that  this  procedure  may  lead  to 
erroneous  conclusions  regarding  the  nutrition  of  the  fungi  in- 
volved. 

Investigations  of  the  mineral  nutrition  of  fungi  may  be  said  to 
have  beeun  with  the  classical  researches  of  Raulin  (1869),  a 
pupil  of  Pasteur.  He  employed  Aspergillus  niger  as  a  test  organ- 
ism and  secured  optimum  growth  in  a  medium,  now  known  as 
Raulin's  solution,  having  the  following  composition: 

Ammonium  nitrate  4        grams  Iron  sulphate  0.07  gram 

Ammonium  phosphate  0.6    gram  Potassium  silicate  0.07  gram 

Magnesium  carbonate  0.4    gram  Sucrose  70        grams 

Potassium  carbonate  0.6    gram  Tartaric  acid  4        grams 

Ammonium  sulphate  0.25  gram  Water  1500        ml 

Zinc  sulphate  0.07  gram 

He  concluded  that  none  of  the  minerals  contained  in  this  medium 
could  be  omitted  if  optimum  growth  was  to  be  secured. 

Raulin's  studies  stimulated  a  series  of  investigations,  the  out- 
standing of  which  were  those  of  von  Naegeli  (1880),  Benecke 


MINERAL  NUTRITION  OF  FUNGI  3 

(1895),  Molisch  (1892,  1894),  and  Wehmer  (1895).  Von 
Naegeli  believed  that  sulphur  and  phosphorus  are  indispensable 
for  all  molds  and  that  potassium  and  calcium  are  replaceable, 
potassium  by  rubidium  or  caesium,  and  calcium  by  magnesium, 
barium,  or  strontium.  The  experiments  of  Benecke  and  Molisch 
led  them  to  conclude  that  magnesium  is  not  replaceable  by  any 
other  mineral  element.  Benecke  secured  luxuriant  growth  of 
many  species  of  Aspergillus  and  Penicillium  on  a  synthetic  agar 
medium,  the  inorganic  salts  of  which  were  ammonium  phosphate, 
potassium  chloride,  and  magnesium  sulphate.  Wehmer  consid- 
ered especially  the  essentiality  of  iron  and  zinc,  each  of  which 
was  regarded  as  indispensable  by  Raulin  (1869). 

Under  the  stimulus  of  studies  on  the  mineral  nutrition  of  green 
plants  several  other  mineral  nutrient  solutions  were  compounded 
and  employed  not  only  with  green  plants  but  also  with  fungi. 
These  included  the  following: 


Pfejfers  Solution 

Ammonium  nitrate 

10.0  grams 

Cane  sugar 

50.0  grams 

Potassium  phosphate 

Ferrous  sulphate 

Trace 

(monobasic) 

3.0  grams 

Water 

1000  ml 

Magnesium  sulphate 

2.5  grams 

Reaction:  pH 

=  4.3 

- 

Richards'  Soli 

■it  ion 

Potassium  nitrate 

1         gram 

Ferric  chloride 

Trace 

Potassium  acid  mono- 

Saccharose 

3.43  grams 

phosphate 

0.5    gram 

Water 

100  ml 

Magnesium  sulphate 

0.25  gram 

Reaction:  pH 

=  4.2 

Uschinsky's  Solution 

Ammonium  lactate 

6.1      grams 

Sodium  chloride 

5-7    grams 

Sodium  asparaginate 

3-4      grams 

Calcium  chloride 

0. 1  gram 

Potassium  acid  phosphate 

2-2 . 5  grams 

Glycerin 

30-40  grams 

Magnesium  sulphate 

0.3-0.4  gram 

Water 

1000  ml 

Czapek's  Solution 

Magnesium  sulphate 

0.5  gram 

Sodium  nitrate 

2.0  grams 

Potassium  acid  phosphate 

1 .0  gram 

Saccharose 

3-4  grams 

Potassium  chloride 

0.5  gram 

Water 

1000  ml 

Reaction:  pH 

=  6.8 

4  NUTRITION  OF  FUNGI 

Sulphur  requirements.  The  results  obtained  with  these  nu- 
trient solutions  make  a  voluminous  literature.  There  appears 
little  reason  to  doubt  that  these  experiments  prove  the  essentiality 
for  all  fungi  of  appreciable  amounts  of  potassium,  phosphorus, 
magnesium,  and  sulphur.  Inorganic  phosphates  constitute  en- 
tirely satisfactory  sources  of  potassium  and  phosphorus.  Mag- 
nesium sulphate  serves  well  as  the  source  of  magnesium,  but  not 
all  fungi  are  able  to  use  sulphates  as  a  source  of  sulphur.  Arm- 
strong (1921)  observed  that  persulphate,  sulphite,  and  sulph- 
hydryl  can  be  substituted  for  sulphates  in  the  nutrition  of  Asper- 
gillus ?iiger,  Penicillium  glaucum,  and  Botrytis  cinerea.  Volkon- 
sky  (1933,  1934)  made  similar  observations  with  certain  water 
molds,  such  as  Achlya,  Aphanomyces,  Dictyuchus,  Isoachlya,  and 
Leptolegnia,  and  pointed  out  that  each  of  these  forms  grows 
better  on  organic  than  on  inorganic  sulphur  compounds.  The 
results  for  inorganic  sulphur  were  substantiated  by  Leonian  and 
Lilly  (1938),  whose  experiments  show  that  the  amino  acid  /-cys- 
tine is  necessary  for  the  growth  of  Saprolegnia  mixta,  Achlya 
conspicua,  Aphanomyces  camptostylus,  and  Isoachlya  ?nonilifera. 
Schade  (1940),  on  the  other  hand,  found  that  Leptomitus  lac- 
teas  and  Apodachlya  brachynema  fill  their  sulphur  requirements 
by  reducing  sulphates.  Steinberg's  (1941)  experiments  show  that 
Aspergillus  niger  utilizes  both  organic  and  inorganic  sulphur.  Of 
the  organic  sulphur  compounds,  alkyl  sulphonates  and  alkyl  sul- 
phinates  are  readily  assimilated,  but  the  alkyl  mercaptans,  sul- 
phides, and  disulphides  are  not  utilized.  In  the  case  of  inorganic 
sulphur  compounds,  the  sulphur  is  first  reduced  to  sulphoxalate 
and  then  converted  to  organic  sulphur. 

Calcium  requirements.  Whether  calcium  is  essential  for  all 
fungi  is  still  a  controversial  question  that  should  be  studied,  the 
best  techniques  known  for  such  tests  being  utilized.  Molisch 
(1894)  came  to  the  conclusion  that  fungi  do  not  require  calcium. 
Mosher  et  al.  (1936)  have  presented  evidence  to  show  that  Tri- 
chophyton inter  digitale  requires  calcium.  Young  and  Bennett 
(1922)  concluded  that  calcium  is  generally  beneficial  in  the 
growth  of  most  fungi  and  is  certainly  required  by  Fiisariinn 
oxysporum,  Rhizopus  nigricans,  and  Aspergillus  niger.  They 
also  grew  species  of  Ascochyta,  Botrytis,  Cercospora,  Colleto- 
trichum,  Dothiorella,  Alacrosporium,  Phoma,  Rhizoctonia,  Sclero- 


MINERAL  NUTRITION  OF  FUNGI  5 

tinia,  Sphaeropsis,  and  Vermicularia  in  Richards'  solution  with 
Ca(N03)2  substituted  for  KNO3  and  maintained,  although  their 
evidence  is  not  conclusive,  that  best  growth  occurred  in  the  solu- 
tions containing  calcium.  They  attribute  this  phenomenon  to 
the  neutralization  by  calcium  of  the  acids  formed  from  sucrose. 
In  support  of  this  theory  they  demonstrated  that  growth,  when 
inhibited  by  acids,  can  be  renewed  after  neutralization  of  the 
acids.  They  also  grew  F.  oxysporum,  A.  niger,  and  R.  nigricans 
on  similar  solutions  with  the  results  shown  in  Table  1 .  These  data 
show,  for  each  fungus,  greatest  growth  in  the  presence  of  calcium. 

TABLE  1 

Comparative  Growth  of  Fungi  in  KNO3  and  Ca(NOs)2 

Weight  of  Mycelial  Mat  {grams) 


Richards'  solution  Richards'  solution 

Organism                             with  KNO3  with  Ca(NOs)2 

Fusarium  oxysporum                      0.2094  0.2428 

Aspergillus  niger                             0.5450  0.8270 

Rhizopus  nigricans                          0 .  201 5  0 .  2787 

Concentration  and  proportion  of  minerals.  Manifestly 
chemical  constitution  is  a  factor  of  primary  importance  in  the 
preparation  of  suitable  mineral  substrata  for  the  growth  of  fungi, 
but  account  must  also  be  taken  of  the  proper  balance  of  elements 
and  of  their  concentration.  Several  important  papers  have  ap- 
peared dealing  with  these  factors.  With  Aspergillus  niger 
Haenseler  (1921)  used  the  same  three-salt  mineral  nutrient  and 
quite  the  same  procedure  as  has  been  utilized  in  physiological 
studies  with  green  plants.  The  salts  consisted  of  Ca(NO:i)2  or 
NaN03,  A4gS04,  and  KH2P04.  Different  concentrations  of  each 
salt,  making  total  concentrations  of  0.5,  2.1,  and  4.2  atm,  were 
employed,  and  to  each  culture  flask  were  added  equal  amounts  of 
sugar  and  other  nutrients.  The  dry  weight  of  the  mycelial  mat 
after  7  days  served  as  Haenseler's  basis  for  evaluating  salt  concen- 
tration and  balance.  The  data  in  Table  2  show  the  plan  employed 
by  Haenseler  in  this  type  of  study. 

Haenseler  concluded  that  at  concentrations  equivalent  to  4.2 
atm.  growth  is  best,  so  that  total  concentration  must  be  regarded 
as  very  important.  Wide  variation  in  the  concentration  of  MgS04 
and  KH0PO4  did  not  greatly  modify  growth.    Better  growth  was 


NUTRITION  OF  FUNGI 


TABLE  2 

Growth  of  Aspergillus  niger  in  a  Three-Salt  Nutrient  Solution,  Showing 
Plan  of  Varying  Concentration  (Molarity)  of  Each  Salt  and  Yield 

of  Mycelial  Mat 

(M) 


Culture 
Number 

ft  t  /   It  k  t  v  1  *       VI        KJ  t»  *■*  J 

Yield 

KH2PO4 

Ca(N03)2 

MgS04 

{grams) 

Rl  CI 

0.00888 

0.00625 

0.08648 

0.347 

Rl  C2 

0.00888 

0.01250 

0.07567 

0.624 

Rl  C3 

0.00888 

0.01875 

0.06486 

0.874 

Rl  C4 

0.00888 

0.02500 

0.05405 

0.956 

Rl  C5 

0.00888 

0.03125 

0.04234 

0.949 

Rl  C6 

0.00888 

0.03749 

0.03243 

0.983 

Rl  C7 

0.00888 

0.04374 

0.02162 

0.985 

Rl  C8 

0.01776 

0.04999 

0.01081 

0.977 

R2C1 

0.01776 

0.00625 

0.07567 

0.351 

R2C2 

0.01776 

0.01250 

0.06486 

0.632 

R2C3 

0.01776 

0.01875 

0.05405 

0.865 

R2C4 

0.01776 

0.02500 

0.04324 

0.947 

R2C5 

0.01776 

0.03125 

0.03243 

0.969 

R2C6 

0.01776 

0.03749 

0.02162 

0.984 

R2C7 

0.01776 

0.04374 

0.01081 

0.991 

R3C1 

0.02664 

0.00625 

0.06486 

0.355 

R3C2 

0.02664 

0.01250 

0.05405 

0.610 

R3C3 

0.02664 

0.01875 

0.04324 

0.875 

R3C4 

0.02664 

0.02500 

0.03243 

0.957 

R3C5 

0.02664 

0.03125 

0.02162 

0.957 

R3C6 

0.02664 

0.04374 

0.01081 

0.976 

R4C1 

0.03552 

0.00625 

0.05405 

0.341 

R4C2 

0.03552 

0.01250 

0.04324 

0.603 

R4C3 

0.03552 

0.01875 

0.03243 

0.874 

R4C4 

0.03552 

0.02500 

0.02162 

0.960 

R4C5 

0.03552 

0.03125    , 

0.01081 

0.966 

R5C1 

0.04440 

0.00625 

0.04324 

0.354 

R5C2 

0.04440 

0.01250 

0.03243 

0.634 

R5C3 

0.04440 

0.01875 

0.02162 

0.867 

R5C4 

0.04440 

0.02500 

0.01081 

0.958 

R6C1 

0.05328 

0.00625 

0.03243 

0.364 

R6C2 

0.05328 

0.01250 

0.02162 

0.636 

R6C3 

0.05328 

0.01875 

0.01081 

0.886 

R7C1 

0.06216 

0.00625 

0.02162 

0.352 

R7C2 

0.06216 

0.01250 

0.01081 

0.625 

R8C1 

0.07104 

0.00625 

0.01081 

0.324 

MINERAL  NUTRITION  OF  FUNGI  7 

secured  with  Ca(N03)2  than  with  NaN03,  the  differences  being 
more  pronounced  at  the  higher  concentrations. 

Young  and  Bennett  (1922)  also  employed  the  triangle  system  in 
determining  the  optimum  concentration  of  Ca(N03)2,  KH2P04, 
and  MgS04  in  solutions  of  these  three  salts.  The  solutions  were 
made  up  by  molarity  so  that  their  osmotic  concentrations  were 
equal.  Sufficient  carbon  to  make  3.43%  was  supplied  from  su- 
crose. Fiisarhim  oxysporum,  Macrosporhim  sarcinaeforme,  and 
Phoma  apiicola  were  the  test  organisms.  After  15  days'  growth 
on  the  solutions  the  mycelial  mats  were  removed,  carefully  dried, 
and  weighed.  The  results  indicate  that  a  proper  balance  of  inor- 
ganic constituents  is  essential  but  that  each  organism  appears  to 
require  a  different  medium  that  can  be  determined  only  bv  trial 
and  by  techniques  of  the  kind  which  Young  and  Bennett  used.  In 
addition,  calcium  and  zinc  should  be  incorporated  in  synthetic 
solutions,  and  it  may  be  necessary  to  test  several  sugars  before 
the  most  desirable  one  can  be  known. 

Mann  (1932)  also  employed  the  triangle  method,  with  Pfeffer's 
solution,  to  determine  the  influence  of  varying  concentrations  of 
the  three  salts,  ammonium  nitrate,  monopotassium  phosphate,  and 
magnesium  sulphate.  She  concluded  that  magnesium  is  absolutely 
essential,  although  good  growth  of  Aspergillus  niger  and  Penicil- 
lium  sp.  was  secured  at  all  concentrations  greater  than  0.0001  gram 
molecule  per  liter  of  culture  solution.  Spectroscopic  analysis 
showed  that  calcium  was  present  as  a  contaminant  in  proportions 
less  than  1  part  per  25  million.  Calcium  chloride  added  to  the 
three  salt  solution  caused  no  pronounced  increase  in  the  growth 
of  A.  niger. 

More  recently  Talley  and  Blank  (1941)  performed  a  carefully 
planned  series  of  factorial  experiments  on  the  response  of  Phyma- 
totrichum  ormiivorum  to  the  three  salts  K2HP04,  MgS04,  and 
KC1  and  on  the  effects  of  changes  in  the  concentration  of  each 
salt  on  responses  to  the  others.  Certain  of  their  data  which  demon- 
strate these  interactions  are  assembled  in  Table  3. 

Optimum  growth  of  P.  omnivorum  was  secured  when  glucose 
and  nitrogen  were  not  limiting.  Solutions  containing  0.008  M 
dibasic  potassium  phosphate,  0.003  M  magnesium  sulphate,  and 
0.002  M  potassium  chloride  were  not  improved,  as  indicated  by 
the  growth  of  P.  omnivorum,  by  increasing  or  by  decreasing  the 
concentration  of  any  one  of  the  salts  or  of  their  ions. 


8 


NUTRITION  OF  FUNGI 


TABLE  3 
Growth  Responses  of  Phymatotrichum  omnivorum  on  Combinations  of  K2HPO4, 

MgSC>4,   AND    KC1   AFTER    INCUBATING    FOR   21    DAYS    AT  28°  C 

(All  solutions  had  4%  glucose,  0.0125  M  NH4NO3,  and  2  ppm  of  Fe,  of  Mn,  and 

ofZn.) 


Solution 

Molar  Concentration  of  Salts 

/.H1 

Mean 
Weight 

Number 

K2HPO4 

MgS04 

KC1 

Original 

Final 

of  Mat 
{milligrams) 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

0.004 
0.004 
0.004 
0.004 
0.004 
0.004 
0.008 
0.008 
0.008 
0.008 
0.008 
0.008 
0.012 
0.012 
0.012 
0.012 
0.012 
0.012 

0.0015 
0.0015 
0.0030 
0.0030 
0.0060 
0.0060 
0.0015 
0.0015 
0.0030 
0.0030 
0.0060 
0.0060 
0.0015 
0.0015 
0.0030 
0.0030 
0.0060 
0.0060 

0.000 
0.002 
0.000 
0.002 
0.000 
0.002 
0.000 
0.002 
0.000 
0.002 
0.000 
0.002 
0.000 
0.002 
0.000 
0.002 
0.000 
0.002 

6.74 
6.78 
6.81 
6.84 
6.77 
6.78 
6.92 
6.93 
6.83 
6.82 
6.72 
6.72 
6.93 
6.92 
6.88 
6.88 
6.85 
6.85 

4.81 
4.55 
4.30 
4.16 
4.30 
4.01 
4.87 
5.56 
4.82 
4.68 
4.84 
5.14 
5.58 
5.33 
5.19 
5.35 
5.27 
5.24 

4.53 
4.90 

4.67 
5.90 

5.82 
5.58 
4.24 
4.63 
5.77 
5.59 
6.12 
5.74 
3.60 
3.49 
4.88 
4.77 
5.87 
6.45 

1  These  figures  represent  averages  of  the  number  for  pH  of  each  of  the  replications 
and  are  not,  of  course,  the  average  pH. 

These  observations  furthermore  indicate  that  a  proper  balance 
between  K2HP04  and  AIgS04  in  the  growth  of  P.  omnivorum  is 
equally  as  important  as  the  direct  effect  of  either  salt.  This  proper 
balance  is  maintained  without  significant  change  in  the  amount 
of  mycelial  growth  even  though  the  concentration  of  K2HP04 
and  A'1jtS04  is  decreased  one-half  or  increased  fourfold.  If  the 
concentration  of  either  salt  is  increased,  however,  the  concentra- 
tion of  the  other  must  be  increased  accordingly  to  maintain  this 
proper  balance.  The  potassium  ion  is  of  more  imoortance  in  main- 
taining balance  than  is  the  phosphate  radical. 


MINERAL  NUTRITION  OF  FUNGI 


The  support  and  maintenance  of  optimum  mycelial  growth  do 
not  constitute  the  only  requirement  of  fungi  for  a  proper  balance 
of  salts.  Pratt  ( 1945)  demonstrated  that  the  synthesis  of  penicillin 
by  Fenicillium  notatum  is  also  conditioned  by  salt  balance.    By  use 


100 


70 


60  50  40 

NaN03  ( percentage ) 


30 


20 


10 


0 


Fig.  1.    Graph  of  triangle  system,  showing  percentage  composition  of  differ- 
ent solutions  to  be  tested.    The  apex  of  each  triangle  represents  the  constant 
molarity.     Each  number  within  a  triangle  corresponds  to  a  culture  or  a 
series  of  identical  cultures.     (After  Pratt.) 

of  the  triangle  system  he  made  up  a  series  of  65  different  nutrient 
solutions  containing  KH2P04,  MgS04,  and  NaN03  in  different 
proportions  and  in  such  way  as  to  have  a  total  molar  concentration 
of  0.04.  Each  solution  contained  in  addition  lactose,  corn-steep 
liquor,  zinc  sulphate,  and  phenylacetic  acid,  and  the  pH  was  ad- 
justed with  NaOH  to  be  the  same  as  that  of  every  other  solution. 
As  a  result  Pratt  found  that  the  best  yields  of  penicillin  were 
secured  in  solutions  containing  not  less  than  8  millimoles  of 
KH2P04  per  liter  and  not  more  than  20  millimoles  of  NaN03  per 
liter.    The  absolute  concentrations  of  the  three  salts  in  the  series 


W  NUTRITION  OF  FUNGI 

of  solutions  giving  the  best  yields  were  as  follows:    KH2P04, 
0.019  M;  MgS04-7H20,  0.002  M;  and  NaNOs,  0.019  M. 

Difficulties  encountered  in  studies  of  mineral  nutrition. 
Lest  it  be  thought  that  the  elements  potassium,  phosphorus,  mag- 
nesium, sulphur,  and  calcium  comprise  all  the  minerals  requisite 
for  the  proper  nutrition  of  fungi,  it  is  pointed  out  at  this  juncture 
that  evidence  has  been  gradually  accumulating  that  iron,  zinc, 
manganese,  and  copper  are  among  other  elements  now  known  to 
be  absolutely  essential  for  the  normal  physiological  processes  of 
fungi.  The  experiments  from  which  these  conclusions  are  drawn 
will  be  considered  subsequently.  It  should  first  be  pointed  out 
that  the  amounts  of  these  elements,  as  Raulin  (1869)  first  showed 
for  iron  and  zinc,  are  so  minute  that  the  term  trace  elements  has 
come  to  be  applied  to  them.  This  terminology  does  not  serve  any 
useful  purpose,  since  the  amount  of  a  particular  element  is  no 
index  or  measure  in  determining  essentiality. 

The  conclusions  from  studies  of  the  nutritional  use  of  these  ele- 
ments—for example,  iron,  calcium,  zinc,  manganese,  and  boron- 
are,  as  mi^ht  be  expected,  contradictory.  This  situation  has  come 
about  because  it  is  now  known  that  certain  of  the  elements  occur 
in  distilled  water  or  come  into  solution  from  test  tubes,  Petri 
dishes,  and  culture  flasks  in  amounts  sufficiently  large  to  meet  the 
metabolic  needs  of  the  organism.  Water  redistilled  from  Pyrex- 
glass  stills  should  be  utilized.  Pyrex  glass  may  be  quite  satisfac- 
tory, particularly  if  it  has  previously  been  used  in  such  a  way  as 
to  leach  out  the  zinc.  In  addition,  the  sugars  and  C.P.  nutrient 
salts  contain  various  elements  as  impurities.  By  spectroscopic 
methods  Steinberg  (1937)  identified  in  C.P.  reagents  commonly 
used  in  nutritional  experiments  with  fungi  the  elements  listed  in 
Table  4. 

The  presence  of  appreciable  quantities  of  various  elements  in 
C.P.  chemicals  constitutes  an  important  difficulty,  especially  in 
studies  that  involve  elements  utilized  by  fungi  in  small  amounts, 
as  are  iron,  zinc,  boron,  copper,  and  manganese.  Repeated  re- 
crvstallization  of  the  nutrient  salts  has  proved  to  be  wholly  un- 
satisfactory [Roberg  ( 1928)  ]  in  purifying  them.  Steinberg  (1919, 
1935)  has  devised  methods  to  effect  practically  complete  removal 
of  such  elements.  He  heats  the  nutrient  solution  in  the  presence 
of  excess  CaCOl3  for  15  minutes  at  15-lb  pressure.  The  increased 
alkalinity  in  the  presence  of  heat  causes  the  undesirable  heavy 


MINERAL  NUTRITION  OF  FUNG!  11 

TABLE  4 

Elements   Shown  to   Be  Present   by  the   Use   o?  Spectroscopic   Methods 

of  Analysis 

Chemical  Reagents  Contaminants 

NH4NO3  Ca,  K,  Mg,  Na 

K2HPO4  Al,  Ag,  Cu,  Mg,  Na,  Pb 

MgS04-7H20  Cu,  Na 

ZnS04-7H20  As,  B(?),  Cu,  Fe,  Mg,  Mn,  Si,  Sn(?) 

CuS04-5H20  Cu,  Fe,  Mg,  Mn,  Pb,  Si 

MnS04-2H20  Al,  Ca,  Cu,  Cr,  Fe,  Mg,  Na,  Si,  V 

Na2Mo04  Al,  Ca,  Cu,  Fe,  K,  Li,  Mg,  Mn,  Na,  Ni,  Si,  V(?) 

Dextrose  Al,  Ag,  B,  Ca,  Cu,  Fe,  K,  Li,  Mg,  Mn,  Na,  Ni, 

Rb,  Rh,  Si,  Sn,  Sr 

metals  to  be  precipitated  as  phosphates,  hydroxides,  or  carbonates. 
In  some  cases  Mo;C03  may  be  substituted  for  heating;. 

Bortels  (1927)  and  Roberg  (1928)  used  activated  charcoal  as 
an  adsorbing  agent  after  adding  (NH4)2S  as  a  precipitant.  Some 
heavy-metal  contaminants  may  be  removed  bv  electrolysis.  Wolff 
and  Emmerie  (1930)  removed  copper  from  their  nutrient  salts  by 
electrolytic  methods. 

The  spores  of  Aspergillus  oryzae  were  found  by  Aso  (1900) 
to  have  iron  among  their  ash  constituents.  Copper  and  doubtless 
other  metals  as  well  occur  in  the  spores  and  mycelium  of  other 
fungi.  These  observations  show  that  in  studies  involving  the  min- 
eral nutrition  of  fungi  an  appreciable  metal  contamination  may  be 
attributed  to  the  inoculum. 

Steinberg  (1935)  determined  that  the  quantity  of  the  elements 
essential  for  optimum  growth  of  Aspergillus  niger  is  0.20  mg  of 
iron,  0.14  mg  of  zinc,  0.06  mg  of  copper,  and  0.03  mg  of  manga- 
nese per  liter  of  solution.  The  amount  of  growth  was  approxi- 
mately doubled  with  as  little  as  0.001  mg  of  zinc  per  liter. 

The  weight  of  evidence  indicates  that  these  metal  contaminants, 
especially  zinc,  copper,  iron,  and  manganese,  serve  in  the  nutrition 
of  fungi,  not  as  structural  materials,  but  as  substances  that  modify 
physiological  activities.  For  this  reason  they  have  come  to  be  re- 
garded as  biocatalysts.  This  conception  is  fostered  by  the  numer- 
ous publications  of  Bertrand  and  of  Javillier,  which  are  reviewed 
by  Foster  (1939),  and  by  the  papers  of  Bortels  (1927),  Steinberg 
(1934),  and  Stern  (1938).  The  heavy  metals  become  organic 
components  of  respiratory  enzymes.     Stern  (1938)  has  stressed 


12 


NUTRITION  OF  FUNGI 


this  fact  in  connection  with  iron  in  Warburg's  cytochrome,  in 
other  heme-respiratorv  pigments,  in  catalase,  and  in  peroxidase. 
Copper  appears  to  act  similarly  in  the  oxidase  molecule.  Manga- 
nese is  well  known  to  act  powerfully  as  a  coenzyme. 

Differences  exist  in  methods  of  measurements  of  fungal  growth 
on  semisolid  substrata.    Some  workers  measure  dailv  radial  incre- 


R8  A  0.324 


Rl 


CI 


C2 


C3 


C4  C5 

KH2P04 


C6 


C7 


Fig.  2.     Diagram  illustrating  triangle  system  of  varying  the  concentrations 
of  three-salt  nutrient  solutions  used  in  nutritional  studies  and  showing  the 

relative  vields.     (After  Haenseler.) 

ments;  others  measure  ring  area.  In  a  recent  report  Worley 
(1939)  indicates  that  several  criteria  should  be  considered  in 
growth  measurements,  namely:  (1)  growth  in  a  radial  direction, 
(2)  growth  in  a  tangential  direction,  (3)  number  of  units  con- 
tributing to  the  subsequent  growth,  (4)  the  relationship  of  new 
increments  of  growth  to  the  substrata  being  compared,  and  (5) 
the  relative  importance  of  radial  and  tangential  growth  quantities. 
The  radial  method  of  measurement  ignores  the  effect  of  criteria 
2,  4,  and  5.    The  ring-area  method  omits  criteria  3  and  4  and  mag- 


MINERAL  NUTRITION  OF  FUNGI  13 

nifies  or  minifies  criterion  5.  Worley  proposes  therefore  a  sector- 
area  method  to  use  in  comparing  the  effect  of  substrata  on  growth 
for  any  given  time  interval. 

In  making  measurements  of  mycelial  growth  on  semisolid  media 
it  must  be  borne  in  mind  that  growth  is  three-dimensional.  On 
one  medium  the  growth  by  a  given  species  may  be  appressed,  on 
another  profuse  and  cottony.  Measurements  of  growth  on  differ- 
ent media  cannot  with  fairness  be  compared,  regardless  of  whether 
radial  measurements,  ring  increments,  or  sector  areas  are  used. 

Iron  as  nutrient.  Raulin  (1869)  w7as  perhaps  the  first  to  main- 
tain that  iron  is  indispensable  for  fungi.  This  hypothesis  was  con- 
firmed by  Molisch  (1892),  Benecke  (1895),  and  many  others,  and 
as  a  result  it  is  now  firmly  established  that  this  element  is  an 
integral  part  of  fungus  protoplasm.  Using  Aspergillus  niger, 
Steinberg  (1919)  secured  a  scant  mycelial  mat  in  solutions  lacking 
iron;  he  obtained  43.7  times  as  much  in  the  presence  of  iron.  In 
similar  studies  with  this  fungus  Roberg  (1928)  secured  75  times 
more  mycelium  in  cultures  containing  iron.  Benecke  (1895) 
found  that  iron  is  essential  both  for  growth  and  for  sporulation 
among  species  of  Aspergillus,  Penicillium,  and  Mucor,  an  obser- 
vation which  Bortels  (1927),  using  refined  techniques,  was  able 
to  verify. 

Little  is  known  about  the  functions  of  iron  in  fungi.  Richards 
(1899)  reported  an  increased  efficiency  in  the  use  of  sugar  by 
Aspergillus  niger  and  Yemcillium  glaiicnm  in  the  presence  of  0.1% 
FeCl3.  Wehmer  (1891)  found  that  in  darkness  the  presence  of 
iron  in  sugar  solutions  being  fermented  by  Aspergillus  results  in 
decreased  production  of  oxalic  acid.  Chrzaszcz  and  Peyros 
(1935),  on  the  other  hand,  reported  markedly  increased  produc- 
tion of  citric  acid  by  Aspergillus  and  Penicillium  when  the  sugar 
solutions  being  fermented  contain  a  small  quantity  of  FeCl3.  Simi- 
larly, others  have  recorded  contradictory  results,  and  this  lack  of 
agreement  can  be  expected  to  prevail  until  the  proximate  function 
of  iron  is  better  understood. 

Copper  as  nutrient.  When  the  growth  of  fungi  in  copper- 
containing  nutrient  solutions  and  in  solutions  lacking  copper  is 
compared,  as  Waterman  [Foster  (1939)],  Bortels  (1927),  and 
McHargue  and  Calfee  (1931)  have  done,  all  investigators  are  in 
accord  in  ascribing  to  copper  the  role  of  an  essential  element.  The 
striking  feature  of  studies  of  this  nature  is  that  minute  amounts 


14  NUTRITION  OF  FUNGI 

produce  such  profound  growth  responses.  The  best  evidence  of 
the  quantitative  essentiality  of  copper  is  offered  by  Wolff  and 
Emmerie  (1930),  who  electrolytically  purified  the  culture  media 
in  which  thev  attempted  to  grow  Aspergillus  niger.  They  secured 
no  growth  in  the  complete  absence  of  copper.  When  they  added 
0.2  y  of  copper  per  250  ml  of  medium,  growth  occurred;  conidia 
were  produced  only  if  a  minimum  of  0.3  y  per  250  ml  was  added. 
In  a  copper-free  medium,  as  produced  by  Metz  (1930),  A.  niger 
was  able  to  produce  conidia,  but  Metz  determined  them  to  be 
twice  as  numerous  in  copper-containing  media  as  in  copper-free 
media. 

Wolff  and  Emmerie  (1930)  also  showed  that  there  is  no  pig- 
mentation of  conidia  of  A.  niger  if  the  amount  of  copper  provided 
is  the  minimum  for  conidial  production,  as  is  maintained  also  by 
Steinberg  (1934).  In  1938  Mulder  [Foster  (1939)]  showed  that 
maximum  pigmentation  in  this  fungus  requires  a  minimum  of 
6.25  y  of  copper  per  100  ml  of  nutrient  solution.  Mulder  also 
ascribed  to  copper  an  influence  in  the  formation  of  acids  during 
fermentation. 

Manganese  as  nutrient.  The  status  of  knowledge  regarding 
manganese  as  a  nutritive  element  for  fungi  has  been  reviewed  by 
Foster  (1939).  A  series  of  studies  by  Bertrand  and  Javillier 
[Foster  (1939)]  and  by  Steinberg  (1936)  shows  that  much  less 
manganese  is  required  than  either  iron  or  zinc.  In  fact,  manga- 
nese in  a  concentration  of  1  part  in  10  billion  is  definitely  stimu- 
latory to  Aspergillus  niger.  Bertrand  believed  his  evidence  to 
show  that  iron,  zinc,  and  manganese  must  have  a  certain  balance 
and  that  thev  function  together  synergeticallv.  With  a  certain 
proportionality  of  manganese,  iron,  and  zinc,  he  secured  a  sparse 
production  of  conidia  by  A.  niger;  with  a  larger  amount  of  man- 
ganese, however,  the  conidia  were  developed  in  abundance.  Stein- 
berg (1935)  was  able  to  confirm  these  observations  to  an  extent 
by  showing  that  a  lack  of  manganese  in  the  nutrient  either  sharply 
reduces  or  entirely  inhibits  conidial  production. 

Stimulation  of  growth,  as  indicated  by  increased  dry  weight, 
followed  the  addition  of  manganese  to  cultures  of  A.  flaws  and 
Rhizopus  nigricans  by  McHargue  and  Calfee  (1931). 

Zinc  as  nutrient.  As  has  been  indicated  by  Foster  (1939),  zinc 
is  the  element  of  first  choice  in  studies  dealing  with  the  mineral 
nutrition  of  fungi.    Numerous  experiments  involving  representa- 


MINERAL  NUTRITION  OF  FUNGI  IS 

tives  of  each  class  of  fungi  show  that  the  presence  of  zinc  in  nu- 
trient media  stimulates  growth  [Metz  (1930)].  Alosher  et  al. 
( 1936)  regard  zinc  as  essential  for  the  dermatophyte  Trichophyton 
inter  digit  ale.  In  comparing  the  growth  of  Aspergillus  niger  in 
media  lacking  zinc  with  that  in  media  containing  zinc  salts,  Porges 
(1932)  noted  that  a  scanty,  thin,  smooth  pellicle  develops  when 
zinc  is  lacking,  whereas  in  its  presence  a  heavy,  wrinkled  mat  is 
produced.  Steinberg  (1919)  secured  an  increase  of  mycelial  mat 
of  A.  niger  amounting  to  as  much  as  230,900%,  the  increases  being 
correlated  with  the  quantity  of  zinc  present  as  an  impurity  in  the 
salts;  as  he  indicates  (1934),  increases  of  this  magnitude  can  hardly 
be  interpreted  as  "stimulatory"  effects. 

Zinc  does  not  uniformly  influence  conidial  production  in  the 
same  manner  in  all  fungi.  Roberg  (1928)  and  Porges  (1932) 
found  that  zinc  inhibits  sporulation  of  A.  niger.  Zinc  represses 
sporulation  of  Trichoderma  koningii  but  stimulates  conidial  pro- 
duction by  Fiisariwn  oxyspornm  [Niethammer  (1938)]. 

Pigmentation  in  fungi,  as  modified  by  the  presence  of  zinc,  has 
been  considered  by  Bortels  (1927),  Roberg  (1928),  and  Metz 
(1930).  Metz's  experiments  involved  species  of  Aspergillus, 
Penicillium,  Fusarium,  Macrosporium,  and  Botrytis.  He  found 
that  the  growth  in  zinc-deficient  cultures  is  abnormal  in  color. 
The  problem  was  further  complicated,  however,  because,  al- 
though mycelial  growth  is  dependent  primarily  on  zinc  and  to  a 
lesser  degree  on  iron  and  copper,  it  is  essential  that  each  of  these 
heavy  metals  be  present  to  produce  normal  colors  in  a  particular 
fungus. 

The  profound  effect  which  zinc  exercises  on  the  growth  and 
sporulation  of  fungi  is  an  index  of  the  influence  which  this  ele- 
ment exerts  on  digestive  and  respiratory  activities.  That  this 
fact  has  long  been  appreciated  is  evident  from  the  work  of 
Richards  (1899)  and  Watterson  (1904). 

The  formation  of  organic  acids  as  waste  products  in  fungus 
metabolism  is  briefly  considered  in  Chapter  4,  but  emphasis  is  not 
placed  upon  zinc  as  a  modifying  factor.  Zinc  has  been  shown  to 
prevent  the  accumulation  of  different  acids  in  cultures.  This  ef- 
fect has  been  demonstrated  by  Bortels  (1927)  and  Wassiljew 
(1935)  with  oxalic  acid  production  by  A.  niger,  by  Bernhauer 
(1928)  and  Chrzaszcz  and  Peyros  (1935)  with  citric  acid  produc- 
tion by  the  same  fungus,  by  Lockwood,  Ward,  and  May  (1936) 


16  NUTRITION  OF  FUNGI 

and  Waksman  and  Foster  (1939)  with  gluconic  acid  production 
by  Rhizopus. 

Other  elements  as  nutrients.  A  lame  number  of  other  ele- 
ments  have  been  tested  to  determine  whether  they  are  essential 
for  the  metabolic  activities  of  fungi.  The  role  of  boron  for 
Penicillhnn  glaucum  and  Aspergillus  niger  was  investigated  by 
Boeseken  and  Watermann  (1912).  Molybdenum  and  gallium 
have  been  found  to  be  essential  for  A.  niger  by  Steinberg  (1936, 
1937,  1938),  and  the  same  investigator  (1920)  determined  that 
uranium  and  cobalt  can  partly  replace  iron  and  zinc  for  this  spe- 
cies. Lockwood  et  al.  (1934)  found  that  columbium,  chromium, 
molybdenum,  and  tungsten  are  favorable  for  the  production  of 
fats  by  Penicillium  javanicum.  Steinberg  (1938)  tested  76  chemi- 
cal elements  with  the  result  that  iron,  zinc,  copper,  manganese, 
gallium,  and  molybdenum  comprise  all  that  may  be  regarded  as 
essential  for  A.  niger.  Other  extended  systematic  studies,  espe- 
cially those  of  Pirschle  (1934,  1935),  involve  the  effects  upon 
growth  of  many  elements.  Javillier  (1913)  concluded  that  co- 
lumbium and  beryllium  cannot  replace  zinc,  which,  when  present 
in  concentrations  of  1  to  2  ppm,  increased  the  amount  of  growth 
of  A.  niger  58  times. 

ORGANIC  NUTRIENTS  OF  FUNGI 

Those  investigators  who  laid  the  foundations  for  an  understand- 
ing of  the  mineral  requirements  of  fungi  also  contributed  to  the 
establishment  of  bases  for  comprehending  the  organic  compounds 
utilized  in  the  growth  of  these  organisms.  They  noted  that  fungi 
vary  in  response  to  the  addition  of  different  carbon  compounds 
employed  to  fortify  synthetic  media.  They  arrived  at  this  con- 
elusion  by  what  is  commonly  designated  the  "trial  and  error 
method."  Apparently  Pfeffer  (1895)  was  the  first  to  study  this 
problem  with  the  planned  purpose  of  determining  the  quantitative 
acceptability  to  a  particular  fungus  of  various  organic  substances. 
In  nearly  all  subsequent  studies  either  of  two  purposes  has  been 
maintained:  (1)  to  find  whether  the  given  fungus  would  grow 
upon  the  proffered  carbon  compound,  in  order  to  determine  its 
enzyme-producing  ability,  or  (2)  to  measure  the  comparative  rate 
of  growth  of  the  fungus  on  different  substrata,  using  the  weight 
of  the  mycelial  mat  or  the  increase  in  diameter  of  colonies  as  a 


ORGANIC  NUTRIENTS  OF  FUNGI  11 

criterion.  These  studies,  as  might  be  expected,  have  determined 
that  cosmopolitan  species  of  Aspergillus  and  Penicillium  thrive 
on  a  wide  variety  of  substrata.  Specialized  pathogens,  on  the 
other  hand,  either  grow  poorly  in  artificial  culture  on  organic  sub- 
strata or  may  even  fail  to  grow  at  all.  A  survey  of  this  situation 
clearly  indicates  that  the  underlying  reasons  for  these  differences 
in  organic  food  requirements  of  fungi  should  be  sought  by  inten- 
sive studies. 

Carbon  requirements.  Those  carbon  compounds  that  can  be 
oxidized  with  the  least  expenditure  of  the  energy  stored  in  the 
compound  or  can  be  assimilated  most  readily  appear  to  constitute 
the  food  of  first  choice  for  fungi.  Evidence  indicates  that,  in 
general,  fungi,  like  bacteria,  prefer  carbohydrates  as  food  sources, 
with  proteins  as  second  choice,  and  that  few  species  thrive  well 
on  fats. 

Fungi  grow  more  rapidly  in  proportion  to  their  body  weight 
than  do  green  plants,  and  consequently  expend  relatively  more 
energy  in  converting  their  food  into  an  assimilable  form.  With 
molds  an  increase  in  body  weight  amounting  to  a  thousandfold 
within  a  10-day  period,  such  as  occurs  in  Phy corny  ces  nitens  and 
Aspergillus  niger,  is  not  uncommon. 

The  method  that  has  been  generally  employed  to  determine  the 
food  value  of  carbon  compounds  is  to  grow  the  fungus  in  a  basal 
mineral-nutrient  solution  and  to  vary  the  carbon  or  the  nitrogen 
added.  By  preliminary  trials  the  time  required  to  attain  maximum 
growth  can  be  determined.  The  mycelial  mat,  if  removed  at  the 
end  of  this  period,  can  be  desiccated  and  weighed.  In  comparison, 
another  figure,  which  is  the  result  of  an  analysis  to  determine  the 
amount  of  compound  that  has  been  used  by  the  mold,  can  be  con- 
sidered. Unfortunately,  as  investigators  have  indicated,  inaccu- 
racies appear  as  a  consequence  of  the  formation  and  accumulation 
of  by-products,  such  as  acids,  alkalis,  staling  products,  and  toxins, 
and  of  the  autolysis  and  utilization  of  dying  and  dead  parts  of  the 
mycelium. 

Another  method  that  has  been  employed  to  only  a  limited  extent 
makes  use  of  microrespirometers.  This  method,  considered  in 
Chapter  3,  is  adapted  for  use  in  determining  whether  the  given 
carbon  compound  is  acceptable  and  also  the  rate  at  which  it  is 
consumed. 


18  NUTRITION  OF  FUNGI 

Diversity  in  ability  to  use  carbohydrates  is  indicated  by  numer- 
ous reports,  but  in  general  the  literature  shows  that  glucose  is  the 
favorite.  It  may  be  removed  first  from  a  solution  containing  a 
mixture  of  sugars,  or  it  may  even  be  the  only  one  removed.  Su- 
crose, if  present,  may  be  first  inverted  into  dextrose  and  levulose. 
If  Aspergillus  niger  is  the  test  organism,  Alolliard  (1918)  found 
that,  when  all  the  dextrose  has  been  utilized,  five-sixths  of  the 
levulose  still  remains. 

Attempts  to  employ  the  amount  of  carbon  dioxide  evolved  as 
the  sole  measure  of  utilization  of  the  carbon  source  may  lead  to 
erroneous  interpretations,  for  the  reason  that  some  of  the  products 
metabolized  may  be  stored  within  the  body  of  the  mold,  where 
they  may  be  oxidized  subsequently.  Most  species  give  better 
yields  on  hexoses  than  on  pentoses,  although  Hawkins  (1915) 
found  that  Glomerella  cingulata  utilizes  the  two  pentoses,  arabi- 
nose  and  xylose.  Weimer  and  Harter  (1921)  tested  the  responses 
to  glucose  of  Botrytis  cinerea,  Diplodia  tubericola,  Fusarium 
acuminatum,  Mucor  racemosus,  Rhizopus  tritici,  Sclerotium  bata- 
ticola,  and  Sphaeronema  fimbriatnm,  finding  that  each  organism 
differs  in  the  amount  of  this  sugar  required  to  produce  a  unit  of 
dry  weight.  Brannon  (1923)  found  that  glucose  and  fructose 
are  equally  acceptable  to  Aspergillus  niger  and  Fenicilliwn  camevi- 
berti.  Fusarium  lini}  however,  is  said  to  be  unable  to  utilize  glu- 
cose [Tochinai  (1926)]. 

In  a  series  of  studies  that  may  well  serve  as  a  model,  Raistrick 
et  al.  (1931)  found  that  glucose,  fructose,  and  sucrose  are  excel- 
lent sources  of  food  for  many  molds.  They  evaluated  these 
sugars  by  keeping  "balance  sheets"  on  the  amount  of  sugar 
utilized  and  the  amount  of  certain  metabolic  products  formed 
or  of  mycelium  produced.  By  means  of  such  techniques  differ- 
ences in  the  nutritive  values  of  various  carbon  sources  can  be 
determined.  Horr's  (1936)  observations  show  that  both  galactose 
and  mannose  constitute  poor  sources  of  carbon  for  Aspergillus 
niger  and  Fenicilliuvi  glaucum.  This  observation  regarding  galac- 
tose is  confirmed  by  Steinberg  (1939),  who  added  that  lactose 
supports  practically  no  growth  of  A.  niger,  that  glycerol  results 
in  poor  yields,  and  that  dextrose,  fructose,  sucrose,  and  /-sorbose 
are  equally  effective. 

Variation  among  species  in  ability  to  utilize  sources  of  carbon 
is  further  shown  by  the  inability  of  Achlya  prolifera,  A.  racemosa, 


ORGANIC  NUTRIENTS  OF  FUNGI  19 

Saprolegnia  jerax,  and  S.  monoica  to  utilize  sucrose  [Pieters 
(1915)  ]  and  by  the  utilization  of  galactose  by  Trichophyton  inter- 
digitale  [Mosher  et  al.  (1936)]  and  Aspergillus  fischeri  [Wenck 
etal  (1935)]. 

Schade's  (1940)  observations  show  that  Apodachlya  brachy- 
nema  grows  well  on  dextrose,  levulose,  and  sucrose  but  is  unable 
to  utilize  maltose  and  galactose,  whereas  Leptomitus  lacteus  uses 
none  of  these  sugars. 

By  respirometric  methods  Wolf  and  Shoup  (1943)  noted  that 
Allomyces  arlniscula,  A.  javanicus,  A.  moniliformis,  and  A.  cysto- 
genns  are  able  to  use  dextrin.  Allomyces  arbuscula  uses  maltose 
and  sucrose;  none  utilizes  d-arabinose,  /-arabinose,  cellobiose,  glu- 
cose, galactose,  lactose,  levulose,  mannitol,  or  starch. 

Certain  pathogens  possess  wide  capabilities  for  utilizing  carbo- 
hydrates, whether  mono-,  di-,  or  polysaccharides,  as  is  illustrated 
by  Moore's  studies  (1937)  of  Thymatotrichum  omnivornm.  She 
determined  that  this  organism  uses  dextrose,  levulose,  galactose, 
maltose,  sucrose,  lactose,  mannite,  xylose,  inulin,  dextrin,  starch, 
glycerin,  and  cellulose  and  introduced  another  factor  into  the 
problem  by  varying  the  oxygen  tension.  Decrease  in  oxygen 
tension  was  accomplished  by  the  removal  of  oxygen  with  pyro- 
gallic  acid;  increase,  by  the  introduction  of  oxygen  from  a  storage 
cylinder.  Oxygen  at  normal  atmospheric  concentration  was 
found  optimum  for  growth. 

Foster  et  al.  (1941)  studied  the  direct  utilization  of  C02  by 
Aspergillus  niger  and  certain  other  molds.  By  employing  radio- 
active carbon  (Cn),  they  were  able  to  show  that  carbon  is  me- 
tabolized into  cellular  material  and  organic  acids.  It  may  achieve 
a  role  in  respiratory  changes  connected  with  the  formation  of 
oxaloacetate  from  pyruvate  and  C02.  The  oxaloacetate  thus 
formed  may  in  turn  give  rise  to  fumaric  acid  or  to  succinic  and 
citric  acids.  Earlier  workers  had  suggested  that  C02  enters  into 
the  metabolism  of  fungi,  but  proof  was  not  forthcoming  until 
Foster  and  his  associates  made  use  of  labelled  carbon. 

Careful  consideration,  beginning  perhaps  with  von  Naegeli's 
(1880)  investigations  in  1880,  has  been  given  to  certain  organic 
acids  as  sources  of  carbon.  A4uch  remains,  however,  to  be  accom- 
plished. The  work  of  Camp  (1923)  with  citric  acid  serves  to  il- 
lustrate the  ability  of  fungi  to  utilize  organic  acids.  He  compared 
the  growth  of  certain  fungi  on  media  containing  citrates  as  a 


20  NUTRITION  OF  FUNGI 

sole  source  of  carbon  with  their  growth  on  media  containing 
both  citrates  and  dextrose.  The  organisms  tested  included  those 
commonly  associated  with  the  decay  of  citrus,  namely  Penicillium 
digitatum,  P.  stoloniferuvi,  Diplodia  natalensis,  Phomopsis  citri, 
Alternaria  citri,  Oospora  citri-aurantii,  and  Sclerotinia  libertiana. 
All  of  them  were  able  to  grow  in  orange  juice  (pH  3.8),  but  only 
P.  stoloniferum,  O.  citri-aurantii,  and  5.  libertiana  achieved  a  fair 
amount  of  growth  on  lemon  juice  (pH  2.5).  None  of  these  fungi 
grew  luxuriantly  when  citrate  was  the  sole  source  of  carbon. 
After  P.  stoloniferum  and  5.  libertiana  had  been  started  in  dextrose, 
they  could,  if  transferred  to  media  containing  citric  acid,  achieve 
fairly  good  growth.  In  general,  these  organisms  attained  better 
growth  in  the  solutions  containing  citrate  plus  dextrose  than  in 
dextrose  alone,  only  Penicillium  digitatum  and  Phomopsis  citri 
being  unable  to  utilize  citrate  as  a  supplement. 

Leptomitns  lacteus  and  Apodachlya  brachyneina  utilized  all 
the  straight  carbon-chain  fatty  acids  up  to  and  including  capric 
acid,  with  the  exception  of  formic  acid  and  propionic  acid 
[Schade  (1940)]. 

A  very  different  approach  to  the  problem  of  utilization  of  or- 
ganic compounds  was  made  by  Tamiya  (1932),  who  attempted 
to  determine  the  relationship  of  chemical  structure  to  assimilabil- 
ity.  For  this  purpose  he  employed  123  organic  compounds  with 
Aspergillus  oryzae  as  the  test  fungus  and  noted  whether  the  com- 
pounds were  favorable  for  spore  germination,  were  suitable  for 
subsequent  growth,  and  were  utilized  in  respiration.  Of  those  he 
studied,  only  51  were  found  suitable  to  promote  mycelial  growth 
and  were  respired  by  A.  oryzae;  8  others  were  used  in  respiration 
although  they  did  not  support  growth.  Tamiya  concluded  that 
the  carbohydrates  and  polyatomic  alcohols  constitute  the  best 
sources  of  carbon. 

The  aromatic  series  of  alcohols  and  the  monoatomic  alcohols 
of  the  aliphatic  scries,  with  the  exception  of  ethyl  alcohol,  were 
not  utilized.  Aldehydes,  ketones,  and  esters  were  unsuitable. 
Citric,  lactic,  malic,  pyruvic,  and  succinic  acids  were  among  those 
utilized.  Tamiya  concluded  that  only  those  compounds  are  as- 
similated which  possess  certain  characteristic  atomic  groups  that 
he  called  "chief  radicals."  These  chief  radicals  must  be  joined 
either  in  a  ring  or  straight  chain  to  "residual  radicals";  and  the 


ORGANIC  NUTRIENTS  OF  FUNGI  21 

may,  for  example,  CH3CHOH-,  =CHCOH=,  CH3CO-, 
CHoOH-CHo — ,  be  split  off  in  degradation. 

The  relationship  of  molecular  configuration  of  sugars  to  utili- 
zation in  amino  acid  formation  by  Aspergillus  niger  has  been 
elucidated  by  Steinberg  (1942).  This  fungus  was  found  to  use 
all  pentoses  and  hexoses  having  an  /- 3 -carbon  atom  and  a  rf-4-car- 
bon  atom  except  the  epimers  of  d- xylose. 

Attention  has  been  called  by  Steinberg  (1939a,  1939b)  to  an- 
other factor  that  must  be  considered  in  tests  to  determine  the  as- 
similability  of  a  given  carbon  compound.  When  A.  niger  was 
grown  in  the  presence  of  lactose,  galactose,  glycerol,  or  mannitol 
alone,  the  yields  were  75,  28,  350,  or  34  mg,  respectively.  When 
the  carbon  source  consisted  of  a  mixture  of  mannitol  and  lactose, 
the  yield  was  234  mg;  of  mannitol  and  galactose,  393  mg;  of  gly- 
cerol and  lactose,  458  mg;  of  glycerol  and  galactose,  155  mg;  of 
mannitol  and  glycerol,  545  mg;  and  of  lactose  and  galactose,  17  mg. 
Steinberg  interpreted  these  improved  yields  from  mixtures  to 
better  proportion  of  molecular  groups. 

An  introduction  to  the  information  concerning  the  use  of  fats 
and  oils  as  sources  of  carbon  may  be  secured  from  reports  of 
Tausson  (1928)  and  Hopkins  and  Chibnall  (1932).  Tausson 
found  that  Aspergillus  flaviis  consumes  olive  oil,  cocoa  butter, 
beeswax,  tripalmitin,  and  higher  paraffins.  His  data  show  that 
591.4  mg  of  paraffin  was  utilized  in  35  days  and  that  289.1  mg  of 
mycelial  mat  was  formed  as  a  result.  Hopkins  and  Chibnall  found 
that  the  higher  paraffins  with  chains  not  exceeding  C34HTo  were 
assimilable  by  A.  versicolor.  In  the  breakdown  of  these  substances 
evidence  indicates  that  ketones  first  arise  and  on  further  oxidation 
yield  fatty  acids.  Among  other  vegetable  oils  that  have  been 
found  to  be  consumed  by  molds  arc  linseed  oil  and  walnut  oil. 

Nitrogen  requirements.  The  numerous  studies  that  have 
dealt  with  the  nitrogen  requirements  of  fungi  have  been  primarily 
directed  toward  finding;-  the  most  suitable  sources  of  nitrogen. 
The  results  of  this  work  until  1930  were  largely  summarized  by 
Czapek  (1930).  Later  Robbins  (1937)  classified  fungi  into  four 
groups  on  the  basis  of  the  form  of  nitrogen  they  are  capable  of 
assimilating.  One  group  utilizes  organic  nitrogen  alone;  the  sec- 
ond, both  organic  nitrogen  and  ammonia;  the  third,  not  only  or- 
ganic nitrogen  and  ammonia  but  also  nitrate  nitrogen.  The  fourth 
"group  is  capable  of  fixing  elemental  nitrogen  and  can  also  utilize 


22  NUTRITION  OF  FUNGI 

any  or  all  of  the  other  forms.  On  this  basis  it  appears  that  fungi 
must  be  regarded  as  differing  among  themselves  fundamentally  in 
metabolic  potentialities  as  far  as  usage  of  nitrogen  is  concerned. 

It  might  be  anticipated  that  amino  acids  would  constitute  the 
nitrogen  form  of  first  choice  for  the  reason  that  they  can  be 
utilized  in  the  synthesis  of  proteins  with  the  least  need  for  energy. 
Evidently,  how  ever,  there  are  other  factors  involved  in  the  choice 
of  nitrogen.  At  anv  rate,  amino  acids  are  well  suited  to  a  large 
number  of  fungi,  and  Bacto-peptone  serves  well  as  a  source  for 
many  species.  Boas  (1919)  interpreted  his  experiments  to  show 
that  amino  acids  can  be  used  only  after  they  have  been  deaminized. 
In  this  process  energy  is  required,  and  Boas  regarded  ammonium 
salts  as  the  most  suitable  nitrogen  source,  they  being  much  superior 
to  peptones. 

In  general  there  is  a  paucity  of  convincing  experiments  on  the 
best  source  of  nitrogen  for  specific  fungi.  In  their  trials  with  20 
plant  pathogens  Young  and  Bennett  (1922)  found  that  each  spe- 
cies could  utilize  nitrate  nitrogen;  thus  they  fall  into  the  third 
of  the  groups  proposed  by  Robbins.  In  1910  Hagem  [Steinberg 
(1939a)]  noted  that  Mucor  cbristianensis,  M.  griseocyamis,  M. 
racemosas,  M.  sphaerospora,  and  M.  spinosus  utilize  either  NH4  + 
or  NOr  with  glycerol.  Aspergillus  fischeri,  according  to 
Wenck,  Petersen,  and  Fred  (1935),  uses  either  NH4+  or  organic 
nitrogen,  thus  falling  into  the  second  of  Robbins'  groups.  Ophio- 
bohis  graminis  requires  organic  nitrogen  [Fellows  (1936)],  and 
Basidiobolus  ranarum  and  Saproleguia  parasitica  need  amino  acids 
[Leonian  and  Lilly  (1938)].  Leonian  and  Lilly  also  used  23  other 
organisms  in  tests  in  which  various  amino  acids,  singly  or  in  com- 
binations,  were  substituted  for  ammonium  nitrate,  they  did  not 
obtain  any  evidence  of  ability  to  utilize  these  amino  acids.  If  they 
added  thiamin  (vitamin  Bi),  however,  proper  amino  acids  induced 
growth  in  14  of  the  23  species.  Observations  by  Klotz  (1923) 
showed  that  Aspergillus  viger,  Diplodia  uatalensis,  and  Spbae- 
ropsis  vialorum  can  utilize  amino  nitrogen.  Neither  Apodachlya 
brachynema  nor  Leptomitus  lacteus  is  able  to  utilize  nitrate  nitro- 
gen or  ammonia,  but  both  find  rf,  /-alanine  and  /-leucine  suitable 
for  growth  and,  if  acetate  is  present,  utilize  also  glycine  and 
asparagine  [Schade  (1940)]. 

Alloviyces  arbuscula  makes  use  of  peptone,  alanine,  aspartic 
acid,  asparagine,  arginine-HCl,  cystine,  glutamic  acid,  and  leucine 


ORGANIC  NUTRIENTS  OF  FUNGI  23 

[Wolf  and  Shoup  (1943)].  Similarly,  Wolf  and  Shoup  found 
that  A.  jcruanicus  employs  peptone,  aspartic  acid,  asparagine,  cys- 
tine, and  glutamic  acid;  whereas  A.  moniliformis  and  A.  cysto- 
genus  utilize  only  peptone,  alanine,  aspartic  acid,  and  glutamic 
acid.  None  of  these  species  was  able  to  use  the  amino  acids  gly- 
cine and  tyrosine. 

Nielsen  and  Hartelius  (1938)  grew  yeast  in  beer  wort,  with 
added  thiamin,  as  a  basic  medium  and  then  added  /2-alanine,  aspara- 
gine, aspartic  acid,  lysine,  and  arginine  singly  and  in  combina- 
tions. They  found  that  alone  each  was  toxic  but  that  growth  was 
improved  when  all  were  added. 

Claims  that  certain  fungi  employ  NH4+  to  the  exclusion  of  all 
other  nitrogen  sources  and  therefore  may  be  called  "ammonia  or- 
ganisms" are  not  fully  supported.  Among  other  factors  account 
has  not  been  taken  generally  in  these  studies  of  the  influence  of 
pH.  This  subject  was  given  special  consideration  by  Rippel 
(1931).  Pirschle  (1934)  found  that  ammonia  organisms  will  uti- 
lize NO3""  provided  that  the  cultures  are  aerated.  This  fact  is 
shown  by  certain  of  his  data  that  contrast  the  weight  of  yeast 
in  nonaerated  and  aerated  cultures.  With  ammonium  sulphate, 
the  dry  weights  in  nonaerated  and  aerated  cultures  were  2.568 
and  6.348  grams,  respectively;  with  calcium  nitrate  0.703  and  8.089 
grams,  respectively;  with  potassium  nitrate  0.443  and  5.296  grams, 
respectively.  Smaller  growth  from  the  nitrates  than  from  the 
ammonium  nitrogen  may  be  accounted  for  by  HN02  formation, 
since  the  consensus  of  opinion  is  that  nitrites  are  toxic.  Removal 
by  aeration  of  this  toxic  effect  in  Pirschle's  cultures  is  evidence 
that  this  hypothesis  is  valid. 

Whether  any  fungi  are  entitled  to  be  grouped  among  the  nitro- 
gen fixers  has  been  the  subject  of  much  controversy.  In  1892 
Frank  [Duggar  and  Davis  (1916)]  maintained  that  Hormoden- 
dron  cladosporioides,  grown  on  -nitrogen-free  media,  fixes  nitro- 
gen. The  following  year  Berthelot  made  a  similar  claim  [Duggar 
and  Davis  (1916)]  for  Aspergillus  niger  and  Alternaria  tenuis. 
The  same  ability  was  attributed  to  fhoma  betae,  A.  niger ,  and 
Mucor  stolonijer  by  Saida  in  1901  [Duggar  and  Davis  (1916)]. 
Latham  (1909),  working  with  A.  niger,  also  reported  the  fixation 
of  appreciable  quantities  of  nitrogen,  but  Pennington  (1911)  was 
unable  to  verify  her  observations. 


24  NUTRITION  OF  FUNGI 

The  studies  of  Duggar  and  Davis  (1916)  on  fixation  of  atmos- 
pheric nitrogen  showed  gains  in  cultures  of  Fhoma  betae  on 
manqel-wurzel  decoction  and  on  suqar-beet  decoction  of  3.022 
mg  and  7.752  mg  of  nitrogen,  respectively.  Under  the  same 
conditions  there  were  no  gains  in  cultures  of  Aspergillus  niger, 
Macrosporium  commune,  Penicillium  digitatum,  P.  expansum, 
and  Glomerella  gossypii. 

Aspergillus  niger  was  employed  in  experiments  involving  fixa- 
tion of  atmospheric  nitrogen  by  Schober  (1930),  but  no  evidence 
of  any  increase  in  nitrogen  in  the  culture  flasks  was  obtained. 
Roberg  (1931)  got  negative  results  of  fixation  not  only  with  13 
strains  of  A.  niger  but  also  with  13  other  species  of  Aspergillus. 
Further  confirmation  of  the  inability  of  A.  niger  to  fix  atmos- 
pheric nitroq-en  was  supplied  by  Allison,  Hoover,  and  Morris 
(1934). 

Certain  symbiotic  fungi,  however,  are  able  to  fix  nitrogen,  as  is 
shown  by  the  work  of  Ternetz  (1904).  She  isolated  varieties  of 
mycorrhizal  fungi  belonging  to  fhoma  radicis  from  ericaceous 
plants  and  compared  their  nitrogen-fixing  capabilities  with  those 
of  Azotobacter  chroococcum  and  Clostridium  pastorianum.  The 
strains  of  P.  radicis  gave  yields  of  18  to  22  mg  of  nitrogen  per 
gram  of  dextrose  used. 

The  nitrogen  requirements  of  fungi  appear  worthy  of  further 
study.  Techniques  patterned  after  those  employed  by  the  bac- 
teriologist should  prove  most  serviceable.  Sources  of  error  in 
the  interpretation  of  results  of  such  studies  should  include  those 
which  have  been  mentioned  valid  in  the  interpretation  of  data 
involving  carbon  sources. 


GROWTH  FACTORS 

The  discovery  by  Wildiers  (1901)  in  1901  of  the  need  of  a 
growth  factor  for  the  cultivation  of  yeast  on  synthetic  media 
marked  the  beginning  of  studies  on  accessory  growth  substances 
for  fungi.  Wilders  attempted  without  success  to  use  a  medium 
which  Pasteur  maintained  was  adequate.  When  he  employed  as 
inoculum  a  few  yeast  cells,  no  growth  occurred  with  this  medium; 
but  when  he  added  a  sizable  mass  of  inoculum,  the  yeast  grew. 
He  interpreted  these  results  as  showing  the  need  for  a  sufficient 
amount  of  a  substance  that  he  called  "bios."    As  a  result  of  this 


GROWTH  FACTORS  25 

discovery  the  interest  of  other  workers  was  directed  toward  de- 
termining- whether  Wildiers'  results  could  be  confirmed,  toward 
learning  whether  other  fungi  have  similar  requirements,  and 
toward  making  attempts  to  discover  the  nature  and  properties 
of  bios. 

As  the  result  of  various  researches  it  gradually  became  apparent 
that  bios  is  a  complex,  containing  several  growth  factors.  These 
are  now  known  to  include  biotin  (vitamin  H),  thiamin  (vitamin 
Bi),  pyridoxine  (vitamin  B0),  /-inositol,  /^-alanine,  pantothenic 
acid,  and  possibly  sterol. 

The  specific  function  of  each  of  the  bios  components  is  not  yet 
satisfactorily  known,  although  the  complex  has  been  subjected  to 
considerable  study.  From  the  attempts  to  learn  their  functions, 
however,  it  may  be  concluded  that  they  regulate  respiration,  re- 
production, and  rate  of  growth  and  that  some  act  as  coenzymes 
and  are  essential  in  chemical  syntheses  effected  by  a  particular 
fungus.  Not  all  species,  however,  seem  to  have  identical  require- 
ments for  growth  factors.  This  observation  has  been  interpreted 
to  indicate  that  the  particular  factor  either  is  elaborated  by  the 
fungus  or  else  is  not  required  at  all. 

Copping  (1929)  found  that  certain  wild  yeasts,  in  a  vitamin- 
free  synthetic  medium,  are  able  to  elaborate  their  own  growth 
factors,  whereas  "domesticated"  or  "tamed"  yeasts  require  that 
the  bios  substances  be  supplied. 

Williams  and  Rohrman  (1936)  maintain  that  the  minimum  com- 
plement of  growth  accessory  factors  required  by  yeast  includes 
aspartic  acid,  pantothenic  acid,  /-inositol,  /3-alanine,  and  thiamin. 
In  their  studies  favorable  growth  responses  with  Trichophyton 
inter  digit  ale  occurred  only  upon  the  addition  to  the  media  of 
pantothenic  acid,  riboflavin  (vitamin  B2),  thiamin,  and  /-inositol 
[Mosher  et  al.  (1936)]. 

Robbins  and  his  associates  (1942)  found  that  Trichophyton 
discoides,  pathogenic  to  calves,  suffers  from  complete  deficiences 
of  thiamin,  pyridoxine,  and  /-inositol.  When  from  1  to  10  m/x 
moles  of  thiamin  and  pyridoxine  and  0.1  to  0.5  mg  of  inositol  were 
supplied,  maximum  growth  was  secured. 

Hawker  (1936)  studied  the  influence  of  /-inositol  isolated  from 
stale  cultures  of  Botrytis  cinerea  and  Gloeosporhnn  fructigenum. 
She  also  utilized  baryta  and  an  extractive  of  lentils  to  secure  a  pre- 
cipitate containing  /-inositol  and  a  filtrate  free  from  this  factor. 


26  NUTRITION  OF  FUNGI 

Both  fractions  were  found  essential  for  the  growth  of  Nemato- 
spora  gossypii,  but  /-inositol  was  not  necessary  for  the  growth  of 
Melanospora  destruens.  Hawker  further  found  that  inositol  pro- 
duced a  sporulation  response  with  Sordaria  fmiicola,  Rosellinia 
necatrix,  and  Zygorhynchns  vwelleri. 

Schopfer  (1936)  demonstrated  that  Thy  corny  ces  blakesleeamis 
will  not  erow  in  a  nutrient  solution  containing  mineral  salts,  as- 
paracrine,  and  dextrose  unless  thiamin  is  added.  Kogl  and  Fries 
(1937)  secured  favorable  growth  responses  from  the  addition 
of  thiamin  to  cultures  of  P.  blakesleeamis,  Phytophthora  cactoruvu 
Nectria  coccinea,  Sclerotinia  cinerea,  Poly  poms  adustus,  P.  abie- 
tinus,  and  Fovies  pinicola,  but  no  benefit  to  the  growth  of  Lenzites 
saepiaria  Mas  apparent.  Biotin  and  inositol  were  each  beneficial 
to   the    growth   of   Neviatospora   gossypii   and    Lophoderinium 

pinastri. 

Robbins  and  Kavanaugh  (1938)  observed  that  the  following 
species  show  increased  growth  in  the  presence  of  thiamin:  Phy- 
tophthora capsici,  P.  cinnamorm,  P.  cryptogea,  P.  drechsleri,  P. 
palm'rcora,  P.  parasitica,  P.  boehmeriae,  P.  cactorwn,  P.  cambivora, 
Phycoviyces  nitens,  Pythium  arrhenovianes,  P.  poly  clad  on, 
Sphaerulina  trifolii,  Schizophylhnn  commune,  Sclerothnn  del- 
phinii,  and  5.  rolfsii.  Schopfer  (1938)  showed  the  need  for  thia- 
min by  several  Mucorales,  including  Absidia  ramosa,  Chaetocla- 
* dhnn  brefeldii,  Choanephora  cucurbit  arum,  Dicranophora  fulva, 
Mucor  ramannianus,  Parasitella  simplex,  Phycoviyces  blakesle- 
eamis, and  Pilaira  anovmla.  Quantz  (1943)  found  that  1  y  of 
thiamin  per  100  ml  of  solution  was  optimum  for  Allomyces 
kniepii  and  Blastocladiella  variabilis. 

Thiamin  increased  the  production  of  dry  matter  by  Colly  bia 
velutipes  400%  [Marczvnski  (1943)]  and  was  definitely  benefi- 
cial to  Stereum  frustulosmn  [Noecker  and  Reed  (1943)].  Both 
riboflavin  and  pvridoxine,  however,  were  ineffective  with  these 
two  wood-destroving  species;  when  biotin  in  amounts  of  5  y 
per  26  ml  of  medium  was  supplied,  definitely  increased  growth 
was  noted  with  S.  frnstulosum. 

Attention  has  also  been  directed  in  the  studies  of  growth  factors 
to  methods  of  assav  of  thiamin,  biotin,  pantothenic  acid,  inositol, 
and  other  substances.  These  methods  depend  upon  the  need 
for  an  external  source  of  accessory  substance  by  a  particular 


GROWTH  FACTORS  21 

fungus.  Phycomyces  was  used  by  Bonner  and  Erickson  (1938) 
to  assay  thiamin.  Williams  and  his  associates  at  the  University 
of  Texas,  who  have  devised  several  ingenious  methods,  em- 
ployed yeast  and  various  bacteria.  The  nutritional  need  for  vita- 
mins by  fungi  has  been  employed  in  bio-assavs  of  the  thiamin 
content  of  green  plants  [Burkholder  and  McVeigh  (1940)1. 
When  they  grew  Floy  corny  ces  blakesleeanns  in  solutions  contain- 
ing minerals,  glycine,  and  glucose  with  additions  of  crystalline 
thiamin,  they  were  able  to  substitute  small  quantities  of  plant 
tissues  for  thiamin.  By  comparison  of  the  weights  of  the  mycelial 
mats  in  the  cultures  supplied  with  crystalline  thiamin  with  those 
of  the  mats  in  the  cultures  in  which  plant  tissues  were  substi- 
tuted, they  could  calculate  the  thiamin  content  of  the  green- 

i  & 

plant  tissues. 

The  work  of  Robbins  and  Kavanaugh  (1938)  shows  that  some 
organisms  are  able  to  synthesize  thiamin,  which  is  composed  of 
pyrimidine  and  thiazole;  others  can  carry  out  the  synthesis  if 
either  or  both  constituents  are  furnished  them;  a  third  group  must 
be  supplied  with  the  intact  compound  if  they  are  to  grow  nor- 
mally. Robbins  and  Kavanaugh  found  that  Floy  corny  ces  nitens 
will  grow  in  a  nutrient  solution  containing  dextrose,  asparagine, 
and  mineral  salts  if  30  units  of  pyrimidine  and  thiazole  are  added, 
but  that  neither  of  these  intermediates  alone  is  effective.  Quite. a 
different  reaction  was  noted  with  Floytoplotloora  fagopyri,  Fytlo'mm 
butleri,  P.  polycladon,  Sclerotium  delphinii,  S.  rolfsii,  and  Sploaeru- 
lina  trifolii.  Each  of  these  species  grows  well  in  this  nutrient  solu- 
tion if  30  units  of  pyrimidine  are  added,  but  thiazole  alone  is  in- 
effective. By  Allomyces  kniepii  and  Blastocladiella  variabilis,  too, 
thiazole  alone  is  not  utilizable  [Quantz  (1943)],  but  a  mixture 
of  thiazole  and  pyrimidine  is  equally  as  good  as  thiamin. 

Such  synthesizing  capabilities  are  further  exemplified  by  the 
researches  of  Leonian  and  Lilly  (1940).  They  report  that 
Fusarium  niveum  and  Rloizopus  minus  possess  the  ability  to  syn- 
thesize thiamin  when  grown  on  a  substrate  of  inorganic  salt,  amino 
acids,  and  dextrose.  On  the  same  medium  Floy  corny  ces  blake- 
sleeanns  can  also  form  thiamin,  but  only  when  furnished  with 
pyrimidine  and  thiazole.  Fytloiomorploa  gonapodioides  can  elab- 
orate its  own  thiazole  and,  if  supplied  with  pyrimidine,  will  link 
the  two  substances  together  to  form  thiamin.     Finally,  Mucor 


28  NUTRITION  OF  FUNGI 

ramannianus  is  able  to  produce  pyrimidine  and,  if  given  thiazole, 
can  unite  the  two  to  form  thiamin.  On  the  nutrient  medium  de- 
scribed above,  Fusarium  niveum,  Mucor  nrmannictmis,  Fythio- 
morpha  gonapodioides,  and  Rhizopus  minus  can  synthesize  their 
own  biotin.  Robbins  and  Ma  (1941)  observed  upon  Fusarium 
avenaceum  a  beneficial  effect  of  biotin,  present  in  amounts  up  to 
1  jug  per  gram  of  the  agar  used.  If  they  employed  crystalline 
biotin  (methyl  ester,  CiiH18NL>0:5S)  stimulation  occurred  with 
the  addition  of  as  little  as  0.001  /xg. 

Graphium  ulmi  responds  in  liquid  cultures  to  the  presence  of 
pyridoxine  (vitamin  B,;)  [Burkholder  and  McVeigh  (1942)]. 
.Marked  increases  in  dry  weight  of  mycelial  mat  followed  the 
addition  of  50  y  of  this  vitamin  per  liter  of  basal  mineral  solution 
plus  asparaqine  and  dextrose.  On  the  other  hand,  this  vitamin 
was  found  to  be  unimportant  in  the  growth  of  Saccharomyces 
cerevisiae  in  media  supplied  with  inositol,  biotin,  and  pantothenic 
acid  [Williams,  Eakin,  and  Snell  (1940)].  The  interaction  of 
biotin,  inositol,  pyridoxine,  pantothenic  acid,  and  thiamin  in  the 
<rrowth  of  yeast  has  been  surveyed  in  a  report  by  Williams  ( 1941 ) . 

Certain  amino  acids  are  considered  as  growth  accessory  factors 
in  yeast  and  in  various  fungi  by  Nielsen  and  Sing-Fang  (1937). 
The  relationship  of  vitamin  deficiencies  to  the  growth  of  many 
specific  fungi  is  treated  in  a  report  by  Robbins  and  Kavanaugh 
(1942).  Work  of  this  kind,  of  course,  is  dependent  largely  on 
the  availability  of  vitamins  and  the  synthesis  and  commercial  pro- 
duction of  some  of  them.  Recently  biotin  was  found  to  be 
identical  with  coenzyme  R,  and  it  can  now  be  synthesized  [Harris 
et  ah  (1943)].  The  excellent  treatise  by  Schopfer  (1943)  sum- 
marizes the  fund  of  knowledge  that  has  been  derived  from  the 
researches  of  vitamins  as  related  to  the  nutrition  of  fungi  and  other 
plants. 

Studies  should  also  be  directed  toward  determining  more  about 
the  proximate  function  of  growth  factors  in  the  physiology  of 
fungi.  Host  specificity  may  be  found  to  be  correlated  with  re- 
quirements for  these  factors.  Growth  factors,  if  speculation  is 
guided  by  the  developments  in  recent  years  regarding  their  in- 
fluence on  the  physiology  of  animals  and  of  chlorophyll-bearing 
plants,  may  be  thought  to  be  morphogenic  or  to  regulate  repro- 
duction. 


IMPLICATIONS  29 

INFLUENCE  OF  OSMOTIC  PRESSURE 

Special  attention  has  been  devoted  to  the  concentration  of  salts 
and  nutrients  in  culture  media  because  spores  can  be  germinated 
and  mycelium  can  be  grown  in  solutions  having  high  osmotic 
equivalents.  Ordinarily  the  media  are  prepared  with  their  con- 
stituents in  such  proportions  that  the  osmotic  pressure  ranges 
from  0.5  to  less  than  10  atm. 

Knowledge  of  osmotic  pressure  finds  practical  application  in 
food  preservation  with  salt  or  sugar.  Increased  percentage  of  salt 
in  brines,  for  example,  is  correlated  with  increased  capabilities  for 
preservation.  Molliard  (1918)  found  that  conidial  formation  by 
Sterigmatocy  stis  nigra  is  prevented  in  a  nutrient  solution  contain- 
ing 1%  NaCl;  within  the  range  of  2  to  5%  mycelial  growth  is 
retarded,  and  with  12%  there  is  complete  inhibition. 

Fungi  differ  greatly  in  their  tolerance  to  salts  with  high  osmotic 
pressures.  Raciborski  (1905)  grew  Torula  sp.  in  a  saturated  solu- 
tion of  sodium  chloride  or  of  sodium  nitrate.  Hawkins  (1916) 
grew  certain  plant  pathogens,  including  Botrytis  cinerea,  Diplodia 
tubericola,  Fusarium  radicicola,  F.  oxysporum,  Sclerotinia  cmerea, 
and  Sphaeropsis  malorum,  in  potassium  nitrate  solutions  with  a 
calculated  diffusion  tension  of  47  atm.  Certain  molds,  such  as 
Aspergillus  niger  and  Femcillium  glauciim,  have  been  grown  in 
solutions  having  an  osmotic  pressure  equivalent  of  157  atm. 

Similarly  the  preservation  of  jelly,  jam,  syrup,  and  such  foods 
against  molds  is  correlated  with  the  osmotic  concentration  of  the 
sugar  used.  Heald  and  Pool  (1908)  found  that  a  mold  which  they 
named  Torula  saccharina  achieved  optimum  growth  in  Pasteur's 
nutrient  solution  containing  45%  sucrose.  Slight  growth  occurred 
in  75  to  80%  sucrose  solutions. 

IMPLICATIONS 

From  the  foregoing  account  it  is  manifest  that  species  of  fungi 
differ  from  each  other  in  nutritional  requirements.  Some  grow 
well  on  almost  any  substrate  that  is  employed  and  for  this  reason 
may  be  regarded  as  "domesticated"  or  "tamed"  fungi.  Others, 
on  the  other  hand,  may  barely  survive  on  these  same  media,  may 
grow  poorly  on  a  limited  number  of  substrates  only,  or  may  not 


30  NUTRITION  OF  FUNGI 

live  on  artificial  media  after  the  reserve  within  the  spore  has  be- 
come exhausted.  Such  species,  in  contrast,  cannot  be  domesti- 
cated. Strange  diets,  never  encountered  in  their  natural  habitats, 
are  forced  upon  them  in  captivity  in  the  test  tube.  Perhaps  the 
mycologist  who  attempts  to  study  their  physiology  in  artificial 
media  may  actually  be  studying  their  pathology. 

Many  published  accounts  dealing  with  the  growth  of  a  given 
species  on  a  wide  variety  of  media  are  quite  pointless  and  con- 
tribute nothing  fundamental  to  an  understanding  of  the  nutritional 
requirements  of  the  species.  Similarly  the  compounding  of  nu- 
trient formulae  may  be  a  misguided  procedure,  and  the  use  of  such 
formulae  may  yield  only  sterile  knowledge.  The  making  and 
using  of  formulae  can  be  condoned  only  if  their  purpose  is  to 
reveal  the  necessity  of  some  factor  that  conditions  a  metabolic 
activity  of  the  fungus. 

In  future  studies  more  attention  should  be  given  to  the  utiliza- 
tion of  specific  organic  and  inorganic  materials  in  particular  meta- 
bolic activities.  This  necessity  is  indicated  by  the  fact  that  some 
substances  do  not  support  growth,  although  they  are  respired.  It 
is  further  indicated  by  the  fact  that  many  fungi  grow  well  in  the 
presence  of  a  given  food  but  do  not  reproduce.  Evidence  shows 
that  some  specific  element,  vitamin,  or  other  growth  factor  is 
essential  for  reproduction  but  may  not  necessarily  limit  any  other 
metabolic  activity  of  the  given  fungus. 

More  should  be  known  regarding  the  mineral  requirements  of 
fungi.  Account  should  be  taken  in  such  studies  of  the  ash  content 
of  the  fungus  at  the  conclusion  of  the  growth  period,  in  com- 
parison to  the  known  ash  content  of  the  nutrient  before  the 
fungus  was  allowed  to  grow  upon  it.  It  is  indicated,  furthermore, 
that  fungi  may  well  be  used  in  analytic  procedures,  especially  in 
the  determination  of  trace  elements  [Niklas  and  Toursel  (1941)1 
or  of  vitamins. 

It  appears  that  a  more  adequate  understanding  of  the  nutrition 
of  fungi  would  result  if  the  terms  parasitic  (paratrophic)  and 
saprophytic  (saprotrophic)  largely  disappeared  from  the  teacher's 
vocabulary.  More  emphasis  would  then  be  placed  upon  the  abil- 
ity of  fungi  to  synthesize  foods  as  well  as  a  variety  of  other  sub- 
stances.  As  a  consequence,  the  fact  that  fungi  do  not  possess 
chlorophyll  would  be  of  little  concern  to  the  teacher,  and  the 


IMPLICATIONS  SI 

student  might  then  come  seriously  to  question  whether  fungi  were 
derived  from  al^ae  by  degradation. 


LITERATURE  CITED 

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centration," Ann.  Mo.  Botan.  Garden,  8:  237-280,  1921. 

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Bernhauer,  K.,  "Uber  die  Saurebildung  durch  Aspergillus  niger.  IV.  Die 
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Boeseken,  J.,  and  H.  I.  Watermann,  "Uber  die  Wirkung  der  Borsaure  und 
einiger  anderer  Verbindungen  auf  die  Entwicklung  von  Penicillium 
glancum  und  Aspergillus  niger,"  Folia  Microbiol.,  1:  342-358,  1912. 

Bonner,  James,  and  James  Erickson,  "The  Phycomvces  assay  for  thiamin 
(Vitamin  Bi).  The  method  and  its  specificity,"  Am.  J.  Botany,  25:685- 
692,  1938. 

Bortels,  H.,  "Uber  die  bedeutung  von  Eisen,  Zink,  und  Kupfer  fur  Mikroor- 
ganismen  unter  besonderer  Berucksichtigung  von  Aspergillus  niger" 
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Brannon,  J.  M.,  "Influence  of  glucose  and  fructose  on  growth  of  fungi," 
Botan.  Gaz.,  16:  257-273,  1923. 

Burkholder,  P.  R.,  and  Ilda  McVeigh,  "Studies  on  thiamin  in  green  plants 
with  the  Phycomyces  assay  method,"  Am.  J.  Botany,  27:853-861,  1940. 
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1942. 

Camp,  A.  F.,  "Citric  acid  as  a  source  of  carbon  for  certain  Citrus-fruit-de- 
stroying fungi,"  Ann.  Mo.  Botan.  Garden,  10:  213-298,  1923. 

Chrzaszcz,  T.,  and  E.  Peyros,  "Optimale  Bedingungen  der  Citronsaurean- 
haufung,  sowie  einiger  Beobachtung  zu  Theorie  der  Citronsaurebil- 
dung,"  Biochem.  Z.,  280:  325-336,  1935. 

Copping,  Alice  M.,  "The  effect  of  bios  on  the  growth  and  metabolism  of 
certain  yeasts,"  Biochem.  J.,  23:  1050-1063,  1929.  ' 

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1930.     (Vide  pp.  344-352.) 

Duggar,  B.  M.,  and  A.  R.  Davis,  "Studies  in  the  physiology  of  the  fungi.  I. 
Nitrogen  fixation,"  Ann.  Mo.  Botan.  Garden,  3:  413-437,  1916. 

Fellows,  H.,  "Nitrogen  utilization  by  Ophiobolus  graminis"  J.  Agr.  Re- 
search, 53:  765-769,  1936. 


32  NUTRITION  OF  FUNGI 

Foster,  J.  W.,  "The  heavy-metal  nutrition  of  fungi,"  Botan.  Rev.,  S:  207-239, 

1939. 
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carbon  as  an  indicator  of  carbon  dioxide  utilization.    VII.    The  assimila- 
tion of  carbon  dioxide  by  molds,"  Proc.  Nat.  Acad.  Sci.,  21:  590-596, 

1941. 
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growth  of  Aspergillus  niger,"  Am.  J.  Botany,  8:  147-163,  1921. 
Harris,  S.  A.,  D.  E.  Wolf,  R.  Mozingo,  and  K.  Folkers,  "Synthetic  biotin," 

Science,  91:  447-448,  1943. 
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the  sporulation  of  Melanospora  destruens  and  some  other  fungi,"  Ann. 

Botany,  SO:  699-717,  1936. 
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pentoses  bv  Glomerella  cingulata"  Am.  J.  Botany,  2:375-389,  1915. 
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7:255-260,  1916. 
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Expt.  Sta.  Ann.  Rept.,  21:  54-68,  1908. 
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higher  paraffins,"  Biochem.  /.,  26:  133-142,  1932. 
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glaucum,"  Plant  Physiol.,  77:81-99,  1936. 
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27:  1021-1038,  1913. 
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nitrogen  metabolism  in  fungi,"  Ann.  Mo.  Botan.  Garden,  10:  299-368, 

1923. 
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Mesoinosit  auf  das  Wachstum  verschiedener  Pilzarten,"  Hoppe-Seyler's 

Z.  physiol.  Chemie,  2-/P:  93-1 10,  1937. 
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fect of  chemical  stimulation,"  Bidl.   Torrey  Botan.  Club,  56^:  235—244, 

1909. 
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Thiamin,  its  constituents  and  the  source  of  nitrogen,"  Phytopathology, 

2^:537-548,  1938. 
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525,  1940. 
Lockwpod,  L.  B.,  G.  E.  Ward,  O.  E.  May,  H.  T.   Herrick,  and  H.  T. 

O'Neill,  "The  production  of  fat  by  Penicillium  javanicum  van  Beijma," 

Zeutr.  Bakt.,  Parasitenk.,  II  Abt.,  90: 411-425,  1934. 
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oryzae"  J.  Agr.  Research,  55:849-857,  1936. 
Mann,    Mary    L.,    "Calcium    and    magnesium    requirements   of   Aspergillus 

niger?  Bull.  Torrey  Botan.  Club,  S9:  443-490,  1932. 


LITERATURE  CITED  33 

Marczynski,  M.,  "Studies  on  the  nutrition  of  Collybia  velutipes  (Curt.) 
Quel.  (Homobasidiomycetes,  Agaricales) ,"  Am.  Midland  Nat.,  30:  164- 
170,  1943. 

McHargue,  J.  S.,  and  R.  K.  Calfee,  "The  effect  of  manganese,  copper,  and 
zinc  on  growth  and  metabolism  of  Aspergillus  flavus  and  Rhizopus 
nigricans,"  Botan.  Gaz.,  91:  183-193,  1931. 

Metz,  O.,  "Uber  Wachstum  und  Farbstoffbildung  einiger  Pilze  unter  dem 
Einfluss  von  Eisen,  Zink,  und  Kupfer,"  Arch.  Mikrobiol.,  1:  197-251, 
1930. 

AIolisch,  H.,  Die  Pflanze  in  ihrer  Beziehung  zu  Eisen.    Jena.    1892. 

"Die  mineralische  Nahrung  der  niederen  Pilze,"  Botan.  Centr.,  60:  167- 
168,  1894. 

AIolliard,  M.,  "Influence  de  certaines  conditions,  sur  la  consommation,  com- 
paree  du  glucose  et  du  levulose  par  le  Sterig?natocystis  nigra  a  portir  du 
saccharose,"  Compt.  rend.,  161:  1043-1046,  1918. 

Moore,  Elizabeth  J.,  "Carbon  and  oxygen  requirements  of  the  cotton-root- 
rot  organism,  Phymatotrichum  ommivorum,  in  culture,"  Phytopathol- 
ogy, 27:918-930,  1937. 

AIosher,  W.  A.,  D.  H.  Saunders,  L.  K.  Kingery,  and  R.  J.  Williams,  "Nu- 
tritional requirements  of  the  pathogenic  mold,  Trichophyton  inter -digi- 
tal e,"  Plant  Physiol.,  11:  795-806,  1936. 

Naegeli,  C.  von,  "Ernahrung  der  niederen  Pilze  durch  Kohlenstoff-  und 
Stickstoffverbindungen,"  K.  b.  Akad.  iviss.  Miinchen  Sitzenber.,  10:  267— 
277,  1880. 

Nielsen,  E.,  and  F.  Sing-Fang,  "Vergleichende  Untersuchungen  liber  Wuch- 
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Nielsen,  E.,  and  V.  Hartelius,  "Wuchstoffwirkung  der  Aminosauren.  III. 
Untersuchungen  iiber  die  Wuchstoffwirkung  von  /3-Alanin,  /3-Alanyl- 
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27^:412-445,  1930. 


34  NUTRITION  OF  FUNGI 

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LITERATURE  CITED  35 

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growth  of  Aspergillus,"  Botan.  Gaz.,  70:465-468,  1920. 
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1934. 
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1935. 
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rey Botan.  Club,  62:81-90,  1935a. 
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niger  upon  its  growth,"  Am.  J.  Botany,  23:  227-231,  1936. 
"Relation    of   accessory   growth    substances    to    heavy   metals,    including 

molvbdenum,  in  the  nutrition  of  Aspergillus  Jiiger,"  J.  Agr.  Research, 

52:439-448,  1936a. 
"Role  of  molybdenum  in  utilization  of  ammonium  and  nitrate  nitrogen 

by  Aspergillus  niger,'''  J.  Agr.  Research,  55:891-902,  1937. 
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J.  Agr.  Research,  51:  569-574,  1938. 
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1939. 
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nutrition  of  Aspergillus  niger,"  Proc.  Third  Internat.  Cong.  Microbiol., 

491-492,  1939a. 
"Sulfur  and  trace-element  nutrition  of  Aspergillus  niger,"  J.  Agr.  Research, 

63:  109-127,  1941. 
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J.  Agr.  Research,  64:618-633,  1942. 
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Tausson,  W.  O.,  "Uber  die  Oxydation  der  Wachse  durch  Mikroorganis- 

men,"  Biochem.  Z.,  193:  85-93,  1928. 
Ternetz,    C,    "Assimilation    des    Atmosphorischen    Stickstoff    durch    einen 

torfbewohnenden  Pilz,"  Ber.  deut.  botan.  Ges.,  22:  267-274,  1904. 
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Colletotrichum  lini"  J.  Coll.  Agr.  Hokkaido  Imp.  Univ.,  14:  171-236, 

1926. 


36  NUTRITION  OF  FUNGI 

Volkonsky,  M.,  "Sur  les  conditions  de  culture  et  le  pouvoir  de  svnthese  de 

Saprolegnia  sp.  Etude  qualitative  de  l'alimentation  carbone,  azotce,  et 

sulfuree,"  Ann.  inst.  Pasteur,  50:  703-730,  1933. 
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Ann.  inst.  Pasteur,  52:  76-101,  1934. 
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1935. 
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vure,"  Cellule,  75*:  311-333,  1901. 
Williams,  R.  J.,  "Growth-promoting  nutrilites  for  veast,"  Biol.  Rev.,  16: 49- 

80,  1941. 
Williams,  R.  J.,  and  E.  Rohrman,  "/3-Alanine  and  bios,"  /.  Am.  Cheni.  Soc, 

58:695,  1936. 
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biotin,  pantothenic  acid,  and  vitamin  B„  to  the  growth  of  yeasts,"  /.  Am. 

Chen?.  Soc,  62:  1204-1207,  1940. 
Wolf,  Fred  T.,  and  C.  S.  Shoup,  "The  effects  of  certain  sugars  and  amino 

acid  upon  the  respiration  of  Allomyces,"  My  col.,  35:  192-200,  1943. 
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on  different  solid  substrata,"  Plant  Physiol.,  14:  589-593,  1939. 
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thetic culture  media,"  Am.  J.  Botany,  9:  559-569,  1922. 


Chapter  2 
ENZYMES  AND  ENZYMIC  ACTIVITIES  OF  FUNGI 

Enzymes  and  catalysts.  Enzymes  may  be  defined  as  organic 
catalyzers,  with  specific  powers  of  reaction,  that  are  formed  by 
living  cells  but  are  capable  of  functioning  independently  of  them. 
This  definition  conveys  a  clear  concept  only  if  the  reader  has  a 
working  understanding  of  catalyzers.  It  has  long  been  known 
that  relatively  small  amounts  of  certain  substances  modify  the 
velocity  of  chemical  reactions.  Finely  divided  platinum,  for  in- 
stance, greatly  speeds  up  the  decomposition  of  hydrogen  peroxide 
into  water  and  molecular  oxvffen.  Alteration  of  rate  of  reaction 
may  not  always  be  in  the  direction  of  acceleration;  it  may  be  in 
the  direction  of  retardation  instead,  so  that  the  velocity  of  reaction 
may  be  either  accelerated  or  retarded  by  catalysts. 

According  to  the  old  conception,  catalysts  are  mysterious 
chemical  substances  which  are  unable  to  initiate  a  reaction  but 
can  change  the  rate  of  one  already  in  progress;  they  do  not  appear 
in  the  end-products,  nor  are  they  used  up  during  the  reaction. 
From  the  newer  viewpoint  catalysts  are  to  be  regarded  as  sources 
of  surface  energy.  They  are  capable  of  functioning  provided 
that  the  spatial  configuration  of  atoms  in  the  surface  of  the 
catalyst  is  such  as  to  cause  certain  oriented  adsorption  relation- 
ships, thus  permitting  the  catalyst  to  contribute  surface  energy  to 
the  system.  Presumably  this  surface  energy  induces  electron  dis- 
placements in  the  adsorbed  and  oriented  molecules,  which  are, 
as  a  result,  chemically  active.  If  in  catalysis  surface-energy  forces 
and  oriented  adsorption  are  the  important  features,  it  can  be 
understood  that  diverse  chemicals  can  be  used  to  catalyze  a 
given  reaction.  Such  a  concept,  moreover,  affords  a  logical  ex- 
planation for  believing  that  catalysts,  by  inducing  electron  shifts 
in  the  reacting  molecules,  may  themselves  initiate  reactions. 

According  to  this  newer  conception,  even  though  the  catalyst 
may  not  actually  appear  in  the  end  products  of  the  reaction,  the 

31 


38  ENZYMES  AND  ENZYMIC  ACTIVITIES  OF  FUNGI 

catalytic  surface  may  have  entered  into  the  reaction,  or  there 
may  have  been  an  oriented  adsorption  at  the  catalyst's  surface 
with  the  result  that  the  reacting  molecules  are  brought  within  the 
sphere  of  chemical  attraction  and  reactivity.  If  then  the  products 
of  the  reaction  are  attracted  to  the  reacting  materials  more  strongly 
than  to  the  catalyst,  there  is  a  continuous  migration  from  the 
catalyst  to  the  reacting  materials  until  the  transformation  has  been 
completed. 

Within  certain  limits  the  degree  of  acceleration  of  a  reaction  is 
proportional  to  the  concentration  of  catalyst  present,  although 
the  final  equilibrium  is  entirely  independent.  With  a  smaller 
amount  of  catalyst,  however,  a  longer  time  may  be  required  to 
produce  a  definite  equilibrium. 

Water  constitutes  one  of  the  most  important  catalysts  known. 
Its  effect  is  evident  in  the  case  of  pure  chlorine  gas  and  hydrogen 
gas,  which  will  not  combine  to  form  HC1  at  a  measurable  rate 
except  in  the  presence  of  water. 

Our  knowledge  of  enzymes  begins  with  the  observations  of 
Pay  en  and  Persoz,  who  in  1833  made  the  observation  that  germi- 
nating seeds  contain  a  substance  which  transforms  starch  into 
sugar.  They  called  this  substance  diastase,  although  amylase  is 
the  preferred  name.  This  discovery  marks  the  beginning  of 
studies  of  "organized  ferments,"  which  were  thought  to  be  the 
agents  that  carried  on  catalytic  processes  within  living  cells,  as 
distinguished  from  "unorganized  ferments,"  which  did  not  re- 
quire  the  presence  of  living  cells.  Confusion  in  the  use  of  the 
word  ferment  led  Kuhne  in  1867  to  suggest  the  name  enzyme  for 
all  organized  ferments.  The  distinction  between  organized  and 
unorganized  ferments  completely  broke  down,  how  ever,  when 
Buchner  in  1897  isolated  diastase  from  yeast.  He  crushed  yeast 
cells  with  sand,  pressed  out  a  straw-colored  fluid,  filtered  it  to 
free  it  from  living  cells  or  their  fragments,  and  found  that  the 
clear  fluid  was  capable  of  producing  alcoholic  fermentation.  He 
also  demonstrated  that  this  alcohol-forming  substance  was  pre- 
cipitable  by  alcohol  and  easily  destroyed  by  heat.  Since  then  an 
enormous  literature  on  enzymes  has  come  into  existence,  much 
too  copious  to  be  summarized  in  one  chapter  or  even  one  volume. 
For  brief  presentations  Waksman  and  Davison  (1926)  or  Tauber 
(1937)  is  very  useful,  and  for  a  more  elaborate  summary  the  set 
of  eight  volumes  edited  by  Nord  and  Weidenhagen  (1932-1939) 


CHEMICAL  PROPERTIES  OF  ENZYMES  39 

and  of  five  volumes  edited  by  Nord  and  Werkman  (1941-1945) 
is  recommended. 

Classification  of  enzymes.  Several  plans  have  been  proposed 
as  bases  for  the  classification  of  enzymes.  The  simplest  of  these 
is  to  group  them  into  extracellular  or  digestive  enzymes  and  intra- 
cellular or  respiratory  enzymes.  The  two  classifications  are  also 
sometimes  designated  as  exoenzymes  and  endoenzymes,  respec- 
tively. Exoenzymes  occur  in  secretions  which  pass  to  the  ex- 
terior of  the  living  cell  through  the  protoplasmic  membrane  and 
cell  wall.  Ptyalin,  the  amylolytic  enzyme  in  saliva,  pepsin,  the 
proteolytic  enzyme  in  the  gastric  juice,  and  sucrase,  the  inverting 
enzyme  of  yeast,  are  extracellular,  and  much  of  our  knowledge  of 
enzymes  has  been  gained  by  study  of  their  activities.  Little  or  no 
energy  that  is  available  to  the  cell  is  liberated  by  these  enzymes. 
The  endoenzymes  act  inside  the  living  cell  and  are  not  excreted 
into  its  environment.  Such  enzymes  are  incapable  of  diffusing 
through  the  cell  membrane.  Some  of  them  can  react  when  re- 
moved from  living  cells,  whereas  others  produce  their  character- 
istic reactions  only  in  vivo.  In  contrast  to  exoenzymes,  they 
liberate  large  quantities  of  energy  to  provide  for  the  metabolic 
activities  of  the  cell.  In  Myxomycetes  and  certain  animals  that 
ingest  their  food,  digestion  is  intracellular  instead  of  extracellular, 
as  is  generally  the  situation  among  fungi. 

Enzymes  may  also  be  classified  according  to  the  type  of  chemi- 
cal changes  produced,  that  is,  whether  they  are  oxidative,  hydro- 
lytic,  reductive,  or  synthetic,  or  on  the  basis  of  the  type  of 
chemical  decomposed,  for  example,  whether  it  is  carbohydrate, 
protein,  fat,  glucoside,  or  pigment.  In  general,  the  name  of  each 
specific  enzyme  is  formed  from  the  name  of  the  substrate  by 
substituting  ase  for  the  last  syllable.  The  list  on  page  40  includes 
a  few  of  the  better-known  enzymes  occurring  in  fungi  and  the 
end-products  of  the  enzymic  reactions. 

Chemical  properties  of  enzymes.  Concerning  the  chemical 
nature  of  enzymes  there  are  two  schools  of  thought.  One  is 
typified  by  the  researches  of  Willstatter,  Oppenheimer,  and  Wald- 
schmidt-Leitz,  and  the  other  by  those  of  Sherman,  Northrop, 
Sumner,  and  others. 

The  first  of  these  theories  is  that  enzymes  contain  a  special 
reactive  or  prosthetic  group  which  possesses  a  specific  affinity 
or  ability  to  combine  with  definite  groupings  in  the  substrate. 


40 


ENZYMES  AND  ENZYMIC  ACTIVITIES  OF  FUNGI 


Name 

of  Enzyn\e 

Substrate 

Esterase 

Esters 

Lipase 

Fats 

Lecithinase 

Lecithin 

Tannase 

Tannin 

Pectase 

Pectin 

Sucrase 

Sucrose 

Invertase 

Rarnnose 

Maltase 

Maltose 

Trehalase 

Trehalose 

Cellulase 

Cellulose 

Cytase 

Hemicellulose 

Diastase 

Starch  and  dextrins 

Inulase 

I  nuli  n 

Raffinase 

RarTinose 

Lactase 

Lactose 

Glucosides 

Glucosides 

Amygdalase 

Amygdalin 

Rennin 

Casein 

Emulsin 

/3-Glucosides 

Pepsin 

Proteins 

Trypsin 

Proteins,     proteoses,     pep- 

tones, peptids 

Erepsin 

Proteoses,  peptones,  peptids 

Urease 

Urea 

Phenolase 

Phenols 

Tyrosinase 

Tyrosine 

Peroxidase 

Peroxides 

Zymase 

Glucose,  fructose,  mannose, 

galactose 

Glycolase 

Sugars 

Fumarase 

Fumaric  acid 

Catalase 

Hydrogen  peroxide 

Luciferase 

Luciferin 

End-products 

Acids  and  alcohols 
Glycerol  plus  fatty  acids 
Cholin    and    glycerophosphoric 

acid  and  fatty  acids 
Glucose  and  tannic  acid 
Pectic  acid 
Fructose  and  glucose 
Fructose  and  melibiose 
Glucose 
Glucose 
Cellobiose 

Dextrins  and  monosaccharides 
Dextrins  and  maltose 
Fructose 

Fructose  and  melibiose 
Fructose  and  galactose 
Glucose  and  other  products 
Gentiobiose   and   benzaldehyde 

plus  hydrocyanic  acid 
Paracasein 

Sugar  plus  nonsugar  residues 
Proteoses  and  peptones 
Peptids  and  amino  acids 

Amino  acids 

Ammonium  carbonate 

Quinones 

Melanins 

Active    oxygen    plus    reduction 

products 
Alcohol  and  carbon  dioxide 

Lactic  acid 
Malic  acid 

Water  plus  molecular  oxygen 
Oxyluciferin  and  light  by  bio- 
luminescent  species 

This  reactive  group  is  attached  to  a  colloidal  carrier,  and  specific 
action  is  determined  in  part  by  the  colloidalitv  of  the  aggregate 
and  in  part  by  the  affinity  of  the  reactive  group  for  the  substrate. 
The  enzyme  becomes  inactivated,  therefore,  when  the  colloidal 
properties  of  the  aggregate  are  destroyed.  The  second  group  of 
investigators  believe  that  enzymes  are  specific,  definite  chemical 
compounds,  probably  proteins,  and  that  enzyme  specificity  is  de- 


COENZYMES  41 

termined  by  the  arrangement  of  the  groupings  in  the  complex 
molecule. 

Evidence  of  the  protein  nature  of  enzymes  rests  upon  such 
observations  as  the  following:  (1)  Many  enzymes  may  be  di- 
gested by  other  enzymes,  as  occurs  when  pepsin  in  acid  solution 
is  brought  into  contact  with  trypsin.  (2)  It  has  been  shown  that 
certain  amino  acids,  such  as  arginine,  aspartic  acid,  cystine,  glu- 
tamic acid,  histidine,  lysine,  tryptophane,  and  tyrosine,  compose 
pepsin  [Calvery,  Herriott,  and  Northrop  (1936)]. 

The  first  enzyme  to  be  obtained  in  purified  crystalline  form 
was  urease,  extracted  by  Sumner  in  1926  from  jack  bean.  Since 
then  several  others  have  been  obtained  in  crystalline  form,  in- 
cluding pepsin,  trypsin,  chymotrypsin,  papain,  catalase,  carboxy- 
polypeptidase,  lipase,  and  the  yellow  respiratory  enzyme  of  War- 
burg. Northrop  (1935)  regards  all  of  these  crystalline  enzymes 
as  specific  proteins.  In  opposition  to  this  theory  it  is  maintained 
that  these  crystalline  proteins  are  not  the  enzymes  themselves 
but  the  adsorption  compounds  of  the  enzymatic  component.  In 
answer  Northrop  points  out  that  no  specific  prosthetic  group  is 
known  for  pepsin,  urease,  trypsin,  and  carboxypolypeptidase.  It 
seems  well  established,  however,  that  certain  catalytic  enzymes 
are  associated  with  a  carrier  and  that  the  facts  necessitate  accept- 
ance of  both  viewpoints.  The  catalytic  activity  of  hematin,  for  . 
example,  is  knowTn  to  increase  ten-millionfold  when  associated 
with  the  colloidal  carrier,  which  leads  to  a  question  regarding  the 
relative  importance  of  the  colloidal  carrier  and  prosthetic  group 
in  this  type  of  enzyme. 

Coenzymes.  Some  enzymes,  as  has  been  indicated,  are  "en- 
zyme systems,"  containing  an  assisting  material  that  also  has 
the  power  of  catalyzing.  These  are  termed  coenzymes.  Some 
coenzymes  are  organic,  whereas  others  are  inorganic.  In  1905 
Harden  demonstrated  that  the  dialysate  of  expressed  veast  juice 
and  the  residue  are  separately  inactive  but,  when  combined,  are 
again  active.  In  this  instance  the  dialyzable  portion  is  the  co- 
enzyme. Among  coenzymes  are  cozymase  (coenzyme  I),  co- 
enzyme II,  cocarboxylase  (vitamin  Bi),  riboflavin,  nicotinic  acid, 
and  glutathione.  Other  vitamins  and  hormones  have  been  postu- 
lated to  function  as  coenzymes;  this  theory,  if  valid,  may  explain 
the  essentiality  of  specific  vitamins  in  the  metabolism  of  certain 
fungi.    Others  are  so  loosely  held  as  to  be  able  to  oscillate  between 


42  ENZYMES  AND  ENZYM1C  ACTIVITIES  OF  FUNGI 

different  enzymes.  Some  behave  catalytically  in  rendering  oxygen 
active;  others  seem  to  function  as  carriers  of  oxvgen,  of  hydro- 
gen, or  of  phosphates. 

Specificity  of  enzymes.  Much  of  the  classification  of  enzymes 
is  based  upon  the  assumption  that  each  enzyme  can  act  upon  a 
single  definite  chemical  compound.  In  order  clearly  to  compre- 
hend this  interpretation,  the  lock  and  key  analogy  has  been 
widely  employed  to  illustrate  enzyme  specificity.  The  substrate 
is  analogous  to  the  lock,  and  the  enzyme  to  the  key.  A  certain  key 
is  required  to  turn  each  lock,  and  hence  a  certain  enzyme  to  de- 
compose each  substrate.  This  analogy  is  very  serviceable  but 
conveys  the  implication  that  certain  enzymes  may  be  master 
enzymes,  since  they  act  as  master  keys.  Zymase,  for  example, 
can  decompose  the  four  stereoisomers  J-glucose,  J-mannose, 
J-levulose,  and  J-^alactose.  Similarly  maltase  will  hydrolyze  the 
a-methvlo-lucosides,  and  emulsin,  the  #-methvlo;lucosides,  but  re- 
ciprocally  these  two  enzymes  are  without  hydrolytic  ability. 

Attention  may  well  be  called  to  the  fact  that  different  enzymes 
may  produce  different  end-products  from  the  same  substrate.  If 
the  trisaccharide  raffinose,  for  example,  is  decomposed  by  inver- 
tase,  melibiose  and  fructose  are  formed;  if  by  emulsin,  sucrose 
and  galactose.  The  fact  that  emulsin  may  be  a  complex  of  sev- 
eral enzymes  may  account  for  this  result.  Similarly  there  is  evi- 
dence that  amylase,  zymase,  and  tryptophanase  are  not  single 
enzymes  but  enzyme  complexes  or  systems. 

Influence  of  reaction,  temperature,  and  time.  In  the  light 
of  our  knowledge  of  the  chemical  nature  of  enzymes  and  of  the 
modifying  effects  of  pH,  temperature,  and  time  on  chemical  syn- 
thesis and  analysis  in  general,  it  should  be  unnecessary  to  elaborate 
on  this  subject  as  applied  to  enzymic  reactions.  These  three  en- 
vironmental factors  are  minutely  correlated,  and  none  operates 
independently  of  the  others.  Each  enzyme  reacts  best  under  a 
definite  environmental  set-up.  With  time  and  temperature  con- 
stant pepsin  shows  its  optimum  activity7  in  a  solution  of  approxi- 
mately pH  2.5,  whereas  trypsin  manifests  its  greatest  activity  at 
approximately  pH  8.0.  With  pH  and  time  constant,  amylase 
shows  greatest  activity  not  at  body  temperature  but  at  60°  C.  It 
would  be  anticipated  that  enzyme  activity  would  double  within 
a  limited  range  for  a  10°  rise  in  temperature,  as  is  postulated  in 
van  t  Hoffs  law. 


ENZYMES  OF  WOOD-DESTROYING  FUNGI  43 

Production  of  enzymes  by  fungi.  Scientific  interest  in  the 
production  of  enzymes  by  fungi  had  its  beginning  in  Pasteur's 
studies  of  the  cause  of  fermentation.  Of  course,  fermentation 
had  been  utilized  by  man  for  centuries  before  Pasteur's  time,  but 
no  adequate  explanation  of  the  process  had  been  offered.  Pasteur 
contended  that  fermentation  was  a  biological  process,  not  a 
mechanical  breakdown  of  the  sugar  molecule  as  Liebig  believed, 
and  that  it  required  the  presence  of  living  yeasts.  The  first  proof 
that  enzymes  produced  by  the  yeasts  induced  alcoholic  fermenta- 
tion was  offered  in  1897,  when  Buchner  extracted  a  fluid  from 
veast  cells  and  caused  sugars  to  be  fermented  wTith  this  fluid. 
Since  then  many  studies  of  the  enzymic  activities  of  fungi,  deal- 
ing either  with  the  enzyme-producing  ability  of  certain  species 
or  with  the  utilization  of  this  ability  in  the  production  of  end- 
products  of  commercial  importance,  have  been  made. 

Methods  for  detection  of  enzymes.  Two  general  methods 
have  been  employed  to  determine  the  production  of  enzymes: 
(a)  the  in  vitro  method,  in  which  some  portion  of  the  fungus  is 
extracted  in  water  and  the  enzyme  is  precipitated,  the  precipitate 
then  being  dried  to  an  "enzyme  powder";  and  (b)  the  in  vivo 
method,  in  which  the  fungus  is  cultivated  on  some  chosen  sub- 
strate and  in  which  utilization  or  nonutilization  of  the  substrate  can 
be  determined.  Each  method  possesses  advantages  and  disadvan- 
tages over  the  other,  and  various  modifications  have  been  instituted 
to  make  each  more  suitable  for  the  problem  in  hand.  In  general, 
the  in  vivo  method,  as  described  by  Crabill  and  Reed  (1915),  is 
open  to  less  valid  criticisms  than  the  in  vitro  method.  Among  the 
criticisms  levelled  against  the  in  vitro  method  are:  (a)  extraction 
diminishes  the  activity  of  enzymes;  (b)  the  proteases  may  decom- 
pose some  of  the  other  enzymes  present  in  the  extracted  fraction; 
and  (c)  certain  enzymes,  especially  intracellular  ones,  may  not  act 
outside  the  living  cell;  that  is,  the  enzymic  reactions  characteristic 
of  the  living  organism  cannot  be  duplicated  with  enzyme  extracts. 

Enzymes  of  wood-destroying  fungi.  A  brief  summary  of 
essential  knowledge  regarding  the  enzymes  produced  by  wood- 
destroying  fungi  has  been  prepared  by  Bose  (1939),  who  indicates 
that  Bourquelot  and  Herissey  (1895)  first  directed  attention  to 
this  problem  in  1895  in  connection  with  their  studies  of  Poly  poms 
sulphur eus.  In  1899  Czapek  (1899)  discovered  that  Merulius 
lacrymans  is  able  to  digest  lignin  by  virtue  of  an  enzyme  that  he 


44  ENZYMES  AND  ENZYM1C  ACTIVITIES  OF  FUNGI 

called  hadromase.  Since  then  a  series  of  studies  have  appeared 
that  form  a  basis  for  a  better  understanding  of  the  metabolism 
of  heartwood-rotting  and  sapwood-rotting  fungi. 

Cellulose  and  lignin  are  the  most  important  constituents  of 
wood.  Some  species  of  fungi  destroy  the  cellulose  portions  but 
are  quite  unable  to  utilize  the  lignin.  They  constitute  a  group 
called  the  ubro\vn-rot  group,"  typified  by  Poly  poms  scbweinitzii. 
Other  species,  which  attack  lignin  primarily  but  are  also  able  to 
decompose  cellulose,  constitute  the  "white-rot  group,"  typified 
by  Tonnes  pint  and  Stereum  frustulosum.  The  enzymic  activity 
of  the  brown-rot  group  is  regarded  as  mainly  hvdrolvtic;  of  the 
white-rot  group,  as  both  hydrolytic  and  oxidative. 

Although  this  grouping  may  be  of  value  to  the  forest  patholo- 
gist, it  should  be  "interpreted  to  mean  that  a  given  species  prefers 
either  cellulose  or  lignin  but  yet  may  be  able  to  use  both  com- 
ponents. Campbell  "(1929,  1932)  divided  the  white  rots  which 
he  studied  into  three  groups.  Some  attack  lignin  in  early  stages, 
and  among  them  the  incidence  of  attack  on  cellulose  is  delayed, 
as  occurs  with  Polystictus  versicolor.  In  another  group,  exempli- 
fied by  Armillaria  mellea,  cellulose  and  associated  pentosans  are 
first  attacked,  and  the  utilization  of  lignin  is  delayed.  In  the  last 
group  both  lignin  and  cellulose  are  utilized  in  varying  proportions, 
as  they  are  by  Ganoderma  applanatum,  Poly  poms  adustus,  P leu- 
rows  ostreatus,  and  Polystictus  abietimis. 

Bavendamm  (1928,  1928a)  devised  a  technique  to  determine  the 
ability  of  a  given  fungus  to  utilize  lignin.  He  prepared  agar  plates 
enriched  with  such  substances  as  tannic  acid,  pyrogallol,  hydro- 
quinone,  resorcinol,  guiacol,  phloroglucinol,  gallic  acid,  or  tyro- 
sine in  varying  concentrations.  On  these  media  he  planted 
Merulius  lacrymans,  Coniophora  cerebella,  Trametes  radiciperda, 
and  Stereiim  purpureum.  After  8  days'  growth  in  the  presence 
of  most  of  these  substances,  red-brown  to  dark-brown  zones  of 
discoloration  had  developed  in  advance  of  the  hyphal  tips  around 
colonies  of  T.  radiciperda  and  S.  purpureum.  The  production 
of  these  zones  was  ascribed  to  the  secretion  into  the  agar  of 
catechol-oxidative  enzymes  similar  to  those  that  cause  the  cut 
surface  of  an  apple  or  a  potato  to  brown.  These  species  use  lignin 
primarily  and  are  white  rots.  M.  lacrymans  and  C.  cerebella,  on 
the  other  hand,  did  not  develop  brown  pigment  and  hence  utilize 
cellulose  and  are  brown  rots. 


ENZYMES  OF  WOOD -DESTROYING  FUNGI  45 

Some  appreciation  of  the  scope  of  investigations  regarding 
enzymes  produced  by  wood-inhabiting  fungi  may  be  gained  from 
Table  5,  in  which  representative  findings  are  assembled.  The  list 
is  not  inclusive;  other  enzymes  have  been  demonstrated  for  some 
of  the  species  listed,  and  most  of  the  species  have  not  been  tested 
to  determine  whether  they  are  capable  of  producing  all  the  en- 
zymes mentioned.  The  most  prominent  feature  shown  by  this 
compilation  is  that  nearly  all  species  are  able  to  produce  amylase, 
catalase,  cellulase,  emulsin,  maltase,  and  sucrase. 

Whether  fungi  that  are  capable  of  producing  many  enzymes 
attack  a  wide  variety  of  woods,  whereas  those  with  restricted 
enzyme-producing  powers  are  limited  to  a  single  species  of  tree 
or  to  closely  related  species,  is  as  yet  unknown.  Studies  of  this 
kind  might  be  fruitful.  Woods  differ  in  nature,  as  is  well  known, 
in  the  amount  and  kind  of  nutrients  present,  aside  from  cellulose 
and  lignin,  and  also  in  their  content  of  toxic  substances.  The 
wood  of  angiosperms  is  notably  higher  in  pentosan  content  than 
is  coniferous  wood.  These  nutritional  factors  may  determine 
the  specificity  of  fungi  for  woods.  Evidence  on  this  point  has 
been  submitted  by  LaFuze  (1937).  In  cultures  he  found  that 
Polystictus  versicolor,  a  generalized  species,  was  able  to  oxidize 
tannin,  resorcinol,  quinol,  tyrosin,  and  guiacol,  whereas  Fomes 
pinicola,  a  specialized  species,  had  very  little  oxidizing  ability. 
Moreover,  P.  versicolor  showed  little  selective  ability  for  kinds  of 
nutrients,  but  F.  pinicola  was  sensitive  to  differences  in  carbohy- 
drates, growing  poorly  in  the  presence  of  pentoses,  galactose,  and 
sucrose.  In  regard  to  toxic  substances  in  woods,  he  suggests  that 
glucosides,  alkaloids,  resins,  oils,  terpenes,  and  phenolic  groups 
may  be  inhibitive  to  growth. 

The  complement  of  enzymes  produced  by  the  assimilatory  por- 
tion of  wood-attacking  fungi  may  be  different  from  that  in  the 
sporophores,  as  suggested  by  Nutman  (1929).  Evidence  in  sup- 
port of  this  contention  is  found  in  the  fact  that  hyphal  growth, 
so  far  as  is  known,  is  apical,  and  that  many  fungi  are  able  to  effect 
penetration  of  woody  tissues  not  by  way  of  the  bordered  pits  but 
by  making  boreholes.  Smith  (1923)  noted  apical  growth  in 
Rhizopus  nigricans,  Phytophthora  parasitica,  Rhizoctonia  solani, 
Botrytis  cinerea,  Pyronema  confliiens,  Aspergillus  niger,  and  Peni- 
cillium  expansum.     Boreholes  in  wood  were  noted  by  Hartig 


46 


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48  ENZYMES  AND  ENZYM1C  ACTIVITIES  OF  FUNGI 

and  other  early  workers  who  studied  the  pathological  effects  of 
wood-inhabiting  fungi. 

Enzymes  of  fungi  associated  with  decay  of  fruits  and  vege- 
tables. The  literature  dealing  with  the  decay  of  fruits  and  ve^e- 
tables  abounds  in  studies  on  the  enzymes  produced  by  the  causal 
fungi.  An  introduction  to  the  problems  involved  may  be  obtained 
by  consulting  the  publications  of  Reed  (1912),  Crabill  and  Reed 
(1915),  Harter  (1921),  Harter  and  Weimer  (1921,  1921a),  Funke 
(1922),  Muhleman  (1925),  Davison  and  Willaman  (1927),  and 
Menon  (1934).  In  soft  rots  of  fruits  and  vegetables,  caused  by 
species  of  Rhizopus,  Sclerotinia,  Botrytis,  and  Glomerella,  the 
middle  lamellae,  or  primary  host-cell  membranes,  are  attacked  by 
pectinase,  and  the  cells  tend  to  separate  intact.  These  organisms 
also  possess  carbohydrases,  by  means  of  which  they  are  able  to 
attack  starches  and  sugars  in  the  decay  of  root  and  stem  crops 
used  by  man  as  food. 

Since  soft-rot-producing  fungi  are  of  so  much  economic  im- 
portance, considerable  attention  has  been  devoted  to  their  enzymic 
activities.  Studies  by  Davison  and  Willaman  (1927)  involved  the 
pectic  enzymes  of  Botrytis  cinerea,  Rhizopus  tritici,  Sclerotinia 
cinerea,  Monilia  fructigena,  and  M.  oregonensis.  They  found,  as 
had  other  workers,  that  pectic  substances  are  complex  carbohy- 
drate derivatives  composed  of  three  types  of  materials:  ( 1 )  proto- 
pectin,  the  parent  pectic  material  which  is  water-insoluble  but 
which  yields  pectins  on  hydrolysis;  (2)  pectin,  the  water-soluble, 
methoxylated,  hydrolytic  product  derived  from  protopectin;  and 
(3)  pectic  acid,  the  water-insoluble,  methoxy-free,  hydrolytic 
product.  In  this  hydrolysis  three  enzymes,  protopectinase,  pec- 
tase,  and  pectinase  are  involved.  Protopectinase  attacks  the  pectic 
constituents  of  the  middle  lamella,  pectin  is  formed,  and  as  a  final 
result  the  plant  tissues  are  macerated.  Pectase  is  able  then  to  hy- 
drolyze  the  pectin  to  pectic  acid,  methyl  alcohol,  and  acetone,  re- 
sults which  show  that  pectin  is  an  ester  of  pectic  acid  and  that 
therefore  pectase  is  an  esterase.  Some  or  all  of  the  products  of 
hydrolysis  are  utilized  as  food  by  the  soft-rot-producing  species. 

Reed  (1912)  studied  the  enzymes,  other  than  pectic  enzymes, 
produced  by  another  soft-rot  fungus  of  apple,  Glomerella  rufor- 
maculans  and  noted  that  it  produced  amidase,  diastase,  emulsin, 
ereptase,  invertase,  lipase,  protease,  and  oxidase. 


OTHER  ENZYMIC  ACTIVITIES  49 

Other  exzymic  activities.  The  pathological  effects  induced 
by  disease-producing  fungi  might  be  understood  if,  in  such  cases, 
the  enzymic  potentialities  of  the  pathogen  were  known.  The 
production  of  "shot  hole"  on  Prunus  by  species  of  Coccomyces 
may  be  used  to  illustrate  and  clarify  this  point.  Higgins  (1914) 
found  that  amy^dalm,  stored  in  the  leaves  of  Prunus,  may  be 
utilized  by  species  of  Coccomyces  which  secrete  an  amvgdalin- 
cleaving  enzyme.  Glucose  resulting  from  cleavage  induces  in- 
creases in  osmotic  pressure  in  invaded  tissues.  In  consequence  the 
cells  become  swollen,  and  an  abscission  layer  is  formed  at  the 
periphery  of  the  invaded  tissues.  All  tissues  inside  the  abscission 
layer  eventually  collapse  and  fall  away,  and  the  leaves  then  have 
the  appearance  of  having  been  perforated  by  a  discharge  of  shot. 

Aspergillus  oryzae,  when  cultured  on  moist  sterilized  bran  for 
approximately  48  hours,  produces  sufficient  growth  so  that  the 
mycelium  may  be  macerated  and  extracted  in  water,  and  the 
enzymes  precipitated  and  concentrated.  This  extract,  wThich  is 
strongly  diastatic,  has  been  used  in  a  variety  of  ways.  In  the 
textile  industry  it  is  employed  in  the  treatment  of  cotton  fabrics 
before  mercerization,  bleaching,  and  preparation  for  printing. 

The  material  from  apple  pomace  or  from  the  peel  of  citrus 
fruit  that  is  to  become  commercial  pectin  is  turbid  when  ex- 
tracted and  must  be  clarified  by  enzymic  extract  from  A.  oryzae. 
Furthermore,  in  clarifying  syrups  and  fruit  juices  it  is  often 
necessary,  in  order  to  facilitate  filtration,  that  the  starch  be  re- 
moved by  the  addition  of  enzymes  prepared  from  this  same 
fungus. 

Diastase  from  A.  oryzae  and  A.  flavus  is  used  in  the  preparation 
of  soya  sauce  and  in  the  fermentation  of  rice  to  make  sake  and  is 
administered  as  a  therapeutic  agent  to  infants  and  invalids  who  ex- 
perience difficulty  in  digesting  starchy  foods.  It  is  also  used  in 
analytical  procedures  to  determine  the  amount  of  starch  present  in 
assays  of  organic  materials. 

The  desired  flavors  of  certain  cheeses,  particularly  Roquefort 
and  Camembert,  are  due  to  the  ability  of  certain  molds  to  decom- 
pose constituents  of  the  cheese.  FemciUhim  roquefortii,  for  ex- 
ample, hydrolyzes  the  butter  fats,  producing  thereby  such  aro- 
matic fatty  acids  as  butyric,  acetic,  capric,  and  caproic. 

Penicillium  brevicaule  is  among  the  molds  that  have  been  used 
in  the  detection  of  suspected  arsenical  poisoning.     When  grown 


SO  ENZYMES  AND  ENZYMIC  ACTIVITIES  OF  FUNGI 

in  a  test  tube  containing  a  sample  of  the  stomach  contents,  this 
fungus  possesses  the  ability  to  transform  metallic  arsenic  into  tri- 
methylarsine,  which  can  be  detected  by  its  pungent  odor,  remi- 
niscent of  garlic. 

The  enzymic  activity  of  fungi  is  involved  in  the  production  of 
a  variety  of  products,  including  alcohol,  organic  acids,  pigments, 
fats,  and  carbohydrates,  as  is  explained  in  Chapter  4.  From  the 
discussion  in  that  chapter  some  appreciation  can  be  gained  of  the 
influence  of  food  supply,  temperature,  reaction,  and  O^  tension 
on  the  enzyme-producing  abilities  of  fungi. 

Certain  cosmopolitan  molds,  such  as  Aspergilhts  niger,  Penicil- 
Ynmi  glaucinn,  and  Khizopns  nigricans,  are  omnivorous  by  virtue 
of  their  ability  to  produce  a  large  number  of  enzymes,  represent- 
ing each  of  the  groups:  carbohydrases,  proteases,  lipases,  oxidases, 
and  reductases. 

Humus  formation  is  associated  with  enzymic  activities,  as  is  evi- 
denced in  striking  manner  by  the  decomposition  of  litter  on  the 
forest  floor.  Many  species  of  soil-inhabiting  molds  are  capable 
of  transforming  the  cellulose  and  lignin  portions  that  are  rather 
resistant  to  decomposition.  The  activities  of  a  few  of  them,  not- 
ably species  of  Trichoderma,  Chaetomium,  and  Aspergillus,  have 
been  studied  in  considerable  detail.  A  comprehensive  idea  of 
these  activities  and  of  their  importance  in  the  economy  of  nature 
is  summarized  in  The  Microbiology  of  Cellulose,  Heviicelluloses, 
Pectins,  and  Gums  by  Thaysen  and  Bunker  (1927). 

General  considerations.  Although  much  has  been  learned 
about  the  ability  of  enzymes  from  fungi  to  effect  analyses  and 
svntheses,  further  knowledge  of  these  matters  should  be  sought. 
Problems  of  host-parasite  relationship,  of  host  specificity,  of  the 
synthesis  of  vitamins  by  fungi,  and  of  antagonistic  and  synergetic 
relationships  among  species  may  all  be  elucidated  when  more  is 
known  about  enzymes.  The  phenomenon  of  autodigestion  among 
fungi  invites  further  consideration.  Pleomorphism,  especially  the 
tendency  of  species  that  are  mycelioid  in  their  natural  habitat  to 
become  yeast-like  on  artificial  media,  or  vice  versa,  may  be  cor- 
related with  enzymic  activity.  Until  techniques  have  been  per- 
fected to  the  extent  that  it  is  possible  to  measure  the  activity  of 
small  groups  of  fungus  cells  or  even  of  single  cells  and  a  body  of 
pertinent  data  has  been  amassed,  material  progress  with  studies 
of  this  kind  may  be  impossible. 


LITERATURE  CITED  51 


LITERATURE  CITED 

Bavexdamm,  W.,  "Neue  Untersuchungen  iiber  die  Lebensbedingungen  holz- 
zerstorender  Pilze.  Ein  Beitrag  zur  Frage  der  Krankheitsempfanglichkeit 
unser  Holzpflanzen.  II.  Alitteilung:  Gerbstoffversuche,"  Zentr.  Bakt. 
Parasitejik.,  16:  172-227,  1928. 
"Uber  das  Vorkommen  und  den  Nachweis  von  Oxydasen  bei  holzzer- 
storenden  Pilzen,"  Z.  Pflanzenk.,  38:  257-276,  1928a.  ' 

Bayliss,  J.  S.,  "The  biology  of  Polystictus  versicolor  (Fr.),"  /.  Econ.  Biol., 
3:  1-24,  1908. 

Bose,  S.  R.,  "Enzymes  of  wood-rotting  fungi,"  Ergeb.  Enzymforsch.,  8:  267- 
276,  1939. 

Bose,  S.  R.,  axd  S.  N.  Sarkar,  "Enzymes  of  some  wood-rotting  polypores," 
Proc.  Roy.  Soc.  London,  B,  123:  193-213,  1937. 

Bourquelot,  E.,  axd  H.  Herissey,  "Les  ferments  solubles  du  Polyporus  sul- 
fureus  (Bull.),"  Bull.  soc.  my  col.  France,  77;  235-239,  1895. 

Buller,  A.  H.  R.,  "The  enzymes  of  Polyporus  squamosus  Huds.,"  Ann. 
Botany,  20:49-59,  1906. 

Calvery,  H.  O.,  R.  M.  Herriott,  axd  J.  L.  Northrop,  "The  determination 
of  some  amino  acids  in  crystalline  pepsin,"  /.  Biol.  Chem.,  273:11-14, 
1936. 

Campbell,  W.  G.,  "The  chemistry  of  white  rots  of  wood.  I.  The  effect 
on  wood  substance  of  Polystictus  versicolor  (Linn.)  Fr.,"  Biochem.  /., 
24:  1235-1243,  1929. 
III.  The  effects  on  wood  substances  of  Ganoderma  applanation  (Pers.) 
Pat.,  Tomes  jomentarius  (L.)  Fr.,  Pleurotus  ostreatus  (Jacq.)  Fr., 
Armillaria  mellea  (Vahl.)  Fr.,  Trametes  pini  (Brot.)  Fr.,  and  Polyporus 
abietinus  (Dicks.)  Fr.,"  Biochem.  J.,  26:  1829-1838,  1932. 

Crabill,  C.  H.,  axd  H.  S.  Reed,  "Convenient  methods  for  demonstrating  the 
biochemical  activity  of  microorganisms  with  special  reference  to  the 
production  and  activity  of  enzymes,"  Biochem.  Bull.,  4:  30-44,  1915. 

Czapek,  F.,  "tiber  die  sogenannten  Ligninreactionen  des  Holzes,"  Hoppe- 
Seylefs  Z.  physiol.  Chem.,  21:  141-166,  1899. 

Davisox,  F.  R.,  axd  J.  J.  Willamax,  "Biochemistry  of  plant  diseases.  IX. 
Pectic  enzymes,"  Botan.  Gaz.,  83:  329-361,  1927. 

Fuxke,  G.  L.,  "Researches  on  the  formation  of  diastase  by  Aspergillus  niger 
van  Tieghem,"  Rec.  trav.  botan.  neerland.,  19:219-275,  1922. 

Garrex,  K.  H.,  "Studies  on  Polyporus  abietinus.  I.  The  enzyme-producing 
ability  of  the  fungus,"  Phytopathology,  28:  839-845,  1938. 

Harter,  L.  L.,  "Amylase  of  Rhizopus  tritici,  with  a  consideration  of  its  se- 
cretion and  action,"  /.  Agr.  Research,  20:  761-786,  1921. 

Harter,  L.  L.,  axd  J.  L.  Weimer,  "Studies  on  the  physiology  of  parasitism 
with  special  reference  to  the  secretion  of  pectinase  by  Rhizopus  tritici" 
J.  Agr.  Research,  27:609-624,  1921. 
"A  comparison  of  the  pectinase  produced  by  different  species  of  Rhi- 
zopus," /.  Agr.  Research,  22:  371-377,  1921a. 


52  ENZYMES  AND  ENZYM1C  ACTIVITIES  OF  FUNGI 

Higgins,  B.  B."  "Contribution  to  the  life  history  and  physiology  of  Cylin- 

drosporium  on  stone  fruits,"  Am.  J.  Botany,  1:  145-173,  1914. 
LaFuze,    H.    H.,    "Nutritional    characteristics    of    certain   wood-destroying 

fungi,  Polyporus  betulinus  Fr.,  Fomes  pinicola  (Fr.)   Cooke,  and  Poly- 

stictus  versicolor  Fr.,"  Plant  Physiol.,  72:625-646,  1937. 
Lanphere,   W.    M.,   "Enzymes   in  the   rhizomorphs   of  Annillaria  viellea" 

Phytopathology,  24:  1244-1249,  1934. 
Mayo,  J.  K.,  "The  enzymes  of  Stereum  purpureum"  New  Phytol.,  24: 162- 

171,  1925. 
McDonald,  J.  A.,  "A  study  of  Polyporus  betulinus  (Bull.)  Fr.,"  Ann.  Ap- 
plied Biol,  2^:289-310,  1937. 
Menon,  K.  P.  V.,  "Studies  in  the  physiology  of  parasitism.    XIV.  Compari- 
son of  enzvmic  extracts  obtained  from  various  parasitic  fungi,"  Ann. 

Botany,  48:  187-209,  1934. 
Montgomery,  H.  B.  S.,  "A  study  of  Fomes  fraxineus  and  its  effects  on  ash 

wood,"  Ann.  Applied  Biol,  23:  465-486,  1936. 
Muhle.man,  G.  W.,  "The  pectinase  of  Sclerotinia  cinerea"  Botan.  Gaz., 

£0:325-330,  1925. 
Xord,  F.  F.,  and  R.  Weidenhagen,  Ergebnisse  der  Enzynrforschung,  Bd. 

I-VIII.    Leipzig,  1932-1939. 
Nord,  F.  F.,  and  C.  H.  Werkman,  Advances  in  enzymology  and  related 

subjects  of  biochemistry.    Vols.  I-V.    Interscience  Publishers,  Inc.,  New 

York.     1941-1945. 
Northrop,  J.  H.,  "The  chemistry  of  pepsin  and  trypsin,"  Biol  Rev.,  10:  263- 

282,  1935. 
Nutman,  F.  J.,  "Studies  of  wood-destroying  fungi.     I.  Polyporus  hispidus 

Fr.,"  Ann.  Applied  Biol,  75:40-64,  1929. 
Reed,  H.  S.,  "The  enzyme  activities  involved  in  certain  fruit  diseases,"  Ann. 

Kept.  Va.  Agr.  Expt.  Sta.,  1911-1912,  51-77,  1912. 
Schmitz,  H.,  "Enzvme  action  in  Echinodontium  tinctorium  E.  and  E.,"  /. 

Gen.  Physiol,  2:613-616,  1920. 
"Enzyme  action  in  Polyporus  volvatus  Pk.  and  Fomes  igniarius  (L.)  Gill.," 

/.  Gen.  Physiol,  3:795-800,  1921. 
"Studies  in  wood  decav.   V.  Physiological  specialization  in  Fomes  pinicola 

Fr.,"  Am.  J.  Botany',  12:  163-177,  1925. 
Schmitz,  H.,  and  S.  M.  Zeller,  "Studies  in  the  physiology  of  fungi.     IX. 

Enzvme  action  in  Annillaria  mellea  Vahl.,  Daedalea  confragosa  (Bolt.) 

Fr.,   and   Polyporus  lucidus    (Leys)    Fr.,"   Ann.   Mo.   Botan.   Garden, 

6:  193-200,  1919. 
Smith,   J.   Henderson,   "On   the   apical   growth   of   fungal   hyphae,"   Ann. 

Botany,  31:  341-343,  1923. 
Tauber,  H.,  Enzyme  chemistry.    John  Wiley  and  Sons.     1937. 
Thaysen,  A.  C,  and  H.  J.  Bunker,  The  microbiology  of  cellulose,  hemicel- 
htloses,   pectins,   and  gums,     vi  +  363    pp.     Oxford    University    Press, 
London.     1927. 
Waksman,  S.  A..   \\i)  W.  C.  Davison,  Enzymes,     xii  +  364  pp.     Williams 

and  Wilkins  Co.     1926. 
Zeller,  S.  M.,  "Studies  in  the  physiology  of  fungi.    II.  Lenzites  saepiaria  Fr. 
with  special  reference  to  enzyme  activity,"  Ann.  Mo.  Botan.  Garden, 
3:439-512,  1916. 


Chapter  3 

RESPIRATION 

Present-day  concepts  of  the  process  of  respiration  in  plants 
come  largely  from  studies  with  green  plants  rather  than  chloro- 
phyll-less ones.  It  would  appear  that  respiration  among  fungi 
is  worthy  of  more  extended  study  than  it  has  been  accorded  in 
the  past  and  that  much  of  value  should  result  from  a  better  under- 
standing of  this  subject.  Just  as  in  green  plants,  respiration  is 
manifested  by  the  disappearance  of  food  substances  within  the 
cells  with  resultant  liberation  of  energy,  by  the  absorption  of 
oxygen,  and  by  the  excretion  of  carbon  dioxide.  Many  other 
products  besides  carbon  dioxide  are  excreted  by  funei.  Quite  a 
goodly  number  of  these  products  are  of  economic  importance, 
and  in  consequence  fungi  have  been  utilized  industrially.  This 
matter  will  be  given  special  consideration  in  Chapter  4,  which 
deals  with  the  biochemistry  of  fungi. 

HISTORICAL  MATERIAL 

Aluch  information  of  value  concerning  the  respiration  of  fungri 
has  come  from  the  gradual  acquisition  of  knowledge  regarding  the 
respiratory  process  commonly  known  as  fermentation.  This  phe- 
nomenon was  undoubtedly  known  to  the  ancients  lone  before  the 
days  of  written  records.  Although  no  attempt  will  be  made  to 
give  an  elaborate  historical  summary  of  the  growth  of  information 
concerning  fermentation,  a  few  of  the  prominent  landmarks 
should  be  indicated  in  order  that  the  complex  nature  of  this  bio- 
logical process  may  be  better  understood.  Among  the  early 
workers  who  contributed  to  scientific  knowledge  of  fermentation 
was  Fabbroni  (1787),  from  studies  of  wine  making.  He  believed 
that  the  sugar  was  decomposed  by  material  of  a  glutenous  vege- 
table-animal nature  that  was  contained  within  the  grapes.  When 
the  grapes  were  crushed,  the  glutenous  material  was  free  to  in- 
duce fermentation.    He  showed  that  air  was  not  essential  to  the 

53 


54  RESPIRATION 

process  and  regarded  alcohol  neither  as  a  constituent  of  the 
grapes  nor  as  a  product  of  fermentation.  Instead  he  considered 
it  to  arise  by  the  reciprocal  action  of  the  sugar  and  the  glutenous 
material. 

The  chemical  studies  of  Lavoisier  (1789)  on  fermentation  led 
him  to  conclude  that  sugar  was  merely  separated  into  two  constit- 
uents, carbon  dioxide  and  alcohol,  and  that  if  the  two  were  re- 
united, sugar  would  be  reconstructed.  He  thought  that  one  con- 
stituent was  oxygenated  at  the  expense  of  the  other,  that  the  oxy- 
genated portion  became  carbon  dioxide,  and  that  the  deoxy- 
genated  portion  became  alcohol. 

Thenard  (1802-1803)  made  the  interesting  observation  that  a 
deposit  resembling  yeast  occurred  during  fermentation  of  the 
juice  of  gooseberries,  cherries,  apples,  or  other  fruits.  When  this 
deposit  was  mixed  with  fresh  juice,  fermentation  was  started.  He 
was  unable  to  determine  whether  this  deposit  came  into  existence 
from  a  soluble  state  or  whether  it  Mas  a  product  of  fermentation. 

In  1838  the  classical  work  of  Cagniard-Latour  (1838),  in  which 
he  described  his  microscopic  studies  of  yeast,  appeared.  He  stated 
that  the  globules  which  he  found  in  wine  and  beer  constituted 
the  yeast  and  belonged  to  the  vegetable  kingdom.  He  correctly 
described  their  propagation  by  budding,  the  buds  at  first  being 
small  and  attached  to  the  mother  cell. 

While  Cagniard-Latour  was  making  his  discoveries,  Schwann 
(1837)  examined  the  deposit  in  beer  and  in  grape  juice  and  came 
to  the  conclusion  that  this  deposit  was  yeast  and  that  yeast  was  a 
fungus.  He  clearly  established  the  relationship  of  yeast  to  fer- 
mentation  by  the  following  phenomena:  (a)  the  constancy  of 
occurrence  of  yeasts  during  fermentation,  and  (b)  the  checking 
of  fermentation  by  heat,  chemicals,  or  other  agencies  that  destroy 
living  organisms.  According  to  him,  alcohol  was  a  waste  product 
left  as  the  yeast  drew  its  food  from  the  sugary  solution.  Schwann 
must  properly  be  credited  with  founding  the  germ  theory  or 
biological  theory  of  fermentation. 

.Meanwhile  the  chemical  theory  of  fermentation  had  its  adher- 
ents in  such  capable  chemists  as  Berzelius  and  Liebig.  They  held 
up  to  contemptuous  ridicule  the  work  of  Cagniard-Latour, 
Schwann,  and  all  others,  notably  Kiitzing,  who  believed  that 
veasts   produce   fermentation.     Liebig   and   his   pupils    [Bulloch 


HISTORICAL  MATERIAL  55 

(1938)]  in  1839  anonymously  published  a  skit  in  which  the  yeast 
globules  were  caricatured  as  blind,  toothless  animalcules  with 
bristly  suctorial  snouts  and  enormously  developed  genitalia. 
These  animalcules  devoured  sugar,  whereupon  alcohol  was  voided 
from  the  anus  and  carbon  dioxide  bubbled  from  the  genital  or- 
gans. If  certain  alkaloids  were  present  in  the  sugar  solution,  the 
animalcules  were  capable  of  emesis,  and  the  vomitus  contained 
fusel  oil.  Liebig  (1839)  also  published  a  technical  treatise  in 
which  he  set  forth  his  views  on  the  whole  matter  of  decomposi- 
tion. He  vigorously  maintained  these  views  for  thirty  or  more 
years.  In  his  opinion  all  decompositions  were  brought  about  by 
chemical  instability  of  a  ferment.  The  ferment  itself  wras  not  an 
actual  chemical  substance,  but  a  nitrogen-containing  carrier  of 
activity  or  inciter  of  decompositions  that  could  transmit  its  in- 
stability to  other  substances.  In  short,  according  to  Liebig,  yeasts 
were  nitrogen-containing,  but  fermentation  was  not  concerned 
with  the  life  activities  of  the  yeast  itself.  Instead  the  yeast  was 
produced  from  the  gluten. 

The  name  of  Blondeau  [Bulloch  ( 1938)  ]  is  also  worthy  of  men- 
tion, since  his  contributions  did  much  to  lay  secure  foundations 
for  Pasteur's  researches  on  fermentation.  Blondeau  made  a  study 
in  1847  of  lactic,  butyric,  and  acetic  fermentations  and  the  decom- 
position of  urea  and  concluded  that  the  different  types  were  in- 
cited by  different  fungi,  notably  Torula  cerevisiae,  Penicillium 
glaucum,  P.  globosum,  and  Mycoderma  vim. 

Finally  came  Pasteur's  epoch-making  series  of  researches,  in 
which  he  proved  that  the  activity  of  living  yeast  is  absolutely 
essential  to  fermentation,  that  alcohol  and  carbon  dioxide  are  by- 
products of  the  respiration  of  yeast,  and  that  sugar  can  be  fer- 
mented in  the  entire  absence  of  atmospheric  oxygen.  This  last 
fact,  it  should  be  recalled,  had  been  established  by  Fabbroni  in 
1787.  Pasteur  studied  not  only  alcoholic  fermentation  but  also 
lactic,  tartaric,  and  acetic  fermentations.  His  zeal  as  a  scientific 
crusader  and  his  professional  acumen  and  forcefulness  are  evident 
in  certain  memoires,  notably  those  dealing  with  his  findings  on 
lactic  and  alcoholic  fermentations  [Pasteur  (1857,  1858,  I860)]. 
That  the  enzyme  of  yeast  can  act  in  the  absence  of  living  cells 
was  first  established  by  Buchner,  in  1897,  nearly  two  years  after 
Pasteur's  death. 


56  RESPIRATION 

TYPES  OF  RESPIRATION 

Ordinarily  respiration  is  arbitrarily  divided  into  two  types, 
aerobic  and  anaerobic.  Aerobic  respiration  occurs  in  the  pres- 
ence of  atmospheric  oxygen.  Anaerobic  respiration,  on  the  other 
hand,  occurs  in  the  absence  of  a  supply  of  atmospheric  oxygen 
and  proceeds  at  the  expense  of  the  oxygen  that  is  combined  in  the 
substance  being  respired.  Presumably  aerobic  respiration  is  of 
most  common  occurrence  among  fungi,  but  many  species  possess 
the  ability  to  respire  either  aerobically  or  anaerobically  and  are 
spoken  of  as  facultative  anaerobes.  Few,  if  any,  species  are  known 
to  be  strict  anaerobes.  The  facultative  anaerobes,  because  of  the 
products  of  their  respiration,  for  example,  alcohol,  acetic  acid,  and 
lactic  acid,  are  of  most  interest  and  importance  to  man. 

Aerobic  respiration.  The  most  important  reason  that  can  be 
given  for  elaborating  upon  aerobic  respiration  in  this  volume  is 
that  such  a  discussion  may  help  to  clarify  certain  misunderstand- 
ings of  this  process  that  are  all  too  commonly  prevalent  and  that 
are  sometimes  transmitted  from  teacher  to  student. 

In  the  first  place  fungi,  in  common  with  all  other  living  things, 
release  energy  for  their  own  metabolic  activities  during  the  proc- 
ess  of  respiration.  In  the  oxidation  of  glucose  such  aerobic  release 
is  conventionally  expressed  as  follows: 

C6H1206  +  602  =  6C02  +  6H20  +  673  Cal 

This  equation,  the  precise  reverse  of  the  reaction  for  photosynthe- 
sis, is  correct  only  in  so  far  as  it  expresses  the  energy  relations 
and  the  final  products.  It  merely  indicates  that  the  complete  oxi- 
dation of  1  molecule  of  glucose  requires  6  molecules  of  oxygen 
and  that,  while  6  molecules  of  carbon  dioxide  and  6  molecules  of 
water  are  formed,  673  calories  of  energy  are  released.  Such  an 
equation  leaves  the  erroneous  impression  that  at  one  instant  glu- 
cose is  present  and  at  another,  by  some  miracle,  the  sugar  has  be- 
come carbon  dioxide,  water,  and  liberated  energy.  As  a  matter 
of  fact,  the  process  is  a  complicated  one,  and  intermediate  prod- 
ucts are  formed.  For  this  reason  it  is  indefensible  to  indicate  aero- 
bic respiration  as  occurring  in  accordance  with  the  foregoing 
equation. 

Anaerobic  respiration.  Consideration  will  be  given  subse- 
quently to  some  of  the  kinds  of  anaerobic  respiration,  products 


TYPES  OF  RESPIRATION  57 

formed  being  used  as  the  basis  of  classification.  Anaerobic  respi- 
ration of  glucose  of  the  alcoholic  type  is  conventionally  expressed 
as  follows: 

C6H1206  =  2C02  +  2C2H5OH  +  25  Cal 

Alcohol 

Here  again,  end  results  alone  are  indicated,  and  no  essential  in- 
formation of  the  steps  and  mechanisms  involved  is  conveyed. 
Moreover,  this  equation  shows  that  only  a  portion  of  the  potential 
energy  of  the  glucose  molecule  has  been  released,  yet  in  this  re- 
spect it  typifies  the  energy-release  relationships  of  all  other 
anaerobically  respired  compounds. 

Interrelations  between  aerobic  and  anaerobic  respiration. 
It  seems  best  at  this  juncture  to  indicate  the  existence  of  evidence 
to  show  that  aerobic  and  anaerobic  respiratory  processes  are  inter- 
related and  that  both  may  be  presumed  to  occur  not  only  amono- 
fungi  but  also  among  green  plants.  Once  this  interrelationship  is 
appreciated,  it  will  be  possible  to  return  to  the  essential  steps  in  the 
process.  Kostytchew  (1927)  has  schematically  represented  the 
relationship  in  the  following  manner: 

2C02  +  2C2H5OH  +  25  Cal 

/ 
Zymase 
Intermediate  prod-    7*  T     , 
C6Hi206  +  Zymase  -»  ucts   of   anaerobic  X     ]n  absence  of  °2 

respiration  \  In  presence  of  °2 

+  602 

Xj    Oxidizing-reducing  enzymes 

6C02  +  6H2O  +  673  Cal 

In  this  scheme  the  zymase  complex  (long  believed  to  be  a  single 
enzyme  but  now  known  to  consist  of  glycolase,  which  converts 
hexoses  into  methylglyoxal,  carboxylase,  which  splits  out  carbon 
dioxide  from  certain  organic  acids,  and  in  addition  certain  co- 
enzymes) is  supposed  to  convert  the  hexose  into  labile  inter- 
mediate products  as  a  first  step  in  both  aerobic  and  anaerobic 
respiration.  This  change  is  an  anaerobic  one  in  either  case,  as 
Kostytchew's  scheme  shows.  Whether  or  not  atmospheric  oxy- 
gen is  available  determines  the  next  step  and  also  the  course  of 
the  subsequent  respiratory  reactions. 

To  support  Kostytchew's  theory  of  the  course  and  sequence 
of  events  in  respiration,  the  following  facts  have  been  marshalled: 


58  RESPIRATION 

1.  Green  plants,  and  unquestionably  certain  fungi  also,  if  de- 
prived of  oxygen,  respire  anaerobicallv. 

2.  Glucose  and  the  enzyme  complex,  zymase,  are  universally 
present  in  plant  cells. 

3.  Acetaldehyde  as  an  intermediate  product  in  the  anaerobic 
respiration  of  glucose  has  been  detected  in  plant  tissues. 

4.  Alcohol,  an  anaerobic  respiratory  product,  has  been  found 
in  higher  plants  and  in  certain  fungi.  Kostytchew  (1908)  found 
that  Agaricus  cavipestris  formed  alcohol  if  the  mycelium  was  sub- 
merged, even  in  media  lacking  sugar.  On  the  other  hand,  Asper- 
gillus niger,  grown  in  similar  media,  failed  to  produce  alcohol. 

.Mechanism  of  aerobic  respiration.  The  mechanism  of  aero- 
bic respiration  among  fungi  has  been  presumed  to  be  like  that 
among  green  plants,  and  in  neither  group  of  plants  have  the  de- 
tails been  fully  substantiated.  Palladin  (1909)  long  ago  postu- 
lated a  theory  whose  general  plan  outlined  the  mechanism  as 
follows: 

Intermediate 
CeH1206  +  Zymase  — >  anaerobic         +  6H20  +  12A 

products  •  Hydrogen  acceptor,  i.e., 

respiratory  pigments, 
cytochrome  in  fungi 

+  Dehydrogenase  -*  6C02  +      12AH2 

Reduced  acceptor 

Then 

12AH2  +  02  +  Oxidase  -►  12A  +  12H20 

This  plan  means,  if  elucidated,  that  after  the  intermediate  an- 
aerobic products  are  formed,  they  are  oxidized  by  the  active  oxv- 
gen  that  comes  from  the  water  molecules,  and  the  freed  hydrogen 
combines  with  the  respiratory  pigments.  As  a  next  step,  the 
respiratory  pigments  in  the  presence  of  oxidase  again  acquire  oxy- 
gen, but  they  take  it  from  the  atmospheric  oxygen.  In  this  proc- 
ess the  sugar  is  completely  oxidized,  and  the  ratio  of  the  volume 
of  CO;,  released  to  the  volume  of  Ol.  utilized  is  unity. 

.Mechanism  of  an  akrobic  respiration  (alcoholic  fermenta- 
tion). Two  theories  have  been  propounded  to  explain  the  mech- 
anism of  alcoholic  fermentation.  One  of  these,  called  the  pyruvic 
acid  theory,  has  been  elaborated  by  Xeuber^  and  his  associates 
[Xeuberg  (1922),  Neuberg  and  Gottschalk  (1924)];  and  the 
other,  commonly  called  the  sugar-phosphate  or  the  Harden  theory 
[Harden  (1932)],  by  .Meyerhof  and  Kiessling  (1935). 


TYPES  OF  RESPIRATION  59 

According  to  the  pyruvic  acid  theory,  the  following  steps  occur 
sequentially: 

a.  The  hexose  molecules  become  "activated";  that  is,  highly 
reactive  y-glucose  or  y-fructose  comes  into  transitory  existence. 
These  sugars  are  not  straight  carbon-chain  complexes,  being  best 
represented  by  a  ring  type  of  formula. 

b.  The  "activated"  y-hexose  is  cleaved  by  glycolase  into  two 
molecules  of  methylglyoxal  and  two  of  water,  formally  expressed 
as: 

C6H1206  +  Glycolase  -*  2(CH3COCHO)  +  2H20 

Methylglyoxal 

c.  As  the  next  step,  one  molecule  of  methylglyoxal  is  reduced 
to  glycerol,  and  the  other  is  oxidized,  by  a  Cannizzaro  reaction,  to 
pyruvic  acid  with  the  two  molecules  of  water.  A  dehydrogenase 
may  catalyze  this  reaction: 

CH3  •  CO  •  CHO  CH2OH  ■  CHOH  •  CH2OH 

+  H2   +  HoO  Glycerol 

+  II  ^  + 

o 
CH3COCHO  •  CH3COCOOH 

Pyruvic  acid 

d.  Immediately  carboxylase  splits  the  pyruvic  acid  into  acetalde- 
hyde  and  carbon  dioxide,  as  follows: 

CH3COCOOH  +  Carboxylase  ->  CH3CHO  +  C02 

Pyruvic  acid  Acetaldehyde 

The  course  of  events  is  identical  up  to  this  point,  as  has  been 
stated,  whether  the  process  is  aerobic  or  anaerobic. 

e.  If  then  anaerobic  conditions  prevail,  the  other  molecule  of 
methylglyoxal  produced  in  step  b  reacts  with  the  acetaldehyde 
molecule  in  step  d,  and  by  a  Cannizzaro  reaction  a  molecule  of 
pyruvic  acid  and  one  of  alcohol  are  formed  in  this  manner: 

CH3COCHO  ">     CH3COCOOH 

Methylglyoxal  O  Pyruvic  acid 

+  +  I!   -  + 

H2 
CH3CHO  CH3CH2OH 

Acetaldehyde  Ethyl  alcohol 

It  is  of  interest  to  note  that  no  energy  is  released  in  the  trans- 
formations that  result  in  the  formation  of  methylglyoxal,  glycerol, 
and  pyruvic  acid. 


60 


RESPIRATION 


If  the  fermentation  is  produced  bv  Saccharomy ces  cerevisiae 
and  sodium  sulphite  is  added  to  the  culture  solution,  the  acetalde- 
hvde  is  fixed,  and  its  presence  can  be  demonstrated.  With  the 
addition  of  a  high  percentage  of  sodium  sulphite,  glycerine  is 
produced  from  the  acetaldehyde,  and  the  reactions  will  yield 
acetic  acid  and  alcohol  also. 

By  the  sulphite  process  as  much  as  37%  of  the  sugar  fermented 
by  the  yeast  may  be  transformed  into  glycerol.  This  fact  is  of 
enormous  interest  and  at  the  same  time  of  great  importance  when 
it  is  recalled  that  in  ordinary  alcoholic  fermentation  the  yield  of 
glycerol  is  less  than  3%.  The  sulphite  modifies  reduction  of 
acetaldehyde  by  hydrogen,  and  hydrogen  can  thus  act  directly 
to  reduce  the  intermediate  compound,  glyceric  aldehyde,  forming 
glycerol. 

These  chemical  changes  may  be  shown  briefly  as  follows: 


C6H1206 

Glucose 


CH2OH 

CHOH 

CHO 

Glyceric 
aldehyde 


CH3 

i 

c=o 

CHO 

Methyl- 

glyoxal 


OH 


CH3 

CH3 

CH3 

c=o    - 

+  c=o  - 

->CHO 

Acetal- 

C—H 

COOH 

dehyde 

/   \ 

OH 

Pyruvic 
acid 

+ 

Methyl- 
glyoxal 

hydrate 

+ 

H2 

co2 

If  sulphite  is  added,  it  may  unite  with  the  acetaldehyde: 
CH3  CH3 

CHO  +  Na2S03  +  H20  +  C02  ->  C— H  +  NaHC03 

l\ 
HO     SOoONa 


In  this  event  the  hydrogen  is  prevented  from  reducing  the 
:etaldehyde  to  alcohol;  instep 
hvde  directly  in  this  manner: 


acetaldehyde  to  alcohol;  instead  it  can  react  with  the  glyceric  alde- 


CH2OH  CH2OH 

CHOH  +  H2  ->  CHOH 


CHO 

Glyceric 
aldehyde 


CH2OH 

Glycerol 


TYPES  OF  RESPIRATION  61 

The  complexity  of  the  respiratory  reactions,  as  they  have  just 
been  presented,  indicates  only  a  portion  of  the  misconception  that  is 
conveyed  by  the  formal  expression  for  fermentation:  C6Hi2Oe  -» 
2C2Hr,OH  +  2COL».  This  point  is  further  emphasized  by  the 
following  data  of  Rubner  [Lutman  (1929)1  on  the  products  of 
fermentation  by  yeast  of  100  grams  of  sucrose  and  the  caloric 
value  of  the  products  formed: 

Kg-cal  Value 

51.1  grams  alcohol  358.36 
3.4  grams  glycerin  14.38 
0.65  grams  succinic  acid  1.99 
1.3    grams  miscellaneous  products                                 5.15 

49.2  grams  carbon  dioxide  0.00 


Total  Kg-cal  value  379.88 

Kg-cal  value,  100  grams  sucrose  396.80 

Energy  released,  Kg-cal  16.92 

According  to  the  sugar-phosphate  theory,  some  phosphate, 
such  as  that  of  sodium  or  potassium,  is  necessary  in  alcoholic 
fermentation.  The  phosphate  reacts  with  the  hexose  to  give  a 
diphosphoric  acid  ester.  Apparently  the  phosphate  is  not  a  co- 
enzyme to  make  possible  the  working  of  zymase,  but  it  acts  as  a 
catalytic  agent.  The  formation  of  the  diphosphoric  acid  ester  is 
accompanied  pari  passu  by  a  second  reaction  that  again  liberates 
the  phosphate  and  the  hexose.  These  reactions  may  be  expressed 
as  follows: 

a.  2C6H1206  +  2R2HP04  +  Zymase  -> 

Hexose  Phosphate 

2C02  +  2C2H5OH  +  2H20  +  C6H10O4(PO4R2)2 

Alcohol  Glucose  di- 

phosphate 

b.  C6H10O4(PO4R2)2  +  H20  ->  C6H1206  +  2R2HP04 

According  to  Meyerhof  and  Kiessling  (1935),  the  hexose  and 
phosphate  react  to  form  both  glucose  monophosphate  and  glu- 
cose diphosphate.  Then  by  oxidation-reduction  the  monophos- 
phate becomes  a  molecule  of  glyceric  aldehyde  phosphoric  ester 
and  one  of  glyceric  aldehyde,  and  the  glucose  becomes  two  mole- 
cules of  glyceric  aldehyde  phosphoric  ester.  As  a  next  step,  the 
glyceric  aldehyde  phosphoric  esters  are  hydrolyzed  to  glyceric 
aldehyde,  and  phosphate  is  again  freed.    The  glyceric  aldehyde 


62  RESPIRATION 

then  may  be  oxidized  to  methylglyoxal,  to  be  in  turn  transformed 
sequentially  into  pyruvic  acid,  acetaldehyde,  and,  as  a  final  prod- 
uct, alcohol.  The  decarboxylation  of  pyruvic  acid  yields  the 
carbon  dioxide  evolved  in  the  process. 

THE  RESPIRATORY  RATIO 

As  is  well  known  and  has  been  stated  previously,  the  complete 
respiration  of  hexose  yields  a  respiratory  ratio  of  unity.  Fungi, 
however,  respire  not  only  hexoses  but  also  various  fats  and  organic 
acids.  When  such  substances  are  oxidized  in  the  respiratory 
process,  it  may  be  anticipated  that  the  ratio  of  02  consumed  to 
C02  released  will  differ  from  that  shown  by  the  respiration  of 
hexoses.  The  anaerobic  respiration  of  oxalic  acid,  for  example, 
should  yield  a  ratio  of  4,  as  is  indicated  by  the  reaction 
2(COOH)  +  02  ->  4CO,  +  2H20  +  60.2  Cal.  Again,  it  should 
be  anticipated  that  the  ratio  will  be  small  if  substances  poor  in 
oxygen  are  respired  completely,  as  appears  from  the  reaction 
involving  the  fat  tripalmitin: 

C5iH9806  +  72.502  ->  51C02  +  49H20  +  7590  Cal 

In  this  case  the  ratio  is  5lC02/72.502,  or  0.7. 

Richter's  experiments  with  fermentation  by  yeast  (1902)  show 
that  factors  other  than  the  character  of  the  substrate  enter  into 
the  problem  of  the  respiratory  ratio.  He  grew  the  organism 
in  large,  flat-bottomed,  hermetically  sealed  flasks  containing  50  ml 
of  nutrient  salt  solution,  consisting  of  K2HP04,  xMgS04,  and  a 
trace  of  Fe.  To  this  solution  he  added  varying  amounts  of  sucrose 
and  peptone.  In  those  to  which  he  added  0.15  gram  sucrose  and 
0.25  gram  peptone,  the  C02/02  ratio  after  24  hours  was  4.26; 
after  48  hours,  2.25.  In  those  to  which  he  added  0.3  gram  sucrose 
and  0.5  gram  peptone,  the  C02/02  ratio  after  24  hours  was  8.32; 
after  48  hours,  6.16.  In  those  to  which  he  added  0.75  gram  sucrose 
and  1.25  grams  peptone,  the  CCX,  02  ratio  after  24  hours  was 
11.16;  after  48  hours,  27.46.  From  these  experiments  he  concluded 
that  yeast  utilizes  sugar  in  preference  to  peptone  as  a  source  of 
energy,  but  that  the  concentration  of  food  in  the  substrate  be- 
comes an  important  factor  in  modifying  both  the  respiratory 
ratio  and  the  rate  of  respiration. 


RESPIRATORY  SYSTEMS  63 

Manifestly  temperature  is  also  a  controlling  factor  in  respira- 
tion, just  as  in  almost  all  other  biological  reactions.  The  time 
factor,  which  is  correlated  with  temperature,  must  also  be  meas- 
ured, as  is  indicated  by  Richter's  experiments.  The  temperature 
effect,  apart  from  time,  is  strikingly  shown  in  the  classical  experi- 
ments of  Muller-Thurgau  [Lutman  (1929)],  involving  Saccharo- 
myces  cerevisiae,  in  which  all  other  conditions  were  identical  and 
fermentation  was  permitted  to  proceed  until  the  maximum 
amount  of  alcohol  had  been  Droduced.  These  experiments  yielded 
the  following  results: 


Constant 

Maximum  Alcohol 

emperature 

Content  by  Weight 

36°  C 

3.8% 

27°  C 

7.5% 

18°C 

8.8% 

9°C 

9-5% 

RESPIRATORY  SYSTEMS 

The  general  subject  of  respiratory  enzymes  is  summarized  in 
an  extensive  compendium,  Ergebnisse  der  Enzymforschimg  by 
Nord  and  Weidenhagen  (1932-1939).  It  need  only  be  stated 
here  that  the  main  respiratory  system  in  plant  and  animal  cells 
is  composed  of  the  following:  Dehydrogenase— Substrate— Cyto- 
chrome—Oxidase— Oxygen.  Not  only  yeasts  but  also  many,  and 
presumably  all,  fungi  that  live  aerobically  contain  cytochrome. 

There  is  evidence  that  some  other  system  operates  in  certain 
anaerobic  organisms.  One  of  these  systems  is  due  to  the  presence 
of  glutathione,  which  can  function  as  an  oxidation-reduction  sys- 
tem.   In  the  oxidized  state  it  would  appear  thus: 

COOH  COOH 

CHNH2  ^        CHNH2 

CH2  CH2 

CH2     COOH  COOH   CH2 

CO— NH— C— H  H— C— NH— CO 


CH2 — S — S — CH2 

Glutathione  (oxidized) 


64  RESPIRATION 

In  the  reduced  form  two  molecules  of  glutathione  give  up  the  hy- 
drogen of  the  sulphhvdrvl  groups  thus: 

COOH  COOH 


CHXH2  CHXH2 

CH2  CH2 

CH2  COOH  CH2 

CO— XH— C— H  +        H— C— XH— CO 

CH2— S— |H     HI— S— CH2 


Glutathione  (reduced) 


These  observations  indicate  that  the  presence  or  absence  of  free 
oxygen  conditions  the  respiratorv  svstems  in  even  the  same  species. 

RESPIROMETRY 

In  recent  vears  use  has  been  made  of  respirometers  of  a  type 
called  the  Warburg  apparatus  and  of  its  several  modifications, 
which  are  especially  adapted  for  use  with  germinating  seeds,  bits 
of  tissue  of  special  organs,  blood  cells,  and  bacteria.  To  date, 
however,  all  too  little  use  of  such  apparatus  has  been  made  in  the 
study  of  respiration  in  fungi. 

One  such  study,  indicating  the  usefulness  of  this  procedure,  was 
made  by  Wolf  and  Shoup  (1943).  They  employed  a  Fenn 
respirometer  to  test  the  ability  of  species  of  the  water  mold,  Al- 
lomvces,  to  utilize  certain  carbohvdrates  and  organic  nitrogen 
compounds.  After  a  period  of  starvation  to  remove  the  reserve 
foods  the  several  species  were  given  various  compounds  singly 
with  the  following  results: 


TABLE 

6 

Utilization 

of  Organic 

Compounds  bv 

Species  of 

Allomyces 

.45- 

As- 

Glu- 

Argi- 

Dex- 

Suc- 

Malt- 

Pep- 

Ala- 

parlic 

para- 

tamic 

Cys- 

ninc- 

Organism 

trin 

crose 

ose 

tone 

nine 

A  cid 

gine 

A  cid 

tine 

IJCl 

.1 

arbuscula 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

,1 

j<i:  aniens 

+ 

— 

— 

+ 

— 

+ 

— 

+ 

+ 

+ 

.1 

moniliformis 

+ 

— 

— 

+ 

+ 

+ 

— 

+ 

— 

— 

A 

cystogenus 

+ 

— 

— 

+ 

+ 

+ 

— 

+ 

— 

— 

INHIBITION  OF  RESPIRATION  65 

It  may  be  indicated,  in  addition,  that  no  species  was  able  to  use 
mannitol,  if-arabinose,  /-arabinose,  glucose,  levulose,  galactose,  lac- 
tose, soluble  starch,  cellobiose,  glycine,  or  tyrosine. 


Fig.  3.  A  Fenn  microrespirometer,  having  identical  glass  vessels  of  15-ml 
capacity.  A  closed  system  is  formed  when  the  stopcocks  are  shut  off.  There 
are  KOH  wells  for  the  absorption  of  C02  in  each  vessel.  The  fungus  to  be 
tested  is  placed  in  a  buffered  nutrient  in  one  vessel  and  buffered  solution 
alone  in  the  other.  The  rate  of  movement  of  a.  droplet  of  kerosene  in 
capillary    toward    the    vessel    with    the    fungus    indicates    the    rate    of    O2 

consumption. 

INHIBITION  OF  RESPIRATION 

Much  information  has  been  acquired  concerning  the  influence 
of  cyanides  and  carbon  monoxide  on  the  respiration  of  animal 
cells  and  bacteria.  Little  consideration,  however,  has  been  ac- 
corded the  influence  of  these  inhibitors  on  the  respiration  of  fungi. 
Such  studies,  for  some  reason,  seem  to  have  been  made  quite  in- 
cidentally. In  a  report  by  Tamiya  (1942)  the  observation  was 
made  that  the  respiratory  rate  of  Aspergillus  oryzae  is  decreased 
26%  in  an  atmosphere  consisting  of  95%  CO  and  5%  02.  He 
also  noted  that  in  liquid  media  submerged  hyphae  of  this  fungus 
are  much  more  sensitive  to  cyanide  than  are  aerial  hyphae,  as  is 
shown  in  Table  7. 


66  RESPIRATION 

TABLE  7 
Inhibition  of  Hvphae  of  Aspergillus  oryzae  by  Cyanide 

Concentration  of  Cyanide 


Hyphae 

0.001  M 

0.002  M 

0.01  M 

Aerial 

14 

18 

71 

Submerged 

78 

85 

•  • 

STIMULATION  OF  RESPIRATION 

That  it  is  possible  to  stimulate  or  increase  the  respiratory  rate 
of  fungi  has  been  shown  by  a  number  of  investigators.  Pratt  and 
Williams  (1939)  determined  that  thiamin  and  pantothenic  acid 
increase  the  respiration  of  certain  yeasts.  Dammann  et  al.  (1938) 
showed  that  Gibberella  saitb'mettii,  in  the  presence  of  thiamin,  is 
able  to  ferment  glucose  at  an  increased  rate  and  that  this  greater 
activity7  is  not  correlated  with  increase  in  mycelial  weight. 

Similarly  Hawker  (1944)  demonstrated  that  thiamin  (aneurin) 
in  the  amount  of  10  y  per  100  ml  of  medium  increases  the  amount 
of  glucose  consumed  per  unit  dry  weight  of  mycelium  by 
Melanospora  destruens. 


IMPLICATIONS 

Problems  related  to  dormancy  of  spores  and  to  their  germina- 
tion and  early  growth  appear  to  be  worthy  of  study  by  respirom- 
etry.  The  Warburg  respirometer  or  some  modification  of  it 
is  also  suitable  for  testing  the  ability  of  the  selected  fungus  to 
utilize  different  nutrient  complexes,  for  discovering  its  metabolic 
rate,  and  for  determining  the  kind  of  enzymes  that  the  organism 
is  able  to  produce.  It  is  possible  that  the  modifying  effect  of  such 
environmental  factors  as  temperature,  pH,  and  perhaps  light  might 
be  better  understood  by  respirometrv.  In  experiments  of  this 
sort  caution  must  be  exercised  in  interpreting  the  results,  for  the 
reason  that  several  substrates  may  be  oxidized  simultaneously.  If 
a  number  of  oxidative  changes  are  proceeding  concurrently  and 
at  equal  rates,  the  respiratory  ratio  cannot  be  known  with  any  de- 
gree of  accuracy.  If  the  evidence  indicates  that  one  substrate  is 
being  oxidized  to  the  extent  that  its  respiration  predominates,  how- 
ever, the  respiratory  ratio  becomes  meaningful.     Again,  if  the 


IMPLICATIONS  61 

total  volume  of  C02  evolved  is  in  excess  of  that  anticipated  by 
calculation  of  the  quantity  which  should  occur  in  the  carbohy- 
drate being  respired,  the  possibility  of  autodigestion  of  reserve 
glycogen,  "mold  starch,"  fats,  or  other  reserves  should  be  con- 
sidered, since  many  fungi  are  known  to  store  foods  and  to  utilize 
them  during  periods  of  stress. 

LITERATURE  CITED 

Bulloch,  William,  The  history  of  bacteriology.    422  pp.    Oxford  Univers- 
ity Press.     1938. 
Cagniard-Latour,  Charles,  "Memoire  sur  la  fermentation  vineuse,"  Ann. 

chim.  phys.,  68:  206-222,  1838. 
Dammann,  E.,  O.  T.  Rotini,  and  F.  F.  Nord,  "Mechanism  of  enzyme  action. 

XVIII.    Biochemistry    of    Fusaria.      V.    Enzvmic    transformations    by 

Fiisariimi  graminacearum  Schwabe   (Gibberella  saubinettii) .     Mode  of 

action  of  hydrocyanic  acid  and  vitamin  B^"  Biochem.  Z.,  291:  184-202, 

1938. 
Fabbroni,  Adamo,  DeW  arte  di  fare  il  vino.    264  pp.    Firenze.    1787. 
Harden,  A.,  Alcoholic  fermentation,  4th  ed.    194  pp.    London.    1932. 
Hawker,  Lilian  E.    "The  effect  of  vitamin  Bi  on  the  utilization  of  glucose 

by  Melanospora  destruens  Shear,"  Ann.  Botany,  8:  79-90,  1944. 
Kostytchew,  S.,  "Der  Einfluss  des  Substrates  auf  die  anaerobe  Atmung  der 

Schimmelpilze,"  Ber.  dent.  Botan.  Ges.,  20:  327-334,  1902. 
"Zweite  Mitteilung  iiber  anaerobe  Atmung  ohne  Alkoholbildung,"  Ber. 

deut.  botan.  Ges.,  26: 167-177,  1908. 
Plant  respiration,    xi  +  163  pp.    P.  Blakiston's  Sons  and  Co.,  Philadelphia. 

(Translated  and  edited  by  J.  C.  Lyon.) 
Lavoisier,  A.  L.,  Traite  elhnentaire  de  Chymie.    Paris.     1789. 
Liebig,  J.  von,  "liber  die  Erscheinungen  der  Garung,  Faiilniss,  und  Ver- 

wesung  und  ihre  Ursachen,"  Ann.  Physik.  Chemie,  2R,  18:  106-150,  1839. 
Lutman,  B.  F.,  Microbiology,    x  -f-  495  pp.    McGraw-Hill  Book  Co.,  New 

York.     1929. 
Meyerhof,  O.,  and  W.   Kiessling,   "Die   Umersterungsreaktion   der  Phos- 

phobrentztraubensaure  bei  der  alkoholischen  Zuckergarung,"  Biochem. 

Zeitschr.,  281:  249-270,  1935. 
Neuberg,  C,  "Von  der  Chemie   der  Garungs-Erscheinungen,"  Ber.  dent. 

chem.  Ges.,  55: 3624-3638,  1922. 
Neuberg,  C,  and  A.  Gottschalk,  "Beobachtungen  iiber  den  Verlauf  der 

anaeroben  Pflanzenatmung,"  Biochem.  Z.,  151:  167-168,   1924. 
Nord,  F.  F.,  and  R.  Weidenhagen,  Ergebnisse  der  Enzymforschnng,  I- VIII. 

1932-1939. 
Palladin,  W.,  "tjber  das  Wesen  der  Pflanzenatmung,"  Bioche?n.  Z.,  18:  151— 

206,  1909. 
Pasteur,  Louis,   "Memoire   sur  la  fermentation   appelee   lactique,"   Comp. 

rend.,  45:913-916,  1857. 


68  RESPIRATION 

Pasteur,  Louis,  "Memoire  sur  la  fermentation  appelee  lactique,"  Ann.  chini. 

phys.,  3nit-  ser.,  52:404-418,  1858. 
''.Memoire  sur  la  fermentation  alcoholique,"  Ann.  chim.  phys.,  3me  ser., 

58:  323-126,  1860. 
Pratt,  E.  F.,  and  R.  J.  Williams,  "The  effect  of  pantothenic  acid  on  respira- 
tion activity,"  /.  Gen.  Physiol.,  22:611-6*1,  1939. 
Richter,    Andreas,    "Kritische    Bemerkungen    zur    Theorie    der    Garung," 

Zentr.  Bakt.,  Parasitenk.,  II  Abt.,  8:  787-796,  1902. 
Schwann,  Theodor,  "Vorlaufige  Mitteilung  betreffend  Versuche  iiber  die 

Wcingahrung  und  Faulniss,"  Ann.  Physik.  Chenrie,  41:  184,  1837. 
Ta.miva,  H.,  "Atmung,  Garung,  und  die  sich  daran  beteiligenden  Enzvme 

von  Aspergillus,"  Advances  in  Enzynwl.,  2:  183-238,  1942. 
Thenard,  Louis  Jacques,  "Sur  la  fermentation  vineuse,"  Ann.  chim.,  An.  XI, 

46:  1802-1803. 
Wolf,  Fred  T.,  and  C.  S.  Shoup,  "The  effects  of  certain  sugars  and  amino 

acids  upon  the  respiration  of  Allomyces,"  My  col,  35:  192-200,  1943. 


Chapter  4 
BIOCHEMISTRY  OF  FUNGI 

Essentially  all  that  is  known  regarding  the  biochemistry  of  fungi 
has  come  from  investigations  made  since  the  turn  of  the  present 
century,  and  the  larger  proportion  of  this  knowledge  has  been 
acquired  during  the  past  few  years.  Interests  in  these  matters  have 
been  divided,  both  the  students  with  purely  academic  viewpoints 
and  those  concerned  with  industrial  applications  having  been  at- 
tracted. There  has  resulted  from  these  studies  of  the  biochemistry 
of  fungi,  including  the  yeasts  and  bacteria,  a  voluminous  litera- 
ture. In  one  volume,  much  less  in  one  chapter,  it  is  impossible  for 
one  person  to  convey  adequately  the  scope  of  these  studies,  to 
indicate  the  evidences  in  them  of  scientific  acuity  and  perspicacity, 
or  to  venture  prophecies  on  their  implications  and  applications. 

Before  the  nineteenth  century  little  about  the  biochemistry  of 
fungi  was  common  knowledge  among  mycologists,  except  per- 
haps that  yeasts  produce  alcohol  and  carbon  dioxide.  Our  pres- 
ent-day concepts  of  this  subject  admittedly  had  their  beginning 
in  Pasteur's  epoch-making  researches  on  fermentations  as  accom- 
plished through  the  agency  of  yeasts.  To  be  sure,  yeasts  were 
used  by  man  in  the  making  of  bread  and  the  preparation  of  alco- 
holic drinks  long  before  anything  fundamental  about  them  or 
about  their  biochemical  activities  was  known.  For  the  develop- 
ment of  industrial  uses  of  fungi,  the  initial  impetus  doubtless  came 
from  Hansen's  classical  work  with  yeasts  and  from  the  studies  of 
Wehmer,  performed  about  the  same  time,  on  the  production  of 
oxalic  and  citric  acid  by  Penicillium.  Such  a  mass  of  data  on  mold 
biochemistry  is  now  available  that  only  the  intrepid  would  ap- 
praise it  or  venture  to  view  it  in  perspective  and  to  speculate  on 
the  many  problems  that  have  been  brought  into  focus  and  that 
await  solution.  For  an  introduction  to  this  subject  the  excellent 
summaries  of  Raistrick  (1931),  Raistrick  et  al.  (1931),  Raistrick 
(1938),  Iwanoff  (1932),  IwanorT  and  ZwetkorT  (1933,  1936),  Bir- 

69 


10  BIOCHEMISTRY  OF  FUNGI 

kinshaw  (1937),  Lockwood  and  Aioyer  (1938),  and  Tatum  (1944) 
will  be  found  very  serviceable. 

In  these  biochemical  researches  it  is  of  more  than  passing  in- 
terest to  note  that  members  of  the  cosmopolitan  genera  Aspergillus 
and  Penicillium  have  been  very  commonly  employed.  In  fact, 
Aspergillus  niger  is  the  biological  agent  in  so  many  tests  that  it  is 
easy  to  understand  why  this  species  may  appropriately  be  desig- 
nated the  "fungus  guinea  pig."  This  epithet  may  be  applied 
equally  appropriately  to  Venicillium  glaucum.  The  reason  for  the 
use  of  these  species  and  of  closely  related  ones  lies  in  their  ability 
to  produce  a  wide  variety  of  enzymes,  making  it  possible  for  them 
to  utilize  many  kinds  of  substrata  as  foods,  as  is  indicated  in 
Chapter  1.  In  the  discussion  that  follows,  emphasis  will  be  placed 
on  the  metabolic  products  formed  by  fungi,  only  incidental  at- 
tention being  given  to  the  influence  of  nutritional  factors.  (The 
nutrition  of  fungi  is  considered  separately  in  Chapter  1.)  Inade- 
quate emphasis  must  of  necessity  be  placed  upon  the  mechanisms 
by  which  these  metabolic  products  come  into  being,  mainly  be- 
cause they  are  in  many  instances  quite  unknown  or  at  least  not  yet 
fully  understood. 

ORGANIC  ACIDS  AND  OTHER  PRODUCTS  HAVING 
SIX  OR  FEWER  CARBON  ATOMS 

The  foundations  for  our  understanding  of  the  genesis  of  organic 
acids  by  fungi  were  established  between  1896  and  1897  by  the 
classical  studies  of  Wehmer.  These  studies  involved  the  common 
carboxvlic  acids,  but  later  observers  have  devoted  themselves  to 
the  production  of  acids  belonging  to  other  groups  as  well.  Cer- 
tain essentials  regarding  the  mechanisms  in  these  fermentations 
have  been  elucidated  by  such  workers  as  Bernhauer,  Chrzaszcz, 
Butkewitsch,  Neuberg,  Cohen,  Raistrick,  and  Birkinshaw  and 
their  associates  and  pupils. 

Oxalic  acid.  Wehmer  (1891 )  observed  that  crystals  of  calcium 
oxalate  are  present  in  the  mycelium  of  Aspergillus  niger  and  in  the 
culture  medium  in  which  this  organism  grows.  He  was  first  to 
recognize  that  this  acid  is  a  by-product  in  the  fermentation  of  a 
variety  of  substrates  and  that  with  the  addition  of  calcium  carbo- 
nate to  the  substrate  very  large  yields  may  be  obtained.  Subse- 
quently others  have  confirmed  these  findings  with  A.  niger  and 


ORGANIC  ACIDS  AND  OTHER  PRODUCTS 


11 


have  shown  that  this  acid  is  produced  by  fermentations  induced  by 
A.  ochr ace ous  and  A.  violaceiis-fuscus.  Currie  and  Thorn  (1915) 
described  a  species,  which  they  named  Penicillium  oxalicum,  that 
has  the  same  ability.  Indeed  many  mycologists  have  noted  that  a 
wide  variety  of  fungi,  grown  in  nutrient  agars,  induce  the  produc- 
tion of  oxalic  acid,  evident  as  octahedral  crystals  of  calcium 
oxalate. 

Butkewitsch  and  FedororT  (1930)  observed  that  Mucor  stoloni- 
fer  can  convert  acetates  into  oxalic  acid,  and  they  postulated  that 
this  conversion  is  possible  by  either  of  these  two  courses: 


a.  CH3 
COOH 

Acetic  acid 

b.  COOH 
CH3 
CH3 
COOH 

Acetic  acid 


• 


o 


Q 

+o     CH2OH    _H2     I  +0 

>  - — >  > 


-H2 


COOH 

Glycolic  acid 

COOH 


COOH 

Glyoxalic  acid 

COOH 


CH2 
CH2 
COOH 

Succinic  acid 


-H2 


COOH 


CH 
CH 
COOH 

Fumaric  acid 


COOH 


+H20 
> 


COOH 
COOH 

Oxalic  acid 

COOH 
CHOH 
CH2 
COOH 

Malic  acid 


-H2 


C=0     +H2    COOH 

> 


CH, 


CH, 


COOH 

Keto- 
succinic  acid 


COOH 

Oxal- 
acetic  acid 


As  another  essential  condition  for  oxalic  acid  production 
Chrzaszcz  and  Tiukow  (1930,  1930a)  found  that  the  process  varies 
with  the  amount  and  kinds  of  amino  acids  present. 

Citric  acid.  The  production  of  citric  acid  from  the  fermenta- 
tion of  hexose  sugars  was  demonstrated  by  Wehmer  in  1893.  He 
identified  the  molds  concerned  as  members  of  a  new  genus,  Citro- 
myces,  and  named  them  C.  glaber  and  C.  pfefferiammi.  He  found, 
as  with  oxalic  acid  production,  that  improved  yields  can  be  ob- 
tained when  calcium  carbonate  is  present  in  the  medium.    Later 


12  BIOCHEMISTRY  OF  FUNGI 

he  established  that  Penicillium  luteum  has  the  same  fermentative 
ability.  Subsequently  P.  expansum,  P.  divaricatiim,  P.  citrimmi, 
and  P.  spimilosum  and  several  species  of  Aspergillus,  including 
A.  niger,  A.  clavatns,  and  A.  parasiticus,  were  employed  under 
similar  conditions  to  produce  citric  acid.  Wehmer  separated 
Citromvces  from  Penicillium  because  of  this  ability  to  produce 
citric  acid,  but  it  soon  became  apparent  that  this  physiological 
characteristic  constituted  an  untenable  generic  basis.  The  species 
of  Citromvces,  totalling  about  twenty,  have  therefore  come  to  be 
included  in  the  Genus  Penicillium. 

A  number  of  studies  have  been  concerned  with  the  conditions 
required  for  the  production  of  citric  acid.  Molliard  (1922)  re- 
ported that  an  insufficient  quantity  of  nitrogenous  material  in  the 
substratum  supplied  to  Aspergillus  niger  was  correlated  with  the 
accumulation  of  citric  acid;  this  finding  was  not  substantiated, 
however,  in  the  experiments  of  Bernhauer  (1926). 

Butkewitsch  (1923)  reported  that  both  Penicillium  glaucmn 
and  A.  niger  must  be  grown  in  an  acid  medium  to  stimulate  the 
formation  of  citric  acid.  If  the  medium  was  neutral,  oxalic  and 
nitric  acid  were  produced;  if  it  was  alkaline,  oxalic  acid  alone  was 
formed. 

In  his  studies  on  citric  acid  production  by  A.  niger  Porges 
(1932)  used  an  inorganic  mineral  nutrient  to  which  sucrose  was 
added  as  a  source  of  carbon.  He  found  that  it  was  necessary  first 
of  all  to  secure  a  heavy  mycelial  mat  over  the  surface  of  the 
nutrient  solution.  As  a  source  of  nitrogen  NaN03  proved  far 
superior  to  (NH4)2S04.  Both  Fe  and  Zn  were  essential.  Sugar 
concentrations  of  15  to  20%  gave  best  yields.  As  a  final  condition, 
it  was  requisite  that  the  mat  be  undisturbed  in  order  to  provide  a 
partially  anaerobic  environment. 

In  1917  Currie  (1917)  observed  that  in  sugar  solutions  fer- 
mented by  the  A.  niger  group  the  lag  in  acidity  can  be  accounted 
for  by  citric  acid,  which  made  up  the  difference  between  total 
acidity  and  oxalic  acid. 

Kostytchew  and  Tschesnokow  (1927)  noted,  that  so  long  as  no 
nitrogen  is  being  absorbed,  citric  acid  is  not  accumulated.  At  the 
end  of  approximately  48  hours  the  mycelial  mat  of  A.  niger  will 
have  covered  over  the  nutrient  solution.  This  solution  must  then 
be  replaced  by  a  sugar  solution  that  lacks  mineral  elements.  After 
3  days'  growth  on  such  a  medium  A.  niger  will  have  produced  a 


ORGANIC  ACIDS  AND  OTHER  PRODUCTS 


13 


maximum  of  citric  acid  and  will  have  utilized  40  to  50%  of  the 
sugar  present.  This  mineral-nutritional  relationship  is  substanti- 
ated by  Butkewitsch  and  Timofeeva's  results  (1935)  with  cultures 
deprived  of  phosphorus,  sulphur,  and  nitrogen. 

Several  mechanisms  have  been  suggested  to  account  for  the 
formation  of  citric  acid.  Butkewitsch  and  Fedoroff  (1929,  1930) 
and  Chrzaszcz  and  Tiukow  (1930,  1930a)  maintain  that  it  forms 
through  acetic  acid  or  from  acetates  of  sodium  or  potassium.  For 
the  formation  from  acetic  acid  their  scheme  is: 


COOH 


COOH 


COOH 


COOH 


CH 
CH, 


3         _h2 


CH2 
CH, 


-H2 


CH 
CH 


+H20 


CH2 
CHOH 


COOH 

Acetic  acid 


COOH 

Succinic  acid 

CH3 
+  COOH  —?* 

Acetic  acid 


COOH 

Fumaric  acid 

CH2  •  COOH 
COH  •  COOH 
CH2  •  COOH 

Citric  acid 


COOH 

Malic  acid 


Bernhauer  and  Siebenauger  (1931)  have  shown  that  A.  niger 
can  convert  ethyl  alcohol  into  citric  acid.  Bernhauer  and  Bockl 
(1932)  obtained  yields  of  citric  acid  from  alcohol  up  to  25%  of 
the  theoretical  amount.  They  also  showed  another  possible  course 
of  formation,  in  which  aconitic  acid  appears:  acetic  acid  — >  suc- 
cinic acid  — >  fumaric  acid  — >  aconitic  acid  -*  citric  acid.  Their 
proof  rests  upon  experiments  in  which  they  grew  A.  niger  on 
2.4%  potassium  aconitate  and  obtained  23.2  to  25.8%  citric  acid. 

Even  more  convincing  is  Kinoshita's  [IwanofT  and  ZwetkofT 
(1933)]  evidence  from  the  growth  of  A.  itaconicns  on  a  sugar 
solution  containing  calcium  carbonate.  Kinoshita  got  citric  acid, 
which  disappeared,  and  then  itaconic  acid  thus: 

CH2(COOH)COH(COOH)CH2(COOH)  ^> 

Citric  acid 

CH2(COOH)  •  C(COOH) :  CH(COOH) 

Aconitic  acid 


-C02 


>  CH2(COOH)C(:CH2)COOH 

Itaconic  acid 


14  BIOCHEMISTRY  OF  FUNGI 

Raistrick  and  Clark  (1919)  maintain  that  the  hexose  first  be- 
comes a-y-diketoadipic  acid,  that  then  acetic  and  oxalacetic  acids 
arise  bv  hydrolysis,  and  that  finally  they  combine  to  form  citric 
acid. 

Optimum  conditions  for  citric  acid  formation  vary  not  only 
with  the  substrate  but  also  with  the  mold  concerned  and  with  the 
pH.  This  variation  is  indicated  by  an  optimum  pH  of  2.0  for 
A.  niger  and  of  3.0  to  4.0  for  Penicillium  glaber.  Of  the  sub- 
strates tested,  the  following  carbohydrates  have  been  found  suit- 
able for  citric  acid  fermentation:  starch,  sucrose,  glucose,  fructose, 
lactose,  maltose,  glycerol,  and  molasses. 

Whatever  the  mechanism,  it  has  been  found  to  be  commercially 
practicable  to  produce  citric  acid  by  mold  fermentation,  several 
thousand  tons  being  produced  annually,  in  competition  with  citric 
acid  extracted  from  natural  sources.  It  requires  an  initial  concen- 
tration of  about  1 5 c  o  of  sugar,  a  low  concentration  of  ammonium 
nitrate,  and  a  pH  of  3.5. 

J-Gluconic  acid.  Gluconic  acid  is  of  value  when  used  as  a  cal- 
cium salt  in  food  and  medicine.  It  was  first  isolated  by  Molliard 
in  1922  from  among  the  by-products  in  fermentations  induced 
by  A.  niger.  Subsequent  workers,  notably  Bernhauer  (1924), 
Herrick  and  May  (1928),  May,  Herrick,  Thorn,  and  Church 
(1927),  Mover,  May,  and  Herrick  (1936),  and  May,  Herrick, 
Mover,  and  Hellbach  (1929)  have  shown  that  a  variety  of  other 
molds  possess  the  ability  to  ferment  this  acid,  among  them  being 
Aspergillus  cirmamomeus,  Penicillium  glaucum,  P.  purpurogemim 
var.  rubrisclerotvum,  P.  chrysogemim,  and  Finnago  vagans. 

Gluconic  acid  arises  from  the  fermentation  of  glucose  as  fol- 
lows: 

CH2OH       CH2OH 

HCOH       HCOH 

HCOH       HCOH 

I     ^  I 

OHCH       OHCH 

HCOH       HCOH 

CHO        COOH 

(f-Glucose  <f-Gluconic 

acid 


ORGANIC  ACIDS  AND  OTHER  PRODUCTS 


15 


Studies  have  also  been  directed  toward  finding  optimum  condi- 
tions for  the  formation  of  gluconic  acid.  Herrick  and  May  (1928) 
secured  good  yields  in  10-day-old  cultures,  incubated  at  25°  to 
30°  C,  in  the  following  medium: 


Glucose 

Magnesium  sulphate 
Disodium  phosphate 


200.00  grams 
0.25  gram 
0. 10  gram 


Potassium  chloride 
Sodium  nitrate 
Water 


0.05  gram 
1 .00  gram 
1000.00  ml 


Kardo-Ssysojewa  (1933)  recorded  increased  yields  from  de- 
creasing total  salts  but  increased  yields  if  the  nitrates  were  in- 
creased in  acid  media.  He  grew  mats  of  A.  niger  in  nutrient-sugar 
solution  in  the  presence  of  calcium  carbonate,  and  after  pouring 
off  this  solution  replaced  it  with  one  of  20%  sugar  to  which  he 
added  calcium  carbonate.  After  4  days  he  secured  11.89  grams 
of  gluconic  acid  from  11.36  grams  of  sugar,  and  after  5  days  12.19 
grams  of  gluconic  acid  from  11.76  grams  of  sugar.  Traces  of 
citric  acid  were  present  also,  but  no  oxalic  acid. 

Fumaric  acid.  In  1911  Ehrlich  demonstrated  that  Rhizopus 
nigricans  produces  small  amounts  of  fumaric  acid  from  glucose 
and  fructose.  These  observations  have  subsequently  been  con- 
firmed, and  in  1918  Wehmer  (1918)  reported  yields  of  60  to  70% 
from  a  species  of  Aspergillus  that  he  named  A.  fiimaricus.  This 
organism  gradually  declined  in  fumaric  acid-producing  ability 
after  repeated  subculture  and  formed  instead  gluconic,  malic,  and 
citric  acids.  Galactose  and  arabinose  have  also  been  utilized  in 
fumaric  acid  fermentation.  Other  fungi  that  have  been  found 
capable  of  producing  this  acid  include  Rhizopus  oryzae,  R.  tritici, 
and  Yenicillium  griseo-jidvum  [Raistrick  and  Simonart  (1933)]. 

Gottschalk  (1926)  and  Butkewitsch  and  FedorofT  (1929)  se- 
cured calculated  yields  of  fumaric  acid  of  approximately  50% 
from  R.  nigricans.  They  found  that  this  acid  may  arise  in  an 
alcoholic  fermentation  as  follows: 

CHoOHN 
2C02  +  2 


CrHioO 


+02 


12^6 


CH3 

Alcohol 


/COOH 

21 


-H2 


CH3 

Acetic  acid 


CH2  •  COOH 
CH2  ■  COOH 

Succinic  acid 


H2 


CH  •  COOH 
CH  •  COOH 

Fumaric  acid 


16  BIOCHEMISTRY  OF  FUNGI 

Malic  acid.  Although  malic  acid  has  for  years  been  considered 
to  be  among  the  products  formed  by  molds,  proof  was  first  pro- 
vided by  Wehmer  (1928)  in  1928.  He  secured  small  yields  from 
sucrose  fermentation  by  Aspergillus  fumaricus.  Raistrick  et  al. 
(1931)  have  found  that  several  other  fungi,  among  them  species 
of  Aspergillus  and  Clasterosporium,  can  utilize  glucose  to  form 
malic  acid. 

Succinic  acid.  It  has  long  been  known  that  yeasts  produce 
succinic  acid  during  alcoholic  fermentation.  Moreover  Fitz 
(1873)  recorded  its  presence  in  solutions  during  alcoholic  fermen- 
tation induced  by  Mu cor  mucedo.  Raistrick  et  al.  (1931)  showed 
that  a  species  of  Clasterosporium  isolated  from  cotton  pulp,  as 
well  as  Fumago  vagans,  formed  succinic  acid  from  glucose.  It 
has  also  been  shown  to  be  produced  by  Aspergillus  t  err  em 
[Raistrick  and  Smith  (1935)]  and  Penicillium  aurantio-virens 
[Birkinshaw  and  Raistrick  (1932)].  This  ability  is  doubtless  pos- 
sessed by  a  variety  of  fungi. 

Succinic  acid,  as  has  been  shown,  forms  during  fermentations 
that  give  rise  to  such  other  acids  as  citric,  gluconic,  and  fumaric, 
with  which  it  is  chemically  related;  in  consequence  its  origin  may 
be  accounted  for  by  the  oxidative  breakdown  of  sugars.  On  the 
other  hand,  it  may  well  arise  from  yeast  proteins  themselves  or 
from  mold  proteins.  Accord  seems  not  to  have  been  reached  on 
the  matter  of  the  origin  of  succinic  acid. 

Lactic  acid.  Until  recently  it  was  the  general  belief  that  only 
bacteria,  especially  such  species  as  Streptococcus  lactis,  Lactoba- 
cillus acidophilus,  and  L.  bulgaricus,  are  capable  of  causing  lactic 
acid  to  be  formed.  More  recently  however,  several  workers  have 
demonstrated  this  acid  in  sugar  fermentations  by  species  of  Rhizo- 
pus  and  Alucor,  including  Rbizopus  oryzae,  R.  chinensis,  R.  ele- 
gans,  and  R.  tritici.  A  40%  yield  from  R.  japonicus  was  reported 
when  this  species  was  grown  on  10%  sugar  solution  containing 
calcium  carbonate.  Waksman  and  Foster  (1938)  found  a  member 
of  the  R.  arrhizus  group  to  be  a  very  efficient  lactic  acid  former 
when  grown  in  solutions  containing  glucose  or  starch.  In  the 
presence  of  calcium  carbonate  70  to  75%  of  the  carbohydrate 
was  transformed  into  lactic  acid.  This  yield  is  all  the  more  re- 
markable in  that  the  fungus  is  supposedly  strictly  aerobic.  Waks- 
man and  Foster,  however,  permitted  it  to  form  a  film  over  the  sur- 
face of  the  liquid  substrate,  and  within  such  a  film  under  reduced 


ORGANIC  ACIDS  AND  OTHER  PRODUCTS  77 

oxygen  tension  an  intermediate  substance  is  formed  which  be- 
comes converted  into  lactic  acid,  alcohol,  and  carbon  dioxide, 
with  little  loss  of  potential  energy. 

Ethyl  alcohol.  Sac  char  omyces  cerevisiae  has  long  been  known 
for  its  ability  to  metabolize  ethyl  alcohol.  As  long  ago  as  1873, 
however,  Fitz  (1873)  noted  that  Mucor  racemosus  is  also  capable 
of  transforming  sucrose  into  alcohol.  Of  the  closely  related  genus 
Rhizopus,  ethvl  alcohol  is  known  to  be  formed  bv  R.  nigricans, 
R.  tritici,  R.  arrhizus,  and  R.  oryzae. 

Fusarium  lini,  the  cause  of  flax  wilt,  gives  yields  of  the  same 
order  of  magnitude  as  those  from  cultivated  yeasts  [Letcher  and 
Willaman  (1926),  White  and  Willaman  (1928)].  It  will  ferment 
almost  any  hexose  and  in  addition  almost  any  pentose,  the  pentoses 
not  being  utilized  in  this  manner  bv  baker's  yeast.  Many  other 
species  of  Fusarium,  moreover,  are  able  to  decompose  glucose 
with  the  production  of  alcohol,  each  differing  in  relative  yields; 
as  might  be  anticipated,  a  variety  of  other  products  appear  dur- 
ing the  fermentation  [Raistrick  et  al.  (1931)]. 

Species  of  Aspergillus  and  Penicillium  have  been  tested  for  their 
ability  to  produce  alcohol.  As  a  result  it  is  known  that  96  species 
or  strains  of  Aspergillus  and  75  of  Penicillium  possess  this  capa- 
bility. Among  them  are  A.  niger  and  several  members  of  the 
A.  glaiicus  group  and  the  A.  flawis-oryzae-tamarii  group.  Yuill 
(1928)  is  among  those  who  have  studied  alcoholic  fermentation 
by  A.  flavits.  Other  notable  alcohol-forming  molds  are  Eidamia 
catemriata,  E.  viridescens,  Trichoderma  lignorum,  and  Helmintho- 
sporhnn  gemadatiim. 

Ethyl  acetate.  This  fruity  ester  was  demonstrated  by  Rai- 
strick et  al.  (1931)  to  be  formed  by  Fenicillium  digitatum,  a  com- 
mon mold  associated  with  the  decay  of  citrus  fruits,  when  grown 
on  glucose  solution.  They  state  that  it  is  not  known  to  be  formed 
by  any  other  mold.  Presumably  ethyl  acetate  originates  by  a 
Cannizzaro  reaction  from  acetaldehyde,  an  anaerobically  formed 
respiratory  product. 

Glycerol.  Connstein  and  Liidecke  (1919)  considered  the 
principles  involved  in  the  commercial  production  of  glycerol  by 
fermentation.  It  is  a  matter  of  common  knowledge  that  this 
compound  is  formed  during  fermentation  by  yeasts,  and  as  has 
been  shown  in  Chapter  3,  high  yields  can  be  secured  by  the  addi- 


18 


BIOCHEMISTRY  OF  FUNGI 


tion  of  sodium  sulphite  to  the  nutrient  solution.  More  recently 
the  carbonate  has  been  substituted  for  the  sulphite  with  good 
results.  Emmerling  (1897)  reported  that  Mucor  vmcedo  can 
metabolize  glycerol  from  sucrose.  Raistrick  et  al.  (1931)  showed 
that  other  molds,  for  example,  Aspergillus  wentii,  a  Clastero- 
sporium  isolated  from  cotton  pulp,  and  Helm'inthosporhim  geni- 
culatwn,  possess  like  capability. 

Kojic  acid.    This  acid  is  a  y-pyrone  of  the  following  constitu- 
tion: 

CO 

/   \ 
HOC    ,       CH 


HC 


C-CHoOH 


O 

It  is  of  special  interest  to  the  toxicologist  because,  when  orally 
administered  to  dogs,  it  produces  symptoms  like  those  of  epilepsy. 
Kojic  acid  was  first  isolated  by  Saito  in  1907  from  the  mycelium 
of  Aspergillus  oryzae.  This  fungus  was  subsequently  found  cap- 
able of  utilizing  in  the  production  of  kojic  acid  not  only  sucrose 
but  also  maltose,  dulcitol,  succinic  acid,  and  inulin.  Raistrick  et  al. 
(1931)  and  Birkinshaw  (1937)  showed  that  this  capability  is 
possessed  also  by  Aspergillus  flaws,  A.  efjusus,  A.  parasiticus, 
A.  tamarii,  and  Fenicilliwn  daleae.  The  conditions  for  its  produc- 
tion were  studied  by  May,  Moyer,  Wells,  and  Herrick  (1931), 
who  secured  yields  of  45%  of  the  glucose  present.  They  varied 
the  amount  of  nitrogen  and  sugar  in  the  medium,  getting  best 
yields  with  approximately  20%  sugar.  The  mode  of  its  forma- 
tion is  not  established,  but  it  may  be  as  follows: 


HCOH- 
HCOH 


HOCH 
HCOH 

HC 

CH90H 


O 


CHOH- 
HCOH 

c=o 

HCOH 


CH 


O 


HC 


CHoOH 


COH 

c=o 

CH 

C 

CH2OH 

Kojic  acid 


o 


FATS  19 

Mannitol.  Several  workers  have  reported  the  occurrence  of 
the  hexahydric  alcohol,  mannitol,  within  the  tissues  of  molds,  and 
it  has  been  regarded  as  a  reserve  product.  Raistrick  et  al.  ( 193 1 ), 
however,  established  that  mannitol  can  be  formed  in  Czapek-Dox 
glucose  solution,  where  it  appears  as  a  product  of  fermentation. 
Aspergillus  elegans,  A.  nidulans,  A.  wentii,  Penicillium  chrysoge- 
num,  and  Helminthosporium  geniculatum  were  the  organisms  con- 
cerned in  their  experiments.  Coyne  and  Raistrick  (1931)  found 
that  Aspergillus  can  ferment  glucose,  mannose,  and  galactose  with 
the  production  of  mannitol,  and  that  the  pentoses,  xylose  and 
arabinose,  can  likewise  be  fermented  in  the  same  manner.  For 
some  reason  not  understood,  Aspergillus  did  not  form  mannitol 
from  fructose. 

POLYSACCHARIDES 

Many  fungus  structures  have  long  been  known  to  become  blue 
when  stained  with  iodine,  a  reaction  used  to  establish  the  presence 
of  "mold  starch."  Presumably  the  term  mold  starch  applies  to  a 
group  of  closely  related  substances  rather  than  to  a  single  one. 
Boas  (1917,  1922)  found  that  Aspergillus  niger  can  utilize  various 
sugars,  glycerol,  mannitol,  and  several  organic  acids,  such  as  citric, 
malic,  oxalic,  and  tartaric,  in  producing  mold  starch,  provided  that 
high  temperatures  are  maintained  and  free  acids  are  present  in 
the  culture  solution. 

Chrzaszcz  and  Tiukow  (1929,  1929a)  observed  that  many  spe- 
cies of  Penicillium  produce  mold  starch. 

Dox  and  Neidig  (1914)  grew  Penicillium  expansion  on  Raulin's 
solution  containing  <i-glucose.  From  the  mycelium  they  isolated 
a  polysaccharide  which  they  named  mycodextran.  From  Asper- 
gillus niger  grown  on  the  same  medium  they  isolated  both  myco- 
dextran and  another  polysaccharide  that  they  called  mycoga- 
lactan. 

Several  other  polysaccharides  have  been  isolated  [Raistrick 
(1938)],  including  luteic  acid  elaborated  by  Penicillium  luteum, 
mannocarolose  and  galactocarolose  by  P.  charlesii,  and  varianose 
by  P.  varians. 

FATS 

It  is  well  known  that  many  species  of  fungi  store  globules  of 
fats  within  their  spores  and  that  fats  may  be  present  also  within 


80  BIOCHEMISTRY  OF  FUNGI 

the  mvcelia.  According  to  Pearson  and  Raper  (1927),  the  fresh 
mycelium  of  Aspergillus  iiiger  contains  2.4%  fat  and  that  of 
Rhizopus  nigricans  5%.  These  fats  in  Penicillium  aurantio-brun- 
neinn  were  studied  by  Strong  and  Peterson  (1934)  and  were 
found  to  resemble  butterfat.  The  analyses  showed  them  to  con- 
tain 40.2%  oleic  acid,  31.2%  lineolic  acid,  8.6%  palmitic  acid,  and 
5.3%  stearic  acid;  the  remainder  consisted  of  9.1%  glycerol,  1.9% 
ergosterol,  and  a  non-fatty  residue  of  4.5%.  Their  analysis  of 
the  fats  of  Aspergillus  sydoixii  showed  8.8%  palmitic  acid,  11% 
stearic  acid,  29.6%  oleic  acid,  16.3%  lineolic  acid,  and  a  small  per- 
centage of  higher  unsaturated  acids.  Analysis  of  the  fats  of 
Penicillium  javanicum  by  Ward  and  Jamieson  (1934)  revealed 
them  to  consist  of  69.5%  palmitic  acid,  28%  stearic  acid,  and  2.5% 
7;-tetracosic  acid.  Nord  and  A  lull  (1945)  indicated  that  Fusarium 
gramineum  forms  fats  similar  to  those  produced  by  yeasts. 

The  factors  that  influence  the  amount  of  fat  produced  have 
been  investigated  by  Lockwood  et  al.  (1934)  and  Ward  et  al. 
(1934,  1935)  in  a  goodly  number  of  species  of  molds.  They  se- 
cured best  production  with  Penicillium  javanicum  when  it  was 
grown  on  a  medium  containing  40°  '0  glucose.  Sucrose,  xylose, 
and  glycerol  also  served  well  as  carbon  sources.  These  workers 
found  that  the  mycelium  contained  up  to  41.5%  fat  in  old  cul- 
tures. The  studies  of  Prill,  Wenck,  and  Peterson  (1935),  using 
Aspergillus  fischeri,  showed  increased  fat  production  with  higher 
pH  within  the  range  2.0  to  8.0,  along  with  greater  concentration 
of  glucose. 

Even  though  the  syntheses  are  not  understood,  the  procedures 
are  now  so  well  known  that  they  could  be  utilized  industrially 
if  a  supply  of  animal  fats  could  not  be  procured.  In  fact,  one  of 
the  Endomycetales,  Endomyces  vernalis,  has  been  used  for  some 
time  in  the  commercial  production  of  fats. 

Various  hypotheses,  briefly  considered  by  Smedley-AIcLean 
(1936),  have  been  proposed  to  explain  the  mechanisms  involved 
in  the  transformation  of  a  carbohydrate  into  a  fatty  acid.  Con- 
densation of  three  hexose  molecules  to  give  the  stem  of  stearic 
acid  or  of  two  pentose  molecules  and  one  hexose  molecule  to  give 
palmitic  acid  has  been  suggested.  In  support  of  this  hypothesis 
attention  may  be  directed  to  the  fact  that  in  many  naturally 
occurring  fatty  acids  the  number  of  carbon  atoms  is  a  multiple 
of  six. 


STEROLS  AND  VITAMINS  SI 

Another  hypothesis  is  that  acetaldehyde  is  produced  from  lactic 
acid  as  an  intermediate  substance  and  that  by  its  repeated  conden- 
sation the  series  of  fatty  acids  from  butyric  upward  is  produced. 
The  culturing  of  fungi  on  solutions  of  acetaldehydes  has  not 
strongly  supported  this  hypothesis. 

Another  hypothesis,  which  is  looked  upon  with  favor  but  has 
not  been  elucidated,  is  that  the  hexose  is  fermented  to  pyruvic 
acid,  from  which  the  fatty  acid  is  formed. 

STEROLS  AND  VITAMINS 

Within  the  past  few  years  an  appreciation  has  been  developing 
that  sterols  and  vitamins  occur  in  fungi.  This  recognition  has 
come  in  part  from  the  therapeutic  use  of  yeast  to  correct  dietary 
deficiencies.  The  dietetic  value  of  yeast  becomes  all  the  more 
remarkable  when  it  is  remembered  that  the  yeast  plant,  cultured 
on  hexose  solution  containing  ammonium  chloride  together  with 
a  few  drops  of  wort  in  which  yeasts  have  previously  been  grown, 
is  able  to  synthesize  not  only  a  goodly  complement  of  vitamins 
but  also  all  the  amino  acids.  All  these  syntheses  by  a  simple 
plant!  To  date  the  function  of  sterols  (ergosterol,  CosH^O.oo, 
is  the  precursor  of  vitamin  D)  and  vitamins  in  fungi  remains 
largely  unknown.  The  studies  have  centered  largely  on  the  oc- 
currence of  these  substances  and  on  their  employment  in  animal 
feeding.  Evidently  they  are  of  wide  occurrence  among  fungi. 
The  factors  which  condition  their  formation  were  studied  by 
Birkinshaw,  Callow,  and  Fischmann  (1931).  In  1929  Heiduschka 
and  Lindner  [Birkinshaw  (1937)]  determined  the  ergosterol  con- 
tent of  Dematium  pullirtans  to  be  0.3%  of  the  dry  weight;  of 
Penicillium  glaiicum,  0.75%;  and  of  Aspergillus  oryzae,  0.46%. 
Bernhauer  and  Potzelt  (1935)  found  a  variation  in  sterol  content 
of  0.23  to  1.16%  among  16  strains  of  A.  niger. 

Preuss  et  al.  (1931,  1932,  1932a)  studied  the  sterol  content  of  30 
species  of  Aspergillus,  20  of  Penicillium,  and  15  of  other  species 
of  fungi  when  grown  on  a  synthetic  medium  containing  4°  70  glu- 
cose. The  difference  in  sterol  content  among  species  is  shown  by 
the  occurrence  of  0.98%  in  Aspergillus  oryzae,  0.4%  in  A.  niger, 
0.35%  in  Penicillium  expansum,  and  0.16%  in  P.  janthivellum. 
They  found  that  different  strains  of  the  same  species  vary  in 


82  BIOCHEMISTRY  OF  FUNGI 

ability  to  produce  sterol  since,  other  conditions  being  uniform, 
4  strains  of  A.  oryzae  yielded  0.54,  0.63,  0.76,  and  0.98%.  The 
duration  of  the  period  of  cultivation  was  also  found  by  these 
workers  to  influence  the  yield,  since  a  given  strain  of  A.  oryzae 
after  10  days  had  produced  0.63%,  and  after  about  50  days  1.07 
Reindel,  Niederlander,  and  Pfundt  (1937)  found  that  best  yields 
from  Torula  were  produced  in  a  molasses  medium,  increased 
yields  being  correlated  with  increased  sugar  concentration.  Preuss 
et  al.  (1931)  also  administered  in  daily  doses  10  mg  of  dried,  finely 
ground  fungus  material  to  rachitic  rats.  They  used  A.  niger, 
A.  oryzae,  Marasmius  oreades,  Hypholoma  incertum,  and  Seco- 
tium  acuminatum,  with  the  result  that  each  manifested  antirachi- 
tic action.    Among  other  of  the  higher  fungi  that  have  been  found 

O  CO 

to  contain  vitamin  D  are  Psalliota  campestris,  Hehella  esculenta, 
Boletus  edidis,  Cantharellus  cibarius,  C.  clavatus,  Hydnum  ivibri- 
catum,  and  Ganoderma  hicidimi  [IwanofT  and  ZwetkorT  (1936)]. 

Evidence  has  also  been  accumulated  to  show  that  other  vita- 
mins are  present  in  fungi  and  that  some  of  them  can  be  employed 
to  enrich  animal  diets.  Gorcica,  Peterson,  and  Steenbock  ( 1934) 
found  vitamins  Bi  (thiamin),  B2  (riboflavin),  and  B4  in  Asper- 
gillus sydoivii.  Scheunert  and  Reschke  [IwanofT  and  ZwetkofF 
(1933)]  found  that  Cantharellus  cibarius  is  unusually  rich  in  vita- 
min A  (C20H30O).  Lederer  [IwanofT  and  ZwetkorT  (1936)] 
studied  the  carotene  (provitamin  A)  content  of  many  yeasts  and 
fungi.  Its  wide  distribution  among  fungi  is  indicated  by  his 
finding  it  in  the  slime  mold,  Lycogala  epidendrum,  in  the  rust, 
Puccinia  coronifera,  in  the  jelly  fungus,  Tremella  mesenterica, 
and  in  the  near  yeast,  Torula  rubra. 

Much  interest  also  centers  on  the  occurrence  of  growth  sub- 
stances,  notably  heteroauxin,  in  yeasts  and  certain  fungi.  An  in- 
troduction to  this  subject  can  be  obtained  from  Kogl  and  Koster- 
mans'  report  (1934)  of  the  existence  of  heteroauxin  in  Rhizopus 
nigricans  and  Aspergillus  niger.  It  appears  to  be  formed  in  the 
breakdown  of  tryptophane,  since  none  is  produced  in  mineral-nu- 
trient solutions. 

According  to  Xord  and  Mull  (1945),  a  diet  containing  10% 
Fusariuui  lini  as  a  source  of  vitamins,  with  crystalline  vitamin  Bi 
added,  and  37%  proteins  from  the  same  fungus  serves  excellently 
for  growth,  reproduction,  and  lactation  by  mice. 


PIGMENTS  OF  FUNGI  83 

AMINO  ACIDS 

Apparently  many  fungi  are  able  to  synthesize  their  amino  acids 
from  inorganic  nitrogen.  Such  synthesis  may  not  be  sufficiently 
rapid,  however,  for  optimum  growth,  as  is  indicated  bv  the  fact 
that  more  rapid  growth  occurs  after  amino  acids  are  added  to  the 
substrate. 

Steinberg  (1942)  studied  the  utilization  of  amino  acids  as  carbon 
and  nitrogen  sources  for  Aspergillus  niger  and  interpreted  his  ex- 
periments as  showing  that  amino  acids  may  be  formed  from  and 
reconverted  to  sugars.  A  mixture  of  proline,  glutamic  acid,  and 
ornithine  provided  carbon  and  nitrogen  almost  as  satisfactorily 
as  did  sucrose  and  ammonium  salts. 

Biogenesis  of  specific  amino  acids,  as  of  arginine  and  trytophane, 
especially  by  Neurospora  crassa,  has  been  given  consideration 
[Tatum  (1944)].  From  such  investigations  the  accumulated  evi- 
dence indicates  that  the  formation  of  primary  amino  acids  in- 
volves oxidation  of  the  a-hydroxy  acid  and  amination  of  the  keto 
acid. 

PIGMENTS  OF  FUNGI 

To  almost  any  question  regarding  the  pigments  of  fun^i  the 
mycologist  makes  the  embarrassed  answer,  "I  don't  know."  iMany 
species  are  beautifully  pigmented,  and  use  is  made  of  this  fact 
in  classification.  Almost  surely  pigments  serve  some  essential 
function  in  the  metabolic  activities  of  fungi,  presumably  in  respi- 
ration, but  this  field  of  physiology  remains  quite  wholly  unex- 
plored. To  date  the  studies  on  such  pigments  deal  mainly  with 
their  chemical  nature. 

Citromycetin  and  citrinin.  These  two  pigments  were  iso- 
lated by  Raistrick  and  his  associates  (1931),  citromycetin  being 
obtained  from  Pemcillium  glabrum  and  citrinin  from  P.  citrinum. 
The  organisms  were  grown  on  modified  Czapek-Dox  medium 
(NaNOs,  2  grams;  KH,P04,  1  gram;  KC1,  0.5  gram;  MgSCV 
7H20,  0.5  gram;  FeS04-7H20,  0.02  gram;  water,  1  liter;  glucose, 
50  grams).  From  P.  glabrum  Hetherington  and  Raistrick  [Rai- 
strick (1931)]  extracted  in  50%  alcohol  a  substance  that  crystal- 
lized into  lemon-yellow  needle  crystals,  citromycetin,  which  is 
intensely  olive  green  with  ferric  chloride.    The  reactions  of  this 


84 


BIOCHEMISTRY  OF  FUNGI 


dye  indicate  that  it  is  related  to  the  xanthone  and  flavone  group. 
Its  empirical  formula  is  Ci-iHioOy^HjO,  with  the  following 
structural  constitution: 


C4HeO 


The  other  pigment,  citrinin,  also  crystallizes  as  yellow  crystals 
but  is  iodine  brown  in  ferric  chloride  and  discolors  instantly  in 
potassium  permanganate.  Its  empirical  formula  is  given  as 
C13H14O5,  with  the  following  structural  constitution: 

C2H5 
0/S0H 


H3C 

H3C 

H 


COOH 
O 


Carotene.  Certain  Phy corny cetes,  such  as  Phy corny  ces  blake- 
sleeamis,  Mucor  hievmlis,  and  Allomyces  javanicus,  contain  /^-caro- 
tene, the  precursor  of  vitamin  A.  The  gametes  of  Allomyces 
macro gyna  and  A.  moniliformis  contain  y-carotene  [Emerson  and 
Fox  ( 1940)  ] .  Carotene  occurs  also  in  Pilobolus  and  is  not  uncom- 
mon among  Ascomycetes  and  Basidiomycetes,  especially  rusts 
and  jelly  fungi. 

Other  pigments.  Clutterbuck  et  al.  (1932)  isolated  from  Penl- 
cillhim  clnysogemim  a  yellow  pigment  whose  empirical  formula 
is  CisH-.O,;.  From  Monascus  purpureus  two  pigments,  monasco- 
rubrin,  C22H24O5,  and  monascoflavin,  Ci7H_.L.04,  have  been  ob- 
tained. Monascorubrin  is  red  and  may  be  converted  by  hydro- 
gen peroxide  into  monascoflavin,  which  is  yellow  [Birkinshaw 
(1937)].  Two  pigments,  oosporin,  CioH140,;,  and  aurantin, 
C1r.H-.O3,  have  been  obtained  from  Oospora  aurantla. 

Gould  and  Raistrick  (1934)  isolated  from  members  of  the 
Aspergillus  glaucus  group  three  pigments;  flavoglaucin,  C19H28O3, 
auroulaucin,  C^H^O.,,  and  rubro^laucin,  Cir.Hi-O.-. 


PIGMENTS  OF  FUNGI 


85 


Kogl  and  Erxleben  [IwanorT  (1932)]  have  extracted  pigments 
from  a  number  of  the  higher  fungi.  From  Amanita  muse  aria 
they  extracted  a  red  crystalline  glucoside,  muscarufin,  C25Hi609. 
From  Hydmnn  ferrugineum  and  species  of  Thelephora  they  got 
thelephoric  acid,  G>oHi206,  whose  crystals  resemble  in  color  po- 
tassium permanganate. 

A  group  of  interesting  pigmented  compounds  is  produced  by 
each  of  the  more  commonly  known  species  of  Helminthosporium 
pathogenic  to  grasses,  some  compounds  being  obtained  from  more 
than  one  species.  Raistrick  (1937)  and  his  associates  cultured 
these  species  of  Helminthosporium  on  Czapek-Dox  solutions. 
From  such  cultures  of  H.  gramineum,  H.  cynodontis,  H.  catenar- 
ium,  and  H.  tritici-vulgaris  they  isolated  helminthosporin,  Ci5- 
H10O5,  consisting  of  very  dark  maroon  crystals.  From  cultures 
of  H.  cynodontis,  H.  euchlaenae,  and  H.  avenae,  cynodontin, 
CisHioO,;,  consisting  of  bronze  leaf-like  crystals,  was  obtained. 
From  cultures  of  H.  tritici-vulgaris,  tritisporin,  Ci5H10O7,  consist- 
ing of  reddish  brown  platelets,  was  obtained.  Cultures  of  H. 
ravenelii,  a  fungus  widely  present  in  the  southeastern  United 
States  on  smut  grass,  Sporobolus  sp.,  yielded  ravenelin,  Ci4Hi0O5, 
an  intensely  yellow  pigment.  The  following  constitutions  are 
assigned  to  these  four  pigments  from  Helminthosporium  [Birkin- 
shaw  (1937)]: 


OH  CO 


OH  CO  OH 


— CH 


OH  CO  OH 

Helminthosporin 

OH  CO  OH 


HOCH 


OH 


OH 

Tritisporin 


-CH3 


CO  OH 

Cynodontin 

O     OH 

V-CH3 


CO  OH 

Ravenelin 


Wood  lying  in  moist  situations  may  be  discolored  by  Chloro- 
splemum  aeruginosum.  The  pigment  concerned  is  sylindein,  and 
such  wood,  because  of  its  beautiful  verdigris-green  stain,  is  util- 
ized in  making  ornaments  and  souvenirs. 


86 


BIOCHEMISTRY  OF  FUNGI 


Quite  a  goodlv  number  of  other  pigments  have  been  isolated 
and  studied,  but  the  functions  of  most  of  them  have  not  been  given 
any  consideration.  Some  of  them  catalyze  oxidations,  as  does  a 
red  pigment,  phoenicin,  found  in  Penicillium  phoenicttm  and  also 
in  the  bacterium,  Pseudovwnas  aeruginosa.  This  oxidative  func- 
tion may  be  exercised  by  pigments  that  are  associated  with  the 
discoloration  of  agarics  and  boletes  that  have  been  injured.  Stro- 
bilomycol,  a  red  pigment  that  turns  black  in  the  presence  of  the 
oxidizing  enzyme  laccase,  has  been  isolated  from  Boletus  (Stro- 
bilomyces)  strobilaceus.  From  B.  sat  amis  and  B.  luridus  [Iwanoff 
and  ZwetkorT  (1930)1  crystals  of  boletol  have  been  obtained. 
These  crystals  become  blue  on  oxidation  as  they  are  transformed 


into  isoboletol  in  the  following  manner: 


O 


O      O 


HOOC 


OH 


HOOC 


OH 


OH 


O 

Boletol 


O     O 

Isoboletol 


Evidence  is  being  accumulated,  furthermore,  that  many  molds 
and  yeasts  contain  glutathione,  which  can  function  in  respiratory 
processes  as  an  oxidation-reduction  system,  perhaps  in  conjunc- 
tion with  pigments.  Miller  and  Stone  (1938)  record  the  occur- 
rence of  glutathione  in  Monilia  sitophila  and  in  species  of  Peni- 
cillium, Aspergillus,  and  Rhizopus. 


OTHER  METABOLIC  PRODUCTS 

Amonsr  the  products  of  outstanding  interest  produced  by  a 
species  of  Penicillium,  presumably  P.  notatum,  is  a  bactericidal 
substance.  Attention  was  called  by  Fleming  (1929)  to  this  prop- 
erty of  culture  solutions  in  which  an  unnamed  species  of  Peni- 
cillium had  been  grown.  This  solution  inhibited  the  growth  of 
various  organisms  taken  from  the  throat  and  favored  the  growth 
and  isolation  of  Hemophilus  influenzae.  Reid  (1935)  investigated 
the  properties  of  this  germicidal  substance,  now  known  as  peni- 
cillin.    Later  Chain  and  his  associates  (1940)  reported  its  thera- 


OTHER  METABOLIC  PRODUCTS  81 

peutic  action  against  Streptococcus,  Staphylococcus,  and  Clostri- 
dium septique  in  laboratory  animals.  From  the  same  laboratory 
Abraham  et  al.  (1941)  purified  penicillin  and  determined  its  action 
against  body  cells  and  against  bacteria,  indicating  its  therapeutic 
potentialities  to  replace  sulfonamides.  In  fact,  it  was  found  to 
operate  when  sulfonamides  are  ineffective  and  to  be  without  toxic 
effect  against  body  tissues.  It  is  bacteriostatic  to  Staphylococcus 
and  Streptococcus  in  vitro  in  dilutions  of  one  to  a  million.  Its 
chemical  formula,  according  to  Meyer  et  al.  (1942),  is  Ci4Hi9NO«. 

In  a  series  of  reports  additional  important  findings  by  Raistrick 
and  Smith  (1941),  Oxford,  Raistrick,  and  Smith  (1942),  Oxford 
and  Raistrick  (1942),  and  Oxford  (1942)  were  announced  on  the 
production  by  fungi  of  substances  that  inhibit  the  growth  of 
pathogenic  bacteria.  From  Penicillium  citrinnm  these  workers  ob- 
tained penicillin,  and  from  P.  cyclopium  penicillic  acid.  Both 
substances  are  bacteriostatic  to  Staphylococcus  aureus,  and  peni- 
cillic acid  is  inhibitory  also  to  the  typhoid  and  paratyphoid  bac- 
teria. They  isolated  spinulosin  from  Penicillium  spinulosum  and 
fumigatin  from  Aspergillus  fumigatiis.  Fumigatin  is  especially 
potent  against  Bacillus  anthracis,  Staphylococcus  aureus,  and 
Vibrio  cholerae.  The  same  workers  synthesized  both  spinulosin 
and  fumigatin. 

Waksman  and  Schatz  (1943)  found  that  Aspergillus  clavatus 
produces  a  potent  bacteriostatic  substance  designated  clavacin; 
differing  amounts  are  produced  by  different  strains. 

Kochalaty  ( 1943)  purified  an  antibacterial  substance  called  pena- 
tin,  produced  by  Penicillium  notatum,  to  the  extent  that  it  in- 
hibited growth  of  50  species  of  pathogenic  and  non-pathogenic 
bacteria  in  dilutions  of  one  to  ten  millions  or  more. 

Waksman  and  Bugie  (1943)  concluded  that  the  antibiotic  activ- 
ity of  Aspergillus  flavus  is  due  to  two  substances:  (1)  aspergillic 
acid,  which  is  active  against  both  Gram-positive  and  Gram-nega- 
tive bacteria,  and  (2)  flavacin,  which  is  active  against  Gram-nega- 
tive bacteria  and  may  be  identical  with  penicillin.  In  the  produc- 
tion of  these  antibacterial  substances  three  factors  are  involved: 
(1)  differences  in  strains  of  A.  flavus,  (2)  the  composition  of  the 
substrate,  and  (3)  the  conditions  of  growth,  especially  aeration. 

Bergel  et  al.  (1943)  isolated  clavatin  (identical  with  clavacin) 
from  solutions  in  which  Aspergillus  clavatus  had  been  grown. 
Their    analyses    indicated    for    clavatin    the    empirical    formula 


88  BIOCHEMISTRY  OF  FUNGI 

CtH);04.  Furthermore  they  were  able  to  show  that  this  antibac- 
terial substance  is  probably  identical  with  claviformin,  isolated 
from  Penicillium  claviforme  by  Chain  and  his  associates,  and  also 
with  patulin,  isolated  from  P.  patulum  by  Raistrick  and  his  asso- 
ciates. Trichoderma  viride  has  been  shown  to  produce  a  very 
potent  pigment  called  viridin  [Brian  et  al.  (1946)].  Surveys  re- 
veal that  many  fungi  produce  antibiotics  fWilkins  and  Harris 
(1942,  1943,  1945)]. 

Growing  Penicillium  charlesii  on  Czapek-Dox  nutrient  with 
glucose  added,  Clutterbuck  et  al.  (1934)  isolated  a  group  of  re- 
lated substances.  These  included  carolic  acid,  C9H10O4,  carolinic 
acid,  C9H10O7,  carlic  acid,  Ci0HU)Og,  carlosic  acid,  CioH120(;, 
ramigenic  acid,  CioIT.oO,;,  and  verticillic  acid,  Clv.H^Oi-..  Peni- 
cillic  acid,  C^Hind,  has  been  isolated  from  P.  puberultmi  and  P. 
cyclophmi.  Puberulic  acid,  C8H(,0,„  has  been  obtained  from 
P.  puberuluvi.  Mvcophenolic  acid  is  formed  by  both  P.  glaucuvi 
and  P.  stoloniferuvi. 

The  ability  of  molds,  especially  P.  brevicaule  and  Aspergillus 
sydowiij  to  react  with  arsenicals  is  of  peculiar  interest.  These 
organisms  liberate  volatile  arsenical  products  when  growing  on 
arsenic-containing  wallpaper  or  when  inoculated  into  the  stomach 
contents  of  persons  who  have  succumbed  to  arsenical  poisoning. 
Challenger  et  al.  (1933)  found  that  trimethyarsine,  which  has  a 
very  pungent  odor  reminscent  of  garlic,  is  produced  in  this  re- 
action. Among  other  fungi  capable  of  producing  a  similar  re- 
action are  Aspergillus  niger,  A.  virescens,  Mucor  mucedo  and 
M.  raceviosus. 

IMPLICATIONS 

Manifestly  many  problems  in  mycological  chemistry  await 
solution.  In  some  instances,  at  least,  it  seems  unfortunate  that  the 
details  involved  in  the  utilization  of  molds  in  industrial  processes 
have  remained  trade  secrets.  In  this  period  when  vitamin  defi- 
ciencies are  so  widely  encountered,  more  should  be  known  re- 
garding the  possibilities  of  utilizing  fungi  as  sources  of  vitamins. 
The  extent  to  which  vitamins  are  essential  in  the  metabolism  of 
funtn  themselves  is  also  deserving  of  further  elucidation. 

The  manufacture  of  citric  acid  and  gluconic  acid  by  mold 
fermentation  has  already  been  industrialized.  Doubtless,  when 
more  is  known  regarding  the  fermentations  which  give  rise  to 
other  organic  acids,  molds  will  come  to  be  used  in  their  commer- 


IMPLICATIONS  89 

cial  production.  Scarcely  more  than  a  beoinnino-  seems  to  have 
been  made  in  the  study  of  fungus  pigments  and  of  their  uses  to 
man  and  to  the  mold  itself. 

The  study  of  toxin  production  by  fungi  is  still  in  its  infancy. 
Fungus  toxins  may  eventually  come  to  have  an  important  place  in 
therapy  against  pathogenic  bacteria.  The  production  of  sera 
containing  fungus  antitoxins  is  deserving  of  more  consideration. 

Lastly,  the  physiology  of  molds  should  be  studied  in  quite  the 
same  manner  as  has  been  done  with  bacteria.  A  few  studies  of 
this  kind,  typified  by  that  of  Martin  and  Jones  (1940),  in  which 
carbohydrate  fermentations  and  colony  characteristics  were  em- 
ployed to  distinguish  species  of  Candida,  indicate  the  potentiali- 
ties of  these  procedures.  By  such  studies  and  by  the  refinement  of 
techniques  a  better  understanding  may  be  reached  regarding  the 
protein  metabolism  of  fungi  and  the  mechanism  by  which  they 
are  able  to  elaborate  mannose,  glycogen,  toxins,  and  many  other 
substances. 

LITERATURE  CITED 

Abraham,  E.  P.,  E.  Chain,  C.  M.  Fletcher,  A.  D.  Gardner,  N.  G.  Heatley, 

and  M.  A.  Jennings,  "Further  observations  on  penicillin,"  Lancet,  2:  7, 

177-188,  1941. 
Bergel,  F.,  A.  L.  Morrison,  A.  R.  Moss,  R.  Klein,  H.  Rinderknecht,  and 

J.  L.  Ward,  'An  antibacterial  substance  from  Aspergillus  clavatus  and 

Penicillium  clavijorme  and  its  probable  identitv  with  patulin,"  Nature, 

152:150,  1943. 
Bernhauer,  K.,  "Zum  Problem  der  Saurebildung  durch  Aspergillus  niger," 

Biochem.  Z.,  153:517-521,  1924. 
"tTber  die  Saurebildung  durch  Aspergillus  niger.    Allgemeines  und  metho- 

disches  bei  der  Untersuchung  des  Saurebildungs  Vorgange,"  Biochem. 

Z.,  272:296-312,  1926. 
Bernhauer,  K.,  and  N.  Bockl,  "Zum  Chemismus  der  durch  Aspergillus  niger 

bewirkten  Saurebildungsvorgange.     VII.     Uber  die  Umwandlung  von 

Alkolhol  in  Citronensaure,"  Biochem.  Z.,  253:  16-24,  1932. 
VIII.  "Uber  die  Umwandlung  von  Aconitsaure  in  Citronensaure  und  wei- 

teres  tiber  die  Abbau  der  Essigsaure,"  Biochem.  Z.,  253:25-29,  1932a. 
Bernhauer,  K.,  and  G.  Potzelt,  "Uber  Schimmelpilz-sterine.    I.  Die  Sterin- 

bildung  bei  Aspergillus  niger,"  Biochem.  Z.,  280:  388-393,  1935. 
Bernhauer,  K.,  and  Z.  Scheuer,  "Zum  Chemismus  der  durch  Aspergillus 

niger  bewirkten   Saurebildungsvorgange.     VII.   Uber   die   Bildung   der 

Glykol  und  Glykolsaure  aus  essigsauren  Salzen,"  Biochem.  Z.,  253:  11- 

15,  1932. 
Bernhauer,  K.,  and  H.  Siebenauger,  "Zum  Chemismus  der  Citronensaure  - 

bildung    durch    Pilze.     V.    Die    Citronensaurebildung    aus   Essigsaure," 

Biochem.  Z.,  240:232-244,  1931. 


90  BIOCHEMISTRY  OF  FUNGI 

Bernhauer,  K.,  and  H.  Thelen,  "Zum  Chemismus  der  durch  Aspergillus 
niger  bewirkten  Saurebildungsvorgange.     IX.  Uber  die  Abfangung  von 
Acetaldehvd  in  den  Pilzkulturen,"  Biochem.  Z.,  253:  30-36,  1932. 
Birkinshaw,  J.  H.,  "Biochemistry  of  the  lower  fungi,"  Biol.  Rev.,  12:357- 

392,  1937. 
Birkinshaw,  J.  H.,  R.  K.  Callow,  and  C.  F.  Fischmann,  "The  isolation  and 
characterization    of    ergosterol    from    Penicillium    puberulwn    Bainier, 
grown  on  synthetic  medium  with  glucose  as  sole  source  of  carbon," 
Biochem.  J.,  25:  1977-1980,  1931. 
Birkinshaw,  J.  H.,  and  H.  Raistrick,  "Studies  in  the  biochemistry  of  micro- 
organisms.    XXIII.  Puberulic  acid  CHnOo  and  an  acid  CsFUOc,  new- 
products    of    the    metabolism    of    glucose    by    Pemcillium    puberulwn 
Bainier  and  Pemcillium  aurantio-virens  Biourge,"  Biochem.  J.,  25:441- 
450,  1932. 
Boas,  F.,  "Starkebildung  bei  Schimmelpilzen,"  Biochem.  Z.,  78:  308-312,  1917. 
"Wcitere  Untersuchungen  iiber  die  Bildung  starkeahnlicher  Substanzen 

bei  Schimmelpilzen"  Biochem.  Z.,  81:  80-86,  1917a. 
•'Untersuchungen  iiber  Starkewirkung  und  Bildung  loslicher  Starke  bei 
Schimmelpilzen.     II,"  Zentrctl.  Baku  Par asitenk.,  II  Abt.,  55:7-11,  1922. 
Brian,  P.  W.,  P.  J.  Curtis,  H.  G.  Hemming,  and  J.  C.  McGowan,  "The  pro- 
duction of  viridin  bv  pigment-forming  strains  of  Trichoderma  viride," 
Ann.  Appl.  Biol.,  33:  190-200,  1946. 
Butkewitsch,  W.  S.,  "Uber  die  Bildung  der  Citronensaure  aus  Zucker  in 
Kulturen  von  Penicillium  glaucum  und  Aspergillus  niger"  Biochem.  Z., 
755:224-237,   1923. 
Butkewitsch,  W.  S.,  and  A  I.  W.  Fedoroff,  "Uber  Bildung  von  Fumarsaure 
in  den  Zuckerkulturen  von  Mucor  stolonifer  (Rhizopus  nigricans) ,  und 
sein  Verhalten  zur  Bernstaubensaure,"  Biochem.  Z.,  205:440-456,  1929. 
"Uber  die  Umwandlung  der  Essigsaure  durch  Mucor  stolonifer  in  Bern- 
stein- und  Furmarsaure  und  das  Verfahrcn  zur  Trennung  und  qualita- 
tiven  Bestimmung  dieser  Sauren,"  Biochem.  Z.,  207:302-318,  1929a. 
"Uber  die  Yerhaltnisse   zwischen  Essig-,  Bernstein-,  Fumar-,  und   Oxal- 
saure  in  den  Kulturen  von  Mucor  stolonifer  und  einigen  anderen  Pilzen." 
Biochem.  Z.,  219:  87-102,  1930. 
"Uber  die  Umwandlung  des  Aethylalkohol  in  den  Kulturen  von  Mucor 
stolonifer;'  BiochevuZ.,  219:  103-121,  1930a. 
Butkewitsch,  \V.  S.,  and  A.  G.  Timofeeva,  "Einflusz  einzelner  mineralischcr 
Elemente  des  Xahrmediums  auf  die  Saurebildung  bei  Aspergillus  niger" 
Biochem.  Z.,  275:405-415,  1935. 
Chain,  E.,  et  al.,  "Penicillium  as  a  chemotherapeutic  agent,"  Lancet,  2:  226- 

228,  1940. 
Chali  i  \<.i  k,  F.,  C.  Hk.ginbottom,  and  L.  Ellis,  "The  formation  of  organo- 
metalloid    compounds    by    micro-organisms.      I.    Trimethylarsine    and 
dimethvlethvarsine,,,  /.  Chem.  Soc,  1933:  95-101,  1933. 
Chrzaszcz,  T.,  and  D.  Tiukow,  "Uber  die  Saurebildung  der  Penicilliumarten 
(Link),"  Biochem.  Z.,  204:  106-124,  1V29. 
"Die  Starkebildung  bei  den  Schimmelpilzen  (Penicillium  Link),  wic  auch 


LITERATURE  CITED  91 

ihr   Zusammenhang   mit    der    Saurebildung,"    Biochem.    Z.,   201: 39-52, 
1929a. 
Chrzaszcz,  T.,  and  D.  Tiukow,  "Oxalsaure  in  Schimmelpilzkulturen,"  Bio- 
chem. Z.,  218:  73-85,  1930. 
"Biochemische  Umbildung  der  Essigsaure  durch  Schimmelpilze  und  iibcr 

den  Chemismus  der  Citronensaurebildung,"  Biochem.  Z.,  229:  343-357, 
1930a. 
"Der  Zusammenhang  der  Starkebildung  mit  der  Saurenanhaufung  bei  den 

Schimmelpilzen  (Penicillium),"  Biochem.  Z.,  222:  243-258,  1936. 
Clutterbuck,  P.  W.,  W.  N.  Ha  worth,  H.  Raistrick,  G.  Smith,  and  M. 

Stacey,  "The  metabolic  products  of  Penicillium  charlesii  G.  Smith," 

Biochem.  J.,  28:94-110,  1934. 
Clutterbuck,  P.  W.,  A.  E.  Oxford,  H.  Raistrick,  and  G.  Smith,  "Studies 

in  the  biochemistry  of  micro-organisms.  XXIV.  The  metabolic  products 

of  the  Penicillium  brevi-comp  actum  series,"  Biochem.  ].,  26:  1441-1458, 

1932. 
Cohen,  Clara,  "Uber  die  Bildungr  von  Acetaldehvd  bei  den  Umsetzunsen 

von  Zucker  durch  Pilze,"  Biochem.  Z.,  112:  139-143,  1920. 
Connstein,    W.,    and    K.    Ludecke,    "Uber    Glycerin    Gewinnung    durch 

Garung,"  Ber.  dent.  chem.  Ges.,  52:  1385-1391,  1919. 
Coyne,  F.  P.,  and  H.  Raistrick,   "Studies  in  the  biochemistry  of  micro- 
organisms.   XX.  On  the  production  of  manitol  from  hexoses  and  pen- 
toses by  white  species  of  Aspergillus,"  Biochem.  ].,  25:  1513-1521,  1931. 
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Chem.,  31: 15-37,  1917. 
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Biol.  Chem.,  22:287-293,  1915. 
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Biol.  Chem.,  18: 167-175,  1914. 
Emerson,  R.,  and  D.  L.  Fox,  "Carotene  in  the  sexual  phase  of  the  aquatic 

fungus  Allomyces,"  Proc.  Roy.  Soc.  London,  B,  128:  275-293,  1940. 
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50:454-455,  1897. 
Fitz,  A.,  "Uber  alkoholische  Gahrung  durch  Mucor  mucedo,"  Ber.  deut. 

chem.  Ges.,  5:48-58,  1873. 
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special  reference  to  their  use  in  the  isolation  of  B.  influenzae,"  Brit.  J. 

Expt.  Path.,  10:226-236,   1929. 
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92  BIOCHEMISTRY  OF  FUNGI 

Herrick,  H.  T.,  and  O.  E.  May,  "The  production  of  gluconic  acid  bv  the 
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Iwanoff,  N.  A  I.,  'The  biochemistry  of  the  fungi,"  Ann.  Rev.  Biochem., 
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Iwanoff,  N.  M.,  and  E.  S.  Zwetkoff,  "The  biochemistry  of  the  fungi," 
Ann.  Rev.  Biochem.,  2:521-540,  1933;  5:585-612,  1936. 

Kardo-Ssysojewa,  E.,  "Uber  die  Bildung  von  Gluconsaure  durch  Asper- 
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Kochalaty,  W.,  "Purification  and  properties  of  the  second  antibacterial 
substance  produced  bv  PeniciUiuni  notation"  Science,  94:  186-187, 
1943. 

KouL,  F.,  and  D.  G.  Kostermans,  "Hetero-auxin  als  Stoffwechselprodukt 
niederer  pflanzlicher  organismen.  Isolierung  aus  Hefe,"  Hoppe-Seyler's 
Z.  physiol.  Chem.,  228:  113-121,  1934. 

Kostytchew,  S.,  "Der  Einfluss  des  Substrates  auf  die  anaerobe  Atmung  der 
Schimmelpilze,"  Ber.  dent,  botan.  Ges.,  20:327-334,  1902. 
"Uber  die  alkoholgarung  von  Aspergillus  niger"  Ber.  dent,  botan.  Ges., 
25:44-50,  1907;  25:  188-191,  1907a. 

Kostytchew,  S.,  and  W.  Tschesnokow,  "Bildung  von  Citronensaure  und 
^Dxalsaure  durch  Aspergillus  niger"  Planta,  4:  181-200,  1927. 

Letcher,  H.,  and  J.  J.  Willaman,  "Biochemistrv  of  plant  diseases.  VIII. 
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1926. 

Lockwood,  L.  B.,  and  A.  J.  A  [oyer,  "The  production  of  chemicals  bv  fila- 
mentous fungi,"  Botan.  Rev.,  4:  140-164,  1938. 

Lockwood,  L.  B.,  G.  E.  W\rd,  O.  E.  May,  H.  T.  Herrick,  and  H.  T. 
O'Neill,  "Production  of  fat  bv  Penicilliinn  javanicum  von  Beijma," 
Zentr.  Bakt.  Parasitenk.,  II  Abt.,  411-425,  1934. 

Martin,  D.  S.,  and  C.  P.  Jones,  "Further  studies  on  the  practical  classification 
of  the  Alonilias,"  /.  Bact.,  39:  609-630,  1940. 

May,  O.  E.,  H.  T.  Herrick,  A.  J.  Mover,  R.  Hellbach,  "Semi-plant-scale 
production  of  gluconic  acid  bv  mold  fermentation,"  Ind.  Eng.  Chem., 
21:  1198-1203,  1929. 

May,  O.  E.,  H.  T.  Herrick,  C.  Thom,  and  A  I.  B.  Church,  "The  production 
of  gluconic  acid  bv  the  PeniciUiuni  luteum-purpurogenum  group.  I," 
/.  Biol.  Chew.,  75:417-422,  1927. 

May,  O.  E.,  A.  J.  AIoyer,  P.  A.  Wells,  and  H.  T.  Herrick,  "The  produc- 
tion of  kojic  acid  by  Aspergillus  flavus"  J.  Am.  Chem.  Soc,  53:  774-782, 
1931. 

Meyer,  Karl,  et  al.,  "On  Penicillin;'  Science,  96:20-21,  1942. 

Miller,  T.  E.,  and  R.  W.  Stone,  "Occurrence  of  glutathione  in  micro-or- 
ganisms," /.  Bact.,  36:248-249,  1938. 

Molliard,  M.,  "Sur  une  nouvclle  fermentation  acide  produite  par  le  Sterig- 
matocystis  nigra"  Comp.  rend..  774:881,  1922. 

Mover,  A.  J.,  O.  E.  May,  and  H.  T.  Herrick,  "Production  of  gluconic  acid 
by  PeniciUiuni  chrysogemtm"  'Zentr.  Bakt.  Parasitenk.,  II  Abt.,  P5;311- 
324,  1936. 


LITERATURE  CITED  93 

Neuberg,  C,  and  Clara  Cohen,  "Uber  die  Bildung  von  Acetaldehvd  und 
die  Verwicklichung  der  zweiten  Vergarungsform  bei  verschiedenen 
Pilzen,"  Biochem.  Z.,  722:204-224,  1921. 

Nord,  F.  F.,  and  Robert  P.  Mull,  "Recent  progress  in  the  biochemistry  of 
Fusaria,"  Advances  in  EnzymoL,  5:  165-205,  1945. 

Oxford,  A.  E.,  "Antibacterial  substances  from  moulds.  Part  III.  Some 
observations  on  the  bacteriostatic  powers  of  the  mould  products  citrinin 
and  penicillic  acid,"  Cheviistry  &  Industry,  61:48-51,  1942. 
"Part  V.  The  bacteriostatic  powers  of  the  methvl  ethers  of  fumigatin 
and  spinulosin  and  other  hydroxy-,  methoxv-,  and  hvdroxymethoxy  de- 
rivatives of  toluquinone  and  benzoquinone,"  Cheviistry  &  Industry, 
61:  189-192,  1942. 

Oxford,  A.  E.,  H.  Raistrick,  and  G.  Smith,  "Part  II.  Penicillic  acid,  a 
metabolic  product  of  Penicillhtm  puberulum  Bainier  and  Penicillium 
cyclophnn  Westling,"  Chemistry  &  Industry,  61:  22-24,  1942. 

Oxford,  A.  E.,  and  H.  Raistrick,  "Part  IV.  Spinosin  and  fumigatin,  meta- 
bolic products  of  Penicillium  spinuloswn  Thorn  and  Aspergillus  fumi- 
gatus  Fresenius,"  Chemistry  &  Industry,  61:  128-129,  1942. 

Pearson,  L.  K.,  and  K.  B.  Raper,  "The  influence  of  temperature  on  the 
nature  of  the  fat  formed  by  living  organisms,"  Biochem.  J.,  21:  875-879, 
1927. 

Porges,  N.,  "Citric  acid  production  by  Aspergillus  niger"  Am.  J.  Botany, 
19:  559-567,  1932. 

Preuss,  L.  AL,  H.  J.  Gorcica,  H.  C.  Greene,  and  W.  H.  Peterson,  "Wach- 
stum  und  Steringehalt  gewisser  Schimmelpilze,"  Biochem.  Z.,  246:401- 
413,  1932. 

Preuss,  L.  M.,  W.  H.  Peterson,  and  E.  B.  Fred,  "Isolation  and  identifica- 
tion of  ergosterol  and  mannitol  from  Aspergillus  fischeri,"  J.  Biol.  Chem., 
5>7:483-489,  1932a. 

Preuss,  L.  M.,  W.  H.  Peterson,  H.  Steenbock,  and  E.  B.  Fred,  "Sterol  con- 
tent and  antirachitic  activatibility  of  mold  mycelia,"  /.  Biol.  Chem., 
90:  369-384,  1931. 

Prill,  E.  A.,  P.  R.  Wenck,  and  W.  H.  Peterson,  "The  chemistrv  of  mould 
tissue.  VI.  Factors  influencing  the  amount  and  nature  of  the  fat  pro- 
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Raistrick,   H.,   "Biochemistry  of  the  lower  fungi,"   Ergeb.  Enzymforsch., 
1:  345-363,  1931. 
"Certain    aspects    of   the    biochemistry    of    the    lower   fungi    (moulds)," 

Ergeb.  Enzymforsch.,  7:  3 16-348,  1938. 
"Biochemistry  of  the  lower  fungi,"  Ann.  Rev.  Biochem.,  9:571-592,  1940. 

Raistrick,  H.,  et  al.,  "Studies  in  the  biochemistrv  of  micro-organisms," 
Trans.  Roy.  Soc.  London,  B,  220:  367  pp.,  1931. 

Raistrick,  H.,  and  A.  B.  Clark,  "On  the  mechanism  of  oxalic  acid  formation 
by  Aspergillus  niger"  Biochem.  /.,  13:  329-344,  1919. 

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organisms. XXIV.  2:5-Dihydroxybenzoic  acid  (gentisic  acid),  a  new 
product  of  the  metabolism  of  glucose  bv  Penicillium  griseofulvum 
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94  BIOCHEMISTRY  OF  FUNGI 

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1941. 
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by  a  mold,"  /.  Bad.,  29:  215-221,  1935. 
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1944. 
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27:318-322,  1935. 
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LITERATURE  CITED  95 

Wilkins,  W.  H.,  and  G.  C.  M.  Harris,  "Investigation  into  the  production 
of  bacteriostatic  substances  by  fungi.     III.  Preliminary  examination  of 
a  second  100  fungal  species,"  Brit.  J.  Expt.  Path.,  24:  141-143,  1943. 
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chem.  J.,  22: 1504-1507,  1928. 


Chapter  5 
EFFECTS  OF  TEMPERATURE  ON  FUNGI 

Temperature  is  one  of  the  most  important  environmental  factors 
affecting  the  metabolic  activities  of  fungi.  Since  this  fact  is  o-en- 
erally  appreciated,  manv  workers  have  concerned  themselves  with 
problems  involving  the  influence  of  temperature  upon  selected 
species  of  fungi.  These  studies  have  dealt  with  temperature  as  a 
factor  in  spore  germination,  mycelial  growth,  and  reproduction 
of  the  chosen  organisms;  with  determinations  of  their  cardinal 
temperatures,  temperature  coefficients,  and  lethal  temperatures; 
with  attempts  to  correlate  temperatures  that  are  favorable  or  in- 
hibitorv  to  infection  and  the  subsequent  development  of  disease 
or  decav  with  those  that  are  favorable  or  inhibitory  to  the  Growth 
of  the  pathogens;  and  with  attempts  to  establish  a  rational  basis 
to  account  for  the  geographical  distribution  and  seasonal  incidence 
of  fungi.  In  the  aggregate  the  reports  of  these  studies  contain  a 
large  volume  of  data  together  with  varied  interpretations  of  them. 
In  the  account  that  follows  an  attempt  has  been  made  to  select 
from  these  numerous  reports  representative  materials  that  will 
aid  in  evaluating  the  effects  of  temperature  on  fungi. 

It  does  not  seem  to  be  possible  completely  to  isolate  tempera- 
ture as  an  environmental  factor  in  studies  with  fungi.  Such  non- 
temperature  factors  as  relative  humidity,  rate  of  accumulation  and 
concentration  of  staling  products  and  other  by-products,  char- 
acter of  the  substrate,  initial  reaction  and  rate  of  change  of  re- 
action of  the  medium,  and  aeration  of  the  medium,  as  well  as 
factors  internal  to  the  fungus,  such  as  strain  differences  and  a^e 
of  the  mycelium,  exert  an  influence,  whether  the  fungus  is  being 
grown  on  artificial  media  or  on  the  natural  substrate. 

Furthermore  in  experimental  conditions  temperatures  are  either 
maintained  continuously  or  else  fluctuate  to  only  a  small  decree, 
whereas  in  nature  they  vary  continually.  Whether  all  metabolic 
activities  can  be  maintained  at  a  constant  optimal  level  over  indefi- 

96 


CARDINAL  TEMPERATURES  91 

nite  periods  or  whether  one  activity  is  favored  by  a  given  tempera- 
ture whereas  another  is  adversely  affected  by  the  same  tempera- 
ture is  none  too  well  known  at  present.  The  investigator  is  led 
to  suspect,  however,  that  physiologic  unbalance  results  if  tem- 
peratures are  maintained,  because  at  a  constant  level  a  single 
temperature  may  not  necessarily  be  optimum  for  the  germination, 
the  mycelial  development,  and  the  reproduction  of  all  species. 

The  duration  of  exposure  of  a  fungus  to  a  given  temperature 
should  also  be  taken  into  consideration.  This  factor  becomes  im- 
portant in  a  study  of  the  rate  of  growth,  which  varies  within  the 
culture  period,  there  being  a  lag  at  the  initiation  of  growth,  fol- 
lowed by  a  period  of  acceleration  and  eventually  terminated  by  a 
period  of  deceleration.  These  facts  are  expressed  in  the  well- 
known  sigmoid  growth  curve,  characteristic  of  all  organisms. 

Another  difficulty  that  presents  itself,  as  has  been  indicated  in 
Chapter  1,  is  the  inadequacy  of  methods  for  measuring  growth. 
In  nearly  all  reports  use  is  made  of  the  diameter  of  colonies  or  of 
the  amount  of  surface  area  of  colonies,  when  as  a  matter  of  fact 
growth  is  three-dimensional.  These  two  criteria  are  of  value 
in  comparing  the  growth  of  an  organism  at  different  constant  tem- 
peratures on  the  same  medium,  but  they  largely  lose  their  value 
when  a  comparison  is  made  of  the  same  or  different  organisms 
grown  on  different  media.  In  studying  the  rate  of  growth  of 
Verticillium  albo-atrum,  Chaudhuri  (1923)  was  led  to  conclude 
that  the  "rate  of  spread"  on  different  media  may  be  associated 
with  extremely  different  rates  of  mycelial  production. 

CARDINAL  TEMPERATURES 

Each  fungus  may  be  presumed  to  possess  a  minimum,  an  opti- 
mum, and  a  maximum  temperature.  The  minimum  and  the  maxi- 
mum limit  growth  at  low  and  high  temperatures,  respectivelv. 
These  values  are  difficult  to  fix  absolutely  and  usually  are  oniv 
closely  approximated.  The  optimum  temperature  is  that  which 
permits  greatest  metabolic  activity;  it  is  usually  based  upon  meas- 
urement of  the  greatest  increment  of  growth  during  some  defi- 
nite time  interval.  Respiratory  activity  and  mycelial  extension, 
however,  may  be  correlated  with  one  optimum,  whereas,  as  has 
been  indicated  and  will  be  discussed  subsequentlv,  conidial  pro- 
duction may  occur  at  a  different  optimum.     Observations   by 


98  EFFECTS  OF  TEMPERATURE  ON  FUNGI 

Fawcett  (1921)  indicate  that  the  optimum  cannot  be  considered 
apart  from  the  time  factor. 

The  temperature  range  within  which  fungi  are  active  is  rather 
limited  in  comparison  to  that  of  bacteria.  At  0°  C  their  growth 
is  completely  checked,  and  relatively  few  are  active  at  42°  C. 
The  optimum  temperature  is  not  median  in  any  instance  between 
the  minimum  and  the  maximum  temperatures.  In  other  words, 
temperature  does  not  increase  the  rate  of  fungus  activity  uni- 
formly from  the  minimum  to  the  optimum,  and  decrease  it  uni- 
formly from  the  optimum  to  the  maximum. 

In  connection  with  the  rate  of  reaction  (physiological  proc- 
esses) in  fungi,  the  {generalized  rule  of  van't  Hoff,  which  states 
that  for  every  rise  of  10°  C  the  reaction  rate  is  doubled  or  trebled, 
holds  true,  within  the  range  approximating  10°  C  to  30°  C.  At 
high  temperatures,  however,  as  Blackman  (1905)  has  indicated, 
this  rule  is  modified  by  a  time  factor,  for  ".  .  .  when  the  process 
is  conditioned  as  to  its  rapidity  by  a  number  of  separate  factors, 
the  rate  of  the  process  is  limited  by  the  pace  of  the  'slowest 
factor.'  Such  controlling  factors  are  sometimes  spoken  of  as 
"pace-makers."  Their  influence  is  universally  demonstrated  in 
graphs  showing  cardinal  temperatures  in  all  fungi  studied.  The 
growth  curve  is  observed  to  decline  sharply  and  precipitously 
from  the  optimum  to  the  maximum.  In  Table  8  are  assembled 
the  cardinal  temperatures  for  a  few  representative  species  grown 
on  semisolid  media. 

The  most  extensive  study  to  date  involving  temperature  in  rela- 
tion to  the  growth  of  fungi  capable  of  producing  decay  of  wood 
is  that  of  Cartwright  and  Findlay  (1934).  They  measured  the 
diameter  of  colonies  grown  on  2%  malt  agar,  using  the  average 
daily  increment  of  growth  of  five  colonies  as  an  index.  Their  ob- 
servations are  summarized  in  Table  9. 

From  these  data  it  is  apparent,  first  of  all,  that  the  temperature 
requirements  of  species  within  the  families  Thelephoraceae,  Polv- 
poraceae,  and  Agaricaceae  are  variable  between  species,  even 
within  the  same  genus. 

Cartwright  and  Findlay  (1934)  indicate  that  comparative 
growth  rates  on  malt  agar  may  not  necessarily  indicate  the  growth 
rates  on  timber  in  the  forest.  Stereum  purpureum,  for  example, 
grows  rapidly  on  malt  agar  but  slowly  on  wood.  Nevertheless 
a  given  wood-destroying  species,  such  as  S.  frtistitloswn  on  oak, 


CARDINAL  TEMPERATURES 


99 


TABLE  8 

Cardinal  Temperatures  of  Various  Fungi 


Fungus 
Fusarium  coeruleum 

Fusarium  eumartii 

Fusarium  discolor  var.  sulphureum 

Fusarium  oxysporum 

Fusarium  radicicola 

Fusarium  trichothecioides 

Verticillium  albo-atrum 

Verticillium  albo-atrum 
Rhizoctonia  solani 
Merulius  sihestris 
Merulius  domesticus 
Merulius  sclerotiorum 
Polyporus  vaporarius  spumarius 
Verpa  bohemica 
Lenzites  saepiaria 
Polyporus  versicolor 
Lenzites  tigrinus 
Gloeosporium  musarum 
Glomerella  cingulata 
Glomerella  gossypii 
Gloeosporium  jructigenum 
Colletotrichum  lagenarium 
Colletotrichum  lindemuthianum 
Magnusia  nit i da 
Magnusia  brae hy trie hi a 
Pythiacystis  citrophthora 
Phytophthora  terrestris 
Phomopsis  citri 
Diplodia  natalensis 
Ceratostomella  pili/era 
Ceratostomella  coerulea 
Ceratostomella  pluriannulata 
Ceratostomella  ips 


Source  of  Data 

Edson  and  Shapovalov 

(1920) 
Edson  and  Shapovalov 

(1920) 
Edson  and  Shapovalov 

(1920) 
Edson  and  Shapovalov 

(1920) 
Edson  and  Shapovalov 

(1920) 
Edson  and  Shapovalov 

(1920) 
Edson  and  Shapovalov 

(1920) 
Chaudhuri  (1923) 
Lauritzen  (1929) 
Falck  (1907) 
Falck  (1907) 
Falck  (1907) 
Falck  (1907) 
Falck  (1907) 
Lindgren  (1933) 
Lindgren  (1933) 
Lindgren  (1933) 
Edgerton  (1915) 
Edgerton  (1915) 
Edgerton  (1915) 
Edgerton  (1915) 
Edgerton  (1915) 
Edgerton  (1915) 
Sweet  (1941) 
Sweet  (1941) 
Fawcett  (1921) 
Fawcett  (1921) 
Fawcett  (1921) 
Fawcett  (1921) 
Lindgren  (1942) 
Lindgren  (1942) 
Lindgren  (1942) 
Lindgren  (1942) 


Temperatures 
{degrees  C) 


Mini- 
mum 

5 


Opti-      Maxi- 
mum      mum 

25  35 


25 


35 


5  25  35 

5  30 

5  30 

5         25  35 

5         25  35 

10  22.5       30 

2  23  34.5 

3  25  30 
3  22  30 
3  25  30 
3  25  30 
3  22  30 
5  32-35  45 
0  27-32  40 
7         32-35      43 

29-30  37.5 
27-29  37.5 
27-29      37.5 

24-25  34-35 
24  35 

21-23  30-31 
5          32  43 

5  32  43 

8.7      26.5       31.9 

12.0      31.5  36.1 

9.1      27.0  31.4 

8.4      28.0  36.0 

4        28-29  34-35 

3  25-27  32-34 

4  28-29  34-35 
6-8       30-32  37-39 


100 


EFFECTS  OF  TEMPERATURE  ON  FUNGI 


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102  EFFECTS  OF  TEMPERATURE  ON  FUNGI 

may  completely  invade  the  wood  to  the  exclusion  of  all  other 
Thelephoraceae  and  Polvporaceae.  Conceivably  the  temperature 
differential  may  be  an  important  factor  when  two  or  more  species 
are  competing  for  occupancy  of  a  given  piece  of  wood,  but  it  may 
not  necessarily  constitute  the  controlling  factor. 

Another  inference  from  the  data  of  Cartwright  and  Findlay 
(1934)  involves  temperature  as  an  ecological  factor  affecting  the 
geographical  distribution  of  fungi.  It  is  well  known  that  certain 
species,  just  as  is  true  also  of  seed  plants,  are  quite  sharply  re- 
stricted in  their  natural  habitat  to  Arctic  regions,  to  temperate 
regions,  or  to  the  tropics.  In  pathogens  this  distribution  might  be 
anticipated  to  be  coextensive  with  that  of  the  suscepts  and  there- 
fore not  necessarily  governed  primarily  by  temperature.  In  sapro- 
phytic species,  temperature  might  not  be  expected  to  be  as  potent 
a  factor  as  the  kind  of  substrate,  and  saprophytes  might  be  antici- 
pated to  be  cosmopolitan  in  distribution.  Nevertheless,  many 
saprophytes  are  restricted  in  distribution,  but  evidence  indicates 
that  with  them  temperature  is  a  major  factor.  This  conclusion 
finds  support  in  Weimer  and  Harter's  (1923)  studies  on  the  tem- 
perature relations  among  species  of  Rhizopus.  They  found  that 
R.  chinensis  is  distinctly  more  tolerant  of  high  temperature  than 
any  of  the  other  ten  species  tested. 

Humphrey  and  Siggers  (1933)  made  an  extensive  study  of  tem- 
peratures favorable  to  the  growth  of  wood-rotting  fungi  in  cul- 
ture, and  on  this  basis  were  able  to  arrange  them  into  three  groups: 
(1)  a  low-temperature  group  (20°  to  24°  C),  (2)  an  intermediate- 
temperature  group  (24°  to  32°  C),  and  (3)  a  high-temperature 
group  (above  32°  C). 

In  the  first  group  are  included  Coniophora  cerebella,  Stereum 
gausapatuni,  Merulius  lacrymans,  Phlebia  merismoides,  Folypoms 
abietiiuts,  P.  schnveinitzii,  Tomes  amiosus,  F.  officinalis,  F.  mgroli- 
neatns,  Trametes  pini,  and  Colly  bia  velutipes.  In  the  second  group 
Humphrey  and  Siggers  placed  Merulius  sihestris,  At.  tremellosus, 
Corticium  chrysocreas,  C.  effuscatum,  Peniophora  gigantea, 
Stereiim  jrustulosum,  S.  fasciatum,  S.  rameale,  Porta  incrassata,  P. 
subacida,  P.  xantha,  Polyporus  radiatus,  P.  robinophilus,  P.  sinuo- 
susy  P.  sulphireus,  P.  versicolor,  Daedalea  ambigua,  D.  quercina, 
D.  unicolor,  Trametes  serialis,  Tomes  everhartii,  F.  igniarius,  F. 
marmoratus,  F .  pijiicola,  F.  rimosus,  F.  subroseus,  Ganoderma 
applanatum,  Lenzites  berkeleyi,  Irpex  mollis,  Hydnum  ochracewn, 


RESISTANCE  TO  TEMPERATURES  103 

H.  pulcherrimwm,  Lentimis  lepidens,  Schizophyllum  commune, 
and  Pleurotus  o streams.  The  third  group  comprises  Phlebia  stri- 
gosazonata,  Stereum  fuscum,  Poly  poms  hirsutus,  Ganoderma  luci- 
dum,  Lenzites  saepiaria,  L.  trabea,  and  Pamis  riidis. 

Studies  to  date  on  the  temperature  relations  of  wood-destroy- 
ing fungi  have  involved  their  Growth  on  artificial  media  rather 
than  on  wood  [Herrick  (1939)].  It  is  conceivable  that  there  may 
be  little,  if  anv,  correlation  of  growth  rates  on  such  different  sub- 
strates. Lindgren  (1933)  indicated  that  two  reasons  may  be  as- 
signed for  a  lack  of  correlation:  (1)  the  chemical  and  phvsical 
differences  between  nutrient  agar  and  wood;  and  (2)  the  time 
factor,  cultivation  on  agar  being  confined  to  periods  of  short  dura- 
tion and  on  wood  in  nature  to  long  periods.  These  reasons  appear 
to  be  sufficient  to  render  unreliable  anv  predictions  of  the  rate  of 
decay  of  timber  on  the  basis  of  the  rate  of  growth  on  agar  of  the 
causal  fungus. 

RESISTANCE  TO  LOW  TEMPERATURES  AND 
HIGH  TEMPERATURES 

Experiments  to  determine  the  ability  of  fungi  to  survive  when 
subjected  to  temperatures  in  excess  of  those  known  to  inhibit 
growth  and  reproduction  are  meager.  The  results  of  these  experi- 
ments, however,  show  that  fungi  are  much  more  tolerant  of  low 
than  of  high  temperatures.  Evidently,  as  the  temperature  is 
elevated  above  the  maximum  for  growth,  desiccation  and  coagu- 
lation of  proteins  occur,  and  these  reactions  become  the  proximate 
cause  of  death.  At  low  temperatures,  on  the  other  hand,  these 
profound  changes  in  proteins  may  not  be  accomplished,  and 
other  explanations  are  needed  to  account  for  the  death  of  the 
fungus. 

Low  temperatures.  The  temperatures  employed  in  ordinary 
refrigeration  and  cold  storage  are^very  effective  in  inhibiting  the 
growth  of  such  fungi  as  those  causing  decay  of  meats,  fruits,  vege- 
tables, and  other  foodstuffs. 

Lauritzen  (1929)  found  that  a  storage  temperature  of  less  than 
2°  C  is  required  to  prevent  decay  of  turnips,  induced  by  Rhizoc- 
tonia  solam.  At  a  maintained  temperature  of  8°  to  10°  C  this 
fungus  caused  62  to  87%  decay  within  a  period  of  2  years. 

Brooks  and  Cooley  (1917)  stored  apples  inoculated  with  vari- 
ous decay-producing  fungi  at  0°  C  with  the  result  that  the  rots 


104 


EFFECTS  OF  TEMPERATURE  OX  FUXG1 


developed.  The  organisms  involved  included  Alternaria  sp.,  Bo- 
try  t  is  cinerea,  Cephalothechmi  roseum,  Neofabrea  malicorticiSj 
Fenicillhmi  expansum,  Sclerotinia  cinerea,  Sphaeropsis  malonmi. 


0  -1  -2  -3  -4 

Temperature  (degrees  Centigrade) 

Fig.  4.    Effect  of  cold  upon  survival  of  Aethalium  septicum.    A.  Slow  cool- 
ing, followed  bv  exposure  for   10  minutes  at  the  given  temperatures.     B. 
Rapid   cooling,   followed   bv   exposure   for   5   seconds.     C.   Rapid   cooling, 
followed  by  exposure  for  10  minutes.     (After  Gehenio  and  Luyet.) 

and  Vohitella  fn/cti.  Storage  at  10°  C  inhibited  Glomerella  cin- 
gulata;  at  153  C,  Fusarium  radicicola.  These  results  support  the 
observations  of  Schneidcr-Orelli  (1912),  who  grew  on  gelatin  the 
following  species  at  maintained  temperatures  of  0°  C,  4.5°  C,  and 
9.5°  C:  Botrytis  cinerea,  Fusarium  putrefaciens,  Gloeosporhtm 
album,  G.  her barum,  Monilia  fructigena,  Mi/ cor  piriformis,  and 


RESISTANCE  TO  TEMPERATURES 


10$ 


Fenicillium  glaucum.     Neither  Gloeosporiwn  fructigenum  nor 

Rhizopus  nigricans,  however,  grew  at  0°  C,  although  meager  colo- 
nies of  these  organisms  developed  at  4.5°  C.  Since  so  many  decay- 
inducing  fungi  are  able  to  grow  at  or  near  0°  C,  it  is  essential  that 
subzero  conditions  be  provided  for  many  readily  perishable  foods 
that  must  be  kept  for  months  before  they  normally  reach  the  con- 
sumer. Consequently  storage  in  dry  ice  has  been  employed  effec- 
tively to  meet  these  conditions. 


Disease-^, 

^^-Fung 

us  growth 

8 


12 


16  20  24  28 

Temperature  (degrees  Centigrade) 


32 


36 


Fig.  5.     Comparison  under  controlled  conditions  of  temperatures  favorable 

for  the  development  of  tobacco-root  rot  with  those  favorable  for  the  growth 

of  the  causal  fungus.    Tobacco-root  rot  develops  best  at  temperatures  below 

those  optimum  for  the  pathogen.     (After  Jones.) 

Numerous  species  of  fungi  are  able  to  survive  subzero  weather, 
as  their  going  into  dormancy  in  fall  and  their  reappearance  in 
spring  indicate.  The  cold  of  winter  may  decimate  the  fungus 
population,  but  it  does  not  cause  the  extinction  within  a  given  area 
of  any  considerable  number  of  species. 

Buller  and  Cameron  (1913)  exposed  the  fructifications  of 
Schizophyllnm  commune  for  several  winter  months  to  tempera- 
tures that  ranged  between  —  15°  C  and  —40°  C.  After  the  fructi- 
fications  had  been  brought  inside  for  a  few  hours,  they  resumed 
casting  their  spores.  Moreover,  when  fructifications  that  were 
actively  discharging  spores  were  quickly  frozen  at  —  3 1  °  C,  they 
still  retained  their  viability. 

Bennett  ( 193 1 )  subjected  the  vegetative  and  perithecial  stages  of 
Gibberella  saitbinettii  to  —20°  C  every  third  day  for  45  days,  per- 
mitting the  temperature  at  no  time  to  reach  zero.    Afterwards  the 


106  EFFECTS  OF  TEMPERATURE  ON  FUNGI 

cultures  were  more  vigorous  and  produced  perithecia  more  abun- 
dantly than  similar  cultures  that  had  been  kept  at  normal  tem- 
peratures. 

The  ability  of  fungi  to  tolerate  extreme  cold  is  illustrated  by 
Buller's  (1913)  findings  with  Schizophyllum  commune  and  by 
Faull's  (1930)  findings  with  Neurospora  crass  a.  Buller  exposed 
the  fructifications  of  5.  commune  to  —  190°  C  for  3  weeks  without 
apparent  injury,  and  Faull  subjected  the  ascospores  of  N.  crassa 
to  temperatures  from  — 170°  to  —  190°  C  for  24  to  48  hours  with- 
out delaying  their  germination.  When  wet,  the  conidia  of  this 
species  were  unimpaired  by  exposure  to  —80°  C  for  1  hour;  when 
dry,  to  —170°  to  —190°  C  for  an  equal  period.  Toleration  of 
these  extremely  low  temperatures  leads  the  investigator  to  antici- 
pate that  the  spores  of  certain  species  will  be  found  to  survive 
at  absolute  zero  (  —  273°  C),  the  point  at  which  all  reactions  and 
hence  all  biological  processes  are  theoretically  supposed  to  be  in- 
hibited, provided,  of  course,  that  the  period  of  exposure  is  not 
too  protracted. 

Becquerel  (1910)  dried  the  conidia  of  Aiucor,  Rhizopus,  Asper- 
gillus, and  Sterigmatocvstis,  sealed  them  in  tubes  under  vacuum  in 
which  the  pressure  was  reduced  to  10-4  cm  of  mercury,  and  ex- 
posed them  at  — 190°  C  for  77  hours;  after  2  years'  storage,  they 
germinated  normally. 

In  the  experiments  of  Kadisch  (1931)  with  several  dermato- 
phytes, Achorion  gypseum  survived  3  hours1  exposure  to  —252°  C 
in  one  instance,  and  in  another  withstood  2  hours  at  —268°  C, 
followed  by  4  hours  at  —268.8°  C  and  then  1  )<>  hours  at  —272°  C. 

It  would  be  anticipated  that  mycelia  cannot  tolerate  as  extreme 
temperatures  as  can  spores.  Evidence  in  support  of  this  supposi- 
tion has  been  presented  by  Bartetzko  (1910),  Lindner  (1915), 
and  Lipman  (1937).  Bartetzko  (1910)  subjected  germinating 
spores  of  Aspergillus,  Penicillium,  Botrytis,  and  Phycomyces  in 
liquid  nutrient  media  to  —  14°  for  2  hours  without  injury.  When 
the  young  hyphae  of  Aspergillus  in  1%  glucose  solution  were  ex- 
posed to  —12°  for  2  hours,  they  were  killed,  whereas  in  5%  glu- 
cose solution  there  was  no  apparent  injury  at  —26°  for  an  equal 
period.  The  other  species  exhibited  similar  differences  in  glucose 
solutions  of  different  concentrations. 

Lindner  ( 1915)  exposed  Aspergillus  niger  and  Penicillium  glau- 
cumy  growing  on  3%  gelatin,  to  —10°  to  —13°  C.     Age  of  the 


RESISTANCE  TO  TEMPERATURES  101 

hyphae  and  duration  of  exposure  were  found  to  be  important 
factors.  Twenty-four-hour-old  cultures  were  more  easily  killed 
than  48-hour-old  cultures.  Aerial  hyphae  were  more  easily  killed 
than  submerged  hyphae. 

Lipman  (1937)  employed  12  species  of  fungi,  cultured  for  24 
hours  on  synthetic  agar  or  on  potato  agar.  After  gradual  cooling 
he  immersed  them  in  sealed  tubes  for  48  hours  in  liquid  air;  he 
then  gradually  warmed  them.  Of  the  12  species,  belonging  in 
Aspergillus,  Penicillium,  Rhizopus,  Mucor,  Absidia,  Mortierella, 
Rhizoctonia,  Armillaria,  Trichoderma,  Pythium,  and  Fusarium, 
8  survived.  As  an  explanation  Lipman  hypothesizes  that  this  ex- 
traordinary tolerance  may  be  causally  related  to  the  tiny  spaces 
that  exist  between  the  colloidal  micelles,  which  because  of  their 
small  size  prevent  dehydration  through  ice  formation. 

Not  all  fungi  are  capable  of  tolerating  the  extremes  of  tempera- 
ture which  have  been  mentioned.  Gehenio  and  Luyet  (1939)  ex- 
posed the  plasmodium  of  Aethalhun  septimm  so  as  to  study  the 
effect  of  cold  on  vitality  and  the  influence  of  the  duration  of  ex- 
posure, as  well  as  to  determine  whether  cold  per  se  or  the  sud- 
denness of  the  temperature  change  is  responsible  for  injury.  They 
found,  first  of  all,  that  there  may  be  marked  injury  at  tempera- 
tures of  freezing  or  slightly  above  if  the  plasmodia  are  cooled 
abruptly,  whereas  with  slow  cooling  the  injury  may  not  be  ap- 
preciable until  the  temperature  descends  to  about  —2.5°  C.  They 
also  noted  that  the  plasmodia  may  be  killed  after  exposure  of  only 
5  seconds  to  temperatures  of  —1°  or  —  2°  C.  This  sensitivity  to 
cold  finds  support  in  the  observations  that  some  tropical  species 
of  seed  plants  are  killed  if  exposed  to  temperatures  above  0°  C.  In 
these  cases  death  cannot  be  attributed  to  the  formation  of  ice 
crystals.  Here  the  mechanism  of  death,  as  postulated  by  Gehenio 
and  Luyet,  consists  of  gelation  of  the  protoplasmic  sol  under  the 
action  of  cold,  the  gelation  being  accompanied  by  syneresis.  The 
squeezing  out  of  the  dispersion  medium,  if  gelation  is  complete,  is 
not  a  reversible  process  and  hence  is  lethal. 

The  problem  of  the  causes  of  death  by  low  temperatures  in 
fungi,  in  other  plants,  and  in  animals  is  summarized  in  the  mono- 
graph by  Luyet  and  Gehenio  (1940).  Their  summary  indicates 
that  death  from  cold  has  been  attributed  to  the  following  causes: 
(1)  bursting  of  the  cells  by  expansion  in  ice  formation,  with  con- 
sequent mechanical  injury;  (2)  destruction  of  the  fine  structure 


108  EFFECTS  OF  TEMPERATURE  ON  FUNGI 

of  the  protoplasm  bv  ice  crystals;  (3)  crushing  between  the  ice 
masses  as  freezing  progresses;  (4)  thawing  at  too  rapid  a  rate;  (5) 
dehydration  of  protoplasm,  resulting  in  increased  permeability, 
increased  viscosity,  coagulation  of  proteins,  ionic  dissociation,  loss 
of  water-binding  properties  of  cytoplasm,  and  or  svneretic  re- 
lease of  water. 

High  temperatures.  Fungi,  it  has  been  pointed  out,  generally 
are  unable  to  tolerate  exposure  to  high  temperatures.  The  de- 
cline in  ability  to  germinate  or  to  grow  is  normally  very  sharp  in 
the  zone  beyond  the  optimal. 

The  lethal  effects  of  temperature  on  germination  of  spores  is 
considered  in  Chapter  9  and  therefore  need  not  be  discussed  here. 
In  many  instances  such  temperatures  as  inhibit  germination  and 
growth  or  are  lethal  are  not  excessive.  For  example,  Wolf  et  al. 
(1934)  found  that  sporangia  of  Peronospora  tabacina  exposed  to 
85°  F  for  1  hour  are  incapable  of  germination. 

Fawcett  and  Barger  (1927)  observed  that  oranges  kept  at  90.5° 
F,  which  is  above  the  maximal  limit  for  Pemcillhmi  italicum  and 
P.  digitatimi,  are  not  decayed  during  28  days'  exposure.  On  the 
other  hand,  Faull  (1930)  noted  that  the  ascospores  of  Neurospora 
crassa,  when  heated  for  more  than  1  hour  at  50°  C,  retain  their 
ability  to  grow. 

In  the  fermentation  of  cigar  tobaccos,  temperatures  of  140°  to 
150°  F  are  not  unusual.  Aspergillus  niger,  commonly  present  on 
the  cured  leaves,  is  unable  to  develop  at  these  temperatures  but 
may  induce  spoilage  if  too  much  time  elapses  for  the  bulk  to  be- 
come hot  or  to  cool  after  fermentation.  Temperatures  near  100°  F 
approximate  the  optimum  for  this  mold. 

Treatment  with  hot  water  has  been  employed  to  free  seed  oats 
from  loose  smut,  caused  by  Ustilago  avenae,  and  wheat  from 
naked  smut,  caused  by  U.  tritici.  Such  treatment  is  practicable 
because  the  temperature  lethal  for  the  smut  fungi  is  lower  than 
that  which  kills  the  cereal  embryos.  Similarly,  cotton  seed,  if 
slowly  desiccated,  can  be  rendered  free  from  viable  external 
conidia  and  internal  mycelium  of  the  anthracnose  fungus,  Glomc- 
rella  gossypii.  Lehman  (1925)  predried  cotton  seeds  at  50°  C, 
for  36  hours  or  at  60°  C  for  18  to  24  hours  and  then  heated  their; 
to  95°  C  for  10  to  12  hours,  without  reducing  their  percentage 
germination  and  with  complete  elimination  of  the  anthracnose 
fungus. 


INFLUENCE  OF  TEMPERATURE  ON  INFECTION  109 

In  some  cases  seed  disinfection  does  not  require  exposure  to  ex- 
cessive temperatures.  Edgerton  (1915)  found  that  30°  to  31°  C 
is  maximum  for  the  growth  in  culture  of  Colletotrichinn  linde- 
muthianum  and  has  been  able  to  produce  in  Louisiana,  during 
summer,  anthracnose-free  bean  seed  from  a  crop  planted  with 
infected  seed. 


INFLUENCE  OF  TEMPERATURE  ON  INFECTION 

The  severity  of  certain  soil-borne  diseases,  especially  those 
caused  by  Fusarium,  Verticillium,  Rhizoctonia,  Sclerotinia,  and 
Thielaviopsis,  is  known  to  be  correlated  with  temperature.  Data 
bearing  on  this  matter  have  been  amassed  from  the  use  of  soil- 
temperature  tanks  equipped  with  thermostatic  controls.  Plans 
for  the  construction  and  operation  of  this  type  of  apparatus  are 
described  by  Jones,  Johnson,  and  Dickson  (1926).  Their  account 
should  be  carefully  read  to  obtain  an  appreciation  of  the  problems 
relating  to  the  influence  of  temperature  in  the  development  of 
plant  diseases  and  to  the  construction  and  operation  of  ecostats. 
These  workers  conclude  that  disease  is  the  resultant  of  the  "inter- 
action of  the  plastic  host  and  a  plastic  parasite  under  the  play  of 
variable  environment."  Temperature,  as  a  variable,  modifies  the 
metabolic  activity  not  only  of  the  host  but  also  of  the  parasite, 
and  it  may  happen  that  such  temperatures  as  approximate  opti- 
mum for  the  one  may  exercise  an  adverse  influence  upon  the  other. 

By  means  of  soil-temperature  tanks  Gilman  (1916)  determined 
that  symptoms  of  cabbage  yellows,  caused  by  Fusarium  conglu- 
tinans,  are  absent  at  maintained  soil  temperatures  between  12°  and 
16°  C,  but  that  characteristic  symptoms  appear  within  the  range 
17°  to  22°  C.  When  this  organism  is  grown  in  culture,  its  opti- 
mum, indicated  by  a  daily  increase  in  the  diameter  of  colonies, 
approximates  25°  C. 

Johnson  and  Hartman  (1919),  also  using  soil-temperature  tanks, 
found  that  soil  temperatures  of  17°  to  23°  C  are  most  favorable  for 
the  development  of  tobacco-root  rot.  The  disease  gradually  di- 
minished in  severity  above  26°  C  and  was  absent  at  29°  to  30°  C. 
As  they  indicate,  account  must  be  taken  in  experimentation  of 
such  other  factors  as  soil  moisture,  soil  reaction,  supplv  of  nu- 
trients in  the  soil,  and  amount  of  infestation,  none  of  which  can  be 
isolated  and  evaluated  completely.     The  sum  total  of  all  these 


110 


EFFECTS  OF  TEMPERATURE  ON  FUNGI 


factors,  whether  favorable  or  unfavorable  to  the   development 
of  the  disease,  determines  the  severity  of  the  attack. 

The  destruction  of  stem  tissues  of  potato  and  injury  to  the 
growing  points  by  Corticium  vagum  are  limited  within  the  range 
9°  to  27°  C,  [Richards  (1921)  |,  with  greatest  damage  between 
15°  and  21°  C.  The  severity  of  attack  decreases  very  rapidly 
above  21°  C,  and  damage  is  minor  at  24°  C  and  above. 

7  C 


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Soil  temperature  (degrees  Centigrade) 


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38 


Fig.  6.    Relation  of  the  growth  rate  of  Fusarium  conglutinans  and  the  de- 
velopment   of    cabbage    yellows    at    various    controlled    soil    temperatures. 
Both  have  quite  the  same  optima.     (After  Jones,  Johnson,  and  Dickson.) 

Infection  of  onions  by  Urocystis  cepulae  is  governed  by  soil 
temperature  [Walker  and  Wellman  ( 1926)  ] .  Abundant  infection 
by  this  smut  fungus  occurs  at  temperatures  as  low  as  10°  to  12°  C, 
which  is  about  the  minimum  permitting  germination  and  growth 
of  onions.  Temperatures  extending  up  to  25°  C  favor  infection, 
but  above  this  point  the  amount  of  infection  is  rapidly  decreased. 
At  29°  C  and  above,  the  onion  seedlings  remain  free  from  in- 
fection. 

Observations  of  the  foregoing  type  afford  a  basis  in  accounting 
for  the  seasonal  incidence  of  certain  plant  diseases  and  for  their 
geographical  distribution.  Jones  (1924)  pointed  out  that  onion 
smut  does  not  occur  in  southern  Texas,  although  the  pathogen 
has  been  repeatedly  introduced  into  this  region.    The  soil  temper- 


TEMPERATURE  AND  REPRODUCTION  111 

ature  is  above  that  lethal  to  the  smut  fungus  during  the  period 
when  the  seedlings  are  being  grown  in  seed  beds  and  are  being 
transplanted.  The  prevalence  of  peach-leaf  curl  and  apple  scab  is 
correlated  with  cold,  wet  spring  weather.  Late  blight  of  potatoes 
is  entirely  absent,  or  at  least  never  epiphvtotic,  in  the  Coastal 
Plains  area  of  the  southeastern  United  States  if  the  crop  matures 
in  late  May  or  in  June,  when  summer  temperatures  prevail.  The 
fundus  which  causes  downy  mildew  of  tobacco  disappears  rather 
quickly  after  a  few  warm  days  with  temperatures  in  excess  of  85° 
F  [Dixon,  McLean,  and  Wolf  (1936)].  The  observations  of 
Stevens  (1917)  led  him  to  conclude  that  temperature  is  the  chief 
climatic  influence  in  the  growth  of  the  chestnut-blight  fungus, 
Endothia  parasitica.  Sclerotium  rolfsii  is  limited  to  warm  regions 
and  becomes  of  importance  only  during  hot  weather. 

TEMPERATURE  AND  REPRODUCTION 

There  is  abundant  evidence  that  temperatures  favorable  for 
germination  or  for  growth  of  fungi  may  be  slightly  lower  than 
those  favorable  for  reproduction.  In  some  instances  mycelial 
growth  occurs  at  high  temperatures  that  are  inhibitory  to  repro- 
duction. Ames  (1915)  determined  that  the  spores  of  Thielaviop- 
sis  paradoxa  germinate  at  5°  to  6°  C,  and,  although  there  is  slight 
growth  at  10°  C,  this  organism  must  be  provided  with  tempera- 
tures in  excess  of  10°  C  to  induce  fruiting.  If  the  temperature 
is  elevated  to  36°  C,  however,  the  mycelium  develops,  but  conidia 
are  not  produced.  Similar  differences  were  noted  at  both  the 
upper  and  lower  limits  for  Glomerella  rufomacirians,  which  ger- 
minates at  4°  C,  but  requires  a  minimum  of  12°  C  to  produce 
spores.  Pemcillhnn  digitatinn  is  able  to  germinate  and  grow  at 
30°  C,  but  no  conidia  are  formed  at  this  temperature. 

Sweet  (1941)  recorded  that  the  formation  of  cleistothecia  by 
Magnnsia  nitida  and  M.  brachytrichia  occurs  throughout  the 
range  16°  to  38°  C,  although  conidial  germination  is  secured 
throughout  the  range  1.5°  to  43°  C.  Production  of  conidia, 
however,  is  limited  to  the  range  10°  to  38°  C  in  M .  nitida,  and  16° 
to  40.5°  C  in  M.  brachytrichia. 

Sporulation  by  Peronospora  tabacina  occurs  within  a  range  of 
temperature  from  42°  to  63°  F  and  is  most  abundant  at  56°  F 


112 


EFFECTS  OF  TEMPERATURE  OX  FUNGI 


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Temperature  (degrees  Centigrade) 

Fig.   ".     Relation  of  CO2  production  per  unit  weight  of  mycelial  mat  to 

temperature  for  Polystictus  versicolor,  and  of  Oj  tension,  COL>  production, 

and  temperature.     (After  Scheffer  and  Livingston.) 


TEMPERATURE  AND  REPRODUCTION 


113 


[Dixon,  McLean,  and  Wolf  (1936)].    Mycelial  growth,  however, 
may  occur  at  temperatures  either  below  or  above  this  range. 

Sawyer  (1929)  found  that  a  temperature  of  approximately  21° 
C  is  most  favorable  for  growth  and  reproduction  by  Entomoph- 


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Time  (days) 


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Fig.  8.    Effect  of  aeration  of  liquid  media  on  the  dry  weight  of  mycelial  mat 
produced  by  Verticillium  albo-atriim.     (After  Chaudhuri.) 

thora  sphaerosperma.    Although  growth  occurs  at  12°  C,  conidia 
are  not  formed. 

Temperatures  within  the  range  21°  to  25°  C  were  observed  by 
Longree  (1939)  to  be  optimum  for  sporulation  of  Sphaerotheca 
pannosa  var.  rosae,  but  mycelial  growth  occurs  well  beyond  both 
of  these  limits.  Crosier  (1933)  reported  21°  C  as  optimum  for 
sporangial  production  by  Phytophthora  infestans.  Krause  (1930) 
concluded  that  perithecial  formation  by  Neocosmospora  vasin- 
fecta  and  Nectria  coccinea  is  markedly  influenced  by  temperature. 
At  7°  C  Nectria  coccinea  requires  45  days  to  produce  perithecia; 


114  EFFECTS  OF  TEMPERATURE  ON  FUNGI 

at  22.5°  C,  30  days;  and  at  30°  C,  17  days.  At  22.5°  C  Neocos- 
vwspora  vasinfecta  requires  45  days;  at  28.5°  C,  30  davs;  and  at 
31.5°  C,  17  davs.  Undoubtedly  low  temperature  is  a  primary 
factor  in  the  formation  of  sporophores  by  many  Thelephoraceae 
and  Polyporaceae,  but  not  all  species.  This  statement  is  substan- 
tiated by  the  occurrence  in  North  Carolina  of  fresh  sporophores 
of  Fomes  annosus,  Poly  poms  abietinus,  P.  sanguineus,  Sterenm 
lobatum,  and  S.  jasciatinn  at  any  time  in  the  interval  from  Oc- 
tober to  March. 


TEMPERATURE  AND  ZONATIOX 

Alternation  of  light  and  darkness  is  known  to  stimulate  the  pro- 
duction of  daily  bands  of  conidia  and  hence  of  zonation  in  various 
fungi  grown  in  Petri  dishes,  as  described  in  Chapter  6.  Tempera- 
ture may  also  play  an  important  role  in  zonation.  Bisby  (1925) 
made  the  observation  that  Fnsariimi  discolor  sulphureum,  which 
forms  zones  in  response  to  alternating  light  and  darkness,  can  be 
induced  to  form  zones  in  constant  darkness  provided  that  tem- 
perature is  favorable.  At  a  temperature  of  16°  to  18°  C  zonation 
does  not  occur,  even  though  the  cultures  are  exposed  to  alternate 
light  and  darkness.  At  21°  C  zones  can  be  formed  under  the 
stimulus  of  lisrht,  but  similar  cultures  in  constant  darkness  are 
without  zones.  At  30°  C,  however,  rings  were  formed  when  the 
cultures  were  maintained  in  constant  darkness. 

TEMPERATURE  COEFFICIENTS 

By  temperature  coefficient  is  meant  the  ratio  of  the  rate  of  a 
given  physiological  process,  for  example,  respiration,  at  any  given 
temperature  to  the  rate  at  which  this  process  proceeds  at  another 
temperature.  Temperature  coefficient  is  frequently  represented 
by  the  symbol  Qut,  meaning  that  the  interval  is  10°  and  that  the 
rate  at  the  given  higher  temperature  is  divided  by  the  rate  at  the 
temperature  10°  lower.  Biologists  well  appreciate  the  fact  that 
within  a  range  which  approximates  the  minimal  and  maximal 
temperature  limits  for  the  given  organism,  the  reaction-velocity 
changes  follow  van't  HoiTs  rule.  According  to  this  rule,  Qu>  for 
the  physiological  orocess  in  question  should  lie  between  2  and  3 
as  a  minimum. 


TEMPERATURE  COEFFICIENTS 


115 


116 


EFFECTS  OF  TEMPERATURE  OX  FUNGI 


Temperature  coefficients  have  been  abundantly  determined  and 
interpreted.  Fawcett  (1921)  measured  the  growth-temperature 
coefficients  of  Pythiacystis  citrophthora  and  Fhytophthora  terres- 
tris  within  the  range  8°  to  36°  C,  of  Fhovwpsis  citri  within  the 
rans;e  8°  to  32°  C,  and  of  Diplodia  natalensis  within  the  range  8° 
to  45°  C.    He  found  that  for  each  24-hour  observation  period,  the 


320 


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Temperature  ( degrees  Centigrade ) 


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Fk..  10.  The  extent  of  decav,  measured  in  terms  of  diameter  of  lesions, 
induced  in  turnips  bv  Rhizoctonia  solani  at  various  maintained  temperatures. 

(After  Lauritzen.) 

Qiu  for  mycelial  growth  is  greatest  for  the  lowest  temperature 
shown  and  becomes  smallest  for  the  highest  temperatures.  At  8° 
to  18°  C  Fhytophthora  terrestris  showed  a  coefficient  of  30,  and 
at  26°  to  36°  C  a  coefficient  of  0.4".  lor  the  8°  to  18°  C  range 
the  Oio  of  Fhowopsis  citri  was  4.0;  for  the  21°  to  31°  C  range,  0.5. 
Within  the  range  investigated,  the  coefficient  of  Pythiacystis 
citrophthora  was  12.3  for  the  lowest  temperature  and  0.05  for  the 
highest;  that  of  Diplodia  natalensis  was  16.7  for  the  lowest  tem- 
perature and  0.05  for  the  highest. 

ScherTer  (1936)  determined  the  rate  of  carbon  dioxide  produc- 
tion bv  Polystictus  versicolor.     He  found  that  production  was 


TEMPERATURE  AND  OXYGEN  TENSION  111 

greater  as  temperature  was  increased,  and  at  29.5°  C  was  critical. 
The  loss  of  carbon  (as  CO;.)  was  least  within  the  range  25.5°  to 
29.5°  C;  it  was  relatively  great  at  17.5°  and  at  33.5°  C.  Moreover 
the  rate  of  C02  production  per  unit  of  mycelial  area  and  the  rate 
of  growth  were  quite  alike  within  the  range  17.5°  to  29.5°  C. 

TEMPERATURE  AND  OXYGEN  TENSION 

In  the  light  of  findings  that  the  respiratory  quotient  is  highest 
at  the  lowest  temperatures  and,  conversely,  lowest  at  the  highest 
temperature,  it  would  be  expected  that  oxygen  tension  would  also 
modify  physiological  processes.  Evidence  of  such  modifying 
effect  has  been  presented  by  Scheffer  and  Livingston  (1937). 
They  grew  Polystictus  versicolor  on  malt  agar  in  special  tubes, 
by  means  of  which  they  could  modify  the  oxygen  tensions  and 
then  keep  them  at  constant  levels.  At  the  same  time  they  main- 
tained constant  temperatures  by  means  of  thermostatically  con- 
trolled incubators.  By  these  procedures  they  found  that  C02 
production  per  unit  area  of  mycelial  mat  was  always  most  rapid 
as  02  pressure  became  greater.  At  33.5°  C  with  745-mm  pres- 
sure of  02,  C02  production  was  most  rapid;  it  was  least  rapid  at 
17.5°  C  with  zero  02  pressure.  Mycelial  growth,  however,  was 
most  rapid  at  the  optimum  temperature  for  P.  versicolor,  that  is, 
at  29.5°  C,  at  all  02  pressures  from  16  mm  to  745  mm.  When 
C02  production  in  atmospheres  of  pure  02  was  compared  with 
that  in  pure  N2,  Scheffer  and  Livingston  noted  that  the  rate  per 
unit  of  mycelial  area  was  two  to  five  times  as  rapid  in  oxygen  as 
in  nitrogen. 

The  availability  of  02  is  known  to  operate  in  another  manner, 
as  has  been  demonstrated  by  Chaudhuri  (1923).  He  aerated 
liquid  nutrient  media  on  which  Verticillhim  albo-atram  was  being 
grown  at  different  temperatures,  employing  rate  of  spread  as  a 
measure  of  yield  of  fungus  material.  His  data  show  that  aeration 
markedly  increases  both  the  rate  of  growth  and  the  total  amount 
of  growth  in  a  given  volume  of  liquid  media.  Since  V .  albo- 
atnnn  is  known  to  produce  staling  products,  Chaudhuri  postu- 
lates that  these  increases  are  to  be  attributed  to  the  oxidation  of 
wraste  products. 


118 


EFFECTS  OF  TEMPERATURE  ON  FUNGI 


90 


85 


80 


75 


70 


65 


60 


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Fusarium  discolor 
var.  sulphureum 


Fusarium 
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Fusarium 
radicicola 


15        20         25 
Degrees  Centigrade 

Fig.  11.  The  growth,  measured  in  terms  of  diameter  of  colonies,  of  soil- 
inhabiting  pathogens  as  influenced  by  temperature.  Verticillhtm  albo-atrwn 
has  the  slowest  growth  rate;  25°  C  is  the  optimum  temperature.      (After 

Edson  and  Shapovalov.) 


IMPLICATIONS  U9 


IMPLICATIONS 


Experiments  involving  the  maintenance  of  fungi  in  culture  at 
a  given  constant  temperature  for  considerable  periods  have  a 
limited  usefulness.  This  conclusion  finds  support  in  the  fact  that 
in  nature  fungi  do  not  encounter  constant  temperature.  Experi- 
ments with  controlled  temperature  have  demonstrated,  it  appears, 
that  optimal  temperature  requirements  exist  for  each  metabolic 
activity  of  a  given  fungus  and  for  each  phase  in  its  developmental 
cycle.  It  is  desirable  therefore  that  a  much  larger  body  of  data 
showing  these  facts  be  accumulated,  for  from  such  experiments 
would  certainly  come  increased  understanding  of  temperature  as 
an  environmental  factor  in  fungus  activities. 

Some  persons  are  inclined  to  make  light  of  the  popular  idea  that 
"diseases  are  caused  by  weather."  Indeed,  such  persons  may  with 
fairness  be  accused  of  overemphasizing  the  "germ  theory."  They 
are  content  to  stress  the  primary  cause  of  disease  and  to  overlook 
secondary  or  attendant  causes.  Since  temperature  is  one  of  the 
components  of  weather,  it  cannot  be  ignored  in  its  influence, 
among  pathogenic  fungi,  upon  such  sequential  phenomena  as 
spore  dispersal,  spore  germination,  incubation  and  severity  of  the 
resultant  disease,  and,  finally,  the  development  of  reproductive 
elements  by  the  pathogen. 

LITERATURE  CITED 

Ames,  A.,  "The  temperature  relations  of  some  fungi  causing  storage  rots," 

Phytopathology,  5: 11-19,  1915. 
Bartetzko,  H.,  "Untersuchungen  iiber  das  Erfrieren  von  Schimmelpilzen," 

Jahrb.  iviss.  Botan.,  41:  57-98,  1910. 
Becquerel,  P.,  "Recherches  experimentales  sur  la  vie  latente  des  spores  des 

Mucorinees  et  des  Ascomycetes,"  Conip.  rend.,  150:  1437-1439,  1910. 
Bennett,  F.  T.,  "Gibberella  saubinettii  (Mont.)  Sacc.  on  British  cereals.    II. 

Physiological  and  pathological  studies,"  Ann.  Applied  Biol.,  18:  158-177, 

1931. 
Bisby,   G.   R.,   "Zonation   in   cultures   of  Fusarhmi   discolor  sulphureum," 

My  col.,  11:  89-97,  1925. 
Blackman,  F.  F.,  "Optima  and  limiting  factors,"  Ann.  Botany,  19:  281-295, 

1905. 
Brooks,  Charles,  and  J.  S.  Cooley,   "Temperature  relations  of  apple-rot 

fungi,"  /.  Agr.  Research,  8:  139-164,  1917. 


120  EFFECTS  OF  TEMPERATURE  ON  FUNGI 

Brooks,  Charles,  and  J.  S.  Cooley,  "Temperature  relations  of  stone-fruit 

fungi,"  /.  Agr.  Research,  22:451-465,  1922. 
"Time-temperature   relations   in   different  types  of  peach-rot  infection," 

/.  Agr.  Research,  31:  507-543,  1928. 
Buller,  A.  H.  R.,  "Upon  the  retention  of  vitality  by  dried  fruit  bodies  of 

certain  Hvmenomvcetes,  including  an  account  of  an  experiment  with 

liquid  air,"  Trims.  Brit.  Mycol.  Soc,  4:  106-112,  1913. 
Buller,  A.  H.  R.,  and  A.  T.  Cameron,  "On  the  temporary  suspension  of 

vitality  in  the  fruit  bodies  of  certain  Hvmenomvcetes,"  Proc.  Trans. 

Roy.  Soc.  Canada,  6:73-78,  1913. 
Cartwright,  K.  St.  G.,  and  W.  P.  K.  Findlay,  "Studies  in  the  physiology 

of  wood-destroving  fungi.     II.  Temperature  and  the  rate  of  growth," 

Ann.  Botany,  48: 481-495,  1934. 
Chaudhuri,  H.,  "A  studv  of  the  growth  in  culture  of   Verticillium  albo- 

atrum  B.  and  Br.,"  Ann.  Botany,  31:  519-539,  1923. 
Crosier,  YVillard,  "Studies  in  the  biology  of  Phytophthora  infestans  (Mont.) 

de  Barv,"  Cornell  Agr.  Expt.  Sta.  Menu,  755:40  pp.     1933. 
Dickson,  J.  G.,  "Influence  of  soil  temperature  and  moisture  on  the  develop- 
ment of  the  seedling  blight  of  wheat  and  corn  caused  by  Gibberella 

saubinettii,"  J.  Agr. ^Research,  25:830-870,  1923. 
Dixon,  L.  F.,  Ruth  A.  McLean,  and  F.  A.  Wolf,  "Relation  of  climatological 

conditions   to    tobacco    downy   mildew,"   Phytopathology,   26: 735-759, 

1936. 
Edgerton,  C.  W.,  "Effect  of  temperature  on  Glomerella,"  Phytopathology, 

5:  247-259,  1915. 
Edson,  H.  A.,  and  M.  Shapovalov,  "Temperature  relations  of  certain  potato- 
rot  and  wilt-producing  fungi,"  /.  Agr.  Research,  18:  511-524,  1920. 
Falck,  R.,  "Wachstumsgesetze,  Wachstumsfaktoren,  und  Temperaturwerte 

der   holzzerstorenden   Mycelien,"   Moller's   Hausschivammforschungen, 

Hefte  7:53-152,  1907. 
Faull,  J.  H.,  "On  the  resistance  of  Neurospora  crassa,"  My  col.,  22:288-303, 

1930. 
Fawcett,  H.  S.,  "The  temperature  relations  of  growth  in  certain  parasitic 

fungi,"  Univ.  Calif.  Pub.  Agr.  Sci.,  4:  183-232,  1921. 
Fawcett,  H.  S.,  and  W.  R.  Barger,  "Relation  of  temperature  to  growth  of 

Penicillhim  italicum  and  P.  digitatnm  and  to  citrus-fruit  decay  produced 

by  these  fungi,"  /.  Agr.  Research,  55:925-931,  1927. 
Gehenio,  P.  M.,  and  B.  F.  Luyet,  "A  study  of  the  mechanism  of  death  in 

the  plasmodium  of  Mvxomycetes,"  Biodynaviica,  no.  55:  1-22,  1939. 
Gilman,  J.  C,  "Cabbage  yellows  and   the  relation  of  temperature  to  its 

occurrence,"  Ann.  Mo.  Botan.  Garden,  3:  25-82,  1916. 
Herrick,  J.  A.,  "The  growth  of  Sterenm  gausapatum  Fries  in  relation  to 

temperature  and  acidity,"  Ohio  J.  Sci.,  39:  254-258,  1939. 
Humphrey,  C.  J.,  and  P.  V.  Siggers,  "Temperature  relations  of  wood-de- 
stroying fungi,"  /.  Agr.  Research,  41:  997-1008,  1933. 
Johnson,  James,  and  R.  E.  H\rtman,  "Influence  of  soil  environment  on  the 
root  rot  of  tobacco,"  /.  Agr.  Research,  11:  41-86,  1919. 


LITERATURE  CITED  121 

Jones,  L.  R.,  "The  relation  of  environment  to  disease  in  plants,"  Am.  J. 

Botany,  11:  605-609,  1924. 
Jones,  L.  R.,  James  Johnson,  and  J.  G.  Dickson,  "Wisconsin  studies  upon 

the  relation  of  soil  temperature  to  plant  disease,"  Wis.  Agr.  Expt.  Sta. 

Bull,  11:  144  pp.     1926. 
Kadisch,  E.,  "Beitrage  zur  Wirkung  der  Kalte  auf  pathogene  Fadenpilze, 

Hefen,  und  Bakterien.     Ausdehnung  dieser  Versuche  bis  in  die  Nahe 

des    absoluten    Nullpunktes    (bis    — 272°  C),"    Med.    Klin.,    27th    year: 

1074-1078,  1109-1112,  1931. 
Krause,  A.  W.,  "Untersuchungen  uber  den  Einfluss  der  Ernahrung,  Belich- 

tung,   und   Temperatur   auf   die   Perithecienproduktion   einiger   Hypo- 

creaceen.    Beitrag  zur  Kulturmethodik  einiger  parasitischer  und  sapro- 

phytischer  Pilze,"  Z.  Parasitenk.,  2:  419^176,  1930. 
Lauritzen,  J.  I.,  "Rhizoctonia  rot  of  turnips  in  storage,"  /.  Agr.  Research, 

3£:  93-108,  1929. 
Lehman,  S.  G.,  "Studies  on  treatment  of  cotton  seed,"  N.  C.  Agr.  Expt.  Sta. 

Tech.  Bull.,  26:71  pp.     1925. 
Lindgren,  R.  M.,  "Decay  of  wood  and  growth  of  some  Hymenomycetes  as 

affected  by  temperature,"  Phytopathology,  25:73-81,  1933. 
"Temperature,  moisture,  and  penetration  studies  of  wood-staining  Cera- 

tostomellae  in  relation  to  their  control,"  U.  S.  Dept.  Agr.  Tech.  Bull., 

801:  35  pp.    1942. 
Lindner,    J.,    "Uber    den    Einfluss    giinstiger    Temperaturen    auf    gefrorene 

Schimmelpilze.    Zur  Kenntnis  der  Kaltresistenz  von  Aspergillus  niger" 

Jahrb.  iviss.  Botan.,  55:  1-52,  1915. 
Lipman,  C.  B.,  "Tolerance  of  liquid  air  temperatures  by  spore-free  and  very 

young  cultures  of  fungi  and  bacteria  growing  on  agar  media,"   Bull. 

Torrey  Botan.  Club,  64:531-546,  1937. 
Longree,   K.,   "The   effect   of  temperature    and    relative   humidity   on   the 

powdery  mildew  of  roses,"  Cornell  Agr.  Expt.  Sta.  Mem.,  223: 43  pp. 

1939. 
Luyet,  B.  F.,  and  P.  M.  Gehenio,  Life  and  death  at  low  temperatures.    341 

pp.    Biodynamica,  Normandy,  Mo.     1940. 
Richards,  B.  L.,  "Pathogenicity  of  Corticium  vagum  on  the  potato  as  af- 
fected by  soil  temperatures,"  /.  Agr.  Research,  27:459-482,  1921. 
Sawyer,  W.   H.,   "Observations   on   some   entomogenous   members   of  the 

Entomophthoraceae    in   artificial   culture,"   Am.   J.   Botany,   16:81-121, 

1929. 
Scheffer,  T.  C,  "Relation  of  temperature  and  time  to  carbon  dioxide  pro- 
duction and  growth  in  continuously  aerated  malt-agar  cultures  of  Poly- 

st ictus  versicolor,'''  Plant  Physiol.,  11:  535-564,  1936. 
Scheffer,  T.  C,  and  B.  E.  Livingston,  "Relation  of  oxvgen  pressure  and  tem- 
perature to  growth  and  carbon  dioxide  production  in  the  fungus  Poly- 

stictus  versicolor"  Am.  ].  Botany,  24:  109-119,  1937. 
Schneider-Orelli,  Otto,  "Versuche  liber  die  Wachstumbedingungen  und 

Verbreitung  der  Faulnispilze  des  Lagerobstes,"  Xentr.  Bakt.,  Parasitenk., 

II  Abt.,  32:  161-169,  1912. 


m  EFFECTS  OF  TEMPERATURE  ON  FUNGI 

Stevens  N  E.,  "The  influence  of  temperature  on  the  growth  of  Endothia 
parasitica?  Am.  J.  Botany,  4: 112-118,  1917. 

Sweet  H  R.  "Studies  on  the  biology  of  two  spec.es  of  Magnusia.  I.  Effect 
of'  temperature  on  germination  of  spores  and  on  growth  and  repro- 
duction" Am.  J.  Botany,  28:  150-161,  1941. 

™  T  r    axo  F   L  Wellm^x,  "Relation  of  temperature  to  spore  ger- 

"^^'^o^Uroc^s  ****  h  4*  *—*>  *»*- 

wiTt  and  L.  L.  Harter,  'Temperature  relations  of  eleven  species 

of  RhizoDus  "  /.  Aer.  Research,  24:  1-40,  1923. 
Woi  SuC  R»™  McLean,  and  F.  R.  D.kk.s,  "Downy  m.l- 

dew  of  tobacco,"  Phytopathology,  24:  337-363,  1934. 


Chapter  6 

EFFECTS  OF  RADIATION  ON  FUNGI 

Although  students  of  fungi  have  long  been  interested  in  the 
reactions  to  light  of  this  group  of  organisms,  little  progress  in  this 
field  was  made  until  after  the  beginning  of  the  present  century. 
The  primary  reason  for  this  state  of  affairs  is  that  the  existence  of 
radiations  other  than  visible  light  was  unknown  until  approxi- 
mately 1900.  From  physical  researches  it  is  now  known  that 
radiations  of  the  following  groups  exist,  some  of  them  possessing 
wavelengths  in  excess  of  those  of  visible  light  and  others  being 
shorter. 

1.  Hertzian  rays,  the  wavelengths  of  which  range  from  1  X  106 
to  3  X  1014  Angstrom  units,  an  Angstrom  unit  (A)  being  1/10,- 
000,000  of  a  millimeter.  Those  waves  in  the  upper  portion  of  the 
range  between  1  X  1011  and  3  X  1014A  are  used  in  radio  com- 
munication. 

2.  Infrared  or  heat  rays,  the  wavelengths  of  which  range  from 
8000  to  4  X  106  A,  thus  overlapping  the  lower  end  of  the  range 
of  Hertzian  waves. 

3.  Visible  light  rays,  the  wavelengths  of  which  range  from  ap- 
proximately 4000  to  8000  A. 

4.  Ultraviolet  rays,  the  wavelengths  of  which  range  from  136 
to  4000  A. 

5.  X-rays,  the  wavelengths  of  which  range  from  0.06  to  1000  A, 
thus  overlapping  the  lower  end  of  the  ultraviolet  range. 

6.  Gamma-rays,  the  wavelengths  of  which  range  from  0.01  to 
1.4  A. 

7.  Cosmic  rays,  the  wavelengths  of  which  range  down  to 
1/10,000  A. 

Of  these  groups,  infrared  rays,  visible  light  rays,  ultraviolet 
rays,  and  X-rays  have  been  used  in  experimentation  with  fungi. 
Such  studies  have  been  concerned  mainly  with  the  morphogenic 
effects  of  radiation,  the  fungicidal  effects,  and  the  modifying 

123 


124 


EFFECTS  OF  RADIATION  ON  FUNGI 


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MORPHOGENY  REACTIONS  125 

effects  upon  reproduction.  Unfortunately  many  of  the  results, 
especially  those  with  visible  light,  are  not  reproducible  because 
account  has  not  been  taken  of  three  correlated  factors:  (a)  quan- 
tity or  intensity  of  light,  (b)  quality  of  light  or  wavelength  of 
radiations,  and  (c)  duration  of  exposure  or  total  radiation.  Even 
in  some  studies  employing  monochromators  intensity  was  not 
kept  constant  or  was  not  measured  when  quality  was  changed. 
It  is  all  too  apparent,  furthermore,  that  such  other  factors  as  age 
of  the  culture,  hydrogen-ion  concentration,  temperature,  and 
screening  effects  from  the  culture  media  and  from  the  massing 
of  hyphae  must  be  considered  in  experimentation  on  the  reactiv- 
ity of  fungi  to  radiation.  Since  this  has  not  always  been  done, 
a  barrage  of  criticisms  may  be  levelled  against  the  experimental 
procedures  and  consequently  against  the  conclusions.  In  the 
account  that  follows  some  of  the  extensive  publications  in  this 
field  are  brought  together,  but  many  meritorious  ones  have  been 
excluded  from  the  discussion.  Although  certain  generalizations 
may  be  drawn  from  these  publications,  none  appears  to  rest  on 
too  secure  a  basis,  and  the  only  broad  statement  warranted  ap- 
pears to  be  that  much  further  work  is  needed.  Such  studies 
should  be  attempted,  however,  only  by  mycologists  well  grounded 
in  the  physical  principles  of  light  and  other  radiations.  Much  of 
value  on  the  effects  of  radiation  will  be  found  in  the  summary 
by  Smith  (1936). 

MORPHOGENIC  REACTIONS 

A  survey  of  studies  to  determine  whether  light  is  required  for 
the  development  of  fructifications  by  fungi  reveals  that  light 
exerts  a  profound  influence  upon  some  species  but  that  others 
appear  to  be  completely  indifferent  to  it.  Several  early  mycolo- 
gists noted  that  in  the  complete  absence  of  light  the  stipes  of 
some  species  of  Hymenomycetes  are  longer  than  normal,  that 
other  species,  normally  sessile,  develop  stipes,  and  that  other 
species,  normally  pileate,  branch  in  clavarioid  fashion.  Coprinus 
stercorarius,  in  darkness,  has  been  observed  to  grow  stipes  2  to 
3  ft  long.  Buller  (1906)  noted  that  Poly  poms  squamosw,  kept 
in  the  dark,  developed  coal-black  stag-horn-shaped  sterile  stro- 
mata,  15  cm  tall  and  having  white  tips,  in  place  of  normal  stalked 
pilei.    The  formation  of  the  pileus  is  entirely  conditioned  by  the 


126 


EFFECTS  OF  RADIATION  ON  FUNGI 


presence  of  daylight,  exposure  for  a  single  hour,  even  if  followed 
by  return  to  the  darkroom,  being  sufficient  to  result  in  the  pro- 
duction of  pilei.  Likewise  in  Lentinus  lepideus  [Buller  (1905)] 
the  stimulus  of  light  is  necessary  for  formation  of  the  pileus. 
Fruiting  bodies  grown  in  weak  light  have  grotesque  shapes.  Al- 
though stipes  are  at  first  positively  heliotropic  and  indifferent  to 


Fig.  13.    Petri-dish  culture  of  Aspergillus  clavatus  in  ordinary  diffuse  light. 

geotropism,  by  the  time  pilei  begin  to  form  they  lose  this  reactiv- 
ity to  light,  and  negative  geotropism  dominates  pilear  develop- 
ment. Aspergillus  clavatus  forms  short  conidiophores  when 
grown  in  total  darkness,  whereas  conidiophores  of  two  lengths, 
one  short  and  the  other  an  inch  or  more  long,  are  produced  on 
exposure  to  diffuse  daylight  [Wolf  (1938)].  The  colonies  pro- 
duced under  these  considerations  might  be  suspected  to  belong 
to  two  distinct  species  of  Aspergillus. 

Psalliota  campestr'is,  the  cultivated  mushroom,  when  grown  in 
caves  or  cellars  that  are  illuminated  only  to  permit  gathering  the 
crop,  is  completely  indifferent  to  light.  Many  subterranean 
fungi,  as  would  be  anticipated,  are  unaffected  by  light.  Evidence 
has  accumulated,  moreover,  that  a  considerable  number  of  slime 


MORPHOGENY  REACTIONS 


121 


molds,  Hyphomycetes,  Pyrenomycetes,  and  Basidiomycetes  can 
develop  in  the  absence  of  light.  Long  and  Harsch  (1918),  for 
example,  found  that  sporophores  of  Polyporus  cinnabar  inns,  P. 
farloivii,  and  Trametes  serialis  develop  in  culture  in  absolute  dark- 
ness. 

Zonation.    A  variety  of  morphogenic  effects  may  be  expressed 
by  those  species  that  respond  to  light.    Perhaps  the  most  striking 


Fig.  14.    Culture  of  Aspergillus  clavatus  grown  in  blue  light. 

is  zonation,  resulting  from  alternation  of  day  and  night,  for  it  has 
been  encountered  by  all  who  have  cultivated  fungi.  Moreau 
(1912)  observed  the  zone  of  conidia,  produced  daily,  in  Penicil- 
lium  glaucum,  Hedgcock  (1906)  in  Cephalothecinm  roseum,  and 
Bisby  (1925)  in  Fusarium  discolor  sulphur  eum.  Bisby  reported 
that  exposure  of  the  cultures  to  bright  daylight  for  a  period  of 
%  to  y2  second  was  sufficient  to  produce  a  ring  of  conidia.  As  a 
more  accurate  measure,  he  noted  that  exposure  to  a  2  5 -candle- 
power  tungsten  light  for  2  to  2%  minutes  was  sufficient. 

In  order  to  relate  zonation  to  radiation  of  certain  wavelengths, 
Hedgcock  (1906)  subjected  Cephalothecinm  roseum  and  Reide- 


128 


EFFECTS  OF  RADIATION  ON  FUNGI 


meister  (1909)  exposed  Botrytis  cinerea  to  illumination  in  which 
portions  of  the  spectrum  were  screened  out.  The  results  of  their 
studies  and  those  of  others  are  contradictory.  In  red  lisrht  and 
in  darkness  few  conidia  of  B.  cinerea  were  noted  by  Reidemeister 
(1909),  but  they  formed  abundantly  in  blue  light.  Colonies  of 
Aspergillus  clavatus  grown  in  blue  light  produced  tall  conidio- 


Fig.  15.    Culture  of  Aspergillus  clavatus  grown  in  total  darkness  or  in  red 

light. 

phores  with  a  few  short  ones,  whereas  in  red  light  and  in  dark- 
ness all  were  short  [Wolf  (1938)]. 

Since  some  fungi  produce  concentric  zones  in  total  darkness, 
the  alternation  of  day  and  night  must  be  regarded  as  only  one  of 
the  complex  factors  involved  in  this  phenomenon.  Bisbv  (1925) 
induced  zonation  in  Fusarium  discolor  sulphur eum  in  total  dark- 
ness if  the  temperature  was  alternated.  The  effect  of  temperature 
has  been  substantiated  by  more  recent  studies  with  other  species. 
In  an  analysis  of  his  studies  on  Fusarium  and  Monilia  jructigena 
Brown  (1925)  showed  that  zonation  in  response  to  light  changes 
is  correlated  with  the  following  factors:   (1)  the  capacity  of  the 


PHOTOTROPISM  129 

species  to  react  to  light  in  the  matter  of  sporulation,  (2)  staling 
produced  by  mycelial  growth,  provided  that  the  amount  of  stal- 
ing does  not  in  any  way  impede  the  extension  of  the  mycelium, 
and  (3)  the  concentration  of  nutrients  available,  which  should 
not  permit  of  sporulation  so  intense  as  to  interfere  with  the  pro- 
duction of  successive  daily  zones. 

PHOTOTROPISM 

The  fact  that  fungi  lack  chlorophyll  and  that  certain  species 
are  capable  of  completing  their  entire  developmental  cycle  in 
the  absence  of  light  might  at  first  thought  incline  the  student  to 
the  belief  that  they  would  not  react  phototropically.     On  the 
other  hand,  it  might  be  anticipated  that  radiant  energy  would 
influence  rate  of  growth,  and  that  consequently  species  in  which 
growth  or  elongation  is  localized  might  respond  to  differences  in 
the  intensity  of  light.     Species  with  long  sporangiophores,  such 
as  Pilobolus  or  Phy  corny  ces  nitens,  or  with  long  conidiophores, 
such  as  Aspergillus  clavatus,  should  be  especially  suited  for  studies 
of  this  sort,  since  they  respond  to  unilateral  illumination.     It 
should  be  possible  with  such  species  to  determine  the  minimal 
amount  of  light  required  to  stimulate  a  phototactic  response  and 
to  establish  that  quality,  quantity,  and  duration  of  exposure  are 
functions  of  each  other.     In  P.  nitens  it  has  been  found  that 
response  follows  a  change  of  %  to  %  candlepower  per  meter 
per  second.     Response  may  not  occur  immediately,  so  that  re- 
action time  may  be  said  to  consist  of  an  exposure  and  a  latent 
period.     The  duration  of  this  latent  period  is  constant  for  any 
particular  intensity  unless  the  exposure  time  is  reduced  below  the 
minimum  threshold;  below  this  minimum  the  reaction  time  in- 
creases progressively  as  the  duration  of  exposure  decreases. 

Among  Phycomycetes.  In  response  to  light,  Phy  corny  ces 
nitens  has  long  been  known  to  bend  in  a  zone  just  beneath  the 
sporangium.  Blaauw  (1914),  who  investigated  the  phototropic 
response  of  this  fungus  by  use  of  physical  methods,  regarded  the 
sporangiophore  as  a  cylindrical  lens  which  concentrates  the  light 
on  the  cell  wall  opposite  the  source,  causing  greater  photochemi- 
cal activity  in  this  area.  The  net  result  of  this  photochemical 
action  is  bending  of  the  sporangiophore,  a  response  to  unequal 


130 


EFFECTS  OF  RADIATION  OX  FUNGI 


rates  of  growth  on  opposite  sides  of  the  growing  zone.  This  ex- 
planation is  not  entirely  satisfactory  if  it  is  borne  in  mind  that 
the  sporangiophores  are  radially  symmetrical  and  that  the  regions 
of  sensitivity  and  of  growth  coincide. 


4 


Fig.  16.  Response  of  Phycomyces  to  incident  light.  In  A,  grown  in  air, 
the  sporangiophores  bend  to  direct  the  sporangia  toward  the  light.  In  B, 
the  sporangia  are  surrounded  with  paraffin  oil  and  have  turned  away  from 
the  source  of  light.     Density  of  the  surrounding  medium   conditions  the 

(After  Buder.) 


direction   of  refraction   of  light. 


Further  evidence  to  clarify  this  problem  was  presented  by 
Buder  (1918).  He  grew  P.  nit  ens,  with  the  sporangiophores  di- 
rected vertically,  in  chambers  whose  vertical  sides  were  parallel. 
He  then  immersed  the  sporangiophores  in  one  chamber  in  paraf- 
fine  oil;  in  the  control  chamber  the  sporangiophores  were  sur- 
rounded by  air.  Illuminating  both  unilaterally,  he  found  that 
those  in  oil  were  negatively  phototropic,  whereas  those  in  air 
were  positively  phototropic.     In  explanation  Buder  pointed  out 


PHOTOTROPISM  131 

that,  since  air  is  a  less  dense  medium  than  is  the  content  of  the 
sporangiophore,  the  rays  of  light  refracted  from  the  front  half  of 
the  cylindrical  cell  converge  on  the  side  opposite  the  source  of 
light.  Similarly,  the  oil  is  a  more  dense  medium  than  is  the  con- 
tent of  the  sporangiophore,  and  hence  the  rays  of  light  after 
refraction  diverge  from  one  another.  When  air  is  the  medium, 
the  back  half  of  the  growing  zone  is  lighted  the  more  intensely; 
when  oil  is  the  medium,  the  front  half.  The  growth  response  is 
therefore  in  opposite  directions  in  the  two  cases. 

Castle  (1933)  has  also  contributed  to  an  understanding  of  the 
response  of  P.  nitens  to  light.  His  solution  of  the  problem  is 
based  upon  three  assumptions:  (1)  bending  is  a  resultant  of  un- 
equal absorption  of  light  by  the  two  halves  of  the  cell  (the  half 
toward  the  source  of  light  and  the  half  most  distant  from  the 
source);  (2)  the  primary  action  of  light  is  upon  the  protoplasm; 
and  (3)  the  absorption  of  light  is  brought  about  by  a  substance 
or  substances  (pigment)  equally  distributed  within  the  cell.  From 
these  reasonable  assumptions  he  deduces  that  the  factors  which 
govern  the  unequal  action  of  light  in  the  two  halves  of  the  cell 
are  the  following:  (1)  the  refractive  index  of  the  cell,  (2)  the 
size  of  the  cell,  more  specifically  its  radius,  and  (3)  the  coefficient 
of  absorption  possessed  by  the  intracellular  pigment. 

All  known  species  of  Pilobolus,  which  commonly  occur  on 
the  fresh  dung  of  herbivors  when  it  is  kept  in  a  moist  chamber, 
exhibit  photic  reactions.  Among  those  who  have  investigated 
the  response  of  these  species  to  light  are  Allen  and  Jolivette 
(1914),  Parr  (1918),  Pringsheim  and  Czurda  (1927),  van  der 
Wey  (1929),  and  Buller  (1934).  Allen  and  Jolivette  admitted 
light  through  a  pinhole  and  found  that  Pilobolus  aimed  point- 
blank  at  the  light.  The  accuracy  of  the  aiming  was  remarkable, 
for  when  the  culture  was  20  cm  distant  from  the  opening,  95% 
of  the  sporangia  struck  within  a  ring  4  cm  in  diameter,  the  remain- 
ing 5%  being  within  the  next  1  or  2  cm.  A  greater  degree  of 
precision  was  obtained  with  white  or  blue  light  and  less  accuracy 
with  yellow  light;  the  aiming  was  very  inaccurate  with  red  light. 
Of  course  the  distance  that  the  sporangia  needed  to  travel  modified 
the  precision.  Allen  and  Jolivette  also  made  the  interesting  obser- 
vation that,  when  Pilobolus  was  exposed  to  two  equal  beams  of 
white  light  with  the  angle  between  them  greater  than  10°  of  arc. 


132 


EFFECTS  OF  RADIATION  ON  FUNGI 


the  aiming  was  as  accurate  as  if  one  source  of  lioht  was  nonexist- 
ent.  The  sporangia  were  aimed  at  one  or  the  other  source  of  light, 
not  midway  between  the  two.  Allen  and  Jolivette  were  unable  to 
explain  how  this  result  was  achieved,  but  Buller  (1934)  later 
found  the  mechanical  basis  to  reside  in  the  ocellar  structure  of  the 
subsporangial  swelling. 


L 


J L 


1 


J L 


J L 


J 


0  12 

Millimeters 

Fig.  17.  Median  longitudinal  section  of  Pilobohis  kleinii.  The  fructification 
is  directed  toward  the  source  of  light.  The  basal  sporangial  wall  has  gelat- 
inized, and  the  broken  line  indicates  where  the  sporangium  has  separated 
from  its  attachment.  Certain  ravs  cannot  penetrate  the  black  sporangium, 
which  fits  as  a  cap  at  the  apex  of  the  subsporangium.  The  ravs  which  pene- 
trate the  upper  sporangial  wall  converge  at  the  basal  perforated  septum, 
which  is  red.  The  photochemical  changes  induced  bv  converged  light 
within  the  subsporangium  induce  swelling  and  eventual  bursting  at  the  tip. 
The  sporangium  is  carried  away  in  toto  with  the  squirt.     (After  Buller.) 

Later  Parr  (1918)  concerned  herself  with  precise  measurements 
of  the  responses  of  Pilobohis  to  wavelengths  of  the  different  re- 
gions of  the  spectrum,  to  the  presentation  time,  and  to  the  energy 
values  involved.  Her  important  conclusions  include  the  follow- 
ing: (1)  Pilobohis  responds  phototropicallv  to  light  in  all  re- 
gions of  the  spectrum.  ( 2 )  The  presentation  time  required  to 
react  phototropicallv  increases  gradually  from  the  red  rays  to 
the  violet;  that  is,  Pilobohis  is  more  sensitive  to  violet  than  to  red. 
(3)  The  presentation  time  varies  in  inverse  ratio  to  the  square 
root  of  the  wave  frequency.  (4)  For  any  given  light  source  the 
total  energy  value  may  be  expressed  as  the  product  of  the  square 
root  of  the  wave  frequency  multiplied  bv  the  presentation  time. 


PHOTOTROP1SM 


133 


This  value  decreases  with  a  decrease  in  energy  value  of  the  spec- 
tral regions. 

The  method  bv  which  Pilobolus  aims  and  discharges  its  spo- 
rangia toward  the  source  of  light  was  elucidated  by  Buller  in  a 
series  of  observations  that  began  in   1919.     He  discovered  that 


c 

& 


750* 

» 

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\ 

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c 

»\ 
\ 

700 

\ 

\ 

\ 

o 

^ 

\ 

\ 

\ 

650 

*\ 

< 

k 

o  \ 

\^-  Tungsten 

> 

^-Nernst 

V 

600 

°\ 

\ 

\ 
°\ 

\ 
\ 

\ 

c\ 

t 

\ 

550 

< 

>  \ 

\ 

\ 

\ 

\ 

\ 

500 

c\ 

\ 

S 

°\ 

\o 

\ 
\ 

450 

> 

\ 

\ 

> 

400 

50 


55  60  65  70 

Presentation  time  (minutes) 


75 


Fig.  18.  Response  of  Pilobolus  to  light  from  two  sources  to  show  relation 
of  presentation  time  to  frequency  of  light.  Presentation  time  is  regarded  as 
the  time  required  for  one-half  of  the  sporangiophores  to  respond.  The  time 
required  for  heliotropic  response  is  seen  to  decrease  progressively  from  red 
light  waves  (those  with  low  frequency)  through  yellow,  green,  blue,  violet, 
and  indigo   (those  with  high  frequency).     (After  Parr.) 


134  EFFECTS  OF  RADIATION  ON  FUNGI 

the  subsporangial  swelling  is  an  ocellus  which  acts  as  a  lens. 
When  the  fruiting  structures  are  in  heliotropic  equilibrium,  the 
light  is  focussed  on  a  red  perforate  septum  at  the  base  of  each 
subsporangium.  The  red  color  is  imparted  by  a  carotinoid  pig- 
ment. The  sporangium  itself  is  black  and  hence  casts  a  shadow 
on  some  part  of  the  subsporangium  beneath.  According  to  Buller 
(1934),  the  sequence  of  events  is  somewhat  as  follows:  Light 
strikes  the  upper  end  of  the  fruiting  body,  and  the  incident  rays 
enter  the  part  of  the  upper  wall  of  the  subsporangium  that  bulges 
around  the  sporangium.  They  are  focussed  on  the  wall  below, 
where  a  region  of  greater  photochemical  activity  is  thereby  pro- 
duced. The  stimulus  is  thus  transmitted  to  the  motor  region  of 
the  stipe  (stalk  of  sporangiophore),  and  in  response  differential 
growth  occurs.  .Most  rapid  growth,  as  has  been  discussed  in 
Phy  corny  ces  mteiis,  occurs  on  the  side  of  the  stipe  nearest  the 
area  where  the  light  is  focussed.  As  a  consequence  the  ocellar 
mechanism  is  tilted  until  the  rays  fall  symmetrically  upon  the 
red  perforate  ring  at  the  base  of  the  subsporangium.  In  this  posi- 
tion a  state  of  physiological  equilibrium  becomes  established,  and 
the  sporangium  is  directed  head  on  toward  the  light.  Some  ap- 
preciation of  the  rate  of  response  may  be  gained  from  Buller's 
observation  on  P.  longipes,  in  which  he  found  the  stipe  capable  of 
turning  through  an  angle  of  90°  and  of  completely  orienting  the 
sporangium  in  about  an  hour. 

The  discharge  of  the  sporangium  is  also  the  result  of  photic 
effects.  When  the  rays  are  properly  centered,  the  photochemical 
reactions  on  the  protoplasmic  content  of  the  subsporangium  re- 
sult in  increased  osmotic  pressure.  Eventually  the  pressure  is 
sufficient  to  separate  the  subsporangial  and  sporangial  walls,  the 
rupture  beginning  as  a  collar  around  the  periphery  of  their  zone 
of  contact.  When  this  release  of  tension  occurs,  the  subsporangial 
wall,  being  weakest  beneath  the  sporangium,  bursts.  The  spo- 
rangium is  thus  carried  away  by  a  squirting  process. 

Among  the  striking  observations  on  Pilobolus  made  by  Allen 
and  Jolivette  (1914),  as  has  been  mentioned,  was  that,  if  two 
equal  beams  of  white  light  are  converged  upon  the  fruiting  bodies, 
with  an  angle  of  convergence  greater  than  10°,  the  sporangio- 
phores  direct  the  sporangia  toward  one  or  the  other  of  the  two 
sources  of  light.  Contrary  to  expectations,  the  aim  of  the  spo- 
rangiophores  is  therefore  not  in  the  direction  of  the  resultant  of 


PHOTOTROPISM  13$ 

these  two  forces.  The  explanation  for  this  response  occurs  in 
the  accounts  of  Pringsheim  and  Czurda  (1927)  and  van  der  Wey 
(1929)  and  has  been  confirmed  by  Buller  (1934).  All  are  in 
accord  that  this  response  may  be  explained  by  these  assumptions: 
(1)  the  subsporangium  acts  as  an  ocellus,  and  (2)  the  red  annular 
area  in  the  base  of  the  subsporangium  is  the  region  for  light  per- 
ception. Then,  when  two  spots  of  light  become  focussed  along 
the  basal  wall,  the  one  nearest  the  annular  area  gives  the  greater 
stimulus  to  the  motor  region  of  the  stipe.  In  consequence  the 
stipe  bends,  and  when  the  nearest  spot  comes  to  rest  directly  on 
the  annular  area,  heliotropic  equilibrium  becomes  established. 

Among  Ascomycetes.  The  position  of  the  fruiting  bodies  of 
many  Discomycetes  and  Pyrenomycetes  within  or  on  the  sub- 
stratum and  the  orientation  of  their  asci  may  be  presumed  to  be 
governed  by  phototropism  or  by  geotropism.  Some  of  these 
fungi,  for  example,  subterranean  species,  may  be  wholly  unaf- 
fected. In  fact,  little  is  known  about  the  specific  effect  of  either 
of  these  tropic  forces  on  Ascomycetes.  This  subject  constitutes 
a  fertile  field  for  study,  especially  in  connection  with  leaf-inhabit- 
ing species. 

As  long  ago  as  1890  the  tips  of  the  asci  of  Ascobohis  demidatits 
were  known  to  bend  phototropically.  The  meager  studies  sub- 
sequently made  on  phototropic  responses  among  disk  fungi  are 
assembled  and  interpreted  by  Buller  (1934).  Discomycetes  pos- 
sess hymenia  that  are  plane,  concave,  or  convex.  If  the  hymenia 
are  plane,  no  structural  adaptations  are  required  to  enable  the 
ascospores  to  be  discharged  without  striking  some  part  of  the 
hymenial  surface.  In  certain  species  with  concave  or  convex 
hymenia  it  has  been  shown  that  the  ends  of  the  asci  may  be 
curved  phototropically,  or  else  the  opercula  of  the  asci  may  be 
asymmetrically  situated  near  the  apices.  By  this  means  ascospores 
are  ejected  into  the  environment  and  do  not  lodge  on  the  oppos- 
ing walls  of  the  fruit  bodies. 

In  Ascobohis  magnificiis  and  A.  stercorarius  [Buller  (1934)] 
the  tip  of  the  ascus  protrudes  above  the  hymenium.  This  tip, 
containing  the  ascospores,  curves  toward  the  source  of  light,  and 
eventually  the  ascospores  are  discharged  toward  the  light.  In 
C Maria  (Lachnea)  scutellata,  which  normally  is  plane  and  nor- 
mally possesses  straight  asci,  curvature  may  be  induced  by  uni- 
lateral  illumination.     In   Aleuria  vesiculosa  both   asci   and   pa- 


136 


EFFECTS  OF  RADIATION  ON  FUNGI 


raphyses  are  positively  phototropic.  Since  its  hymenial  surface  is 
hemispherical,  the  amount  of  bending  of  the  ascus  tip  is  related 
to  the  position  of  the  ascus.  Asci  near  the  center  are  straight, 
whereas  those  near  the  periphery  may  be  bent  through  an  anp;le 
of  45°.  In  Morchella  cornea,  M.  crassipes,  and  Ptyc  hover  pa 
(Verpa)  bohem'ica  the  fertile  portions  of  the  fruit  bodies  may  be 
regarded  as  compound  disks.  The  asci  are  phototropic  and  be- 
have as  though  each  alveolus  were  a  disk.    The  stipes  of  some  of 


12  M.       6  P.M. 


12  P.M. 


6  A.M. 


12  M. 


6  P.M. 


Fig.    19.     Diurnal   cycle   of  development  of  asci  by   Tctphrina  deformans. 

(After  Yarwood.) 

these  stalked  species  bend  in  response  to  light,  thus  carrying  the 
fertile  tissues  into  the  position  most  favorable  for  ascospore  dis- 
charge and  dissemination. 

A  diurnal  rhythm  in  the  discharge  of  ascospores  is  known  to 
exist  in  certain  species.  Ingold  (1939)  observed  that  Hy  poxy  Ion 
jusciim  discharges  its  spores  nightly  during  the  approximate  pe- 
riod between  9  p.m.  and  5  a.m.  In  Nectria  cimiabarina  and 
Podospora  curvula,  however,  ascospore  discharge  occurs  in  the 
daytime. 

By  direct  microscopic  examination  and  by  use  of  spore  traps, 
Yarwood  (1941)  found  that  in  Taphrina  deformans  the  ascoge- 
nous  cells  give  rise  to  asci  in  the  evening  and  that  nuclear  division 
and  increase  in  size  of  asci  occur  throughout  the  night.  During 
the  following  daylight  period  the  ascospores  become  morpho- 
logically mature,  and  maximum  discharge  occurs  during  the  early 
portion  of  the  succeeding  night.  This  rhythm  is  attributed  to 
alternating  light  and  darkness,  but  the  significant  effect  of  light 


LUMINESCENCE 


131 


is  not  understood.    In  T.  deformans  discharge  at  night  appears  to 
be  an  adaptation  favoring  infection. 

The  perithecial  beaks  of  Neurospora  sitophila  have  been  shown 
[Backus  (1937)]  to  be  positively  phototropic  and  to  discharge 
their  spores  toward  the  light.  Observations  indicate  also  that  the 
beaks  of  such  rostrate  fungi  as  Gnomonia,  Ceratostomella,  and 
Diaporthe  are  positively  phototropic.  The  phototropic  responses 
of  such  genera  as  Linospora  and  Ophiodothella,  whose  perithecia 


May  18 


May  19 


May  20 


May  21 


s 

3 

3 

3 

3 

3             3              3 

3 

3 

3 

3 

3 

co 

r-i 

Pu 

Ph 

9 

< 

to 

CO 
r-i 

CU         Ph         < 

CO             CO             <£, 

Intervals  of  time 

r-i 

Ph 

Ph 
CO 

T-i 

< 

CO 

CO 

T-I 

Fig.  20.  Period  of  ascospore  output  from  a  stroma  of  Hypoxylon  jus  cum 
at  a  temperature  within  the  range  17  to  19.5°  C.     (After  Ingold.) 

and  asci  lie  horizontally  and  whose  beaks  stand  vertically,  should 
constitute  an  interesting  subject  of  study. 


LUMINESCENCE 

Nearly  everyone  has  noted  that  old  stumps,  decaying  logs,  and 
leaf  mold  may  emit  a  weird  glow  at  night.  This  phenomenon, 
which  has  been  called  "fox  fire,"  is  usually  caused  by  luminous 
fungi,  most  of  which  are  Hymenomycetes.  Various  other  or- 
ganisms, including  species  of  bacteria,  flagellates,  sponges,  jelly- 
fish, hydroids,  bryozoans,  marine  worms,  earthworms,  Crustacea, 
myriapods,  insects,  molluscs,  squids,  and  fish,  are  known  to  emit 
light.  An  informative  treatment  of  this  general  subject  is  given 
in  Harvey's  (1940)  Living  Light.  Buller  (1924,  1934)  studied 
luminescence  in  Paints  stipticns  and  Omphaiia  flavida,  and  his 
account  of  this  phenomenon  among  fungi  will  be  found  very 
stimulating;. 

According  to  Buller's  list  (1924),  the  pilei  of  the  following 
species  are  luminous:  Clitocybe  illndens,  Panns  incctndescens,  P. 


138  EFFECTS  OF  RADIATION  ON  FUNGI 

stipticus,  Pleurotus  incandescensy  P.  facifer,  P.  gardneri,  P.  igneus, 
P.  noctilucens,  P.  olearius,  P.  phosphor eus,  P.  prometheus.  The 
rhizomorphs  of  Armillaria  mellea  and  the  sclerotia  of  Colly  bia 
tuberosa  and  C.  cirrhata  are  luminescent.  Among  other  species 
claimed  to  be  luminous  are  Fomes  annosus,  Poly  poms  sulphur  ens, 
Pomes  piui,  Colly  bia  longipes,  Corticium  coerideum,  Dictyophora 
phalloides,  and  Xylaria  hypoxylon. 

The  mycelium  and  pilei  of  Pamts  stipticus  in  North  America 
are  luminous,  whereas  those  in  England  are  non-luminous  [Buller 
(1924)].  Dried  fruit  bodies  do  not  glow,  but,  if  revived  by 
moistening,  they  again  emit  light.  Not  only  moisture  but  also 
favorable  temperature  relations  are  necessary  for  luminescence. 
The  minimum  temperature  for  P.  stipticus  is  —2°  to  —  4°  C,  the 
maximum  35°  to  37°  C,  and  the  optimum  10°  to  25°  C. 

Oviphalia  flavida  is  of  special  interest  because  it  has  long  been 
known  to  be  the  cause  of  a  serious  leaf  disease  of  the  coffee  tree 
in  the  American  tropics.  Buller  (1934)  discovered  that  the  lesions 
induced  by  O.  flavida  are  luminous  and  reported  that  they  may 
be  seen  in  the  dark  at  a  distance  of  6  to  10  ft.  In  culture  the 
mycelium  too  is  luminous.  This  organism  is  capable  of  forming 
peculiar  structures  called  gemmifers  and  gemmae  if  the  stimulus 
of  alternating  day  and  night  is  provided. 

Luminosity  in  these  fungi,  as  in  other  luminous  organisms,  is 
the  result  of  an  oxidative  change  within  the  cells,  luciferin  bein^ 
acted  upon  by  the  enzyme  luciferase  in  the  presence  of  oxygen. 
Apparently  this  enzyme  has  not  been  extracted  from  fungi,  nor 
has  it  been  demonstrated  to  be  capable  of  functioning  apart  from 
living  cells. 

INHIBITORY  EFFECTS 

Exposure  of  fungi  to  sunlight  has  long  been  known  to  modify 
their  rate  of  growth.  If  the  total  illumination  is  small,  growth 
may  be  retarded,  but  with  larger  amounts  death  may  ensue.  This 
matter  appears  to  have  been  given  rather  extensive  study,  as  Smith 
(1936)  has  indicated. 

It  would  be  anticipated  that  not  all  species  of  fungi  are  equally 
sensitive  to  sunlight.  Abundant  evidence  in  support  of  this  con- 
clusion from  comparative  studies  is  not  available.  Fromme  (1915) 
noted  that  the  germ  tubes  of  urediniospores  of  Puccima  rhamm 
are  negatively  phototropic  and  mentioned  that  a  similar  reaction 


INHIBITORY  EFFECTS 


139 


for  those  of  P.  dispersa  had  earlier  been  recorded.  The  germ 
tubes  of  several  other  fungi,  cited  in  his  report,  are  indifferent  in 
their  reaction  to  light.  It  would  seem  that  the  restriction  of  some 
pathogens  to  the  lower  leaf  surface  instead  of  both  leaf  surfaces 
may  be,  in  part  at  least,  a  light  response.    For  example,  the  downy 


35 


30 


25 


o 
to 

-2 
c 

<D 

a 

CO 

c 

-2 


20 


15 


10 


High  intensity- 


o 

o 

O 

o 

o 

8 

o 

o 

O 

(i 

o 

05 

o 

U3 

^J 

iS 

in 

"t 

CT> 

CO 

00 

OJ 

1-H 

1-H 

T-H 

CM 

CO 

Dosage  (roentgen  units) 

Fig.  21.  Effect  of  dosage  on  mutation  rate  at  low  intensity  (240  r  per 
minute)  and  at  high  intensity  (5400  r  per  minute).     (From  Sansome,  Deme- 

rec,  and  Hollaender.) 

mildews  fructify  quite  commonly  on  unexposed  surfaces,  whereas 
powdery  mildews  behave  in  this  respect  as  though  quite  indiffer- 
ent to  sunlight. 

Numerous  studies  have  been  made  to  determine  which  portions 
of  the  spectrum  are  most  injurious  or  possibly  lethal.  As  might 
be  anticipated,  it  has  been  found  that  radiations  with  shortest 
wavelengths  are  most  effective  in  retarding  growth.  It  has  been 
noted  furthermore  that  the  ultraviolet  regions  are  more  effective 
than  the  blue,  but  in  many  of  these  studies  intensities  are  not 
measured,  and  consequently  the  results  cannot  be  satisfactorily 


140  EFFECTS  OF  RADIATION  ON  FUNGI 

evaluated.  The  methods  employed  by  Oster  (1934)  in  his  study 
of  Sac  char  omyces  cerevisiae  appear  to  be  well  suited  to  similar 
studies  of  other  fungi.  He  used  monochromatic  light  and  found 
that  inhibition  of  colony  size  could  be  obtained  at  a  low  energy 
level.  Under  such  conditions  few  new  buds  were  formed,  giant 
cells  were  sometimes  produced,  and  the  metabolic  functions  were 
retarded,  as  was  shown  by  lowered  02  consumption.  At  a  wave- 
length of  2652  A,  457  ergs/mm2  were  required  to  kill  50%  of  the 
cells,  but  at  3022  A,  23,500  ergs/mm2  were  necessarv.  The  shape 
of  the  curves  for  lethal  action  at  different  wavelengths  suggests 
that  more  factors  than  single  quantum  hits  on  a  sensitive  region, 
that  is,  adsorption  of  energy  by  the  nucleoproteins,  are  responsible 
for  these  effects.  Oster  suggests  that  the  age  of  the  cells  at  the 
time  of  exposure  is  also  a  factor  in  the  energy  relations  involved. 
The  effect  of  temperature  must  always  be  taken  into  considera- 
tion in  experiments  of  this  type. 

Ultraviolet  radiations  of  wavelengths  between  2537  and  2650  A 
were  found  most  effective  in  killing  Trichophyton  mentagroph- 
ytes  [Hollaender  and  Emmons  (1939)].  They  suspended  the 
spores  in  physiological  salt  solution,  using  wavelengths  in  the 
range  2280  to  2950  A  in  measured  quantities.  In  a  subsequent 
report  these  investigators  [Emmons  and  Hollaender  (1939)  |  cor- 
related time  of  exposure  of  spores  of  this  same  species  to  mono- 
chromatic light  of  2650  A  with  energy  required  to  cause  death 
and  with  percentage  survival.  Their  experimental  data  on  these 
points  are  contained  in  Table  10. 


TABLE  10 

ect  of  Ultraviolet  Light  on  Trichoph 

tton  tnentagrof 

Duration  of 

Energy  {ergs  per 

Survival 

Exposure 

spore  in  ten 

Ratio 

{minutes) 

thousandths) 

{percentage) 

5 

7.25 

81.0 

15.5 

22.7 

53.0 

34.0 

50 '.2 

42.5 

53 

78.7 

16.4 

78 

116.7 

7.7 

101 

151.7 

3.93 

132 

200.0 

1.03 

162 

247.4 

0.61 

198 

304.4 

0.24 

280 

436.4 

0.153 

INHIBITORY  EFFECTS 


141 


Dimond  and  Duggar  (1941)  determined  the  lethal  effects  of 
monochromatic  ultraviolet  radiations  2650  A  in  wavelength  on 
Aspergillus  melleus,  Rhizopas  minus,  and  Mncor  disperses.  They 
correlated  ergs  of  energy  required  with  volume  of  the  spores, 
using  the  volume  of  A.  melleus  as  unity.  Their  data,  which  are 
presented  in  Table  11,  indicate  that  resistance  is  not  directly  cor- 

TABLE  11 
Lethal  Effect  of  Ultraviolet  Radiations  on  Three  Species  of  Fungi 


Species 

Ergs  per  Spore  for 
50%  Killing 

Ratio 

Mean  Volume 
of  Spore,  /x3 

Ratio 

Aspergillus  melleus 
Rhizopus  suinus 
Mucor  dispersus 

0.0064 

0.088 

0.12 

1.0 

13.7 

17.5 

8 

28 

113 

1.0 

3.4 

14.1 

related  with  the  volume  of  the  spore.  Pigmentation  of  spores  and 
differences  in  the  number  of  spore  nuclei  are  employed  as  addi- 
tional factors  in  accounting  for  differences  in  the  action  of  radia- 
tions. 

Recently  Sharp  (1938)  made  certain  refinements  in  methods  of 
studying  the  effect  of  ultraviolet  light  on  bacteria  that  would 
appear  to  be  adaptable  for  use  with  fungi.  In  attempts  to  elimi- 
nate the  shielding  or  screening  effects  of  masses  of  bacteria  and 
of  the  medium  he  atomized  broth  cultures  into  the  air,  passed  the 
bacteria-laden  air  through  a  tube  where  thev  were  exposed  to 
monochromatic  ultraviolet  light,  and  then  captured  the  treated 
bacteria  at  the  exit  on  culture  media.  It  should  be  possible  to 
substitute  suspensions  of  spores  in  water  for  broth  cultures  of 
bacteria  in  such  an  apparatus. 

Several  investigators  have  been  concerned  with  the  use  of  ultra- 
violet rays  as  a  potential  fungicide.  Fulton  and  Coblentz  (1929) 
tested  a  group  of  pathogens  by  use  of  a  1 10-volt  quartz  lamp  with 
a  mercury  cathode  and  a  tungsten  anode  operated  on  320  watts 
(80  volts,  4  amp).  The  spores  of  all  organisms  were  at  the  sur- 
face of  the  agar  plates.  The  investigators  eliminated  temperature 
effects  and  found  that  the  following  survived  exposure  for  one 
minute:  Helminthosporium  sp.,  Alternaria  sp.,  Cladosporium  sp., 


142 


STIMULATORY  EFFECTS  143 

Pestalozzia  sp.,  Chaetomella  sp.  (all  from  cranberry),  Diplodia  sp. 
(from  lime  fruit),  Aspergillus  niger,  Penicillium  italicum,  Col- 
letotrichum  gloeosporioides,  and  Ceuthospora  limitata.  The  fol- 
lowing species,  however,  were  killed  by  this  treatment:  Rhizopus 
nigricans,  Penicillium  digitatum,  P.  expansum,  Phomopsis  citri, 
Glomerella  rufo-maculans,  Gloeosporium  limetticolum,  Antho- 
stromella  destruens,  Ac  author  hynchus  vaccinii,  Gloeosporium 
minus,  Alelanconium  sp.  (from  grape),  Fusarium  sp.  (from 
orange),  Botrytis  sp.  (from  apple),  Phytophthora  sp.  (from 
orange),  and  Guignardia  sp.  (from  cranberry).  Similar  studies 
by  Landen  (1939)  were  concerned  primarily  with  attempts  to 
destroy  the  viability  of  chlamydospores  and  sporidia  of  Ustilago 
zeae.  Employing  a  large  crystal-quartz  monochromator,  he  found 
that  sporidia  are  more  sensitive  than  chlamydospores.  Long  ul- 
traviolet rays  between  3022  and  3 130  A  required  a  dosage  of 
1.5  X  10°  ergs/mm2  to  be  lethal.  Dillon-Weston  and  Hainan 
(1930)  irradiated  cultures  of  several  species,  including  Rhizopus 
nigricans,  Dematium  pulhdans,  Neurospora  sitophila,  and  Sclero- 
tinia  trifoliorum.  They  employed  daily  exposures  with  low  in- 
tensities and  therewith  merely  modified  the  rate  of  growth. 

Germination  of  the  urediniospores  of  Puccinia  graminis  tritici 
was  inhibited  if  they  were  floated  on  the  surface  of  water  during 
exposure  to  sunlight,  but  if  they  were  placed  in  the  dark  under 
otherwise  similar  conditions,  they  germinated  readily  [Dillon- 
Weston  (1931)].  Similar  results  followed  if  he  exposed  them 
to  a  mercury-vapor  lamp  for  ultraviolet  radiations. 

STIMULATORY  EFFECTS 

The  evidence  on  stimulation  of  fungi  by  ultraviolet  light  is 
contradictory.  The  results  of  studies  by  a  number  of  workers 
indicate  that  exposure  to  such  light  is  followed  by  an  increased 
growth  rate.  Using  Fusarium  eumartii,  Smith  (1935)  found  that 
irradiated  cultures  were  at  first  retarded,  but  that  the  rate  of 
growth  was  increased  after  the  period  of  retardation.  In  such 
cultures  the  total  growth  was  never  greater  than  that  in  the  con- 
trols. Since  temperature  and  the  accumulation  of  labile  nutritive 
products  also  favored  an  increased  rate  of  growth,  Smith  regarded 
stimulation  as  an  indirect  effect  of  radiation.  This  interpretation 
is  not  in  accord  with  the  results  of  Hutchinson  and  Newton 


144  EFFECTS  OF  RADIATION  ON  FUNGI 

(1930),  who  obtained  most  stimulation  in  slow-growing  cultures 
of  yeast.  They  also  conclude  that  some  wavelengths  result  in 
stimulation,  others  in  retardation,  of  growth.  Since  they  did  not 
take  into  consideration  differences  in  total  energy  in  the  different 
wavelengths  that  they  used,  however,  their  conclusions  cannot  be 
accepted  with  finality. 

EFFECT  ON  SPORULATION 

Among  other  effects  of  ultraviolet  irradiation  is  modification  in 
spore  production.  Ramsey  and  Bailey  (1930),  using  a  quartz- 
mercury-vapor  arc  with  filters  to  screen  out  radiations  below  a 
certain  wavelength,  and  exposing  for  15  to  30  minutes  at  a  dis- 
tance of  60  cm,  found  the  greatest  production  of  conidia  by 
Macrosporhmi  tomato  and  Fusarium  cepae  within  the  range  2535 
to  2800  A.  Radiations  within  this  range  could  also  be  used  to 
inhibit  the  growth  of  these  organisms  or  to  kill  them.  Their  evi- 
dence  indicates  that  increased  sporulation  was  not  the  result  of 
increased  temperature  nor  modification  of  the  medium,  as  was 
suggested  by  Smith  ( 1935)  from  her  studies  of  F.  eumart'u.  When 
the  filters  employed  by  Ramsey  and  Bailey  permitted  the  trans- 
mission only  of  radiations  of  wavelengths  greater  than  3120  A, 
there  was  slight  stimulation  in  spore  production.  Radiations  of 
wavelengths  greater  than  3334  A,  however,  were  without  appre- 
ciable effect  in  this  respect.  They  also  noted  that  the  minimum 
duration  of  exposure  for  stimulation  was  30  seconds  and  that  sev- 
eral exposures  at  short  intervals  were  more  effective  than  a  single 
exposure  equal  in  duration  to  the  sum  of  the  several  short  ex- 
posures. When  irradiated,  their  cultures  of  F.  coeruleum  formed 
conidia,  whereas  this  strain  was  never  observed  to  do  so  in  non- 
irradiated  cultures.  On  the  other  hand,  their  cultures  of  F.  argil- 
laceum,  when  irradiated,  failed  to  form  conidia,  producing  only 
chlamydospores. 

Stevens  (1928,  1930,  1931)  exposed  Glomerella  crngulata  and  a 
species  of  Coniothvrium  to  a  Cooper-Hewctt  quartz-mercury- 
vapor  arc  operated  at  4.5  amp  and  66  volts.  The  agar  plates  were 
uncovered  during  exposure  at  a  distance  of  21  cm  from  the  source 
of  light.  With  exposures  at  less  than  1  min,  perithecia  were 
formed  in  abundance  by  G.  cingulata  and  pvcnidia  by  Coniothv- 
rium.   In  both  species  these  structures  normally  appeared  on  the 


INDUCTION  OF  SALTATIONS  145 

same  medium  but  were  always  sparse.  Stevens  (1931)  induced 
Colletotrichum  lagenarium  to  form  the  perithecial  stage  in  cul- 
ture, whereas  this  stage  had  never  been  observed  previously  under 
any  conditions.  Although  he  did  not  regard  temperature  as  a 
significant  factor,  he  noted  that  the  presence  in  the  medium  of 
such  sugars  as  favor  growth  also  favors  increased  spore  produc- 
tion after  irradiation. 

There  is  evidence  that  ultraviolet  radiation  may  hasten  sporula- 
tion  [Hutchinson  and  Ashton  (1930)].  Short  exposures  induced 
Colletotrichum  phomoides  to  sporulate  earlier,  and  long  exposures 
delayed  sporulation.  Hutchinson  and  Ashton  concluded  that 
within  certain  limits  the  time  of  sporulation  is  an  inverse  expres- 
sion of  the  rate  of  growth. 

EFFECT  OF  X-RAYS 

Both  ultraviolet  and  X-rays  have  been  used  as  therapeutic 
agents,  especially  in  dermatomycosis  and  actinomycosis.  The 
medical  aspects  of  their  use  appear  to  be  better  known  than  their 
general  effects  on  fungi.  The  evidence  concerning  X-rays  indi- 
cates that  fungi  are  rather  insensitive  to  their  action  but  that  large 
dosages  are  lethal.  Haskins  and  Moore  (1934)  found  that  soft 
X-rays  were  2.1  times  as  potent  in  killing  conidia  of  Penicillium 
as  were  hard  X-rays.  The  soft  X-rays  used  by  them  had  a  wave- 
length of  1.3  to  1.5  A;  the  hard  ones,  from  0.18  to  0.21  A.  Lethal 
action  of  X-rays  against  plant  pathogens  was  earlier  reported  by 
Pichler  and  Wober  (1922),  who  successfully  freed  wheat  seed 
from  Ustilago  tritici,  barley  seed  from  U.  mida,  and  potato 
tubers  from  Synchytrhnn  (Chrysophlyctis)  endobioticam. 

Nadson  and  Philippov  (1925)  suppressed  the  formation  of 
zygotes  in  Mucor  genevensis  and  Zygorhyn  chits  moelleri  by 
exposure  of  cultures  to  X-rays.  Marked  changes  in  protoplasmic 
structure  resulted  in  Sac  char  omyces  cerevisiae  and  Nadsonia  ful- 
vescens  after  exposure  to  X-rays  [Nadson  (1937)]. 

INDUCTION  OF  SALTATIONS 

None  of  the  effects  of  radiation  which  have  thus  far  been 
given  consideration  in  the  present  account  can  be  regarded  as 
mutations,  for  evidence  is  lacking  that  they  are  heritable.    Radia- 


146  EFFECTS  OF  RADIATION  ON  FUNGI 

tions  of  short  wavelengths,  however,  have  been  used  to  produce 
heritable  mutations  with  many  biological  materials,  as  is  well 
known,  and  a  voluminous  literature  on  this  subject  exists.  Rela- 
tively few  studies  have  been  made  of  induction  of  heritable  mu- 
tations in  fungi.  Dickson  (1932,  1933)  exposed  malt-agar  cul- 
tures of  Mucor  gevevensis,  Phy  corny  ces  blakesleeamts,  and  the 
ascospores  of  seven  species  of  Chaetomium  to  X-rays  for  50  min- 
utes at  a  distance  of  26  cm.  Changes  in  color  and  amount  of 
mycelium  were  induced  in  colonies  arising  as  subcultures  from  the 
irradiated  materials,  and  these  changes  were  manifest  by  sector- 
ing. Stevens  (1930)  obtained  sectoring  in  cultures  of  Glomerella 
c'nigulata  exposed  to  ultraviolet  radiation.  Greaney  and  Machacek 
(1933)  exposed  cultures  of  Hehninthosporhnn  sativum  to  a  mer- 
cury-arc lamp  (110  volts,  60  cycles)  for  4  minutes  on  each  of  3 
successive  days.  During  exposure  the  cultures  were  placed  at  a 
distance  of  35  cm  from  the  arc.  As  a  result  of  this  treatment  a 
saltant  having  hyaline  mycelium  and  almost  colorless  conidia  ap- 
peared. In  all  these  cases  the  saltants  remained  constant  in  sub- 
cultures through  succeeding-  generations. 

Lockwood  and  associates  (1945)  irradiated  217  isolates  of  Asper- 
gillus t  err  ens  with,  ultraviolet  rays,  and  as  a  consequence  141  were 
changed  morphologically.  Among  the  76  that  were  unchanged 
morphologically,  59  were  found  capable  of  producing  more  ita- 
conic  acid  than  the  parent  strains.  None  of  the  141  strains  that 
were  altered  morphologically,  on  the  other  hand,  was  found  cap- 
able of  this  increased  production  of  itaconic  acid. 

Emmons  and  Hollaender  (1939)  irradiated  the  dermatophyte, 
Trichophyton  mentagrophytes,  and  thereby  induced  the  produc- 
tion of  mutants.  This  organism  lacks  a  sexual  stage,  and  conse- 
quently the  investigators  were  unable  to  make  a  genetical  analy- 
sis of  the  mutants.  By  use  of  Neurospora  cr asset  [Sansome  et  al. 
(1945)],  however,  it  was  found  that  two  types  of  mutants  could 
be  induced,  one  of  which  was  caused  by  chromosomal  aberration. 
They  varied  dosage  and  intensity  and  noted  that  increase  in  in- 
tensity  resulted  in  increase  in  mutation  rate.  At  low  dosage  there 
was  a  straight-line  relationship  between  increase  in  mutation  rate 
and  increase  in  energy. 


.     IMPLICATIONS  141 

MODE  OF  ACTION  OF  SHORT  RADIATIONS 

When  the  percentage  of  survivors  is  plotted  against  the  total 
energy  used  to  kill  yeast,  typical  S-shaped  curves  are  secured  from 
the  data  of  WyckofT  and  Luyet  (1931)  and  Oster  (1934).  Several 
different  explanations  of  why  curves  of  this  type  should  be  ob- 
tained have  been  offered.  Some  workers  regard  them  merely  as 
expressions  of  normal  probability  of  survival  of  the  individuals. 
Others  attribute  the  form  of  the  curve  to  multiple  quantum  hits 
on  a  sensitive  region  of  the  cell,  presumably  on  the  nucleus  or  cer- 
tain of  its  constituent  elements.  A  single  hit  is  regarded  as  the 
adsorption,  by  the  sensitive  region,  of  1  quantum.  The  adherents 
of  the  multiple-quantum  theory,  knowing  the  amount  of  energy 
and  the  survival  percentage,  calculate  the  number  of  hits  required 
to  kill.  Needless  to  say  there  is  little  accord  in  observations  on  the 
number  of  quanta  required.  The  significance  of  this  fact  is  not 
clear,  but  the  situation  might  be  clarified  if  the  influence  of  age, 
nutrition,  acidity,  temperature,  and  such  factors  was  taken  into 
consideration.  In  conclusion,  it  is  apparent  that  many  phenomena 
attributed  to  the  action  of  radiation  are  not  caused  by  light  alone 
but  are  correlated  in  a  causal  relationship  with  other  factors. 

IMPLICATIONS 

It  appears  that  the  present-day  mycologist  and  physicist,  each 
in  his  own  field,  can  do  little  more  to  extend  knowledge  of  the  ef- 
fects of  radiations  on  fungi.  Conceivably  they  might  achieve  re- 
sults were  they  to  collaborate.  In  lieu  of  such  collaboration,  ad- 
vances in  knowledge  will  be  conditional  upon  the  presence  of 
workers  who  may  properly  be  termed  bio-physicists.  This  name 
connotes  possession  of  basic  training  in  both  biology  and  physics 
and,  what  is  more  important,  a  consuming  zeal  to  apply  this 
training  to  explorations  leading  to  the  furtherance  and  dissemina- 
tion of  knowledge  in  mycology.  Such  "myco-physicists"  should 
be  able  to  correct  or  clarify  many  of  the  contradictory  conclu- 
sions and  concepts  now  extant. 


148  EFFECTS  OF  RADIATION  ON  FUNGI 


LITERATURE  CITED 

Allen,  Ruth  F.,  and  H.  D.  Jolivette,  "A  study  of  the  light  reactions  of 

Philobolus,"  Trans.  Wis.  Acad.  Aci.,  77:533-598,  1914.^ 
Backus,  M.  P.,  "Phototxopic  response  of  perithecial  necks  in  Neurospora," 

My  col.,  29:  383-386,  1937. 
Bisby,   G.   R.,   "Zonation   in   cultures   of  Fusariwn   discolor   snlphureimi," 

Mycol.,  11:  89-97,  1925. 
Blaauw,  A.  H.,  "Licht  und  Wachstum,"  Z.  Botan.,  6:  641-703,  1914. 
Brown,  W.,  "Studies  in  the  genus  Fusarium.    II.  An  analysis  of  factors  which 

determine  the  growth  forms  of  certain  strains,"  Ann.  Botany,  39:  375- 

408,  1925. 
Buder,  J.,   "Die   Inversion  des  Phototropism  bei  Phvcomyces,"  Ber.  dent. 

botan.  Ges.,  36:  104-105,  1918. 
Buller,  A.  H.  R.,  "The  reactions  of  the  fruit  bodies  of  Lentinus  lepideus  to 

external  stimuli,"  Ann.  Botany,  19: 427^38,  1905. 
"The    biologv    of    Polyporus    squamosus,    a    timber-destroving    fungus," 

/.  Econ.  Biol,  1:  101-138,  1906. 
Researches  on  fungi.  Vol.   1:   pp.  47-78,   120-121,   1909;  vol.   3:    357-411, 

1924;  Vol.  6:  36-45,  90-130,  264-324,  397-454,  1934.     Longmans,  Green, 

London. 
Castle,  E.  S.,  "The  phvsical  basis  of  the  positive  phototropism  of  Phy- 

comyces,"  /.  Gen.  Physiol.,  17:49-62,  1933. 
Dickson,  Hugh,  "The  effect  of  x-rays,  ultra-violet  light,  and  heat  in  pro- 
ducing   saltants    in    Chaetomiwn    cochliodes    and    other    fungi,"    Ann. 

Botany,  46:  389-404,  1932. 
"Saltation   induced   bv   x-ravs   in   seven   species   of   Chaetomium,"    Ann. 

Botany,  41:  735-754,"  1933.  ' 
Dillon-Weston,  W.  A.  R.,  "Effect  of  light  on  urediniospores  of  the  black- 
stem  rust  of  wheat,  Pnccina  graminis  tritici"  Nature,  128:67-68,  1931. 
Dillon-Weston,  W.  A.  R.,  and  E.  T.  Halnan,  "The  fungicidal  action  of 

ultra-violet  radiation,"  Phytopathology,  20: 959-965,  1930. 
Dimond,  Albert,  and  B.  M.   Duggar,  "Some  lethal  effects  of  ultra-violet 

radiation  on  fungus  spores,"  Proc.  Nat.  Acad.  Sci.,  27:459-468,   1941. 
Emmons,  C.  W.,  and  Hollaender,  A.,  "The  action  of  ultraviolet  radiation 

on  dermatophytes.    II.  Mutations  induced  in  cultures  of  dermatophytes 

by  exposure   of  spores  to  monochromatic   ultraviolet   radiation,"   Am. 

]'.  Botany.,  26:467-475,  1939. 
Fro.mme,    F.    D.,    "Negative    heliotropism    of    urediniospore    germ    tubes," 

Am.  J.  Botany,  2:82-85,  1915. 
Fulton,  H.  R.,  and  W.  W.  Coblentz,  "The  fungicidal  action  of  ultra-violet 

radiation,"  /.  Agr.  Research,  38:  159-168,  1929. 
Gri  \m  y,  F.  J.,  and  J.  E.  Machacek,  "The  production  of  a  white  fertile 

saltant  of  H  ehnimthosporiwn  sativum  by  means  of  ultra-violet  radia- 
tion," Phytopathology,  25:379-383,  1933. 
Harvey,  E.  Newton,  Living  light.     328  pp.     Princeton   University  Press. 

1940.     (Cf.  pp.  37-42.) 


LITERATURE  CITED  149 

Haskins,  C.  P.,  and  C.  N.  Moore,  "The  inhibition  of  growth  in  pollen  and 
mold  under  x-ray  and  cathode-ray  exposure,"  Radiology,  25:710-719, 
1934. 

Hedgcock,  G.  G.,  "Zonation  in  artificial  culture  of  Cephalothecium  and 
other  fungi,"  Mo.  Botan.  Garden,  Ann.  Rept.,  1906:  115-117,  1906. 

Hollaender,  A.,  and  C.  W.  Emmons,  "The  action  of  ultraviolet  radiation 
on  dermatophytes.  I.  The  fungicidal  effect  of  monochromatic  ultra- 
violet radiation  on  the  spores  of.  Trichophyton  mentagrophytes"  J. 
Cellular  Comp.  Physiol.,  IS:  391-402,  1939. 

Hutchinson,  A.  H.,  and  M.  R.  Ashton,  "The  effect  of  radiant  energy  in 
growth  and  sporulation  in  Colletotrichinn  phomoides"  Can.  J.  Re- 
search, 3:  187-198,  1930. 

Hutchinson,  A.  H.,  and  D.  Newton,  "The  specific  effects  of  monochro- 
matic light  on  the  growth  of  yeast,"  Can.  J.  Research,  2:  249-263,  1930. 

Ingold,  C.  T.,  Spore  discharge  in  land  plants.  178  pp.  Clarendon  Press, 
Oxford.     1939. 

Landen,  E.  W.,  "Spectral  sensitivity  of  spores  and  sporidia  of  Ustilago 
zeae  to  monochromatic  ultra-violet  light,"  /.  Cellular  Comp.  Physiol., 
14:217-226,  1939. 

Lockwood,  L.  B.,  K.  B.  Raper,  A.  J.  Mover,  and  R.  D.  Coghill,  "The 
production  and  characterization  of  ultraviolet-induced  mutations  in 
Aspergillus  terreus.  III.  Biochemical  characteristics  of  the  mutations," 
Am.  J.  Botany,  52:214-217,  1945. 

Long,  W.  H.,  and  R.  M.  Harsch,  "Cultures  of  wood-rotting  fungi  on  arti- 
ficial media,"  /.  Agr.  Research,  72:33-82,  1918. 

Moreau,  F.,  "Sur  les  zones  concentriques  que  forment  dans  la  cultures  les 
spores  de  Penicillium  glaucum"  Bull.  soc.  hot.  Trance,  59: 491-495,  1912. 

Nadson,  G.  A.,  "De  certaines  irregularities  des  changements  de  la  'matiere 
vivante'  sans  l'influence  des  facteurs  externes,  principalement  des  ravons 
X  et  du  radium,"  Actualites  Sci.  hid.,  513:  1-26,  1937. 

Nadson,  G.  A.,  and  G.  Philippov,  "Influence  des  rayons  X  sur  la  sexualite 
et  la  formation  des  mutantes  chez  les  champignons  inferieurs  (Muco- 
rinees),"  Compt.  rend.  soc.  biol.,  93:Ml-M5,  1925. 

Oster,  R.  H.,  "Results  of  irradiating  Saccharomyces  with  monochromatic 
ultra-violet  light,"  /.  Gen.  Physiol.,  18:  71-88,  1934. 

Parr,  Rosalie,  "The  response  of  Pilobolus  to  light,"  Ann.  Botany,  32:  177- 
205,  1918. 

Pichler,  F.,  and  A.  Wober,  "Bestrahlungsversuche  mit  ultraviolettem  Licht, 
Rontgenstrahlen,  und  Radium  zur  Bekampfung  von  Pflanzenkrankhei- 
ten,"  Zentr.  Bakt.,  Parasitenk.,  II  Abt.,  57:  319-327,  1922. 

Pringsheim,  E.  G.,  and  V.  Czurda,  "Phototropische  und  ballistiche  Prob- 
leme  bei  Pilobolus,"  Jahrb.  iviss.  Botan.,  66:  869-872,  1927. 

Ramsey,  G.  B.,  and  A.  A.  Bailey,  "Effects  of  ultra-violet  radiation  on 
sporulation  in  Macrosporium  and  Fusarium,"  Botan.  Gaz.,  89:  113-136, 
1930. 

Reideaieister,  W.,  "Die  Bedingungen  der  Sklerotien  und  Sklerotienringbil- 
dung  von  Botrytis  cinerea  auf  kunstlichen  Nahrboden,"  Ann.  Mycol., 
7:  19-44,  1909. 


150  EFFECTS  OF  RADIATION  ON  FUNGI 

San  some,  E.  R.,  A  I.  Demerec,  and  A.  Hollaender,  "Quantitative  irradia- 
tion experiments  with  Neurospora  crassa.  I.  Experiments  with  X-ravs," 
Am.  J.  Botany,  32:218-226,  1945. 

Sharp,  D.  G.,  "A  quantitative  method  of  determining  the  lethal  effect  of 
ultra-violet  light  on  bacteria  suspended  in  air,"  /.  Bact.,  35:  589-599,  1938. 

Smith,  Elizabeth  C,  "Effects  of  ultra-violet  radiation  and  temperature  on 
Fusarium.    II.  Stimulation,"  Bull.  Torrey  Botan.  Club,  62:  151-164,  1935. 
"Effects  of  radiation  on  fungi."     In  Biological  effects  of  radiation,  II: 
889-918,  1936. 

Stevens,  F.  L.,  "Effect  of  ultra-violet  radiation  on  various  fungi,"  Botan. 
Gaz.,  86:210-225,  1928. 
"The    response    to    ultra-violet    irradiation    shown    bv    various    races    of 

Glomerella  cingulata"  Am.  J.  Botany,  77:870-881,  1930. 
"The  ascigerous  stage   of  Colletotrichum  lagenarium  induced  by  ultra- 
violet irradiation,"  My  col.,  23:  134-139,  1931. 

\Ye\,  H.  G.  van  der,  "Uber  die  phototropische  Reaction  von  Pilobolus," 
Proc.  konink.  Akad.  Wetenschappen  Amsterdam,  32:4-13,  1929. 

Wolf,  Frederick  A.,  "Fungal  flora  of  Yucatan  caves,"  Carnegie  Inst.  Wash- 
ington Pub.,  491:  19-2 1"  1938. 

AYyckoff,  R.  W.  G.,  and  B.  F.  Luyet,  "The  effects  of  x-ravs,  cathode,  and 
ultra-violet  rays  on  yeast,"  Radiology,  11:  1171-1175,  1931. 

Yarwood,  C.  E.,  "Diurnal  cycle  of  ascus  maturation  of  Taphrina  deformans," 
Am.  J.  Botany,  2^:355-357,  1941. 


Chapter  7 
EFFECTS  OF  REACTION  OF  SUBSTRATE  ON  FUNGI 

Amono-  the  chemical  environmental  influences  to  which  fungn 
are  generally  known  to  respond  is  the  reaction  of  the  substrate. 
Long  ago  the  theory  was  advanced  that  the  chemical  activities  of 
acids,  bases,  and  salts  may  be  attributed  chiefly  to  the  ionized 
portions.  Abundant  experience  has  shown  that  fungi  are  more 
tolerant  of  acid  ions  [H+]  than  of  basic  ions  [OH-].  If,  for 
example,  it  becomes  necessary  to  separate  mixed  cultures  of  fungi 
and  bacteria,  the  growth  of  bacteria  may  be  inhibited  by  the 
addition  of  lactic  acid  in  the  proportion  of  1  drop  of  50%  lactic 
acid  to  10  ml  of  agar  in  making  the  poured  plates  that  are  to  be 
planted  with  the  mixed  cultures. 

Many  fundamental  facts  regarding  the  effects  of  the  ionized 
portions  were  established  before  the  differences  between  total 
acidity  (titratable  acidity)  and  active  acidity  (hydrogen-ion-con- 
centration) were  appreciated.  The  work  of  Clark  (1899)  is  not- 
able in  this  connection.  He  studied  the  effects  of  the  concentra- 
tion of  a  variety  of  mineral  and  organic  acids  upon  the  germina- 
tion of  spores  and  mycelial  development  of  Sterigmatocystis 
nigra,  Oedocephahim  albidzmi,  Pemcillium  glaiicwn,  and  Botrytis 
cinerea.  As  a  result  he  found  that  the  OH~  group  is  rather 
more  toxic  to  all  species  than  the  H+  ions  and  that  molds  differ 
specifically  in  tolerance.  Furthermore,  to  inhibit  the  germina- 
tion of  these  molds,  a  concentration  of  the  mineral  acids  200  to 
400  times  that  fatal  to  higher  plants  is  required. 

Subsequently  the  classical  studies  of  Michaelis  and  S0rensen  on 
the  theory  of  the  hydrogen  ion  and  its  measurement  laid  the 
foundations  of  present-day  knowledge.  These  matters,  an  under- 
standing of  which  is  essential  to  all  biologists  regardless  of  their 
special  field  of  interests,  are  summarized  and  elucidated  in  a  vol- 
ume by  Clark  (1928).  With  the  help  of  this  book  the  student  can 
learn  the  fundamentals  of  ionization,  conductivity,  and  use  of  in- 
dicators, at  least  to  a  sufficient  degree  to  be  able  to  measure  hvdro- 

151 


152      EFFECTS  OF  REACTION  OF  SUBSTRATE  ON  FUNGI 

gen-ion  concentration,  without  mastering  the  underlying  theories 
and  principles. 

Meaning  of  hydrogen-ion  concentration.  Substances  are  con- 
ceived to  be  aggregates  of  molecules;  a  molecule  is  the  smallest 
unit  of  mass  that  possesses  the  characteristics  of  the  given  sub- 
stance. A  molecule  is,  however,  conceived  to  be  an  aggregate 
of  atoms,  which,  if  all  alike,  constitute  an  element. 

Included  in  atomic  structure  are  positive  electric  units  or 
charges  (protons)  and  negative  units  (electrons).  In  each  ele- 
ment protons  and  electrons  are  arranged  according  to  a  definite 
configuration,  which  is  concerned  with  the  behavior  of  the  atoms. 
A  complete  atom  may  be  deprived  of  one  or  more  positively 
charged  electrons,  whereupon  the  remaining  particle  is  a  posi- 
tively charged  ion  and  is  designated  a  cation.  Some  atoms,  how- 
ever, are  able  to  acquire  extra  electrons,  thereby  becoming  nega- 
tively charged  ions  which  are  designated  anions. 

The  behavior  of  acids,  bases,  and  salts  in  water  solutions  is  at- 
tributed to  the  activities  of  their  constituent  ions.  If,  for  example, 
an  acid  (base  or  salt)  is  dissolved  in  water,  its  molecules  become 
dissociated  to  a  certain  amount.  The  radical  of  the  molecule  ac- 
quires an  electron  from  the  acid  hydrogen  atom,  becoming  a 
negatively  charged  ion  and  leaving  the  nucleus  of  the  hydrogen 
atom  positively  charged.  This  hydrogen  ion  is  designated  as  H+ 
to  distinguish  it  from  the  complete  atom  H;  the  remainder  of  the 
molecule  may  be  symbolized  by  A-.  Dissociation  of  an  acid  may 
therefore  be  formally  expressed  as  follows:  [HA]  ^±  [H+]  + 
[A~  ].  This  reaction  is  shown  to  be  reversible,  but  if  temperature 
is  kept  constant,  equilibrium  will  eventually  become  established. 

ThCn  [H+]  X  [A-]  =  „ 

[HA]  ai 

meaning  that  the  product  of  the  number  of  positively  charged 
ions  and  negatively  charged  ions,  divided  by  the  number  of  un- 
dissociated  molecules,  is  a  constant  for  each  given  acid.  It  follows 
from  this  concept  that  if  the  value  of  K  is  large,  the  numerator 
must  be  large  in  proportion  to  the  denominator.  Such  acids  arc 
strong  acids.  If,  on  the  other  hand,  the  numerator  is  small  in 
proportion  to  the  denominator,  the  acid  is  a  weak  acid.  The  in- 
tensity of  reaction  of  an  acid  therefore  depends  upon  the  hydro- 
gen-ion concentration. 


SIGNIFICANCE  OF  THE  SYMBOL  pH  153 

Measurement  of  hydrogen-ion  concentration.  The  concen- 
tration of  hydrogen  ions  is  expressed  numerically  in  terms  of  a 
normal  solution.  A  normal  hydrogen-ion  solution  contains  1 
gram  of  hydrogen  ions  or  the  equivalent  per  liter.  Normal  solu- 
tions are  therefore  made  up  on  the  basis  of  molecular  weight  to 
secure  a  solution  containing  1  gram  of  hydrogen  or  the  equivalent 
per  liter.  The  dissociation  constant  of  a  IN  solution  of  the 
strongest  acid,  HC1,  at  25°  C  is  essentially  1.  The  dissociation 
constant  of  the  weakest  acid,  pure  water,  has  been  determined  to 
be  1/10,000,000  N,  which  constitutes  neutrality.  It  follows  there- 
fore that  the  dissociation  constants  of  all  other  acids  are  fractions 
that  range  between  these  extremes. 

The  dissociation  of  pure  water  at  25°  C,  if  expressed  formally, 
would  be  written 

[H+]  X  [OH-]  _ 
[HOH]         ~  Au" 

If*the  concentration  of  hydrogen  ions  in  water  is  1/10,000,000 
gram  (or  10 ~7),  if  expressed  logarithmically)  and  water  is  neutral, 
then  the  concentration  of  hydroxy  1  ions  is  also  1/10,000,000  gram 
(or  10~7).  The  number  of  molecules  of  water  dissociated  is 
so  small  in  comparison  with  the  total  number  that  [HOH]  may 
be  considered  unity  and  omitted,  making  the  formal  equation 
[H+]  x  [OH-]  =  Kw,  or  [H+]  (10"7)  X  [OH~]  (10~7)  = 
Kw  (lO-1^). 

Significance  of  the  symbol  pH.  Since  the  hydrogen-ion  con- 
centration of  a  solution  is,  with  few  exceptions,  a  fraction  of  the 

normal,  it  may  be  expressed  as  jtt+i,  that  is,  the  reciprocal  of 

[H+  ] .  By  use  of  the  reciprocal  the  negative  exponent  is  avoided. 
The  symbol  pH  is  therefore  used  to  designate  the  logarithm  of  the 
reciprocal  of  the  hydrogen-ion  concentration.  The  hydrogen-ion 
concentration  of  pure  water,  for  example,  is  1/1*0,000,000  N. 
Expressed  otherwise, 

[H+]  =  1  X  10-7, 
or 

r+ 


or 


log  [H+]  =  -7, 
-  log  [H+]  =  +7, 


or  j 

log  jjpj  =  7, 

or 

pH  =  7. 


154      EFFECTS  OF  REACTION  OF  SUBSTRATE  ON  FUNGI 

The  pH  of  a  solution  is  rarely  an  even  decimal  fraction  of  nor- 
mal. For  this  reason  the  quantity  between  two  succeeding  frac- 
tions may  be  indicated  by  a  multiplying  factor.  If,  for  instance, 
the  concentration  of  ions  is  0.000273  N,  it  may  be  written  2.73  X 
10  ~4.  By  the  use  of  the  logarithm  table,  it  will  be  found  that  the 
logarithm  of  2.73  =  +0.434  and  that  of  lO"4  =  -4.000.  Since 
the   logs   are   added   when   multiplying,    +0.434+  (—4.000)  = 

—  3.566.    Therefore  losr   rTT  ,  ,  =  3.566,  or  pH  =  3.566. 

&   [H  +  J  r 

If  the  actual  figure  for  the  hydrogen-ion  concentration  is  sought 
when  the  pH  value  is  given,  it  can  be  determined  by  the  reverse 
of  the  procedure  of  calculation  just  described.  Suppose  that  the 
given  pH  value  is  9.63,  which  may  be  expressed  thus:  [H+  = 
1  X  10~963.  The  exponent  —9.63  =  — 10  plus  +  0.37;  or,  other- 
wise stated,  it  equals  10-10  X  10  +  0-37.  The  logarithm  table  shows 
that  +0.37  corresponds  with  the  number  2.34.  Substitution  of 
this  number  in  the  original  equation,  [H+]  =  1  X  10_9G3,  gives 
the  identity  [H+]  =  2.34  X-IO"10. 

In  acids  dissociated  in  water,  the  concentration  of  hydrogen  ions 
must  be  greater  than  that  of  the  water  itself  and  therefore  must 
range  between  pH  7.0  (the  hydrogen-ion  concentration  of  water) 
and  pH  0.  Likewise,  bases  dissociated  in  water  have  a  hydroxyl- 
ion  concentration  greater  than  that  of  water  itself,  so  that  this 
concentration  can  range  between  pOH  7.0  (the  hvdroxvl-ion 
concentration  of  water)  and  pOH  0  (the  hvdroxvl-ion  concen- 
tration of  a  normal  basic  solution).  Since  the  acid  or  base  was  dis- 
sociated in  water,  [OH-  ]  ions  are  always  present  in  acid  solutions 
and  [H+  ]  ions  in  basic  solutions.  The  concentration  of  hydrogen 
ions  therefore  varies  inversely  as  the  concentration  of  hydroxvl 
ions,  and  vice  versa,  the  product  of  the  concentration  of  both  kinds 
being  always  1  X  10-14.  From  this  relation  it  is  evident  that,  if 
the  concentration  of  either  ion  is  known,  that  of  the  other  can  be 
readily  computed.  Thus  if  the  pH  of  a  solution  is  10  ~4,  the  pOH 
is  10-10.  From  the  foregoing  discussion  it  is  apparent  that  any 
pH  value  between  0  and  7  indicates  an  acid  solution,  with  decreas- 
ing acidity  as  the  number  increases.  Similarly,  any  pH  value  be- 
t\\  een  7.0  and  14.0  indicates  a  basic  solution  with  increasing  basic- 
ity  (decreasing  acidity)  as  the  number  increases. 

.Measurement  of  pH.  Two  methods  are  employed  in  measur- 
ing hydrogen-ion  concentration,  one  electrometric,  the  other 
colorimetric.    The  electrometric  method  is  the  more  accurate  and 


pH  AND  GROWTH 


155 


requires  the  more  expensive  and  elaborate  apparatus.  The  colori- 
metric  method  yields  approximate  measurements  that  can  be 
simply  and  quickly  achieved.  The  electrometric  method  depends 
upon  the  ability  of  solutions  of  acids,  bases,  and  salts  to  conduct 
an  electrical  current,  differences  being  attributable  to  concentra- 
tion; the  colorimetric  method  involves  changes  in  the  colors  of 
indicators,  each  within  a  given  range  of  pH,  and  the  matchino- 
of  colors  with  standards. 

pH  and  growth.  Hydrogen-ion  concentration  does  not  equally 
influence  all  the  vital  processes  or  activities  of  fungi,  as  might  be 
anticipated.  Much  of  what  has  been  learned  about  the  effects 
of  pH  and  pOH  on  fungi  has  come  from  studies  on  the  influence 
of  reaction  upon  growth  rather  than  upon  individual  processes, 


TABLE  12 

Range   of  Hydrogen-Ion    Concentration   Permitting   Growth    of   Various 

Fungi 


Authority 

Sherwood  (1923) 
Herrick  (1939) 
Johnson  (1923) 
Johnson  (1923) 
Johnson  (1923) 
Johnson  (1923) 
Johnson  (1923) 
Johnson  (1923) 
Meacham  (1918) 
Meacham  (1918) 
Meacham  (1918) 
Meacham  (1918) 
Webb  (1919) 
Webb  (1919) 
Webb  (1919) 
Webb  (1919) 
Jackson  (1940) 
Jackson  (1940) 
Wolpert  (1924) 
Wolpert  (1924) 
Wolpert  (1924) 
Wolpert  (1924) 
Wolpert  (1924) 
Wolpert  (1924) 
Wolpert  (1924) 
Wolpert  (1924) 


Organism 

Fusarium  lycopersici 
St  ere  um  gausapatum 
Mucor  glomerula 
Fusarium  bullatum 
Aspergillus  oryzae 
Aspergillus  terricola 
Penicillium  i  tali  cum 
Penicillium  var labile 
Lenzites  saepiaria 
Fomes  roseus 
Merulius  lacrymans 
Coniophora  cerebella 
Lenzites  saepiaria 
Aspergillus  niger 
Penicillium  cyclopium 
Botrytis  cinerea 
Pythium  sp. 
Rhizoctonia  solani 
Lenzites  saepiaria 
Daedalea  confragosa 
Polystictus  versicolor 
Ar  miliaria  me  lie  a 
Pholiota  adiposa 
Polyporus  adustus 
Pleurotus  ostreatus 
Schizophyllum  commune 


Range  within  Which  Growth 
Occurred 

2.8  and  8.4 
2.0  and  8.2 
3.2-3.4  and  8.7-9.2 
2.3-2.2  and  9.2-11.2 
1.6-1.8  and  9.0-9.3 
1.6-1.8  and  9.0-9.3 
1.9-2.2  and  9. 1-9.3 
1.6-1.8  and  10.1-11.1 

1.9  (optimum,  3.0) 
1.9  (optimum,  3.0) 
1.0  (optimum,  3.0) 
1.9  (optimum,  3.0) 
Below  2.8  and  7.4 

2.8  and  7.4-8.8 

Below  2.8  and  approximately  9.6 
Below  2.8  and  7.4 
2.5-3.5  and  8.5 
2.5  and  7.5-8.5 

3.4  and  7.3 

3.5  and  7.2 
2.5  and  7.6 

2.9  and  7.4 
2.8  and  7.0 
3 . 5  and  7 . 6 
3.0  and  7.5 
3.4  and  7.0 


156      EFFECTS  OF  REACTION  OF  SUBSTRATE  ON  FUNGI 


such  as  reproduction,  respiration,  and  enzyme  production.  In 
general,  these  studies  have  been  concerned  with  establishing  the 
range  of  pH  within  which  growth  can  be  accomplished.  All 
show  that  optimum  growth  occurs  if  the  media  are  acid,  and  there 
is  abundant  evidence  to  indicate  that  the  range  of  pH  that  will 
permit  growth  varies  with  the  species,  with  the  composition  and 

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Fig.  23.  Growth  of  certain  Basidiomycetes  in  Richards'  solution  adjusted 
to  different  initial  degrees  of  aciditv.    Cultures  maintained  at  25°  C.     (After 

Wolpert.) 

the  initial  reaction  of  the  culture  medium,  and  with  temperature. 
Representative  results  of  the  influence  of  reaction  upon  growth 
of  fungi  are  assembled  in  Table  12. 

The  most  significant  feature  indicated  by  Table  1 2  is  that  essen- 
tially  all  the  region  of  pH  permitting  growth  lies  within  the  acid 
range.  As  a  secondary  feature  it  is  apparent  that  each  species 
may  differ  in  the  limits  of  this  range.  It  should  be  indicated  that 
the  optimum  pH  does  not  occur  at  the  midpoint.  The  under- 
lying reasons  for  these  facts  seem  to  rest  upon  the  isoelectric  points 
of  the  constituent  proteins  of  the  different  species,  as  shown  by 
Robbins  (1924).    In  Rhizopus  nigricans  and  Fiisarinm  ly coper sici 


VARIATION  OF  pH  RANGE  WITH  MEDIA  151 

the  isoelectric  points  of  the  proteins  were  shown  to  be  in  the 
vicinity  of  pH  5.0  and  5.5,  respectively.  When  Robbins  stained 
the  mycelial  mat  of  R.  nigricans  with  an  acid  dye,  it  retained  the 
dye  on  the  acid  side  of  the  isoelectric  point,  but  the  mycelium 
was  unstained  on  the  basic  side.  This  result  was  determined  by 
washing  mycelia  stained  with  eosin,  for  example,  with  solutions 
of  pH  3.5,  3.9,  4.5,  5.7,  5.8  and  6.9.  These  solutions  were  made 
with  appropriate  mixtures  of  0.1  M  phosphoric  acid  and  of  0.1  M 
sodium  hydroxide.  After  thorough  washing  with  a  buffer  solu- 
tion of  pH  3.5  or  3.9,  the  mycelia  were  bright  red;  with  a  solution 
of  pH  4.5,  intermediate  red;  with  a  solution  of  pH  5.7  or  5.8, 
pink;  with  a  solution  of  pH  6.9,  hyaline. 

Variation  of  pH  range  with  media.  Failure  of  various  work- 
ers to  agree  on  the  pH  range  that  will  support  growth  in  a  ^iven 
fungus  may  be  attributed  to  differences  in  culture  media.  These 
differences  involve  kind  and  proportion  of  nutrients,  buffering, 
and  initial  reaction.  The  influence  of  the  composite  of  these 
factors  is  illustrated  bv  the  work  of  Wolpert  (1924).  He  em- 
ployed a  modified  Richards'  solution,  on  the  one  hand,  and  a 
2.5%  peptone-mineral  nutrient,  on  the  other,  with  the  results 
shown  in  Table  13. 

TABLE  13 

Comparison  of  pH  Range  of  Certain  Basidiomycetes  on  Two  Different 

Media 

pH  Range   That  Inhibits  Growth 


Organisms  Richards'  solution        Peptone  solution 

Lenzites  saepiaria  3 . 4  and  7.3  2.8  and  7 . 5 

Daedalea  confragosa  3 . 5  and  7.2  2.8  and  7 . 6 

Polystictus  versicolor  2 . 5  and  7.6  2.5  and  7 . 5 

Armillaria  mellea  2.9  and  7.4  2.0  and  7.8 

Pholiota  adiposa  2 .  8  and  7.0  2.8  and  7 .  8 

Pleurotus  ostreatus  3-.  0  and  7.5  3.0  and  8 .  5 

Schizophyllum  commune  3.4  and  7.0  2.8  and  8.5 

During  growth  each  species  increased  the  acidity  in  Richards' 
solution,  Lenzites  saepiaria  being  the  most  active  acid-producer. 
All  of  them  except  L.  saepiaria  and  Pleiirotns  ostreatus  decreased 
the  acidity  in  peptone  solution  when  the  initial  reaction  was  less 
than  pH  6.0  and  increased  it  when  the  initial  reaction  was  greater 
than  pH  6.0. 


158      EFFECTS  OF  REACTION  OF  SUBSTRATE  ON  FUNGI 

As  is  well-known,  temperature  modifies  the  rate  of  growth,  but 
it  is  also  an  important  factor  in  modifying  the  pH  range.  Tem- 
peratures favorable  for  optimal  development  tend  to  be  corre- 
lated with  the  widest  pH  range.  Wolpert  (1924)  grew  each  of 
the  species  listed  in  Table  13  at  15°  C,  25°  C,  and  35°  C,  all  other 
factors  being  identical.  Lenzites  saepiaria,  Pleurotits  ostreatus, 
and  Arnnllaria  mellea  have  high  optimal  temperatures,  Schizo- 
phyllum  commune  has  a  low  one,  and  the  remainder  have  inter- 
mediate optimal  temperature  requirements. 

The  comparative  growth  of  Ophiobohts  graminis  on  Czapek's 
nutrient  fortified  with  cane  sugar  and  on  corn-meal  decoction  led 
Webb  and  Fellows  (1936)  to  conclude  that  the  nutritional  and 
physical  nature  of  the  media,  irrespective  of  all  other  factors, 
greatly  modifies  the  influence  exerted  by  free  hydrogen  or  hy- 
droxvl  ions  on  the  growth  of  fungi. 

pH  of  fungus  tissues.  Essentially  nothing  is  known  about  the 
hydrogen-ion  concentration  of  fungus  tissues.  Armstrong  (1929) 
measured  the  reaction  of  the  juice  of  crushed  stipes  and  pilei  of 
certain  fleshy  fungi,  with  the  results  shown  in  Table  14. 

TABLE  14 
Hydrogen-Ion  Concentration  of  Fungus  Tissues 


Fungus 

pH 

Agaric  us  campestris 

Ca.  5.9 

Amanita  muse  aria 

6.2 

Ar miliaria  mellea 

5.6-5.9 

Clavaria  rugosa 

Ca.  6.2 

Clavaria  corniculatus 

Ca.  6.2 

Clitocybe  laccata 

6.2 

Collybia  radicata 

5.9 

Coprinus  atramentarius 

6.2-6.8 

Coprinus  micaceus 

5.6-5.9 

Cortinarius  violaceus 

6.2 

Hekella  crispa 

6.2 

Hypholoma  fasciculare 

Ca.  5.9 

Lactarius  blennius 

Ca.S.6 

Leotia  chlorocephala 

5.6-6.2 

Mycena  pura 

Ca.  5.9 

Mycena  vulgare 

Ca.  5.9 

Panus  torulosis 

5.6-5.9 

Polystictus  versicolor 

5.9 

Typhula  incarnata 

Ca.  5.9 

CORRELATION  OF  REACTION  OF  THE  SOIL  159 

These  determinations  of  pH  may  not  necessarily  be  those  of 
the  vacuolar  sap,  just  as  the  pH  of  the  crushed  tissues  of  green 
plants  may  not  be  that  of  the  cell  sap.  They  appear  of  interest 
in  indicating  that  fungus  tissues  are  acid.  Recognition  of  their 
significance,  however,  awaits  the  development  of  methods  for 
determining  true  pH  values  of  fungus-cell  sap. 

pH  and  pigmentation.  The  pigments  in  many  species  of 
fungi  may  function  as  natural  indicators  that  change  color  with 
a  change  of  reaction.  One  factor  that  controls  the"  development 
of  pigment,  moreover,  is  the  reaction  of  the  medium.  The  pres- 
ence of  appropriate  carbohydrates  may  also  constitute  a  control- 
ling factor.  These  relationships  with  species  of  Fusarium  were 
studied  by  Sideris  (1925).  If  he  employed  dextrose  solutions  and 
made  no  attempt  to  control  the  changes  in  reaction  during  growth, 
pigment  was  produced  within  the  range  pH  3.0  to  7.5.  If  the  pH 
was  kept  constant,  pigment  was  produced  only  within  the  rano-e 
3.5  to  5.5. 

pH  and  enzymic  activity.  The  effect  of  pH  on  enzymic  ac- 
tivity was  mentioned  in  Chapter  2.  Evidently  the  effect  of  re- 
action upon  individual  metabolic  processes  in  fungi  has  not  been 
the  subject  of  much  study.  Karrer  ( 192 1 )  recorded  that  Fusarium 
sp.  from  cotton,  when  grown  in  nutrient  solution,  yield  the  great- 
est total  amount  of  amylase  if  the  initial  reaction  is  pH  4.5  and  the 
final  reaction  is  pH  7.8;  Collet otrichum  gossypii,  if  the  initial  re- 
action is  pH  7.0  and  the  final  is  pH  7.9.  For  Fenicilliinn  italicum 
pH  3.0  and  pH  4.5  are  equally  favorable.  Amylase  accumulation 
is  completely  inhibited  within  the  range  pH  9.0  to  1 1.0  in  Fusarium 
sp.  and  in  C.  gossypii,  and  at  pH  9.0  in  P.  italicum.  Further  evi- 
dence of  the  influence  of  hydrogen-ion  concentration  upon  the 
activity  of  amylase  was  presented  by  Sherman,  Thomas,  and  Bald- 
win (1919).  They  showed  that  pancreatic  amylase  is  active  within 
the  range  pH  4.6  to  10,  pH  7.0  being  optimum;  malt  amylase 
within  the  range  pH  2.5  to  9.0,  pH  4.4  to  4.5  being  optimum';  and 
amylase  from  Aspergillus  oryzae  within  the  range  pH  2.6  to  8.0, 
pH  4.8  being  optimum. 

Correlation  of  reaction  of  the  soil,  optimum  pH  of  the 
pathogen,  and  incidence  of  disease.  Experimentation  involving 
these  matters  in  connection  with  soil-borne  pathogens  has  en- 
gaged the  attention  of  certain  plant  pathologists,  notably  Chupp 


160      EFFECTS  OF  REACTION  OF  SUBSTRATE  ON  FUNGI 

(1928),  Maclnnes  (1922),  Schaffnit  and  Meyer-Hermann  (1930), 
Sherwood  (1923),  and  Sideris  (1929). 

Schaffnit   and    Meyer-Hermann    (1930)    determined    the    pH 
optima  for  growth  of  a  group  of  soil-borne  fungi  as  a  basis  for 


5.8 


6.0 


6.2  6.4  6.6  6.8 

Hydrogen -ion  concentration 


.0 


7.2 


7.4 


Fig.  24.     Relation  of  hydrogen-ion  concentration  to  infection  of  cabbage 
by   Plasmodiophora   brassicae.     Infection   is   inhibited   as   alkalinity   is   ap- 
proached.    (After  Chupp.) 

their  field  trials.     From  these  results  thev  concluded  that  such 
organisms  may  be  grouped  as  follows: 

1 .  Litrophilic:  those  that  prefer  alkaline  soils,  including  Pythhnn 
de  baryanum,  Momlwpsis  aderholdii,  Fusarium  nivale,  F.  equiseti, 
Ophiobohts  graminis,  and  Typhula  grarmneum.    If  the  soils  are 


CORRELATION  OF  REACTION  OF  THE  SOIL  161 

made  acid,  F.  nivale,  O.  gramhiis,  and  T.  gramineum  may  dis- 
appear. 

2.  MesanthrophiUc:  those  that  thrive  best  in  neutral  soils,  in- 
cluding Fusariimi  aurantiacum,  F.  avenaceum,  F.  herbarum, 
Phoma  betae,  and  Thielavia  basicola. 

3.  Oxyphilic:  those  that  thrive  best  in  acid  soils,  including 
Plasmodiophora  brassicae  and  Rhizoctonia  violacea.  If  the  soil 
reaction  reaches  pH  7.5,  P.  brassicae  is  checked.  Synchytrium 
endobioticnm  may  also  be  placed  within  the  oxyphilic  group,  but 
it  is  actually  intermediate  between  this  group  and  the  aestatic 
group. 

4.  Aestatic:  those  that  possess  the  ability  to  thrive  in  a  wide 
range  of  soil  reactions,  including  Fusarium  cidmorum,  F.  poly- 
morphum,  Helminthosporium  sativum,  Ophiobolus  herpotrichus, 
and  Rhizoctonia  solani. 

SchafTnit  and  Meyer-Hermann  (1930)  indicate  that  not  only  is 
the  reaction  changed  by  the  addition  of  acid  or  basic  materials 
to  soil  but  also  that  such  changes  are  always  accompanied  by 
changes  in  the  physical  properties  of  the  soil.  Furthermore  it  has 
become  a  matter  of  common  knowledge  that  changes  in  reaction 
may  not  be  permanent  and  that  changed  availability  of  minerals 
to  growing  crops  accompanies  changes  in  soil  reactions. 

Chupp  (1928)  noted  that  pH  7.2  to  7.4  is  the  upper  limit  at 
which  Plasmodiophora  brassicae  causes  club  root  of  crucifers  and 
that  in  the  range  more  acid  than  pH  6.0  all  the  plants  may  be 
affected. 

In  black-root  rot  of  tobacco,  soil  reaction  and  soil  tempera- 
ture are  correlated  factors.  Doran  (1929)  observed  that  this  dis- 
ease does  not  develop  at  any  temperature  provided  that  the  pH  of 
the  soil  is  5.6  or  lower.  Marked  injury  is  apparent,  however,  at 
15°  C  with  pH  5.7;  at  18°  C  with  pH  5.7  to  5.8;  at  21°  C  with  pH 
5.8;  at  27°  C  with  pH  5.8  to  5.9.  M  30°  C  there  was  little,  if  any, 
injury  with  pH  values  of  6.0  to  6.9. 

That  acid  soils  yield  a  scab-free  crop  of  potatoes,  unless  lime  is 
applied,  is  the  common  experience  of  potato  growers.  Studies  by 
Gillispie  (1918)  on  the  scab  organism,  Actinomyces  cloromo genus, 
showed  that  it  is  inhibited  at  pH  4.8  to  5.2,  varying  with  the  iso- 
lates. He  correlated  these  results  with  the  fact  that  the  acidity 
of  Caribou  loam  of  Maine  ranges  from  4.9  to  5.5  and  hence  may 
restrain  the  growth  of  the  scab  organism. 


162      EFFECTS  OF  REACTION  OF  SUBSTRATE  ON  FUNGI 

Alkaline  fungicides.  In  the  lio-ht  of  observations  that  fungi 
generally  grow  better  in  acid  than  in  basic  media,  various  attempts 
have  been  made  to  utilize  this  fact  in  wood  preservation  and  the 

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Fig.  25.    Growth  of  certain  Basidiomvcetes  at  25°  C  in  peptone  nutrient  solu- 
tions with  varying  initial  reactions.     Comparison  with  Fig.  23   shows  that 
nutrition  is  also  a  factor  in  growth.      (After  Wolpert.) 

prevention  of  decay  in  fruits.  Stains  of  sapwood  can  be  largely 
prevented  if  the  lumber  is  dipped  into  an  alkaline  bath  immedi- 
ately after  it  is  sawn  [Scheffer  and  Lindgren  ( 1 940 )  | .  Such 
treatment  gives  protection  until  the  water  content  of  the  lumber 
can  be  reduced  to  20%  or  less,  at  which  point  lack  of  moisture 
inhibits  the  growth  of  sapwood-staining  species. 


IMPLICATIONS  163 

Attempts  to  prevent  the  decay  of  apples  and  oranges  by  use  of 
alkaline  dips  have  been  less  successful.  Marloth  (1931)  recorded 
that  sodium  tetraborate  is  more  toxic  to  Penicillium  dlgitatwn 
than  to  P.  italicum,  but  that  sodium  bicarbonate  is  more  toxic  to 
P.  it  ah  cam.  Attempts  to  prevent  decay  of  citrus  fruits  by  these 
molds  and  by  Pbomopsis  citri  and  Diplodia  natalensis  have  not 
been  uniformly  successful,  presumably  because  the  mycelia  early 
become  internal  to  the  "buttons"  or  cut  pedicels  and  because  the 
spores  of  Penicillium  are  difficult  to  wet. 

Implications.  The  totality  of  evidence  from  studies  of  the  ef- 
fects  of  reaction  on  fungi  shows  convincingly  that  pH  is  an  en- 
vironmental factor  of  enormous  consequence  in  modifying;  their 
metabolic  activities.  There  is  specificity  of  minimal,  optimal,  and 
maximal  pH  requirements,  but  it  must  not  be  overlooked  that  the 
effects  of  the  concentration  of  hydrogen  ions  cannot  be  isolated 
completely  from  those  induced  by  other  ions.  These  effects  are 
always  intricately  correlated.  For  this  reason  it  is  not  unlikely 
that  in  the  past  too  much  consideration  has  been  given  to  the 
influence  of  the  hydrogen  ion  and  too  little  to  that  of  other  ions. 
No  doubt  this  situation  prompted  the  supercilious  suggestion 
that  doctoral  dissertations  dealing  with  these  problems  may  be 
regarded  as  fulfilling  requirements  for  the  "pH  D." 

So  long  as  growth  continues  in  a  fungus  culture,  the  reaction 
of  the  medium  continues  to  change,  although  the  changes  may  be 
masked  by  relatively  large  amounts  of  buffer  substances  present 
in  the  medium.  In  other  words,  the  analytic  and  synthetic  proc- 
esses that  occur  during  utilization  of  organic  substrates  result  in 
the  production  of  many  kinds  of  organic  acids  and  such  other 
products  as  pigments,  polysaccharides,  sterols,  and  vitamins  (see 
Chapter  4).  Among  the  acids  known  to  be  producted  by  fungi 
are  aconitic,  carlic,  carlosic,  carolic,  dimethylpyruvic,  fulvic,  fu- 
maric,  gallic,  glycolic,  glycuronic,  itaconic,  kojic,  malic,  cf-man- 
nonic,  mycophenolic,  oxalic,  penicillic,  puberulic,  pyruvic,  spiculi- 
sporic,  succinic,  and  terrestric.  It  would  seem  that  determination 
of  the  kinds  of  acids  produced  in  fungus  metabolism  and  the  con- 
ditions influencing  their  production  should  be  given  increasing 
consideration,  rather  than  devoting  so  much  attention  to  accumu- 
lation of  data  on  pH  changes  during  growth. 


164      EFFECTS  OF  REACTION  OF  SUBSTRATE  ON  FUNGI 


LITERATURE  CITED 

Armstrong,  J.  I.,  "Hydrogen-ion  phenomena  in  plants.  I.  Hvdrion  con- 
centration and  buffers  in  fungi,"  Proto  plasma,  8:  222-260,  1929. 

Chupp,  C,  "Club  root  in  relation  to  soil  alkalinity,"  Phytopathology,  18:  301- 
306,  1928. 

Clark,  W.  M.,  The  determination  of  hydrogen  ions,  3rd  ed.  xvi  -f-  717  pp. 
Williams  and  \\  llkins  Co.,  Baltimore.    1928. 

Clark,  J.  F.,  "On  the  toxic  effect  of  deleterious  agents  on  the  germination 
and  development  of  certain  filamentous  fungi,"  Botan.  Gaz.,  28: 289- 
327,  378-404,  1899. 

Dorax,  W.  L.,  "Effects  of  soil  temperature  and  reaction  on  growth  of  to- 
bacco infected  and  uninfected  with  black-root  rot,"  /.  Agr.  Research, 
39:  853-872,  1929. 

Gillispie,  J.  L.,  "The  growth  of  the  potato-scab  organism  at  various  hv- 
drogen-ion  concentrations  as  related  to  the  comparative  freedom  of 
acid  soils  from  potato  scab,"  Phytopathology,  8:257-269,  1918. 

Herrick,  J.  A.,  "Growth  and  variability  of  Stereum  gausapatam  in  culture," 
Phytopathology,  7^:504-511,  1939.' 

Jackson,  L.  W.  R.,  "Effects  of  H-ion  and  Al-ion  concentrations  on  damp- 
ing-off  of  conifers  and  certain  causative  fungi,"  Phytopathology, 
SO:  563-579,  1940. 

Johnson,  H.  W.,  "Relationships  between  hvdrogen-ion,  hvdroxvl-ion,  and 
salt  concentrations,  and  the  growth  of  seven  soil  moulds,"  Iowa  Agr. 
Expt.  Sta.  Research  Bull,  16: 307-344,  1923. 

Karrf.r,  Joanne  L.,  "Studies  in  the  phvsiologv  of  the  fungi.  XIII.  The  ef- 
fect of  hvdrogen-ion  concentration  on  amvlase  produced  by  certain 
fungi,"  Ann.  Mo.  Botan.  Garden,  8:  63-96,  1921. 

MacInnes,  Jean,  "The  growth  of  the  wheat-scab  organism  in  relation  to 
hvdrogen-ion  concentration,"  Phytopathology,  12:  290-294,  1922. 

Marloth,  R.  H.,  "The  influence  of  hvdrogen-ion  concentration  and  of 
sodium  bicarbonate  and  related  substances  on  Penicillium  italicum  and 
P.  digitatwn"  Phytopathology,  21:  169-198,  1931. 

Meacham,  A  I.  R.,  "Note  upon  the  hvdrogen-ion  concentration  nccessarv  to 
inhibit  the  growth  of  four  wood-destroving  fungi,"  Science,  48:  499-500, 
1918. 

Robbins,  W.  J.,  "Isoelectric  points  for  the  mvcelium  of  fungi,"  /.  Gen. 
Physiol.,  5:259-271,  1924. 

Schaffntt,  E.,  and  K.  Mf.ver-Her.m ann,  "Ubcr  den  Einfluss  der  Bodenreak* 
tion  auf  der  Lebenweise  von  Pilzparasiten  und  das  Ycrhalten  ihrer  Wirt- 
pflanzen,"  Phytopath.  Z.,  2:99-166,  1930.   • 

Scheffer,  T.  C,  and  R.  M.  Lindgren,  "Stains  of  sapwood  and  sapwood 
products  and  their  control,"  U.  S.  Dept.  Agr.  Tech.  Bull.,  114:  124  pp. 
1940. 

Sherman,  H.  C,  A.  C.  Thomas,  and  M.  E.  Baldwin,  "Influence  of  hydrogen- 
ion  concentration  upon  enzvmic  activity  of  three  typical  amylases," 
Am.  Chem.  Soc.  ].,  41:  181-239,  1919. 


LITERATURE  CITED  165 

Sherwood,  E.,  "Hvdrogen-ion  concentration  as  related  to  the  Fusarium  wilt 
of  tomato  seedlings,"  Am.  J.  Botany,  10:  537-553,  1923. 

Sideris,  C.  P.,  "The  role  of  the  hvdrogen-ion  concentration  on  the  develop- 
ment of  pigment  in  Fusaria,"  /.  Agr.  Research,  30:  1011-1019,  1925. 
"The  effect  of  the  H-ion  concentration  of  the  culture  solution  on  the 
behavior  of  Fusarium  chromophythoron  and  Allium  cepa  and  the  de- 
velopment of  pink-rot-disease  symptoms,"  Phytopathology,  19:  233-268, 
1929. 

Webb,  R.  W.,  "Studies  in  the  physiology  of  the  fungi.  X.  Germination  of 
the  spores  of  certain  fungi  in  relation  to  hydrogen-ion  concentration," 
Ann.  Mo.  Botan.  Garden,  6:  201-222,  1919. 

Webb,  R.  W.,  and  H.  Fellows,  "The  growth  of  Ophiobohis  gramims  Sacc. 
in  relation  to  hydrogen-ion  concentration,"  /.  Agr.  Research,  33:  845- 
872,  1936. 

"Wol^ert,  F.  S.,  "Studies  in  the  phvsiologv  of  the  fungi.  XVII.  The  growth 
of  certain  wood-destroving  fungi  in  relation  to  the  H-ion  concentration 
of  the  media,"  Aim.  Mo.  Botan.  Garden,  11:48-96,  1924. 


Chapter  8 
SPORE  DISSEMINATION 

All  students  of  fungi  are  impressed  with  the  seemingly  limitless 
profligacy  of  these  organisms  in  the  production  of  spores.  Arthur 
(1929)  records  that  more  than  2  billion  sporidia  may  be  formed 
by  a  single  gall  of  Gymnosporangimn  juniperi-virginianae. 
Fovies  applanatiis,  which  may  attain  a  size  of  0.75  X  0.5  meters, 
may  have  an  annual  production  of  5  million  million  spores.  The 
crop  of  aeciospores  from  a  single  barberry  bush  was  found  by 
careful  computation  to  be  64,512,000,000.  The  pileus  of  Psalliota 
ccnnpestris  may  produce  1,800,000,000  basidiospores,  that  of 
Coprimts  comatus  5  billion,  and  that  of  Poly  poms  squamosus  1 1 
billion. 

Meyer  (1936)  reported  that  a  sporophore  of  Tomes  fomentarius 
shed  1115  grams  of  spores  in  a  period  of  20  days.  Each  spore  had 
a  computed  weight  of  0.000,000,000,146  gram.  The  calculated 
number  of  spores  produced  by  this  sporophore,  therefore,  was 
7,636,986,301,369. 

Moss  ( 1940)  estimated  the  number  of  spores  formed  by  Calvatia 
gigantea  as  20  million  million.  This  ability  to  produce  spores  in 
abundance  is  made  possible  among  many  Basidiomycetes  by  the 
lar^e  size  of  the  fructifications  and  by  such  structural  modifica- 
tions  as  gills  and  pores  that  increase  the  spore-bearing  surface. 
Certain  leathery  and  woody  polypores  have  been  found  to  be 
capable  of  shedding  spores  continuously  for  6  months  or  longer. 
Organisms  in  other  groups  may  shed  spores  in  abundance  only 
under  special  conditions.  Monilia  sitophila,  for  example,  may 
cover  burned  sugar-cane  stubbles  to  the  extent  that  acres  of  land- 
scape look  pink.  The  metal lic-lustered  Blakeslca  trispora  may  be 
equally  widely  prevalent  on  mowed,  withered  Sida  spinosa  and 
other  weeds  in  orange  groves.  Heald  (1937)  states  that  Tilletia 
tritici  may  be  so  abundant  during  the  threshing  season  in  eastern 

166 


DISTRIBUTION  OF  SPORES  161 

Washington  that  over  5  million  smut  spores  lodge  on  each  square 
foot  of  soil. 

Of  much  more  interest  than  the  ability  of  fungi  to  produce 
spores  in  abundance  is  the  development  of  mechanisms  or  devices 
that  serve  to  provide  maximum  distribution  of  these  spores. 
Survival  of  given  species  mav  in  large  part  be  conditioned  by  dis- 
persal into  habitats  where  food  is  available.  In  most  species  of 
fungi  special  mechanisms  are  lacking,  and  hence  distribution, 
among  both  aquatic  and  terrestrial  forms,  appears  to  be  largely 
fortuitous. 

DISTRIBUTION  OF  SPORES 

Aquatic  fungi.  The  environment  in  which  aquatic  species  ex- 
ist is  more  constant  than  the  habitat  of  terrestrial  species,  and  cor- 
related with  this  fact  is  the  possibility  that  a  larger  proportion  of 
their  spores  may  germinate  and  develop  into  new  individuals.  For 
these  reasons  problems  of  dissemination  of  aquatic  fungi  might  not 
be  expected  to  stimulate  as  much  interest  as  similar  problems  in- 
volving terrestrial  fungi.  Nearly  all  aquatic  fungi  are  among  the 
Phycomycetes,  the  spores  of  many  of  which  are  motile  (planetic). 
The  most  primitive  of  these  are  holocarpic.  Each  such  plant  pro- 
duces 20  to  30  spores,  each  of  which  possesses  a  single  flagellum. 
After  a  brief  period  of  motility,  which  rather  closely  restricts  the 
distance  that  the  spore  may  migrate  from  the  parent  plant,  the 
spore  initiates  the  assimilatory  phase  of  the  cycle  of  development. 
After  a  few  days  the  sporangium  is  again  mature,  and  conditions 
for  dispersal  have  once  more  been  prepared. 

Other  more  highly  specialized  species  possess  differentiated 
sporangia  or  other  sporiferous  cells,  from  which  cells  having  two 
flagella  are  liberated.  Evidence  is  lacking  that  biflagellate  species 
are  significantly  better  able  to  disseminate  themselves  and  to  com- 
pete to  greater  advantage  than  monoflagellate  ones.  Undoubtedly 
diplanetism,  that  is,  two  morphologically  distinct  motile  stages 
that  always  occur  sequentially,  so  highly  developed  among  the 
Saprolegniales,  must  be  regarded  as  an  evolutionary  advance  over 
monoplanetism.  In  the  Saprolegniales  diplanetism  is  accompanied 
by  certain  morphological  differences  in  spores  whose  significances 
are  wholly  unknown.  Typically,  on  first  escaping  from  the  spo- 
rangium the  swarm  spores  are  pear-shaped  and  terminally  biflagel- 
late.    After  swarming  for  a  brief  period,  they  encyst  and  then 


168  SPORE  DISSEMINATION 

escape  from  the  cvst  as  reniform,  laterally  biflagellate  swarmers. 
Encvstment  follows;  after  this  stage  they  give  rise  to  germ  tubes. 
This  pattern  of  behavior  varies  in  the  different  genera.  Sometimes 
polvplanetism  occurs  as  reported  bv  Weston  (1919)  in  Dic- 
tvuchus,  bv  Hohnk  (1933)  in  Saprolegnia  torulosa  and  Achlya 
racemosa,  and  bv  Salvin  ( 1940)  in  Achlva,  the  number  of  swarm- 
ings  beimj  controlled  by  reserve  food  in  the  swarm  spore  and  by 
unknown  environmental  factors. 

Terrestrial  fungi.  Various  adaptations  occur  among  terres- 
trial fungi  to  aid  in  their  geographic  distribution.  The  spores  of 
many  are  pulverulent,  so  that  dissemination  bv  air  currents  is 
favored.  Others  accumulate  in  a  mucous  matrix  that  is  water  sol- 
uble, the  occurrence  of  dews  and  rains  being  required  for  spore 
dissemination.  Some  become  wet  with  ease,  others  with  difficulty; 
some  have  thin  walls,  others  very  thick,  resistant  walls;  some  are 
smooth,  others  are  armed  with  spines,  tubercles,  or  echinulations. 
The  fructifications  of  some  species  are  malodorous,  encouraging 
visitation  by  flies,  bees,  ants,  and  other  insects,  whereas  others 
are  attractive  to  mvcophagous  animals,  such  as  nematodes,  beetles, 
snails,  slugs,  and  rodents. 

For  convenience  of  discussion  the  dissemination  or  dispersal  of 
fungi  may  be  considered  to  be  accomplished  by  (a)  agencies  re- 
lated to  the  environment  of  the  species  and  (b)  the  fungus  itself 
through  structural  adaptations. 

The  environmental  agencies  include  movement  of  air  as  con- 
vection  currents  and  winds,  movement  of  water,  occurring  as 
dew,  rains,  and  streams,  and  transport  by  insects  and  other  animals, 
including  man.  Many  species  are  dispersed  on  seed,  fruits,  cut- 
tings, seedlings,  and  transplants. 

Air  currents  as  a  factor  in  dispersal.  For  nearly  150  years 
it  has  been  taken  for  granted  from  observational  evidence  that  the 
spores  of  fungi  are  wind-borne.  Proof  that  wind  is  an  important 
agency  in  the  spread  of  pathogenic  fungi  has  been  forthcoming 
only  in  recent  years.  It  arose  from  attempts  to  explain  the  occur- 
rence of  epidemics,  especially  of  rusts.  According  to  Arthur 
(1929),  Marshall  reported  the  following  observations  made  in 
1782  upon  the  results  of  planting  a  barberry  bush  in  a  field  of 
wheat:  "About  the  barberry  bush  there  appeared  a  long  but 
somewhat  oval-shaped  stripe  of  a  dark  livid  color,  obvious  to  a 
person  riding  on  the  road  at  a  considerable  distance.     The  part 


DISTRIBUTION  OF  SPORES  169 

affected  resembled  the  tail  of  a  comet,  the  host  itself  representing 
the  nucleus,  on  one  side  of  which  the  sensible  effect  reached  about 
twelve  yards,  the  tail  pointing  toward  the  southwest,  so  that  prob- 
ably the  effect  took  place  during  a  northeast  wind.  ...  As  the 
distance  from  the  bush  increased,  the  effect  was  less  discernible, 
until  it  vanished  imperceptibly."  Ward  (1882),  in  connection 
with  studies  on  Hemileia  vastatrix  in  Ceylon,  was  among  the  first 
to  demonstrate  that  rusts  are  wind-borne;  he  trapped  the  uredinio- 
spores  on  slides  coated  with  glycerin.  Klebahn  (1904)  believed 
wind  responsible  for  bringing  grain-rust  spores  to  Germany,  be- 
cause during  a  dust  storm  which  swept  from  northern  Africa  to 
northern  Europe,  he  caught  3800  spores  of  Puccinia  gramijjis  at 
Hamburg  and  5600  at  Thiiringen  in  cotton-batting  spore  traps, 
4  in.  in  diameter. 

Within  the  United  States  a  volume  of  evidence  has  been  ac- 
cumulated to  show  that  the  grain  rusts  are  unable  to  survive  the 
winter  in  the  cold  climates  of  the  central  part  of  the  Cereal  Belt, 
where  the  alternate  host  is  absent,  and  that  urediniospores  are  car- 
ried northward  from  Mexico  and  Texas  toward  Canada.  By 
means  of  aeroplanes,  Stakman  and  his  associates  (1923)  entrapped 
viable  rust  spores  during  April  over  Waco,  Texas,  at  various  alti- 
tudes ranging  from  1000  to  16,500  ft.  In  late  summer  in  Manitoba 
at  an  altitude  of  5000  feet,  259  urediniospores  were  entrapped  on 
2  sq  in.  of  surface  in  one  instance,  and  116  urediniospores  in  an- 
other. 

The  later  work  of  Stakman  et  al.  (1940)  showed  that  the  telio- 
spores  of  Puccinia  gramims  are  of  no  consequence  in  the  annual 
cycle  of  this  rust  in  the  South.  The  uredinial  stage  does  not  sur- 
vive the  winters  north  of  Texas  or  the  summers  in  Texas  and 
areas  southward.  In  the  North  rust  is  dependent  on  barberry  and 
on  urediniospores  blown  in  from  farther  south.  Toward  the  end 
of  summer  and  in  the  fall  urediniospores  are  blown  southward, 
and  the  rust  survives  the  winter  in  fields  of  early-sown  wheat  in 
Texas  and  northern  Mexico. 

Observations  by  Pennington  (1924)  indicate  that  aeciospores  of 
Cronartium  ribicola,  while  usually  carried  only  a  few  hundred 
feet,  may  under  exceptional  conditions  be  transported  150  to  200 
miles  and  then  cause  infection.  Gyimiosporanghnn  juniperi-vir- 
ginianae  was  found  by  Schneiderhan  (1926)  to  have  produced 


110 


SPORE  D1SSEMIXAT10\ 


11.5  spots  per  leaf  on  apple  trees  1%  miles  away  from  infected 
cedars  and  0.32  spot  per  leaf  on  trees  3  miles  distant. 

The  foregoing  evidence  regarding  dispersal  of  rusts  bv  air  cur- 
rents is  representative  for  this  group  of  fungi  but  is  inadequate  in 
indicating  the  importance  of  this  agencv  for  other  groups  of  fungi. 
Stakman  and  his  coworkers  (1923)  identified  other  genera,  such 
as  Alternaria,  Helminthosporium,  Cladosporium,  Cephalothecium, 
and  Ustilago,  on  their  spore  traps.    Heald  et  al,  (1915)  found  that 


^& 


Fig.  26.    Spore  trap  of  weather-vane  type.    A.  The  dish  whose  inner  surface 
is  coated  with  glvcerin  remains  directed  toward  the  wind.    B.  Dishes  may 

be  stacked  during  transport. 

ascospores  of  Endothia  parasitica  may  be  entrapped  in  the  air  in 
considerable  numbers  300  to  400  ft.  from  diseased  chestnuts,  sub- 
stantiating the  observations  of  others.  Many  similar  observations 
have  been  recorded  for  Venturia  hiaequalis.  Burrill  and  Barrett 
(1909)  showed  that  Diplodia  zeae  is  distributed  bv  winds;  Wolf 
(1916)  made  the  same  observation  for  Cercospora  personata. 
Peronospora  tabacina  is  verv  quickly  dispersed  from  infected  to- 
bacco seed  beds  to  healthy  ones  several  miles  distant  [Wolf  et  al. 
(1934)],  and  it  is  reasonable  to  assume  that  its  introduction  into 
New  England  and  Canada  was  the  result  of  the  carriage  of  spo- 
rangia several  hundred  miles  through  the  air. 

The  aerial  dissemination  of  plant  pathogens  is  briefly  treated 
in  a  recent  report  by  Craigie  (1939).  His  studies  show  that  the 
funp-i  causing  stem  rust  of  cereals,  leaf  rust  of  wheat,  and  crown 
rust  of  oats  are  air-borne  in  western  Canada,  being  carried  several 


DISTRIBUTION  OF  SPORES 


111 


Open 


>f  Cover- 


hundred  miles  from  their  place  of  origin.    In  conclusion  it  may 
be  said  that  ample  evidence  has  shown  that  fungus  spores  "fly 
through  the   air  with  the  great- 
est of  ease"  [Keitt  (1942),  Chris-  closed 
tiansen  (1942),  Durham  (1942)]. 

Spore-trapping  devices.  Vari- 
ous devices  for  determining  the 
presence  and  movement  of  wind- 
borne  spores  have  been  em- 
ployed. These  techniques  were 
described  and  illustrated  in  a  re- 
port by  the  Committee  on  Appa- 
ratus in  Aerobiology  ( 1 941 ) .  The 
simplest  method  consists  of  expos- 
ing a  surface  coated  with  vaseline, 
glvcerin,  gelatin,  or  agar. 

Rittenberg  (1939)  exposed  agar 
plates  on  shipboard  during  cruises 
in  the  Pacific  in  the  area  from 
Monterey  to  the   Cedros  Islands 


and  extending  seaward  400  miles. 
He  entrapped  such  soil-borne  or- 
ganisms as  Alternaria,  Catenularia, 
Cephalosporium,  Cladosporium, 
Penicillium,  Spicaria,  Sporotri- 
chum,  Stemphylium,  and  Tri- 
choderma.    . 

Some  workers  have  employed 
aspirators,  by  means  of  which  a 
definite  volume  of  spore-laden  air 
is  drawn  through  a  filter  of  steri- 
lized cotton  or  sugar  crystals. 
Others  expose  dishes  containing 
water  or  cotton  batting.    All  de- 


Coated 
glass 
slide- 


Air 
current 


i>\ 


I 


Hook  or 
handle 


Fig.    27.      Schematic    representa- 
tion of  "sky-hook"  type  of  spore 
trap.     (Adapted  from  Meier  and 
Lindberg.) 


vices    are   serviceable.     In   order 

to  keep  the  sticky  surface  directed  toward  the  wind,  the  exposure 
plates  may  be  fastened  to  a  weather  vane  or  may  be  inclined  from 
the  vertical  for  protection  from  rains.  The  most  ingenious  ap- 
paratus used  is  the  "sky  hook,"  as  employed  by  A4eier  and  Lind- 


112  SPORE  DISSEMINATION 

bersr  (1935)  in  their  aerobiologncal  studies  in  the  Arctic.  Proctor 
(1934)  at  the  Massachusetts  Institute  of  Technology  used  an 
ingenious  automatic  device. 

Rate  of  fall  of  spores.  Rate  of  fall  of  spores  in  still  air  has 
been  given  consideration  by  a  number  of  investigators,  including 
Buller  (1909),  Ukkleberg  (1933),  Stephanov  ( 1935),  and  Gregory 
(1945).  In  general  the  terminal  velocity  has  been  found  to  be  of 
the  order  expected  from  Stokes'  law.     According  to  this  law, 


where  V  =  terminal  velocity,  p  =  density  of  the  spore,  a  =  den- 
sity of  the  medium,  g  =  acceleration  due  to  gravity,  r  =  radius  of 
the  spore,  and  /x  =  viscosity  of  the  medium.  Deviations  from  the 
expected  rate  may  be  ascribed  to  the  following  factors:  ( 1 )  shape 
of  spore;  that  is,  they  are  seldom  ideal  spheres;  (2)  irregularities 
in  outer  surface  of  spore  wall;  (3)  rapid  desiccation  during 
falling;  and  (4)  inaccuracy  in  determining  the  density  of  the 
spores. 

Buller  (1909)  found  that  the  rate  of  fall  of  basidiospores  of 
Colly bia  dryophila  is  0.49  mm  per  second  and  of  Coprinus  plica- 
tilis  4.29  mm  per  second.  Ukkleberg  (1933)  determined  that  the 
rate  of  fall  of  urediniospores  of  Pnccinia  graminis  tritici  is  11.57 
mm,  of  P.  graminis  secalis  10.58  mm,  of  P.  coronata  avenue  10.00 
mm,  and  of  P.  triticina  12.62  mm  per  second.  He  found  that  the 
rate  of  fall  of  aeciospores  of  P.  graminis  tritici  is  10.56  mm,  and 
of  P.  graminis  secalis  10.20  mm  per  second. 

Insects  as  vectors  of  fungi.  It  is  well  known  that  such  in- 
sects and  arachnids  as  ticks,  fleas,  flies,  mosquitoes,  lice,  bees,  wasps, 
beetles,  and  mites  are  capable  of  transmitting  microorganisms, 
especially  species  responsible  for  important  diseases  of  man  and 
various  animals.  Much  less  is  known,  however,  regarding  the  role 
that  animals  play  in  the  transmission  of  species  pathogenic  to 
plants.  Although  the  presence  of  certain  virus  diseases  of  plants 
appears  to  require  the  presence  of  specific  insects  as  vectors,  for 
instance,  aster  yellows,  carried  by  Cicadula  sexnotata,  curly  top 
of  beets,  carried  by  Eutetix  tenella,  and  kroepoek  of  tobacco,  car- 
ried by  Bemesia  gossipiperda,  no  portion  of  the  life  cycle  of  the 
pathogen,  whether  virus,  bacterium,  or  fungus,  appears  to  develop 
within  the  body  of  the  vector.     Instead  the  infective  agent  is 


DISTRIBUTION  OF  SPORES  113 

merely  taken  into  the  body  of  the  insect  and  passes  unharmed 
through  the  alimentary  tract,  or  is  regurgitated  or  accidentally  ad- 
heres at  the  surface,  or  is  mechanically  transferred  to  the  host 
plant.  The  relation  of  insects  to  disease  in  plants  is  therefore  less 
spectacular  than  in  animals  but  is  none  the  less  quite  as  important. 

Rand  and  Pierce  (1920)  are  among  the  first  to  bring  together 
from  widely  scattered  sources  the  information  extant  on  insects  as 
agents  in  the  transmission  of  fungi.  The  later  accounts  of  Rand, 
Ball,  Caesar,  and  Gardner  (1922)  and  the  comprehensive  works 
of  Leach  (1935,  1940)  describe  the  present  status  of  this  topic.  In 
the  appendix  to  the  volume  by  Leach  (1940)  is  a  long  list  of  in- 
sect-transmitted fungi. 

Abundant  evidence  is  at  hand  to  show  that  the  brown-rot  fungus 
of  stone  fruits,  Sclerotinia  fructicola,  is  transported  by  bees,  wasps, 
May  beetles,  and  squash  bugs  at  the  season  when  the  fruit  is  ripen- 
ing. Heald  [Arthur  (1929)]  demonstrated  that  mites  are  carriers 
of  Sporotrichum  anthophihim,  the  cause  of  bud  rot  of  carnations. 
Punctures  made  by  the  cabbage  maggot,  Pegomya  brassicae,  af- 
ford portals  of  entry  for  Phoma  oleracea,  the  cause  of  cabbage 
blackleg.  The  woolly  aphis,  Schizoneura  lanigera,  is  associated 
with  the  spread  of  the  apple-canker  fungus,  Nectria  ditissima. 
Similarly  Ehrlich  (1934)  showed  that  N.  coccinea  infects  beech, 
but  only  if  the  bark  is  infested  with  Cryptococcus  fagi.  Initial 
infection  is  possible  provided  that  the  living  tissues  of  the  bark 
have  been  injured  by  the  insect  while  feeding.  The  fungus  then 
grows  parasitically  and  kills  the  beeches  within  2  or  3  years. 

Certain  species  of  Orthoptera,  Lepidoptera,  Coleoptera,  and 
Hemiptera  were  found  by  Wolf  (1916)  to  distribute  Cercospora 
personata  on  peanuts.  Among  these  orders  grasshoppers,  because 
of  their  powers  of  flight,  were  regarded  as  especially  important 
vectors  of  this  peanut-leaf-spot  fungus.  A  single  longicorn 
beetle,  Leptostyhis  maculata,  was  found  to  transport  320,000 
spores  of  Endothia  parasitica  and,  according  to  Studhalter  and 
Ruggles  (1915),  19  other  insect  species  also  act  as  carriers  of  this 
fungus. 

The  larval  forms  of  many  species  find  rust  spores  to  be  suitable 
food,  and  they  effectively  aid  in  distributing  them.  Arthur  (1929) 
records  that  the  larvae  of  Smyrithurus  sp.,  a  neuropterous  insect, 
carries  Puccinia  rubigo-vera  iritici,  and  the  larvae  of  Diplosis  sp., 


114  SPORE  DISSEMINATION 

a  cecidomyid,  transports  Uroviyces  bid enti cola.  Honeybees  dis- 
tribute the  urediniospores  of  rust  on  Populus  and  the  aeciospores 
of  Caeovia  nit  ens.  The  scarabeid  beetle,  Serica  sericea,  is  among 
many  species  that  transport  Cronarticum  ribicola. .  Basidiobohis 
ranarum  is  carried  to  froo-s  and  salamanders  within  the  bodies  of 
various  beetles.  Gypsy-moth  larvae,  Porthetria  dispar,  have  been 
found  by  actual  count  to  bear  from  1120  to  23,320  aecio- 
spores of  Cronartium  ribicola.  Arthur  (1929)  records  that  Rat- 
hay  noted  135  species  of  Coleoptera,  Hymenoptera,  Hemiptera, 
and  Diptera  as  carriers  of  rust  spores,  Diptera  being  especially  at- 
tracted to  the  saccharine  exudate  of  pycnia.  Doubtless  they  are 
important  agents  in  the  spermatization  of  rusts. 

The  Dutch  elm  pathogen,  Ceratostomella  ulmi,  is  transported 
by  bark  beetles,  Scolytus  scolytus  and  5.  multistriatus.  Several 
species  of  Ips  and  Dendroctonus  are  known  to  be  capable  of  dis- 
seminating spores  of  fungi  (various  species  of  Ceratostomella) 
associated  with  blue  stain  of  loos  and  lumber. 

The  spore  dispersion  of  Phallales  appears  to  be  dependent  upon 
sarcophagid  and  muscid  flies.  The  sporiferous  tissue  of  Phallales 
becomes  slimy  at  maturity  and  is  nauseatingly  putrid.  This  pene- 
trating odor  is  attractive  to  flies,  and  in  consequence  they  carry 
the  spores  externally  and  also  void  them  intact  in  their  excreta. 
Ithyphallus  coralloides,  suspected  of  causing  root  rot  of  sugar 
cane,  is  so  attractive  to  flies  that  they  can  be  driven  away  from  the 
fructifications  only  with  difficulty.  Various  ants  and  beetles  are 
also  attracted  to  this  species  and  no  doubt  carry  the  spores  under- 
ground to  situations  favorable  for  germination  and  development. 
Various  flies  are  also  attracted  to  the  saccharine  exudate  contain- 
ing conidia  of  the  sphacelial  (conidial)  stage  of  Claviceps,  espe- 
cially C.  purpurea  and  C.  paspali. 

Brodie  (1931)  has  shown  that  flies  transport  the  conidia  of 
Coprimts  lagop7is,  as  a  result  of  which  the  mvcelia  become  diploi- 
dized.  Similarly  the  transfer  of  pycniospores  of  Puccima  graminis 
and  P.  helianthi  by  flies  and  other  insects  attracted  to  the  sugary 
exudate  has  been  demonstrated  [Craigie  (1931)]. 

The  tree  cricket,  Oecanthns  niveus,  actively  transports  the 
spores  of  Leptosphaeria  comothyrhivu  the  cause  of  canker  on 
apple  trees. 

The  flea  beetle,  Epitrix  cucimieris,  the  Colorado  potato  beetle, 
Leptinotarsa  decemlineata,  and  the  horn  worm,  Protoparce  caro- 


DISTRIBUTION  OF  SPORES  115 

Una,  have  been  found  to  have  conidia  of  Alternaria  solani  and  of 
Septoria  ly  coper  sici  on  their  bodies. 

Hendree  (1933)  isolated  from  the  fecal  pellets  of  termites  and 
from  the  frass  and  wood  enclosing  their  burrows  33  genera  of 
fungi,  among  them  Trichoderma  and  Penicillium.  In  her  opinion 
these  fungi  are  a  common  dietary  element  of  the  termites  Reticuli- 
termes  hesperus,  Zootermopsis  angiisticollis,  and  Kalotermes 
minor. 

Such  insect  visitors  as  honeybees,  bumblebees,  carpenter  bees, 
thrips,  and  ants  were  found  [Smith  and  Weiss  (1942)]  to  be 
capable  of  transporting  spores  of  Ovulinia  azaleae,  causing  flower 
spot  on  cultivated  azaleas. 

It  has  been  noted  that  the  females  of  certain  woodwasps,  Sir  ex 
gigas  and  S.  cy  aliens,  always  have  elements  of  the  wood-rotting 
fundus,  Sterenm  sanguine  olentum,  in  the  pouches  at  the  anterior 
end  of  the  ovipositor.  Whether  this  association  is  symbiotic  is  not 
known. 

The  only  conclusion  warranted  from  the  foregoing  discussion, 
which  is  representative  of  a  large  volume  of  reports  of  insects  as 
disseminating  agents,  is  that  many  species  of  insects  are  concerned. 
Furthermore,  many  fungi,  both  pathogenic  and  saprogenic,  are 
insect-borne.  It  remains  to  be  determined  whether  virulence  in 
fungi  is  modified  by  passage  through  the  alimentary  tract.  It  is 
known  that  some  species  have  already  germinated  when  the  fecal 
pellets  are  voided,  although  essentially  nothing  is  known  about  the 
effects  of  digestive  enzymes  on  germination. 

More  attention  should  be  given  also  to  the  necessity  of  host  in- 
juries by  the  insect  for  inoculation  and  infection.  In  this  connec- 
tion there  is  evidence  that  sugar  cane  injured  by  the  sugar-cane 
borer,  Spenophorns  obscnrus,  is  more  subject  to  attack  by  Col- 
letotrichiim  jalcatnm.  Moreover,  onions  infested  with  thrips  are 
predisposed  to  infection  by  Feronospora  destrnctior,  and  grasses 
punctured  by  aphids  are  more  susceptible  to  Erysiphe  graminis. 

Leach  (1935)  has  expressed  the  opinion  that  insects  are  not 
merely  disseminators  of  inoculum  in  the  case  of  pathogenic  fungi, 
but  that  the  insect-fungi  relationship  is  highly  organized  and  has 
broad  biologic  and  evolutionary  significance. 

Other  animals  as  vectors  of  fungi.  Besides  insects,  many 
other  animals  transport  fungi,  but  usually  dissemination  by  them 
is  entirely  fortuitous.    Among  the  animals  known  to  be  or  sus- 


116  SPORE  DISSEMINATION 

pected  of  being  carriers  are  slugs,  snails,  sow  bugs,  various  rodents, 
birds,  and  domestic  animals.  Slugs  and  snails  feed  upon  a  large 
variety  of  fungi,  especially  powdery  mildews,  discomycetes,  rusts, 
mushrooms,  polypores,  and  leathery  fungi  [Buller  (1922),  Wolf 
and  Wolf  (1940)].  The  spores  either  are  voided  or  are  dragged 
along  and  scattered  by  the  migrations  of  these  animals  in  search 
of  food.  Fleshy  Hymenomvcetes  appear  to  be  especially  attrac- 
tive. Poisonous  species  are  devoured  with  impunity.  The  pos- 
session of  a  highly  developed  olfactory  sense  guides  the  animals 
in  the  location  of  the  fruit  bodies  of  these  species.  Gravatt  and 
.Marshall  (1917)  made  the  observation  that  slugs  (Agriolimax 
agrestris),  snails  (Sabulina  octona),  and  sow  bugs  (Armadillidium 
-j nl gave)  eat  and  distribute  spores  of  Cronartium  ribicola.  Heald 
and  Studhalter  (1914)  found  that  birds,  especially  woodpeckers, 
are  of  importance  in  the  dissemination  of  Endothia  parasitica.  An 
estimate  of  the  numbers  of  spores  of  this  fungus  carried  by  two 
downy  woodpeckers  {Dryobates  piibescens  medianus)  was  757, 
074  and  624,341  and  by  a  brown  creeper  (Certhia  jamiliaris  ameri- 
cana),  254,019. 

A  number  of  fungi,  notably  species  of  Pilobolus,  Sordaria, 
Panaeolus,  Anellaria,  and  Coprinus,  normally  occur  on  dung  and 
are  regarded  as  coprophilous.  Their  spores  are  distributed  by 
such  herbivorous  animals  as  horses,  cattle,  sheep,  goats,  rabbits, 
and  geese.  These  animals  swallow  the  spores  and  herbage  to- 
gether, and  either  the  spores  pass  undamaged  through  the  ali- 
mentary tract  or  else  their  germination  is  favored  by  the  digestive 
enzymes  which  they  encounter  en  route.  After  having  been 
eaten,  the  spores  of  these  coprophilous  species  may  remain  for 
hours  within  the  alimentary  tract  before  being  voided  in  the  feces. 
Meanwhile  the  animal  may  transport  them  for  miles.  Soon  after 
discharge  from  the  animal's  body  the  spores  will  develop  into  new 
plants,  and  their  fruiting  bodies  will  mature.  Some  dung-fungi 
are  especially  adapted  to  such  habitats.  Buller  (1934)  has  shown, 
for  example,  that  the  sporangia  of  Pilobolus,  on  being  shot  away, 
adhere  to  herbage  3  to  8  ft.  distant  from  the  dung  heap.  The 
sporangia  cling  by  virtue  of  the  gelatinous  material  that  arose  by 
dissolution  when  the  sporangium  separated  from  the  swollen 
subsporangium.  Since  these  sporangia  cannot  be  wet,  they  are 
not  affected  by  rains  and  in  consequence  may  adhere  intact  to  the 


DISTRIBUTION  OF  SPORES  111 

vegetation  for  several  weeks.     Moreover  the  sporangial  wall  is 
black,  so  that  injurious  radiations  are  screened  out. 

There  is  no  evidence  that  certain  other  coprophilous  species, 
for  example,  Lachnea  stercorea  and  Humaria  gramdata,  have  any 
structural  adaptations  for  such  habitats.  Undoubtedly  many 
species  grow  in  dung  quite  by  accident.  At  any  rate,  mycologists 
have  come  to  recognize  that  herbivorous  animals  are  excellent 
collectors  of  fungi. 

The  human  agency.  lYian,  unwittingly  and  wittingly  in  the 
distribution  of  seed,  seedlings,  cuttings,  nursery  stock,  bulbs,  and 
roots,  has  spread  and  will  continue  to  spread  fungi  of  economic 
importance  throughout  the  world.  Many  of  these  fungi  have 
caused  him  enormous  financial  losses.  To  relieve  and  prevent  this 
situation,  both  state  and  federal  inspection  services  have  been 
instituted  and  quarantines  established. 

In  North  America  alien  or  exotic  species  appear  to  be  much 
more  destructive  than  indigenous  ones,  as  is  evident  from  the 
ravages  of  chestnut  blight  (Endothia  parasitica),  blister  rust  of 
white  pines  (Cronarthnn  ribicola),  Dutch  elm  disease  (Ceratosto- 
mella   idmi),    late    blight   of   potato    (Phytophthora   infestans), 
downy  mildew  of  tobacco  (Feronospora  tabacina),  and  willow- 
scab  (Fusicladhnn  saliciperdum) .    Furthermore,  there  is  evidence 
that  pathogens  introduced  from  one  continent  into  another  may 
find  conditions  in  the  new  land  more  favorable  for  development 
in  epidemic  proportions,  as  did  grape  mildew  (Plasviopara  viti- 
cola)  and  late  blight  of  potato  (Phytophthora  infestans),  intro- 
duced into  Europe  from  the  New  World,  and  coffee  rust  (Hemi- 
leia  vastatrix),  introduced  into  Ceylon,  presumably  from  Africa. 
A  list  of  rusts  [Arthur  (1929)]  in  Australia  in  1906,  comprising 
161  species,  is  said  to  contain  30  species  that  are  not  indigenous. 
Arthur  also  lists  41  species  of  rusts  that  have  been  introduced  into 
^orth  America,  including  such  important  ones  as  Cronarthnn 
ribicola,   Uromyces  appendicidatus  phase oli,   U.  appendicidatus 
vignae,  U.  betae,  U.  caryophyUimis,  U.  trifolii,  Puccini  a  arachidis, 
P.  asparagi,  P.  chrysanthemi,  P.  glumarum,  P.  graminis  phlei  pra- 
tensis,  P.  graminis  tritici,  and  P.  mahaceamm.    Undoubtedly  man 
distributes  many  fungi  that  cling  to  hands  and  clothing  and  are  in- 
oculated onto  healthy  plants  inadvertently  as  he  passes  to  them 
after  handling  diseased  plants. 


118  SPORE  DISSEMINATION 

Seed-borne  fungi.  In  1733  Jethro  Tull  recorded  seed  disin- 
fection by  the  use  of  brine.  Wheat  being  shipped  to  England 
became  wet  in  the  hold.  Some  of  it  was  planted,  and  the  resulting 
crop  was  observed  to  be  free  from  stinking  smut.  From  this  ob- 
servation came  the  use  of  salt-water  steeps  to  prevent  seed-borne 
diseases.  Moreover,  before  this  earlv  period  some  of  the  tribes 
in  Asia  Minor  passed  their  seed  grain  through  flames  and  thereby 
removed  the  highly  inflammable  smut  spores.  Thev  did  this, 
however,  as  a  religious  ritual,  because  fire  has  long  been  regarded 
as  a  means  of  purification. 

Subsequent  studies  have  shown  that  many  grass  smuts  are  seed- 
borne.  In  addition,  such  other  pathogenic  agencies  as  certain 
viruses,  bacteria,  many  fungi  from  nearly  every  important  tax- 
onomic  e^roup,  nematodes,  and  insects  are  known  to  be  carried 
with  the  seed.  Orton  (1931)  assembled  a  bibliography  of  seed- 
borne  diseases  which  should  serve  as  a  basis  for  studies  by  others. 
In  his  long  list  are  such  important  pathogens  as  Gibberella  sau- 
binettiij  C oil etotri chum  lindemuth'iamim,  Phovia  Ihigam,  Septoria 
apii,  Diplodia  zeae,  Glomerella  gossypii.  Collet otrichwn  lagena- 
riitm,  Phomopsls  vexans,  Sclerospora  grcnninicolay  Urocystis 
cepnhe,  Ascochyta  pisi,  Tilletia  tritici,  and  Ustilago  avenae. 

Soil-borne  fungi.  Vascular  and  root-rot  parasites,  including 
species  of  Fusarium,  Verticillium,  Cephalosporium,  Thielaviopsis, 
Sclerotium,  Phytophthora,  Pythium,  and  Rhizoctonia,  commonly 
persist  in  the  soil  and  are  distributed  by  numerous  agencies. 
These  include  movement  of  the  infested  soil  by  washing  rains  or 
its  transport  by  streams,  carriage  of  infested  soil  on  seedlings, 
rooted  cuttings,  bulbs,  corms,  or  roots,  and  transport  on  imple- 
ments, machinery,  tools,  hoofs  of  farm  animals,  and  shoes  of  man. 

Observations  in  the  East  Indies  and  in  the  United  States  leave 
little  doubt  that  fields  which  are  flooded  or  overflowed  after  rains 
may  become  infested  with  Phytophthora  nicotianae,  causing  to- 
bacco black-shank.  The  rowward  spread  of  Fusarium  wilts  is  a 
matter  of  common  observation.  Carriage  of  fungi  with  soil  or 
on  seedlings  may  not  be  an  unmixed  evil.  Evidence  assembled 
by  Hatch  (1936)  shows  that  in  afforestation  the  planting  of  seed 
may  fail,  whereas  the  transplanting  of  seedlings  may  succeed. 
The  reason  for  this  anomaly  is  the  dependence  of  tree  species 
upon  certain  fungi  which  become  associated  in  the  mycorrhizal 
relationship. 


HYGROSCOPIC  MECHANISM  IN  MYXOMYCETES  119 

Water  as  a  vector  of  fungi.  Water  may  sometimes  serve  as 
an  important  agency  for  dissemination  of  fungi,  although  there 
is  a  dearth  of  direct  data  on  this  point.  Rain  splash  is  known  to 
be  responsible  for  the  spread  of  conidia  of  apple  bitter-rot 
(Glomerella  rufo-maculans),  cotton  anthracnose  (G.  gossypii), 
bean  anthracnose  (Colletotrichiim  lindemiithiamim) ,  and  brown- 
spot  needle  disease  of  pines  (Systremma  acicola).  The  conidia 
of  these  fungi  and  of  many  others  are  produced  in  a  matrix  that 
is  corneous  when  dry  but  that  dissolves  when  moist.  Such  fungi 
are  adapted  for  distribution  at  times  favorable  for  spore  germina- 
tion and  infection.  Others  are  mechanically  transported  by  dews 
or  rains  and  thus  find  lodgment  on  new  substrata.  In  Colorado 
years  ago  Cercospora  beticola  was  found  to  be  present  in  water 
in  irrigation  ditches  and  to  be  spread  to  non-infected  beets  by 
irrigation.  Arthur  (1929)  mentions  an  outbreak  of  Puccinia 
sorghi  on  Oxalis  in  a  corn-field  that  was  overflowed. 

STRUCTURAL  ADAPTATIONS  FOR  EXPULSION  OF  SPORES 

At  maturity  or  soon  thereafter  the  spores  of  many  species  of 
fungi  are  forcibly  discharged.  Expulsion  of  spores  from  the 
structures  within  which  they  are  delimited  or  upon  which  they 
are  borne  must  be  regarded  as  a  device  to  further  the  geographical 
distribution  of  the  particular  species. 

HYGROSCOPIC  MECHANISM  IN  MYXOMYCETES 

Within  the  sporangia  of  certain  slime  molds,  notably  Trichia 
and  Hemitrichia,  the  capillitial  threads  are  thickened  in  spiral 
bands.  When  the  sporangial  wall  is  ruptured  as  the  result  of  dry- 
ing, the  tangled  capillitia  may  be  noted  to  be  interspersed  among 
the  spores.  As  the  capillitia  dry,  they  writhe  and  twist  by  virtue 
of  the  unequal  thickenings  of  the  wall.  As  the  ends  of  the 
threads  spring  free,  they  fling  adhering  spores  into  the  air.  This 
behavior  is,  therefore,  quite  like  that  in  the  liverwort,  Marchantia, 
and  is  very  efficient  in  conjunction  with  air  currents  in  causing 
the  spores  to  be  widely  disseminated.  Dissemination  of  other 
species,  however,  appears  to  be  wholly  fortuitous. 

The  mechanisms  involved  in  spore  discharge  are  quite  different 
and  need  not  indicate  phylogenetic  relationships. 


180  SPORE  DISSEMINATION 

SPORE  EXPULSION  AMONG  PHYCOMYCETES 

Among  some  aquatic  fungi,  such  as  the  Chvtridiales  and  Sapro- 
legniales,  sporangiospores  are  merely  ejected  to  the  exterior  of  the 
sporangium,  where,  by  virtue  of  their  flagella,  they  become  rather 
widely  distributed.  Members  of  these  orders  generally  possess  an 
exit  tube  or  papilla.  As  the  result  of  increased  turgor  after  de- 
limitation of  sporangiospores,  the  sporangium  opens  at  the  exit 
tube  or  papilla,  and  the  sporangiospores  are  rapidly  ejected,  either 
en  masse  or  singly.  In  Achlya  and  Aphanomyces  they  are  quies- 
cent on  expulsion  and  collect  in  a  hollow  sphere  at  the  orifice. 
In  Saprolegnia  and  Leptolegnia  they  emerge  in  an  actively  motile 
condition.  In  the  related  Aplanes  they  are  retained  within  the 
sporangium.  In  Dictyuchus  the  sporangial  content  is  cleaved  into 
segments,  a  pore  is  developed  from  each  segment,  and  the  proto- 
plast escapes  from  each  segment  as  a  motile  spore,  leaving  behind 
a  reticulum  of  emprv  cells.  In  Saprolegnia  two  planetic  (motile) 
stages  normally  occur,  a  phenomenon  no  doubt  well  adapted  for 
increased  dissemination  of  the  species. 

Apparently  none  of  the  Peronosporales,  except  species  of 
Sclerospora,  forcibly  expels  its  sporangia.  As  observed  by  Wes- 
ton (1919),  S.  Philippine  mis  and  5.  gram'inis,  occurring  on  maize, 
possess  a  double  wall  separating  the  tip  of  the  sterigma  and  the 
sporangium.  At  first  these  two  walls  in  contact  with  each  other 
are  plane.  As  the  sporangium  grows  and  turgor  increases,  these 
membranes  tend  to  bulge  outward,  and  this  tendency  is  restrained 
by  adhesion  of  the  two  surfaces  in  contact.  Eventually  adhesion 
is  overcome  by  the  stress  from  increased  turgor,  and  with  a  sud- 
den  snap  both  membranes  bulge  outward,  catapulting  the  spo- 
rangium away.  It  can  then  be  caught  by  air  currents  and  trans- 
ported  to  near-by  maize  plants. 

In  Peronospora  t abaci na  and  certain  other  species  of  Perono- 
spora  the  sporangia  are  effectively  liberated,  but  by  an  entirely 
different  mechanism.  The  sporangiophores  grow  closely 
crowded.  Each  sporangiophore  looks  like  a  little  tree,  and  to- 
gether the  sporangiophores  constitute  a  miniature  forest  with 
interlocking  branches.  The  entire  tree,  including  its  twig  tips, 
sterigmata,  is  a  single,  inflated  coenocytic  cell.  A  slight  change 
in  relative  humidity  in  the  immediate  environment  of  the  sporan- 


SPORE  EXPULSION  AMONG  PHYCOMYCETES 


181 


giophore  occasioned  by  air  currents  or  increased  temperature 
causes  the  crown  of  the  little  tree  to  twirl  and  twist.    In  conse- 


Fig.  28.  Discharges  of  spores  by  various  Phycomycetes.  A.  Olpidium 
brassicae.  B,  C,  D,  E.  Physoderma  maydis.  F,  G.  Lagenidium  rabenhorstii. 
H,  1,  J.  Saprolegnia  sp.     K,  L,  M.  Pythium  de  Baryamnn.     O,  P,  Q,  R. 

Albugo  Candida. 

quence  of  these  hygroscopic  movements  the  sporangia  are  dis- 
lodged [Pinckard  (1942)].  Long  ago  attention  was  called  to 
this  phenomenon  by  de  Bary  (1887),  who  stated  from  his  ob- 


182  SPORE  DISSEMINATION 

servations  on  Peronospora,  Fhytophthora  infestans,  and  Botrytis, 
"The  slightest  change  in  the  humidity  of  the  surrounding  air,  such 
for  instance  as  may  be  caused  by  the  breath  of  the  observer,  at 
once  produces  changes  in  their  turgescence  and  torsion;  the  lat- 
ter give  a  twirling  motion  to  the  extremity  of  the  gonidiophore 
and  the  ripe  spores  are  thereby  thrown  in  every  direction." 

Link,  in  1809,  was  among  the  earliest  observers  to  consider  the 
problem  of  discharge  of  sporangia  bv  Pilobolus.  Since  then  many 
others  have  recorded  their  studies  of  this  phenomenon,  and  grad- 
uallv  a  clear  conception  of  the  mechanism  involved  has  evolved. 
The  ingenious  experimentation  bv  Buller  is  especially  pertinent 
and  illuminating.  Members  of  this  genus  are  coprophilous  and 
can  best  be  studied  by  cultivation  on  fresh  dung  of  herbivorous 
animals,  collected  and  placed  in  the  laboratory  in  moist  chambers. 
After  a  few  davs  a  crop  of  sporangia  should  have  formed,  and 
new  crops  may  form  each  day  for  several  successive  days.  Each 
sporangiophore  consists  of  a  hat-shaped,  black  sporangium  that 
surmounts  a  bulbous  subsporangial  swelling,  the  upper  portion  of 
the  stipe.  This  subsporangial  swelling  functions  both  as  an 
ocellus  that  causes  the  stipe  to  direct  its  free  end  toward  the  source 
of  light  and  as  a  part  of  the  squirting  apparatus  that  propels  the 
sporangium. 

A  laver  containing  bright  red  pigment,  carotene,  is  formed  in 
the  basal  wall  of  the  subsporangial  swelling.  This  layer  extends 
partly  across  the  stipe  and  forms  a  centrally  perforate,  biconcave 
septum.  Immediately  beneath  this  perforate  septum  is  the  motor 
region,  which  responds  in  such  fashion  as  to  direct  the  sporangium 
head  on  toward  the  light,  when  heliotropic  equilibrium  is  estab- 
lished. In  this  position  the  incident  light  is  centered  on  the  per- 
foration of  the  septum.  Bending  is  a  photochemical  response,  as 
is  also  the  increased  pressure  of  turgor  in  the  subsporangium  that 
follows  when  the  sporangium  faces  the  light.  At  the  time  of 
expulsion  this  pressure  in  Pilobolus  longipes  may  be  equivalent 
to  approximately  5.5  atm. 

While  these  phototropic  reactions  are  taking  place,  the  spo- 
rangium wall  splits  into  two  layers,  the  inner  of  which  remains 
intact  to  enclose  the  spores.  The  expansion  of  the  columella, 
which  presses  upward  against  the  sporangium,  together  with  the 
liquefaction  of  the  outer  wall  circumferentially  around  the  base 
of  the  sporangium,  results  in  Assuring  of  the  outer  wall.     The 


SPORE  EXPULSION  AMONG  PHYCOMYCETES 


183 


upper  portion  persists  as  a  convex  cap  over  the  sporangium;  the 
lower  portion  remains  attached  to  the  base  of  the  sporangium 
with  the  jelly-like  mass  formed  around  the  fissure.  The  sporan- 
gium is  now  ready  for  discharge,  and  this  phenomenon  occurs  as 
soon  as  the  swelling  of  the  subsporangium  reaches  the  limits  of 
extensibility.  Since  the  papil- 
lar  area  constitutes  the  weak- 
est portion  of  the  wall,  the 
subsporangium  opens  at  this 
point,  squirts  away  about 
one-half  the  fluid  content  of 
the  subsporangium  and  stipe, 
and  carries  along  the  sporan- 
gium with  the  jet  of  sap.  The 
gelatinous  mass  present  around 
the  base  of  the  sporangium 
before  discharge  is  carried 
along  with  the  sporangium 
and  sticks  it  to  vegetation. 
When  the  plants  are  eaten, 
the  spores  pass  through  the 
alimentary  tract  and  are 
evacuated,  undigested  and 
unharmed. 

The  initial  velocity  of  the 
sporangia  of  P.  longipes  and 
P.  kleini  approximates  20  ft. 
per  second.    Buller's  observa- 


Fig.  29.  Stages  in  discharge  of  spo- 
rangia bv  Pilobolus.  A.  Mature  spo^ 
rangium  atop  the  subsporangial  swell- 
ing. B.  Circumscissile  rupture  of  outer 
membrane  of  sporangium  and  lique- 
faction around  base  of  sporangium. 
C.  Collapsed  subsporangium  after 
discharge.      (After  Buller.) 

tions  showed  that  the  ex- 
plosive force  is  sufficient  to  carry  sporangia  to  a  vertical  height 
of  72.5  in.  and  a  horizontal  distance  of  91.5  in.  in  P.  longipes 
and  90.5  in.  in  P.  kleini.  When  he  prepared  a  special  drum  with 
tissue  paper  as  the  membrane  forming  its  head,  the  impingement 
of  sporangia  was  audible  at  a  distance  of  21  ft.  Moreover  the 
sporangia  are  discharged  with  sufficient  force  to  be  felt  when 
they  strike  the  face. 

Nearly  everyone  has  observed  that  flies  may  become  attached 
to  windows  in  attics  and  other  little-used  rooms.  Upon  closer 
observation  a  whitish  halo  may  be  noted  to  surround  such  flies. 
This  halo,  2  or  3   cm  in  diameter,  is  produced  by  discharged 


184 


SPORE  DISSEMINATION 


conidia  of  the  entomogenous  fungus,  Entomophthora  imiscae. 
When  the  fly,  sluggish  because  of  the  infection,  succumbs,  rhi- 
zoidal  hvphae  grow  out  from  crevices  between  the  sclerites  and 
anchor  the  fly  to  the  pane.  Expulsion  of  conidia  by  this  fungus 
and  most  other  species  of  Entomophthora  is  accomplished  by  the 
same  mechanism.  In  a  report  Sawyer  (1931)  described  this  type 
of  spore  discharge  in  Entomophthora  sphaerospenna,  parasitic  on 


Fig.  30.  Stages  in  spore  discharge  by  Entomophthora  sphaerosperma.  A. 
Conidiophore  with  papillar  apex.  B.  Bud-like  enlargement  at  the  apex  of 
conidiophore.  C.  The  conidium  has  been  delimited  bv  a  septum,  and 
there  occur  two  closely  opposed  membranes.  D.  The  conidiophore  tip  im- 
pinges into  the  conidium  that  has  just  been  freed.  E.  The  tip  of  the 
conidium   becomes   everted    after   release   of   pressure   from    conidiophore. 

(After  Sawyer.) 

the  larvae  of  Rhopobota  vacciniana,  attacking  cranberries,  Vac- 
cinium  vmcrocarpon.  He  noted  that  a  bud,  the  initial  of  the 
conidium,  forms  at  the  blunt  apical  portion  of  the  conidiophore. 
Into  this  developing  conidium  a  nucleus  passes,  the  conidia!  wall 
thickens,  and  a  short  neck  becomes  differentiated  between  coni- 
dium and  conidiophore.  A  septum  then  forms  across  the  base 
of  the  spore.  This  septum  consists  of  two  membranes  in  close 
apposition,  one  being  the  basal  wall  of  the  conidium,  the  other 
the  apical  wall  of  the  conidiophore.  As  growth  continues,  the 
greater  hydrostatic  pressure  within  the  conidiophore  forces  the 
opposed  walls  to  bulge  convexly  into  the  conidium.  Eventually 
the  pressure  becomes  so  great  that  the  attachment  between  the 
conidium   and   the   conidiophore   is   ruptured   circumferentially. 


SPORE  EXPULSION  AMONG  PHYCOMYCETES 


185 


The  recoil  of  the  basal  wall  of  the  conidium  against  the  impinging 
apical  wall  of  the  conidiophore  acts  as  a  spring,  and  in  conse- 
quence the  conidium  is  violently  pushed  into  space.  Its  passage 
through  the  field,  when  material  in  the  humid  atmosphere  of  a 
Van  Tieghem  cell  is  viewed  with  a  microscope,  appears  like  a 


Fig.  31.  Schematic  diagrams  showing  stages  in  sporangial  (conidial)  dis- 
charge in  Basidiobolus  ranarum.  (After  Ingold.)  A.  Zone  of  weakness 
apparent  near  base  of  subsporangial  swelling.  B.  Sporangium  liberated  from 
upper  part  of  subsporangium.  C.  Sporangium  freed,  but  with  empty, 
thimble-like  subsporangium  attached.  D.  Germination  of  conidium  with 
secondary   discharge   in   progress,   a   repetitional   phenomenon. 

streak  of  light.  The  roughened  ring,  marking  where  the  conidium 
was  torn  from  its  attachment  of  the  conidiophore,  can  also  be 
observed  readily,  the  end  of  the  conidium  being  normally  everted 
on  lodging. 

The  accounts  by  Levisohn  (1927)  and  Ingold  (1934)  of  the 
mechanism  in  Basidiobolus  ranarum  indicate  that  it  is  quite  dif- 
ferent from  that  in  Entomophthora,  being  more  nearly  like  that 
in  Pilobolus.  Basidiobolus  ranarum  occurs  in  frog  excreta  and 
can  readily  be  made  to  develop  and  discharge  its  conidia  on  ab- 


186  SPORE  DISSEMINATION 

sorbent  paper  in  a  moist  chamber.  This  fungus  possesses  a  sub- 
conidial  bulb,  and  a  line  of  dehiscence  consisting  of  two  mem- 
branes  in  apposition  develops  toward  the  base  of  this  bulb.  The 
upper  membrane  is  the  more  elastic.  When,  with  increased 
turgor  inside,  the  rupture  of  the  conidiophore  takes  place  along 
the  line  of  separation,  the  upper  part  of  the  bulb,  which  is  least 
extensible,  contracts,  and  the  basal  septum  bursts.  The  effect  is 
that  the  sap  is  squirted  backward,  carrying  away  all  parts  above 
the  line  of  dehiscence  on  the  recoil.  During  the  rocket-like  flight 
the  conidium  may  become  separated  from  the  adhering  upper 
part  of  the  subconidial  bulb  or  may  fail  to  separate.  The  conidio- 
phore tip  pushes  into  the  conidium  at  the  juncture  to  effect  separa- 
tion, just  as  it  does  in  Entomophthora. 

Evidently  all  Entomophthorales,  except  perhaps  Massospora,  are 
capable  of  forcibly  liberating  their  spores. 


SPORE  DISCHARGE  AMONG  ASCO.MYCETES 

Spore  discharge  among  erysiphaceae.  As  mi^ht  be  antici- 
pated,  cleistocarpous  fungi,  such  as  the  powdery  mildews,  require 
a  mechanism  to  liberate  their  spores  that  is  quite  unlike  that  of 
Pyrenomycetes  and  Discomycetes.  Ingold  (1939)  has  assembled 
the  observations  made  on  spore  liberation  among  the  Erysiphaceae. 
According  to  him,  there  are  two  types  of  spore  liberation  in  this 
family.  In  Sphaerotheca  mors-ircae,  which  illustrates  one  type, 
the  cleistothecium  remains  dormant  throughout  winter,  but  in 
spring  the  single  ascus  swells  to  the  extent  of  causing  the  cleisto- 
carp  wall  to  rupture,  permitting  the  ascus  to  protrude  through 
the  fissure.  The  protruded  ascus  continues  to  swell,  finally  burst- 
ing in  a  thin  region  at  the  tip  and  squirting  out  the  ascospores. 

In  1884  the  other  type  of  discharge  was  graphically  described 
for  Erysiphe  by  W.  G.  Smith  [Ingold  (1939)  ]  as  follows:  "When 
they  [the  cleistocarps]  burst,  the  contained  bladders  or  asci  often 
burst  at  the  same  time,  and  the  living  sporidia,  after  their  six 
months'  rest,  fly  into  the  air.  At  other  times  the  bladders  or  asci 
themselves  fly  out  of  the  perithecia,  and  sail,  each  with  its  little 
load  of  eight  sporidia,  through  the  air.  When  in  the  air,  the  asci 
burst,  and  the  spores  are  set  free  into  the  atmosphere."  This  type 
might  well  be  called  the  rocket  type  of  discharge.    The  operation 


SPORE  DISCHARGE  AMONG  ASCOMYCETES  181 

of  this  mechanism,  as  it  applies  to  Podosphaera  leucotricha,  has 
been  confirmed  by  Woodward  [Ingold  (1939)]. 

Discharge  among  other  Ascomycetes.  It  is  a  matter  of  com- 
mon knowledge  anions  those  who  have  studied  Ascomycetes  that 
many  species  of  this  class  forcibly  expel  their  ascospores  [Ziegen- 
speck  (1926)].  Even  though  this  phenomenon  has  been  ob- 
served in  connection  with  a  relatively  small  proportion  of  the  vast 
assemblage  of  widely  different  species  that  constitute  the  Asco- 
mycetes, undoubtedly  most  of  them  will  be  found  capable  of 
such  forcible  discharge.  Many  of  those  who  attempt  to  isolate 
Ascomycetes  in  pure  culture  utilize  the  phenomenon  of  expulsion. 
They  have  found  that  the  simplest  procedure  to  employ  in  isolat- 
ing is  to  place  inverted  agar-poured  plates  above  mature  perithecia 
at  a  suitable  height.  If  favorable  moisture  conditions  are  then 
provided,  an  abundance  of  ascospores  will  be  found  to  have  been 
ejected  onto  the  surface  of  the  agar  after  a  few  hours. 

The  height  to  which  the  ascospores  are  propelled  varies  with 
the  species,  being  governed  by  the  size  of  the  spores  or  of  the 
spore  mass  as  one  of  the  correlated  factors.  Hypomyces  lacti- 
fliiorum  has  been  found  to  shoot  its  spores  to  a  height  of  10  mm, 
Endothia  parasitica,  22  mm,  Sordaria  fimicola,  60  mm,  Podospora 
fimiseda,  300  mm,  and  P.  curvicola,  450  mm.  In  P.  curvicola 
Weimer  (1917)  found  that  the  spore  mass  of  approximately  500 
spores,  held  together  in  a  gelatinous  matrix,  had  a  diameter  of 
168  to  266  /x  and  that  they  were  hurled  up  into  the  necks  of 
2-liter  culture  flasks. 

Rate  of  ascospore  discharge.  The  rate  of  ascospore  discharge 
from  perithecia  is  controlled  by  the  external  factors  of  moisture, 
temperature,  and  light.  These  factors  are  interdependent,  and  in 
no  species  does  discharge  occur  unless  the  water  content  of  peri- 
thecial  tissues  approximates  the  maximum.  As  may  be  expected, 
the  output  of  spores  is  low  at  low  temperature  and  increases  to  a 
maximum  with  a  rise  in  temperature.  With  further  increase  there 
is  a  very  rapid  decline  in  the  rate  of  discharge.  As  far  as  light  is 
concerned,  some  species  are  stimulated  by  it,  such  as  Nectria  cin- 
nabar'ma  and  Podospora  curvula,  whereas  others  are  inhibited,  for 
example,  Hy  poxy  Ion  fuscum  [Ingold  (1939)]. 

For  a  few  species  the  rate  of  discharge  has  been  recorded.  In- 
gold (1939)  has  assembled  certain  data  on  this  point;  they  are 
shown  in  Table  15. 


188 


SPORE  DISSEMINATION 


Fig.    32.     Types   of  spore   discharge   among   Ascomvcctes.     A.   Podospora 

curvzda  (adapted  from  Ingold).    B.  Sphaerotheca  mors-uvae  (adapted  from 

Salmon).    C  and  D.  CeratostoviclLi  ampullacea  (adapted  from  Ingold).    E. 

Lecanidion  atratum  (adapted  from  Butler). 


SPORE  DISCHARGE  AMONG  ASCOMYCETES  189 


TABLE 

15 

if  Ascospore  Discharge 

BY 

Several  Ascomycetes 
Spore  Output  per 

Species 

■ 

Perithecium  per  Hour 

Podospora  minnta 

24 

Podospora  curvula 

40 

Sporormia  intermedia 

184 

Hypoxylon  coccineum 

1 ,  800 

Diatrype  disciformis 

23,000 

Endothia  parasitica 

14,000 

Spore  discharge  among  Discomycetes.  Evidently  the  earliest 
observations  of  ascospore  discharge  were  made  upon  the  larger 
Discomycetes.  Micheli  (1729)  described  spore  ejection  of  Peziza 
as  being  "like  smoke."  Bulliard  (1791)  recorded  that  "their  seeds 
ascend  like  steam,"  if  the  observer  shakes  the  fructifications  or 
blows  his  breath  upon  them.  De  Albertini  and  de  Schweinitz 
(1805)  saw  "clouds  of  smoke"  in  Rhytisma  salicinum.  A  very 
graphic  account  of  spore  discharge  by  Morchella  gigcis  is  given 
bv  Plowright  (1880-81),  who  observed  the  spore  cloud  as  seen 
against  a  dark  background  with  the  aid  of  a  beam  of  light:  "When 
acted  upon  by  a  gentle  current  of  air  such  as  would  be  produced 
by  gently  waving  the  hand,  it  swayed  to  and  fro  without  mani- 
festing any  tendency  to  become  dispersed.  The  component  spo- 
ridia  were  in  constant  motion,  rising  and.  falling  and  circling 
about,  as  if  the  law  of  gravity  were  a  myth,  existing  only  in  the 
imagination  of  philosophers.  When  the  cloud  was  quite  blown 
away  by  a  more  powerful  air  current,  it,  in  the  course  of  a  few 
seconds,  reformed."  In  his  chapter  on  the  liberation  or  purring 
of  spores  by  Discomycetes  Buller  (1934)  assembled  many  inter- 
esting features  from  the  accounts  of  early  observers  and  added 
the  results  of  his  own  observation  and  experimentation  and  those 
of  his  contemporaries  [Falck  (1916),  (1923)]. 

Dickson  and  Fisher  (1923)  described  a  technique  for  photo- 
graphing discharge  by  Sclerotinia  libertiana  that  is  applicable  to 
other  large  Discomycetes.  Buller's  (1934)  observations  show 
that  Sarcoscypha  protracta  can  become  a  miniature  geyser,  hurl- 
ing a  column  of  spores  to  a  height  of  about  3  in.  before  the  spores 
lose  their  vertical  momentum  and  begin  to  be  dispersed  into  a 
cloud.     The  puffing  by  Urmda  geaster,  having  ascomata  which, 


190  SPORE  DISSEMINATION 

before  dehiscence,  are  brown  and  cigar-shaped,  has  earned  for 
this  fungus  the  common  name,  "devil's  cigar."  Discharge  by 
these  larger  disk  fungi  creates  a  blast  of  air  that  carries  along  the 
spores,  so  that  thev  appear  like  a  cloud. 

Among  the  Discomycetes  spore  discharge  is  not  only  visible 
but  also  audible.  An  easily  perceptible  hissing  sound  is  emitted 
by  many  species.  The  noise  is  best  heard  if  the  fruit  bodies  that 
have  been  maintained  in  a  moist  chamber  are  held  near  the  ear. 
As  indicated  by  Buller  (1934),  Desmazieres  noted  the  emission 
of  sound  by  Helvetia  epihipphnn  nearly  100  years  ago.  De  Bary 
noted  it  in  Peziza  acetabulum  and  Hehella  crispa,  Stone  in  H. 
elastica,  Johnstone  in  Otidea  leporina,  and  Buller  in  Aleuria 
re  panda,  A.  vesiculosa,  Asco  bolus  ster  cor  arms,  Caloscy  pha  ful- 
gens,  Ciliaria  scutellata,  Galactinia  badia,  Peziza  aurantia,  Pseudo- 
pie ctania  mgrella,  Pustidaria  cat  i  mis,  Pyronevia  con  flu  ens,  Rbizina 
in  flat  a,  Sarcoscypba  protract  a,  S.  cor  on  aria,  Urnula  crater'unn, 
and  U.  geaster.  The  sound  produced  resembles  most  nearly  the 
fizzing  of  a  freshly  drawn  carbonated  drink.  The  "effervescence" 
of  some  species,  especially  the  larger  ones,  is  protracted,  lasting 
for  several  minutes;  in  others  it  can  be  heard  for  a  few  seconds 
only. 

Among  the  Discomycetes  known  to  puff  [Buller  (1934)]  are 
Arachnopeziza  aurata,  Ascobolus  crouani,  Cblorospleniuv?  aeru- 
ginosinn,  Dasyscypha  virginea,  Helotium  scutula,  Lachnea  setosa, 
Mollisia  cinerea,  Orbilia  xantbostigvia,  and  Rhytisvia  acerinwn. 
The  writers  have  noted  its  occurrence  in  Diplocarpon  earliana, 
D.  rosae,  Peziza  repanda,  Sclerotinia  fructicola,  and  S.  trijolium. 

Spore  discharge  among  Pyrenomycetes.  De  Bary  (1887)  was 
among  the  first  to  assemble  the  extant  information  regarding  spore 
ejection  among  Pyrenomycetes.  He  pointed  out  that  there  are 
two  types  of  expulsion:  simultaneous  and  successive.  In  the  first 
type  all  the  spores  and  much  of  the  fluid  content  of  the  ascus 
are  ejected  as  a  unit;  in  the  second,  each  ascospore  is  discharged 
separately.  De  Bary  augmented  his  account  with  his  own  obser- 
vations. Subsequently  many  other  investigators  have  noted  forci- 
ble spore  liberation  and  have  reported  their  findings  with  particu- 
lar species.  Much  of  our  knowledge  of  this  phenomenon  comes 
from  the  recent  studies  by  Buller  (1933)  and  Ingold  (1933,  1939). 
Among  Pyrenomycetes  the  spores  of  most  genera,  but  not  all, 
are  forcibly  liberated.     These  fungi  may,  for  convenience,  be 


SPORE  DISCHARGE  AMONG  ASCOMYCETES  191 

arranged  into  spore-liberation  types  [Ingold  (1933)].  In  the  first 
type  are  species  of  Chaetomium,  Ascotricha,  Daldinia,  and  Dia- 
trype  and  Ceratostoviella  fimbriata.  Their  ascus  wall  is  very  deli- 
cate and  ephemeral,  and  as  a  consequence  the  ascospores  are  freed 
and  lie  intermixed  with  gelatinous  material  within  the  perithecial 
cavity.  The  gelatinous  material  absorbs  water  readily  and  swells, 
and  the  spore  mass  is  squeezed  out  through  the  ostiole,  like  tooth- 
paste from  a  tube. 

The  second  type,  first  correctly  described  by  Zopf  [de  Bary 
(1887)],  occurs  in  Sordaria  and  Podospora  and  certain  other 
coprophilous  species,  which  develop  on  the  dung  of  herbivorous 
animals  [Griffiths  (1901)].  The  perithecia  are  pear-shaped,  and 
the  ostiolar  canal  is  lined  with  hyphae  directed  toward  the  open- 
ing. The  perithecial  walls  are  thin  enough  for  spore  discharge 
to  be  satisfactorily  observed.  Ingold  (1939)  mounted  entire 
perithecia  of  Podospora  curvula  in  water  in  a  hanging  drop 
and  noted  that  they  contain  asci  in  different  stages  of  maturity. 
The  asci  and  interspersed  paraphyses  are  attached  to  a  stroma 
occupying  the  bottom  of  the  perithecium  and  remain  attached 
to  this  stroma  during  discharge.  On  looking  through  the  peri- 
thecial wall,  the  observer  may  note  that  mature  asci  elongate  by 
growth  and  by  the  pressure  exerted  by  the  surrounding  cells. 
The  greatly  distended  elastic  ascus  extends  into  the  neck  canal, 
and  the  ascus  tip  slips  through,  being  "lubricated"  by  the  hyphae 
within  the  canal,  until  it  protrudes  slightly  beyond  the  ostiole. 
At  this  stage  the  tip  of  the  ascus  opens  by  a  circumscissile  rup- 
ture, and  the  cap  formed,  together  with  the  mass  of  8  ascospores 
and  much  of  the  ascus-sap,  is  shot  upward.  Immediately  after 
discharge  the  empty  ascus,  being  attached  to  the  basal  stroma, 
snaps  back  inside  the  perithecium,  and  another  ascus  elongates, 
opens,  discharges,  and  is  withdrawn  seriatim,  until  the  perithecial 
content  is  exhausted.  Since  each  ascospore  of  P.  curvula  possesses 
two  terminal  gelatinous  appendages  that  become  entwined,  the 
spore  mass  is  a  rather  large  projectile  and  can  be  hurled  for  a  dis- 
tance of  20  cm  or  more.  The  neck  of  the  perithecium  being 
phototropic,  the  ascus  content  is  discharged  directly  toward  the 
source  of  li^ht. 

The  third  type  has  asci  of  "jack-in-the-box"  construction,  as 
aptly  designated  by  Ingold  (1933).  This  type  has  many  variants, 
but  in  each  kind  the  elongated  ascus  extends  to  the  exterior  of  the 


192  SPORE  DISSEMINATION 

perithecium.  It  was  first  correctly  described  by  Pringsheim 
(1858)  from  observations  on  Fleospora  scirpicola  (Sjphaeria 
scirpi).  Since  then  this  type  of  discharge  has  been  observed  by 
numerous  mycologists  in  various  genera,  and  the  accounts  of 
Hodgetts  (1917),  Weimer  (1920),  Atanasoff  (1919),  Ingold 
(1933,  1939),  and  Butler  (1939)  may  well  be  consulted.  In  her 
account  Butler  lists  the  following  fungi  as  having  jack-in-the-box 
dehiscence:  Ascospora  beijerinckii,  A.  ruborum,  Cucurbit  aria 
laburni,  Lecanidion  atratum,  Leptosphaeria  acuta,  Metasphaeria 
asparagi,  Mycosphaerella  rubina,  Fleospora  herbarium,  Pl&wrightia 
ribesia,  Physalospora  malorum,  Sphaeria  inquinana,  S.  ellipsocarpa, 
S.  lanada,  S.  lemaneae,  Sporormia  bipartis,  and  Venturia  iuaequalis. 
Such  dehiscence  has  been  noted  in  many  other  pyrenomycetous 
£enera  and  also  in  several  discomycetous  ones. 

The  essential  structure  that  makes  this  type  of  discharge  pos- 
sible is  the  double  ascus  wall,  consisting  of  an  outer,  thick,  fairly 
riqid,  inextensible  membrane,  sometimes  called  the  ectoascus,  and 
an  inner,  thin,  elastic  membrane,  the  endoascus.  It  may  be  im- 
possible to  distinguish  the  membranes  as  entities  until  the  moment 
discharge  is  begun.  At  maturity  the  ascus  imbibes  water  as  the 
result  of  transformation  of  stored  olycooen  into  osmotically  active 
compounds.  Endosmosis  occurs,  but  the  outer  ascus  membrane 
does  not  permit  any  considerable  stretching  to  increase  the  di- 
ameter. Enlargement  proceeds  to  the  point  where  the  ectoascus 
is  ruptured,  whereupon  the  endoascus  suddenly  elongates  to  one 
to  three  times  its  original  intact  length. 

There  are  several  types  of  rupture  of  the  ectoascus.  In  Lecani- 
dion atratum  the  tip  of  the  ascus  is  lifted  off,  forming  a  thimble- 
like cap  at  the  tip  of  the  endoascus.  The  remainder  of  the  ecto- 
ascus slips  down  toward  the  base  of  the  ascus,  or  its  edge  is 
folded  or  rolled  as  stockings  are  by  some  wearers. 

In  Mycosphaerella  a  thin  place  may  appear  in  the  ectoascus 
wall,  in  some  species  near  the  tip,  in  others  well  down  along  the 
side.  Rupture  takes  place  at  this  thin  area  when  sufficient  in- 
ternal pressure  has  been  developed,  and  the  ectoascus  tip  persists 
as  a  flap  at  the  side  of  the  extended  endoascus.  At  any  rate,  the 
sudden  release  of  the  endoascus  permits  its  apex  to  spring  through 
the  ostiole.  If,  as  in  Sporormia,  the  ascospores  are  to  be  dis- 
charged simultaneously,  the  further  increased  pressure  ruptures 
the  ascus  tip,  and  the  spores  are  squirted  en  masse.    If,  as  is  more 


SPORE  DISCHARGE  AMONG  ASCOMYCETES  193 

common,  the  spores  are  to  be  discharged  successively,  they  be- 
come compressed  into  a  single  row  with  long  diameters  lying  in 
the  direction  of  the  longitudinal  axis  of  the  ascus.  Then  a  con- 
tractile  pore  forms  in  the  apex,  and  each  spore  is  ejected  endwise. 
Discharge  of  the  8  spores  requires  a  period  of  a  few  seconds  to  a 
minute  or  two.  While  the  first  half  of  the  ascospore  of  Mycos- 
phaerella  is  passing  through  the  contractile  pore,  its  velocity  is 
diminished,  and  it  has  been  observed  to  stop  momentarily  at  the 
constriction.  Its  rate  of  ejection  increases  as  the  second  half 
passes  through  the  pore,  and  the  spore  is  snapped  into  space,  some- 
what after  the  fashion  of  a  watermelon  seed  when  compressed 
between  the  fingers.  The  next  spore  in  line  instantly  plugs  the 
pore,  and  the  process  is  repeated  until  all  8  are  ejected.  The 
empty  ascus  then  contracts,  and  its  place  is  taken  by  another 
mature  ascus  or  complement  of  mature  asci. 

A  fourth  type  of  discharge  is  exhibited,  especially  by  long- 
necked  or  rostrate  Pyrenomycetes.  In  this  type,  as  illustrated  by 
Gnomoma  riibi,  Ophiobolus  careciti,  Endothia  parasitica,  and 
Ceratostomella  ampallacea  [Ingold  (1939)],  the  asci  at  maturity 
become  detached  and  for  a  time  remain  free  and  intact  within 
the  perithecial  cavity.  As  more  asci  are  formed  from  the  stro- 
matic  tissue  within  the  basal  portion  of  the  perithecium,  they  be- 
come freed  and  displace  those  first  detached.  As  a  consequence 
a  stream  of  asci  is  squeezed  into  the  long  neck  canal,  the  asci  pass- 
ing up  in  single  file.  In  Ceratostomella  ampiillacea  the  asci  swell 
quickly  as  soon  as  they  protrude  from  the  ostiole,  the  lower  end 
being  firmly  held  by  the  rigid  jaws  of  the  ostiole.  The  ascospores 
are  dispelled  by  the  bursting  of  the  ascus,  and  the  empty  ascus  is 
pushed  out  by  the  next  ascus  in  the  series,  and  so  on.  In  some 
rostrate  species,  such  as  Linospora  gleditsiae,  the  asci  collect  in  a 
mucoid  droplet  at  the  orifice  of  the  ostiole  and  must  be  dissemi- 
nated by  water. 

Still  another  structural  mechanism  has  been  described  in  other 
Pyrenomycetes.  In  Glomerella,  for  example,  the  ascus  is  apically 
thickened,  and  exit  is  provided  through  a  papillar  perforation. 
The  ectoascus  remains  intact.  As  the  intra-ascal  pressure  increases, 
the  thickened  pore  resists  stretching,  but  the  ascospores  are 
squeezed  through  the  perforation.  As  each  emerges  at  the  tip  of 
the  pore,  it  is  snapped  into  space. 


194  SPORE  DISSEMINATION 

SPORE  DISCHARGE  AMONG  BASIDIOMYCETES 

Most  of  our  knowledge  of  spore  discharge  among  the  Basidio- 
mycetes  comes  from  the  painstaking  researches  of  Buller  (1924, 
1933).  Throughout  this  entire  group  with  its  numerous  species, 
except  for  the  Gastromycetes,  which  is  constituted  of  relatively 
few  species,  essentially  the  same  mechanism  of  discharge  prevails. 
This  generalized  mechanism  has  been  termed  the  "drop-excretion 
mechanism."  As  a  matter  of  fact,  no  satisfactory  explanation  of 
how  this  mechanism  causes  the  spores  to  be  forcibly  expelled  is 
as  yet  forthcoming,  but  the  problem  can  be  properly  appreciated 
if  the  structure  of  the  basidium  is  first  learned  and  is  kept  clearly 
in  mind.  The  hymenium,  whether  plane  or  having  pores,  gills, 
teeth,  or  other  modification  to  increase  the  spore-bearing  surface, 
is  composed  of  a  palisade  of  basidia.  In  some  species  sterile  cells 
(paraphyses  or  cystidia)  are  interspersed  among  the  basidia.  Each 
basidium  is  a  turgid  clavate  to  saccate  cell.  Apically  on  this  cell 
are  formed  typically  four  conical  projections,  the  sterigmata. 
The  tip  of  each  sterigma  soon  becomes  slightly  bulbous,  and  the 
inflated  portion  increases,  simulating  the  appearance  of  a  soap 
bubble  being  blown.  These  portions  are  the  basidiospores,  which 
vary  in  shape  and  surface  markings  among  the  different  species. 
Mature  basidiospores  are  always  inequilateral,  with  the  more  plane 
surfaces  of  the  quartet  of  spores  directed  toward  each  other.  The 
hilum  of  each  points  inward  and  is  thus  asymmetrically  placed. 
Presumably  a  wall  eventually  forms  to  separate  the  basidiospore 
from  the  tip  of  the  sterigma. 

As  far  as  the  structural  features  just  recounted  are  concerned, 
all  investigators  are  in  accord.  In  connection  with  discharge  it- 
self and  the  forces  involved,  however,  there  remain  unexplored 
possibilities.  For  a  long  time  it  was  generally  believed  that  a 
water-squirting  mechanism  somewhat  comparable  to  that  in  Pilo- 
bolus  causes  discharge.  This  would  be  expected  to  operate  most 
effectively  if  all  4  spores  of  a  basidium  were  discharged  simul- 
taneously. As  a  matter  of  fact,  the  basidiospores  are  discharged 
successively  one  at  a  time.  Of  course  this  type  of  mechanism 
might  still  be  capable  of  operating  to  discharge  the  spores  succes- 
sively if  the  tip  of  the  sterigma  were  to  be  sealed  before  appreci- 
able loss  of  turgor  within  the  basidium.    That  there  is  actually  no 


SPORE  DISCHARGE  AMONG  BAS1DIOMYCETES 


195 


loss  of  turgor  of  the  basidium  which  can  be  recognized  by  change 
in  shape  and  size  is  shown  by  Buller's  observations  on  a  rather 
large  number  of  species.     He  found  in  all  cases  that  the  spores 


n 


i         ■  \ 


u 


II 


# 


»r 


„M^, 


• 


G 


Fig.  33.  Diagrams  of  apparatus  and  materials  used  by  Buller  to  secure 
evidence  of  forcible  discharge  of  basidiospores  by  Hymenomycetes.  A. 
Threads  in  ocular  of  microscope.  B.  Section  of  pileus  to  be  mounted  in 
compressor  cell;  C,  shown  in  sectional  view.  D.  Compressor  cell  in 
vertical  position  as  seen  through  a  horizonally  placed  microscope.  There 
is  a  bit  of  pileus  near  the  top  of  the  cell,  moist  paper  at  either  side,  and 
water  at  the  bottom.  E.  Basidium  as  seen  with  such  a  horizonal  microscope, 
one  spore  discharged.  F.  Diagram  showing  paths  of  discharged  basidiospores 
(indicated  by  arrows)  and  the  necessity  of  vertical  arrangement  of  gills  if 
spores  are  to  fall  unimpeded.  G.  Stages  in  basidiospore  discharge  as  seen 
when  viewed  from  hymenial  surface.     (After  Buller.) 

are  violently  discharged  from  the  basidium  in  succession.  More- 
over, just  before  each  spore  is  expelled,  a  drop  of  liquid  exudes 
at  the  hilum.    During  a  period  of  a  few  seconds  this  drop  increases 


196 


SPORE  DISSEMINATION 


in  volume,  and  when  it  reaches  a  definite  size,  the  spore  is  shot 
away,  carrying  the  drop  with  it.  Drop  excretion  mav  be^in  at 
the  hilum  of  one  or  more  of  the  other  members  of  the  quartet 
before  the  first  spore  is  discharged,  and  only  a  few  seconds  or 
minutes  elapse  between  successive  discharge  of  each  member. 
The  sterigmata  are  turgid  after  discharge,  and  apparently  the  tips 


liTTrmniMiiiijj-. 


l—"V/s  :••"». 


.-•,»•'*'?. ■'■•**.,"'>v.  ;:-'.'£. . :  .  • 
.•*«.••■.•■.•■.•:»•>.  * .;•         -  . 

■■■?•■  ■.•■:.■.:■>■. \<*i  ■  '      ■ 

•      "•       ■•'  --l.^  ■'••  '•■•         •      • 

•  .-j&pmsc  .>•••■■  -r 

»«*  •--.:■■?;?•.    ..."  ■ 


■  •  >.■  ■ 

■'::•■' 

.  u--v. 


Fig.  34.  Two  tvpes  of  evidence  of  spore  discharge  among  Hvmenomvcetes. 
A.  Diagram  of  a  spore  print  of  an  agaric,  made  bv  placing  the  ventral 
surface  of  the  pileus  horizontally  on  white  paper  in  a  moist  chamber.  B. 
Diagram  to  indicate  how  spore  discharge  mav  be  observed  in  a  beam  of 
light.  A  fragment  of  pileus  is  attached  to  cork,  fastened  to  cover  of  vessel. 
Basidiospores   are    circulated   bv   convection   currents. 

are  sealed.     Afterward  the  basidia  mav  slowly  lose  turgor,  but 
they  collapse  only  when  death  occurs. 

This  description  of  the  structures  involved  and  the  sequence 
of  events  does  not  offer  any  explanation  to  account  for  the  asym- 
metrical position  of  the  spore  on  its  sterigma,  as  Ingold  (1939) 
points  out,  nor  does  it  explain  how  the  drops  are  excreted.  Con- 
cerning the  force  employed  to  discharge  each  spore,  Bullcr  (1922) 
believes  that  it  is  caused  by  surface  tension  energy.  From  ingeni- 
ous experiments  and  from  calculations  he  found  that  the  surface 
energy  on  a  drop  of  exudate  on  the  spore  of  Psalliota  cavipestris 
is  0.000012  erg.  To  derive  this  figure  the  value  of  surface  tension 
is  considered  as  72  on  a  drop  2.3  \x  in  diameter  with  a  surface  area 
of  0.000000166  sq  cm.     Not  all  this  energy  is  available  for  dis- 


SPORE  DISCHARGE  AMONG  BAS1DIOMYCETES 


191 


charge,  because  the  drop  is  a  hemispherical  mass  in  contact  with 
the  spore.  If  the  surface  tension  between  the  surface  of  the  spore 
and  the  drop  is  considered  negligible,  the  surface  energy  of  the 
hemispherical  drop  is  0.0000095  erg.  Then  the  difference  between 
0.000012  erg  and  0.0000095  erg  is  0.0000025  erg.  This  energy  is 
calculated  to  be  seven  times  that  necessary  for  the  actual  initial 
velocity  of  the  spore  when  it  is 
liberated.  Ingold  (1939)  explains 
how  this  energy  is  mobilized  to 
break  the  connection  of  the  spore 
with  the  sterigrna  and  to  dis- 
charge  it  as  follows:  "At  the  mo- 
ment of  spore  discharge  the  drop 
excreted  at  the  hilum  flows  to  the 
side  of  the  spore,  and,  while  this 
is  happening,  the  spore  will  tend 
to  move  in  the  opposite  direction. 
This  would  involve  pressure  of 
the  spore  on  the  end  of  the 
sterigma.  This  pressure,  sud- 
denly exerted,  might  lead  to  the 
springing  of  the  spore  into  the 
air  just  as  one  jumps  from  the 
ground  by  pressing  suddenly 
downward.  .  .  .  Only  a  small 
fraction  of  the  available  surface- 


Fig.  35.  Spore  discharge,  in  dia- 
gram, of  Psalliota  ccnnpestris. 
(After  Ingold.)  A,  spore  on 
sterigma,  B,  just  before  discharge. 
The  exuded  droplet  of  liquid,  C, 
is  of  full  size.  During  discharge 
the  drop,  C,  takes  up  position,  D, 
and  is  carried  away  on  the  side 
of  the    basidiospore. 


tension  energy  is  required  to  im- 
part the  necessary  initial  velocity  to  the  spore,  and  the  remainder 
is  available  for  breaking  the  connection  between  the  spore  and 
its  sterigma." 

Spore  discharge  in  smuts.  The  chlamydospores  of  smuts  are 
pulverulent,  except  in  a  few  species.  Air  currents  constitute  the 
primary  factor  in  the  dispersal  of  these  spores.  Forcible  expulsion 
of  sporidia  has  not  been  noted  among  the  Ustilaginaceae.  Among 
the  Tilletiaceae,  however,  Buller  (1933)  and  his  associates  have 
studied  violent  spore  discharge  in  Tilletia  tritici,  T.  laevis,  T.  hor- 
rida,  T.  hold,  T.  asperifolia,  Entyloma  ?nemspermi?  E.  lobeliae, 
and  E.  linariae.  When  a  chlamydospore  of  these  species  germi- 
nates, a  short  mycelium,  generally  regarded  as  the  basidium,  is 
produced.    At  the  tip  of  this  mycelium  a  cluster  of  about  a  dozen 


198 


SPORE  DISSEMINATION 


filiform  cells,  which  have  generally  been  regarded  as  basidiospores, 
is  formed.  Buller,  however,  regards  them  as  steri^mata  of  a 
highly  specialized  type  for  two  reasons:  (1)  they  are  never  shot 
away  and  therefore  do  not  serve  to  disseminate  the  fungus,  and 


Fie.  36.  Spore  discharge  by  Tilletia  tritici.  A.  Germination  of  chlamvdo- 
spore,  formation  of  special  sterigmata  that  have  fused  in  H-shaped  fashion, 
and  stages  in  formation  of  true  basidiospores  or  sporidia.  B.  Tip  of  sterigma 
with  mature  basidiospore  and  a  droplet  of  fluid  that  serves  in  forcible  dis- 
charge. C.  Basidiospore  that  has  just  been  discharged  with  droplet  clinging 
to   base   of  basidiospore.      (After  Buller.) 

(2)  while  still  attached  to  the  basidium,  they  oive  rise  to  sickle- 
shaped  spores,  asymmetrically  placed,  that  are  forcibly  expelled. 
These  spores  may  cause  infection,  and  Buller  consequently  regards 
them  as  the  true  basidiospores  of  the  Tilletiaceae. 

As  has  often  been  observed,  the  specialized  sterigmata  may  form 
H-shaped  conjugations.  Either  from  these  pairs  or  from  a  single 
unpaired  member,  a  septate  hypha  may  arise,  from  which  the 
sickle-shaped   basidiospores   are   abstricted.     In   T.   tritici  these 


SPORE  DISCHARGE  AMONG  BASIDIOMYCETES  199 

basidiospores  are  propelled  to  a  vertical  height  of  1 .0  mm  and  to  a 
horizontal  distance  of  1.4  mm. 

Spore  discharge  in  rusts.  Klebahn  (1904)  is  the  first  investi- 
gator to  point  out  that  the  basidiospores  of  rusts  are  forcibly  dis- 
charged. Dietel  (1912)  later  recorded  the  same  phenomenon  in 
connection  with  Puccinia  malvacearum,  P.  glechomatis,  P.  annu- 
laris, Coleosporhmi  campamdae,  C.  petasitidis,  and  Cronartium 
asclepiadeam.  In  some  instances  he  observed  that  a  tiny  droplet 
of  water  appears  at  the  tip  of  the  sterigma  immediately  before 
discharge.  He  determined  that  under  normal  conditions  basidio- 
spores may  be  shot  about  0.3  mm  vertically  and  0.6  mm  horizon- 
tally. For  Gy?nno sporangium  juniperi-virginianae  Coons  (1912) 
recorded  a  horizontal  distance  of  discharge  of  0.26  to  0.36  mm. 
Shortly  thereafter  Buller  (1924)  made  a  detailed  study  of  spore 
discharge,  especially  in  Puccinia  graminis  and  Endophyllum 
euphorbiae-sy haticae.  In  all  essential  features  the  phenomena  of 
discharge  among  the  Hymenomycetes,  which  he  had  previously 
studied,  and  those  in  the  Uredinales  are  alike.  As  differences  be- 
tween the  two  groups,  he  notes  that  the  rust  basidiospores  are 
larger  and  are  usually  shot  farther,  the  distances  being  0.4  to  0.85 
mm  in  the  rusts  and  0.05  to  0.2  mm  in  the  fleshy  Hymenomycetes. 
In  correlation  with  these  differences  he  noted  that  the  droplet 
of  water  exuded  at  the  spore  hilum  in  Uredinales  is  somewhat 
larger  and  requires  from  10  to  40  seconds  to  form,  whereas  in 
Hymenomycetes  only  5  to  10  seconds  is  usually  required. 

Later  Prince  (1943)  reported  that  expulsion  of  basidiospores  by 
Gymno sporangium  nidus-avis  is  accomplished  by  a  different 
mechanism  from  that  described  by  Buller  for  other  rusts.  Prince 
concluded  that  the  mechanism  is  quite  like  that  among  Entomo- 
phthoraceae.  The  basidiospore  arises  as  an  enlargement  of  the 
apex  of  the  sterigma,  so  that  the  primary  membrane  is  common 
to  the  spore  and  the  sterigma.  When  the  spore  attains  mature 
size,  a  septum  is  formed  in  the  sterigma  that  delimits  the  spore  and 
leaves  an  apiculus  at  its  base.  Next  a  wall  is  laid  down  inside  the 
spore  and  also  one  below  the  septum.  Pressures  built  up  in  the 
apiculus  of  the  basidiospore  and  in  the  apex  of  the  sterigma  rup- 
ture the  primary  membrane  at  the  septum,  and  the  instantaneous 
opposed  bulging  of  the  end  of  the  apiculus  and  of  the  sterigma 
results  in  forcible  discharge  of  the  spore. 


200  SPORE  DISSEMINATION 

From  the  evidence  it  seems  entirely  probable  that  Uredinales 
generally  are  capable  of  violently  discharging  their  basidiospores. 
The  urediniospores  are  powdery  and  are  disseminated  by  wind. 
Evidently  aeciospores  in  many  species  are  projected  out  of  the 
aecia  with  considerable  force.  Attention  was  first  directed  to  the 
matter  of  forcible  ejection  of  aeciospores  by  Zalewski  (1883) 
from  observations  on  Uromyces  pisi,  whose  aecia  are  borne  on 
Euphorbia.  He  also  showed  from  experiments  that  Puccinia 
graminis,  P.  calystegia,  P.  coronata,  and  Aecidium  symphyti  dis- 
charge their  aeciospores,  the  oldest,  outermost  aeciospores  of  the 
chain  being  discharged  first.  Dodge  (1924)  observed  the  same 
phenomenon  in  Gymnotelium  myricatum  and  Puccinia  podo- 
phylli.  From  similar  studies  Buller  (1924)  recorded  its  occur- 
rence in  XJroviyces  poae,  Puccinia  clematidis,  P.  fraxinata,  P.  gros- 
sulariae,  P.  graminis,  P.  hieraciata,  P.  impatientis,  P.  poarum,  P. 
pulverulenta,  and  P.  urticata.  The  mechanism  by  which  expulsion 
is  made  possible  consists  of  thickenings  of  the  spore  walls,  which 
push  into  the  spore  wall  opposite.  These  thickenings  serve  as 
fulcra,  against  which  the  elastic  spore  walls  react.  As  the  upper- 
most cells  approach  maturity,  the  pressure  may  be  suddenly  re- 
leased above,  whereupon  the  aeciospore  is  shot  out.  Sometimes 
masses  of  spores  are  expelled.  The  aeciospores  of  P.  graminis 
may  be  discharged  to  a  height  of  7  to  8  mm,  of  Uromyces  pisi, 
15  to  20  mm.  Thus  far  observations  have  dealt  with  cupulate 
and  caeomoid  aecia,  no  studies  having  been  made  of  rostelioid 
and  peridermioid  aecia,  in  some  of  which  the  peridial  layer  reacts 
to  moisture,  and  the  hygroscopic  movements  of  peridial  segments 
expel  the  aeciospores. 

Spore  discharge  among  Hymenomycetes.  Of  course  the 
simplest  procedure  to  demonstrate  that  Hymenomycetes  shed 
their  spores  is  to  place  the  pilei  with  undersurface  downward  on  a 
piece  of  white  paper  to  secure  a  spore  print  or  to  focus  a  beam 
of  licrht  below  the  fruit  body  suspended  in  a  closed  glass  vessel. 
Practically  all  our  knowledge  of  violent  spore  discharge  among 
Hymenomycetes  has  come  from  the  studies  by  Buller,  conducted 
over  a  period  of  about  30  years  and  recorded  in  his  Researches  on 
Fungi.  In  this  period  he  examined  numerous  genera  and  species, 
including  such  well-known  and  widely  distributed  species  as 
Psalliota  cavipestris,  Coprinus  comatus,  C.  atramentarius,  Poly- 
porus  squaviosus,  Lentinus  lepideus,  Psathyrella  disseminata,  Ar- 


SPORE  DISCHARGE  AMONG  BASIDIOMYCETES  201 

miliaria  mellea,  Amanitopsis  v  agin  at  a,  Rnssnla  emetic a,  Panus  stip- 
ticns,  and  Pleurotiis  ostreatus.  All  exhibit  the  following  features 
during  basidiospore  discharge:  (1)  the  four  spores  are  discharged 
in  succession,  not  simultaneously;  (2)  a  droplet  of  exudate  appears 
at  the  hilum  of  the  basidiospore  just  before  discharge  and  is  absent 
on  the  sterigma  after  discharge.  It  is  carried  along  with  the  spore 
and  disappears  as  the  spore  strikes,  causing  it  to  adhere;  (3)  the 
sterigmata  and  basidium  do  not  collapse  as  the  spores  disappear. 

Violent  basidiospore  discharge  is  an  important  phenomenon  in 
this  group  because  the  spores,  when  liberated  into  the  space  be- 
tween gills  or  spines  or  into  pores,  are  prevented  bv  the  position  of 
the  pileus  from  touching  each  other  or  the  hymenial  surface. 
Thev  thus  escape  from  the  pilei.  Each  is  shot  horizontally  for  a 
short  distance,  the  motion  being  rapidly  terminated  because  of 
resistance  of  the  air.  In  Amanitopsis  vaginata  horizontal  move- 
ment of  the  spore  is  completed  in  1/400  second  [Builer  (1909)], 
and  the  initial  velocity  approximates  40  cm  per  second.  When 
horizontal  movement  is  at  an  end,  the  spores  react  in  response  to 
gravity.  Builer  observed  the  rate  of  fall  of  basidiospores  by  use 
of  a  horizontally  placed  microscope.  He  mounted  sections  of 
hymenium  in  a  chamber  and  placed  the  chamber  on  the  micro- 
scope stage.  The  hymenium  was  thus  vertically  disposed.  Three 
silk  threads  were  then  attached  to  the  eyepiece  at  equal  distances 
from  each  other  across  the  field  of  view.  Records  of  the  velocity 
of  spores  passing  through  the  field  of  view  could  then  be  made  on 
an  electrically  rotated  drum  connected  with  a  tapping  key  that 
could  be  depressed  by  the  observer.  By  this  means  Builer  (1909) 
found  that  the  velocity  of  fall  in  millimeters  per  second  for 
Colly bia  dryophila  was  0.37,  for  Plntens  cervinus,  0.67,  for  Psal- 
liota  campestriSy  1.61,  for  Poly  poms  squamosns,  1.03,  for  Boletus 
felleus,  1.22,  for  Rnssnla  emetica,  1.64,  for  Amanitopsis  vaginata, 
2.95,  and  for  Coprinns  commatus,  3.96.  Small  spores  fell  at  a 
slower  rate  than  larger  spores.  These  rates  of  fall  were  found 
to  be  considerably  greater  than  expected  from  calculation  by 
Stokes'  law,  a  discrepancy  for  which  Builer  was  unable  to  offer  a 
satisfactory  explanation.  Presumably  it  is  in  part  related  to  dimi- 
nution in  volume  of  the  mass  (spore  plus  droplet)  as  fall  proceeds. 

Among  other  interesting  facts  established  by  these  studies  on 
violent  spore  discharge  among  Hymenomycetes  is  that,  so  long 
as  corky  and  woody  pilei  have  sufficient  moisture,  they  may  con- 


202  SPORE  DISSEMINATION 

tinue  to  shed  spores.  Species  of  Lenzites,  Daldalea,  Schizophvl- 
lum,  Polvstictus,  and  Stereum,  after  having  been  dried  for  as  long 
as  a  year  or  two,  may  be  revived  in  the  presence  of  moisture, 
\\  hereupon  spore  discharge  is  renewed.  In  the  presence  of  vapors 
of  ether  pr  chloroform  spore  discharge  ceases.  Such  reactions 
leave  no  doubt  that  discharge  is  a  vital  phenomenon. 

The  pilei  of  species  of  Coprinus  are  bell-  or  thimble-shaped. 
Their  srills  undergo  autodigrestion,  commonly  regarded  as  del- 
iquescence.  This  process  is  a  very  important  adaptation  to  insure 
escape  of  the  spores  into  the  air,  which  is  accomplished  because 
the  spores  on  each  gill  mature  and  are  discharged  progressively 
from  the  outer  edge  of  the  gill  toward  the  stipe.  Those  portions 
of  the  gills  from  which  the  spores  have  been  shed  are  digested  and 
removed  soon  after  discharge,  and  in  consequence  space  is  pro- 
vided for  the  shedding  of  spores  just  above,  as  the  pilei  continue 
to  open  outward  like  the  opening  of  an  umbrella. 

Spore  discharge  among  Gastromycetes.  The  Gastromycetes 
include  a  group  of  species  whose  best-known  members  are  called 
"purTballs"  or  "snuffboxes."  The  spore  mass  of  the  larger  propor- 
tion of  species  in  this  subclass  is  dry  and  powdery  and  therefore 
admirably  adapted  for  dissemination  by  air  currents.  The  hygro- 
scopic movement  of  capillitia  aids  in  spore  expulsion  in  certain 
species.  Some  few  are  subterranean,  and  their  spores  are  scat- 
tered by  rodents  or  burrowing  animals  that  find  the  fruit  bodies 
attractive  as  food.  Another  group,  the  stinkhorns,  possesses  a 
glebal  or  spore-bearing  portion  which  is  attractive  to  carrion 
flies  because  of  its  putrid  odor.  These  stinkhorns  appear  to  de- 
velop overnight,  but  actually  the  "eggs,"  encased  in  a  protective 
membrane  or  volva,  have  gradually  been  developing  in  the  decay- 
ing leaf  mold.  When  the  volva  is  ruptured,  the  spongy  stalk  or 
receptacle,  capped  with  the  gleba,  rather  suddenly  elongates  in  a 
jack-in-the-box  fashion.  De  Bary  thought  that  this  straightening 
out  or  elongation  of  the  stalk  was  caused  by  inflation  from  gas 
within  the  tissues.  Burt  (1897)  determined,  however,  that  the 
stretching  is  an  osmotic  phenomenon  and  that  it  occurs  coincident 
with  the  disappearance  of  a  reserve  of  glycogen  in  and  about  the 
receptacle,  whose  cells  merely  increased  rapidly  in  size. 

These  modifications  in  stinkhorns  to  insure  spore  dispersal  are 
much  less  spectacular  and  remarkable  than  those  in  Sphaerobolus. 
Members  of  this  genus  occur  on  rotton  wood  and  on  the  dung  of 


SPORE  DISCHARGE  AMONG  BASIDIOMYCETES 


203 


such  herbivors  as  rabbit,  horse,  cow,  and  elephant.  In  1729  Micheli 
in  his  Nova  Plantarum  Genera  first  described  and  illustrated 
Sphaerobolns  stellatus  in  his  Plate  86,  but  he  employed  for  it  the 
name  "carpobolus."  Fischer  (1884^  gave  an  account  of  the  struc- 


Fig.  37.  Structure  of  Sphaerobolus  stellatus  in  diagram.  A.  Section  of 
mature  sporocarp,  with  six  (1-6)  layers  that  invest  the  central  peridiole  (7). 

B.  Dehiscence  of  sporocarp  at  apex.     The  inner  membrane  has  liquefied. 

C.  Eversion  of  the  remaining  two  inner  layers,  by  which  the  peridiole,  D,  is 

hurled  away. 

tural  mechanism  by  means  of  which  the  gleba,  about  the  size  of  a 
BB  shot,  is  discharged.  Later  Walker  (1927),  Walker  and  Ander- 
sen (1925),  and  Buller  (1933)  have  painstakingly  and  graphically 
worked  out  the  details  of  the  mechanism  of  this  veritable  fungus 
"trench  mortar." 

The  peridium  or  wall  consists  of  six  layers:  (a)  an  outer  layer 
of  loosely  interwoven  hyphae,  (b)  a  gelatinous  layer  penetrated 
by  hyphae,  (c)  a  compact  pseudoparenchymatous  layer,  (d)  a 
narrow  layer  of  tangentially  ramifying  threads,   (e)   a  layer  of 


204 


SPORE  DISSEMINATION 


radially  arranged  pseudoparenchyma,  and  finally  (f)  a  thin  layer 
of  small-celled  pseudoparenchyma. 

Within  this  multiple  periderm  is  the  glebal  mass.  At  maturity 
the  peridium  splits  and  bends  outward  to  expose  the  gleba.  The 
fruit  body  now  consists  of  two  tooth-rimmed  cups,  one  fitting 
inside  the  other  and  the  two  joined  at  the  tips  of  the  teeth.  The 
outer  cup  consists  of  the  three  outermost  layers.    The  innermost 


Fig.  38.     Feeding  tracks  made  by  the  snail  Polygyra  thyroidcus  on  lilac 

leaves  infected  with  powdery  mildew. 

layer  liquefies,  and  this  liquid  accumulates  around  the  spherical 
glebal  mass,  which  is  now  free  and  can  be  rolled  around  in  the 
cup.  The  tanoentially  arranged  layer  and  the  radially  elongated 
layer  are  left  to  constitute  the  inner  cup.  Everything  is  now  ready 
for  discharge,  provided  that  there  is  light,  a  temperature  approxi- 
mating 90°  F,  and  high  relative  humidity.  If  these  conditions  pre- 
vail, the  inner  cup  suddenly  everts  itself  and  in  so  doing  hurls  the 
gleba  away.  If  the  fruit  body  is  tilted  to  get  the  most  suitable 
trajectory,  the  gleba  may  be  projected  a  horizontal  distance  of  546 
cm.  Sphaerobolus  holds  the  long-distance  record  among  fungi 
for  spore  projection. 

The  inner  cup  may  be  ejected  along  with  the  glebal  mass,  but 
more  often  it  remains  as  a  p;listenin«;  dome.  i\fter  a  time  it  may 
assume  its  original  position.    Wax  or  plasticine  spheres  can  then 


IMPLICATIONS  205 

be  substituted  for  the  natural  projectiles,  and  the  "trench  mortars" 
can  be  repeatedly  operated  with  these  artificial  projectiles. 

The  tensions  that  are  responsible  for  eversion  of  the  inner  cup 
arise  from  transformation  of  glycogen  [Errera  (1885),  Walker 
and  Andersen  (1925)]  into  reducing  sugars.  Up  to  the  time  that 
the  peridium  splits  open,  the  radially  arranged  palisade  tissues  are 
filled  with  glycogen,  but  it  has  all  been  digested  by  the  time  dis- 
charge takes  place.  In  conclusion  it  may  be  mentioned  that  spe- 
cies of  Sphaerobolus  are  to  be  regarded  as  among  the  most  fasci- 
nating objects  of  study  among  fungi. 

Evidence  indicates  that  the  peridioles  of  Nidulariaceae  are  dis- 
seminated by  rain  splash  and  adhere  to  near-by  objects  by  means 
of  their  glutinous  coating,  as  was  noted  by  Diehl  (1941).  He 
found  that  the  lower  leaves  of  camellia  bushes  beneath  which 
Cyathus  pallidus  was  fruiting  on  fragments  of  wood  were  studded 
with  black,  button-shaped  peridioles.  xMore  remarkable,  perhaps, 
is  Diehl's  (1941)  re-examination  of  specimens  of  a  fungus  on 
camellia  leaves  collected  over  100  years  ago  and  identified  as 
Leptostroma  camelliae.  This  fungus  proved  to  be  not  a  pycnidial 
form  but  the  peridioles  of  Cyathus  st  ere  or  ens. 

IMPLICATIONS 

The  studies  that  have  been  made  on  dissemination  of  fungus 
spores  are  essentially  of  two  types:  (1)  those  that  deal  with  the 
structural  mechanisms  involved  and  with  the  manner  in  which 
these  mechanisms  function;  and  (2)  those  that  deal  with  the 
vectors  or  agencies  of  dissemination.  Spore  dissemination  is  of 
consequence  to  each  particular  fungus  because  the  perpetuation 
of  that  species  requires  that  spores  be  dispersed.  Perpetuity  is  in- 
sured, all  other  factors  being  favorable,  if  spores  are  brought  into 
contact  with  new  sources  of  food.  - 

A  study  of  spore  dissemination  becomes  meaningful  mainly  in 
relation  to  the  occurrence  and  relative  abundance  of  diseases  of 
plants  and  animals  and  in  relation  to  the  geographical  distribution 
of  the  given  fungus.  The  student  may  even  wonder  why  plant 
and  animal  diseases  are  not  more  prevalent  and  why  more  fungi 
are  not  ubiquitous  in  distribution,  when  once  he  appreciates  that 
many  species  are  incredibly  profligate  in  the  production  of  spores. 


206  SPORE  DISSEMINATION 


LITERATURE  CITED 

Albertini,  J.  B.  de,  and  L.  D.  de  Schweinttz,  Conspectus  fungorum  in 
Lusatiae  superioris  agro  niskiensi  crescentium,  p.  62.    Lipsiae,  1805. 

Arthur,  J.  C,  The  Plant  Rusts.    466  pp.     1929. 

Atanasoff,  D.,  "A  novel  method  of  ascospore  discharge,"  My  col. ,  11:  125— 
128,  1919. 

Barv,  A.  de,  Comparative  morphology  and  biology  of  fungi,  mycetozoa,  and 
bacteria.    Oxford.     1887.     (See  p.  72.) 

Brodie,  H.  J.,  "The  oidia  of  Coprinus  lagopus  and  their  relation  to  insects," 
Ann.  Botany,  45:  315-344,  1931. 

Buller,  A.  H.  R.,  Researches  on  fungi,  Vol.  I:  287  pp.,  1909.  Vol.  II: 
viii  +  492  pp.,  1922.  Vol.  Ill:  xii  +  611  pp.,  1924.  Vol.  V:  xiii  +  416 
pp.,  1933   (see  Chap.  III).     Vol.  VI:  xii  +  513  pp.,  1934. 

Bulliard,  P.,  Histoire  des  cha??2pignons  de  la  France.  Pp.  51-52,  pi.  II,  fig. 
6.    Paris.     1791. 

Burrill,  T.  J.,  and  T.  J.  Barrett,  "Ear  rots  of  corn,"  ///.  Agr.  Expt.  Sta.  Bull., 
755:63-109,  1909. 

Burt,  E.  A.,  "The  Phalloideae  of  the  United  States.  III.  On  the  physiologv 
of  elongation  of  the  receptaculum,"  Botan.  Gaz.,  24:  73-92,  1897. 

Butler,  Ellvs  T.,  "i\scus  dehiscence  in  Lecanidion  atratuvi  and  its  signifi- 
cance," Mycol.,  31:  612-622,  1939. 

Christiansen,  J.  J.,  "Long-distance  dissemination  of  plant  pathogens,"  Aero- 
biology, Am.  Assoc.  Adv.  Set.  Pub.,  77:78-85,  1942. 

Committee  on  Apparatus  in  Aerobiology,  National  Research  Council, 
"Techniques  for  appraising  air-borne  populations  of  microorganisms, 
pollen,  and  insects,"  Phytopathology,  57:201-225,  1941. 

Coons,  G.  H.,  "Some  investigations  of  the  cedar-rust  fungus,  Gymnospor- 
angium  ]uniperi-virginianae"  Nebr.  Agr.  Expt.  Sta.  Ann.  Rept.,  25:  2 17— 
242,  1912. 

Craigie,  J.  H.,  "An  experimental  investigation  of  sex  in  the  rust  fungi," 
Phytopathology,  21:  1001-1040,  1931. 
"Aerial  dissemination  of  plant  pathogens,"  Proc.  Sixth  Pacific  Sci.  Cong., 
4:  753-767,  1939. 

Dickson,  L.  F.,  and  W.  R.  Fisher,  "A  method  of  photographing  spore  dis- 
charge from  apothecia,"  Phytopathology,  75:30-32,  1923. 

Diehl,  W.  YV,  "The  taxonomy  of  Zenker's  Leptostroma  camelliae^  Mycol., 
55:215-219,  1941. 

Dietel,  P.,  "Uber  die  Abschleuderung  der  Sporidien  bei  der  Uredineen," 
Mycol.  Zentr.,  7:355-359,  1912. 

Dodge,  B.  O.,  "Aeciospore  discharge  as  related  to  the  character  of  the  spore 
wall,"  /.  Agr.  Research,  21:  749-756,  1924. 

Durham,  O.  C,  "Air-borne  fungus  spores  as  allergens,"  Aerobiology,  Am. 
Assoc.  Adv.  Sci.  Pub.,  11:  32-47,  1942. 

Ehrlich,  John,  "The  beech-bark  disease.  A  Xectria  disease  of  Fagus,  follow- 
ing Cryptococcus  fagi  (Baer.),"  Can.  J.  Research,  70:393-692,  1934. 


LITERATURE  CITED  201 

Errera,  L.,   "Sur  le  glvcogene   chez  les  Basidiomycetes,"   Rec.  Vinst.   bot. 

Bruxelles,  1:  95,  1885. 
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sensiblen  Diskomyceten,"  Mykol.   Untersiichungen  Berichte,  2: 77-144, 

1916. 
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5:370-403,  1923. 
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42:433-443,  449-462,  465-470,  1884. 
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of    Cronartium   ribicola   in    greenhouses,"    Phytopathology,   1: 368-373, 

1917. 
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Soc,  28:  26-72,  1945. 
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Club,  11:  1-134,  1901. 
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34:22-29,  1936. 
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Co.,  New  York.     1937. 
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semination of  ascospores  of  the  chestnut-blight  fungus,"  /.  Agr.  Re- 
search, 5:443-526,  1915. 
Heald,  F.  D.,  and  R.  A.  Studhalter,  "Birds  as  carriers  of  the  chestnut-blight 

fungus,"  /.  Agr.  Research,  2:  405-422,  1914. 
Heald,  F.  D.,  and  R.  C.  Walton,  "The  expulsion  of  ascospores  from  the 

perithecia  of  the  chestnut-blight  fungus,  Endothia  parasitica    (Murr.) 

And.,"  Am.  J.  Botany,  7:499-521,  1914. 
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77:212-213,  1933. 
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acuta;'  New  Phytol.,  76:  139-146,  1917. 
Hohnk,  W.,  "Polyplanetism  and  zoospore  germination  in  Saprolegniaceae 

and  Pythium,"  Am.  J.  Botany,  20:  45-62,  1933. 
Ingold,  C.  T.,  "Spore  discharge  in  the  Ascomycetes,"  New  Phytol.,  32:  178- 

196,  1933. 
"The  spore-discharge  mechanism  in  Basidiobolus  ranarum^  New  Phytol., 

55:274-277,  1934. 
Spore  discharge  in  land  plants.     178  pp.    Clarendon  Press,  Oxford.     1939. 
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Am.  Assoc.  Adv.  Sci.  Pub.,  11:  69-77,  1942. 
Klebahn,  H.,  Die  wirtwechselnden  Rostpilze.     447  pp.     Gebriider  Born- 

trager,  Berlin.     1904. 
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1935. 
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New  York.     1940. 


208  SPORE  DISSEMINATION 

Levisohn,  I.,  "Beitrag  zur  Entwichlungsgeschichte  und  Biologie  von  Basidio- 
bohts  ranarum  Eidam,"  Jahrb.  wiss.  Botan.,  66:  513-555,  1927. 

Link,  H.  F.,  "Observationes  in  Ordines  plantarum  naturales,"  Magaz.  ges. 
naturf.  frewide  Berlin,  3:  p.  32,  1809. 

Meier,  F.  C,  and  Charles  A.  Lindberg,  "Collecting  micro-organisms  from 
the  arctic  atmosphere,  with  field  notes  and  material,"  Sci.  Monthly, 
40:  5-20,  1935. 

.Meyer,  Helen,  "Spore  formation  and  discharge  in  Fovies  jovientarius" 
Pytopathology,  26:  1155-1156,  1936. 

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1940. 

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Pennington,  L.  H.,  "Wind  dissemination  of  aeciospores  of  Cronartium 
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1929. 

Pinckard,  J.  A.,  "The  mechanism  of  spore  dispersal  in  Peronospora  tabacina 
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1942. 

Plowright,  C.  B.,  "On  spore  diffusion  in  the  larger  Elvellacei,"  Grevillea, 
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Prince,  A.  E.,  "Basidium  formation  and  spore  discharge  in  Gymnospo- 
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Pringshei.m,  N.,  "Uber  das  Austreten  dcr  Sporen  von  Sphaeria  scirpi  aus 
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231,  1920. 

Rittenberg,  S.  C,  "Investigations  of  the  microbiology  of  marine  air,"  /. 
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destroving  fungus,  Entomophthora  sphaerosperma"  Mycol.,  25:411-432, 
1931. 

Schneiderhan,  F.  J.,  "Apple  diseases  in  northern  Virginia,"  Va.  Agr.  Expt. 
St  a.  Bull.,  245:  35  pp.     1926. 

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Stakman,  E.  C,  A.  W.  Henry,  G.  C.  Curran,  and  W.  N.  Christopher, 
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LITERATURE  CITED  209 

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75:341-381,  1926. 


Chapter  9 
GERMINATION  OF  SPORES 

The  process  of  germination  of  spores  is  generally  regarded  as 
belonging  among  growth  phenomena  and  hence  being  subject  to 
modification  by  all  those  factors  that  influence  growth.  Spore 
germination  has  much  in  common  with  seed  germination,  as  might 
be  anticipated,  and  much  of  value  has  been  learned  by  mycologists 
from  the  techniques  and  interpretations  of  those  who  have  studied 
the  termination  of  seeds.  Manifestly  the  factors  that  affect  the 
orermination  of  spores,  just  as  that  of  seeds,  are  of  two  types: 
hereditary  or  internal,  and  environmental  or  external.  Hereditary 
factors  include  the  maturity",  longevity,  dormancy,  and  vitality 
of  spores.  The  environmental  factors  include  the  influence  of 
moisture,  temperature,  pH,  kind  and  concentration  of  nutrients, 
light,  and  the  presence  of  oxygen  and  carbon  dioxide. 

Both  saprophytic  and  parasitic  fungi  have  been  used  in  spore- 
germination  studies,  more  especially  the  parasitic,  because  weather 
conditions  are  known  to  influence  the  incidence  and  relative 
prevalence  of  plant-disease  outbreaks.  In  attempts  to  evaluate  the 
relative  importance  of  environmental  factors  to  plant  diseases, 
the  pathogens  have  been  grown  in  culture,  and,  as  an  incidental 
result,  our  knowledge  of  spore  germination  has  been  increased. 

GERMINATION  TYPES 

Different  kinds  of  spores  germinate  differently.  Sometimes 
the  type  of  germination  is  characteristic  of  a  large  number  of 
closely  related  species.  In  other  cases  environmental  factors  exert 
a  controlling  influence  on  the  type  of  germination  within  the 
same  species.  Among  the  aquatic  Phycomycctes  each  propaga- 
tive  element  is  at  first  a  mother  cell  whose  content  breaks  up 
into  intracellular  units  of  protoplasm,  which,  after  escape  from 

210 


GERMINATION  TYPES  211 

the  mother  cell  and  after  one  or  more  motile  stages,  become 
transformed  into  the  assimilatory  phase  or  thallus.  In  the  simplest 
Phycomycetes  this  transformation  is  accomplished  by  the  imbi- 
bition of  water,  after  which  the  protoplast  increases  in  volume, 
although  remaining  within  the  stretched  parent-cell  membrane; 
more  nuclei  and  more  protoplasm  are  then  formed.  The  spore 
thus  becomes  the  unicellular,  coenocytic,  spherical  thallus.  The 
transition  from  germination  to  subsequent  growth  is  so  imper- 
ceptible that  there  is  little  or  no  evidence  of  delimitation  of  the 
two.  Among  the  higher  Phycomycetes,  for  example,  species 
of  Albugo,  Phytophthora,  Plasmopara,  and  Sclerospora,  the  con- 
tent of  the  mother  cell  (sporangium)  may  break  up  into  intra- 
sporangial  elements  (spores),  or  the  sporangium  may  germinate 
by  the  production  of  a  germ  tube,  depending  upon  temperature, 
as  one  of  the  controlling  factors. 

All  spores  absorb  water  and  swell  as  an  initial  step  in  germina- 
tion. In  most  species  a  germ  tube,  the  primordium  of  the  myce- 
lium, is  then  formed.  In  some,  however,  reserve  food  in  the  form 
of  droplets  of  oil  can  be  noted  to  disappear  as  the  protoplasm 
moves  into  the  developing  germ  tube.  If  the  spore  contents  in 
their  entirety  migrate  into  the  hypha,  an  empty  spore  cavity 
devoid  of  living  content  is  formed. 

In  the  Erysiphaceae,  Peronosporaceae,  and  Uredinales  the  germ 
tube  ceases  to  grow  as  soon  as  the  reserve  food  is  exhausted  un- 
less a  nutritive  relationship  with  an  appropriate  host  plant  has 
been  established.  If  nutrient  is  available,  either  from  the  host 
tissues  or  from  the  culture  medium,  the  germ  tube  continues  to 
grow,  becomes  branched,  and  otherwise  assumes  the  character- 
istics of  the  parent  thallus. 

The  germ  tube  of  the  chlamydospores  of  Ustilaginales  and  of 
the  teliospores  of  the  Uredinales  is,  however,  a  promycelium  or 
basidium.  Its  growth  is  determinates  The  promycelium  produces 
sporidia  which  may  germinate  by  tube  formation.  Among  the 
Ustilaginaceae  the  sporidia  may  germinate  by  budding.  Among 
the  Tilletiaceae  the  thread-like  elements  (so-called  sporidia)  are 
regarded  by  Buller  as  sterigmata  of  a  specialized  type,  wmich  pro- 
duce the  true  sporidia.  In  species  of  Taphrina  and  in  Gloeo- 
sporhtm  aridum,  Microstroma  juglandis,  Protocoronospora  (Ka- 
batiella)  nigricans ,  Catenophora  pruni,  Dematium  pallulans,  Poly- 


212  GERMINATION  OF  SPORES 

spora  lini,  and  many  other  fungi,  the  spores  may  germinate  by 
buddine  and  may  continue  to  grow  by  budding.  In  a  goodly 
number  of  species  the  spores  first  form  a  tube,  and  subsequent 
growth  is  wholly  or  in  large  part  by  budding. 

Some  spores  require  both  water  and  a  supply  of  nutrient  sub- 
stances before  they  can  be  made  to  germinate.  A  lining  of  proto- 
plasm remains  in  their  spore  cavity,  and  the  spore  becomes  an 
integral  part  of  the  mycelium. 

Spores  seldom  form  more  than  a  single  germ  tube  or  at  most 
a  few.  Exceptions  are  the  multicellular  spores  or  large  spores. 
Each  cell  of  a  multicellular  spore  normally  behaves  as  an  entity. 
Lar«e  spores,  such  as  those  of  Pertusaria  and  Megalospora,  may 
develop  simultaneously  fifty  or  more  germ  tubes.  The  tubes  in 
these  genera  are  emitted  through  pores  in  the  thick  wall,  but  they 
possess  no  other  peculiarities. 

METHODS  OF  TESTING  SPORE  GERMINATION 

Hoffman  (1860)  initiated  the  hanging-drop  technique,  which 
now  employs  Van  Tieghem  cells  and  which  is  now  widely  used 
in  spore-germination  tests.    It  is  employed  successfully  not  only 
with  liquid  but  also  with  semisolid  media.    This  method  has  cer- 
tain obvious  advantages  over  the  use  of  drops  of  water  containing 
spores  and  placed  on  microscopic  slides  and  over  the  implanting 
of  spores  on  media  in  Petri  dishes.    None  of  these  features  seems 
to  be  so  important  as  an  understanding  of  how  to  secure  repro- 
ducible results  of  germination  trials.     It  is  quite  apparent  that 
there  is  little  accord  among  the  results  of  investigations  on  spore 
germination.     As  McCallan  and  Wilcoxon  (1932)   have  shown, 
the  variations  in  spore  germination  that  have  been  reported  may 
be  attributed  to  two  causes:   faulty  technique  and  variation  in 
sampling.    Among  the  common  errors  which  McCallan  and  Wil- 
coxon enumerate  are:    (j)  failure  to  state  the  number  of  spores 
counted,  either  germinated  or  not  germinated,  making  it  impos- 
sible to  determine  from  statistical  analysis  the  decree  of  siimiri- 
cance  to  attach  to  the  results;  (b)  counting  the  control  germina- 
tion as  100c;  and  adjusting  the  treatments  accordingly,  thus  pre- 
venting adequate  comparison,  because  small  differences  between 
controls  will  result  in  large  differences  between  treatments;  (c) 


METHODS  OF  TESTING  SPORE  GERMINATION  213 

expressing  the  results  of  progressively  changing  treatments  plotted 
against  germination  of  spores  as  a  jagged  curve,  whereas  this  curve 
should  be  smooth  if  a  sufficient  number  of  spores  has  been  counted. 

In  regard  to  faulty  technique  it  is  essential  that  such  environ- 
mental factors  as  temperature,  time,  nature  of  the  medium  used 
in  germination,  and  cleanliness  of  glassware  be  controlled.  More- 
over,  uniformity  of  source  and  age  of  spores  and  density  of  spore 
suspension  should  be  given  attention.  Repetitions  of  tests  on 
different  days  may  yield  variations  whose  causes  are  not  well 
understood. 

In  connection  with  differences  in  results  between  duplicated 
germination  tests,  it  is  possible  to  determine  whether  these  differ- 
ences are  real  and  also  to  compute  the  degree  of  significance  of 
differences.  Differences  attributable  to  variations  in  sampling  have 
been  found  to  follow  a  mathematical  law.  By  use  of  a  formula, 
that  is,  by  making  the  Chi-square  test  (X2),  and  by  reference  to 
the  tables  of  Fisher  (1930,  pp.  75-98),  which  give  the  probability 
of  occurrence  of  such  values  of  X2,  the  variations  caused  by  errors 
in  sampling  can  be  evaluated.  The  procedures  involved  in  these 
computations  are  not  complicated,  although  detailed  explanation 
of  them  is  wholly  beside  the  purpose  of  this  chapter. 

Some  fungi  do  not  seem  to  require  that  energy-yielding  ma- 
terials be  present  for  germination,  as  noted  by  Lin  (1940),  using 
conidia  of  Sclerotinia  fructicola.  Other  species,  however,  are 
found  dependent  upon  the  presence  of  sugars  and  minerals.  Lin 
(1945)  demonstrated  that  the  conidia  of  Glomerella  cingiilata  re- 
quire carbon,  magnesium,  nitrogen,  and  phosphorus.  He  supplied 
carbon  as  dextrose  in  0.01%  solution  and  minerals  in  1.0  millimols 
with  the  results  shown  in  Table  16. 

TABLE  16 

Nutritional  Requirements  for  Germination  of  Glomerella  cingulata 


Substance  Supplied 

Redistilled  water 

Dextrose 

KXO3  +  KH2PO4  +  MgS04 

Dextrose  +  KNO3  +  KH2P04  +  Na2S04 

Dextrose  +  KXO3  4-  KC1  4-  MgS04 

Dextrose  +  KC1  +  KH2P04  4-  MgS04 

Dextrose  +  KNO3  4"  KH2P04  4"  MgS04 


Percentage  of 

Element  Lacking 

Germination 

Carbbn  and  minerals 

0.0 

Minerals 

0.0 

Carbon 

0.7 

Magnesium 

0.9 

Phosphorus 

1.5 

Nitrogen 

3.9 

None 

92.8 

214  GERMINATION  OF  SPORES 

HEREDITARY  FACTORS  AND  GERMINATION 

Many  observations  on  the  maturity,  longevity,  dormancy,  and 
vitality  of  spores  as  factors  in  germination  have  been  recorded, 
but  very  little  of  a  fundamental  nature  is  known  regarding  them. 
In  general,  conidia  are  capable  of  germination  as  soon  as  they  are 
abstricted  from  the  parent  cell,  just  as  many  seeds  may  be  germi- 
nated as  soon  as  they  are  mature.  The  zygospores  and  oospores 
of  Phycomvcetes,  the  chlamvdospores  of  many  smuts,  and  the 
teliospores  of  certain  species  of  rusts,  however,  are  known  to  re- 
quire a  period  of  dormancy,  which,  as  in  seeds,  is  characterized  by 
thick,  hard,  protective  walls  that  are  presumably  quite  impervious 
to  water  and  oxygen. 

It  may  well  be  that  some  spores  must  undergo  a  period  of  after- 
ripening  also,  as  has  been  reported  in  connection  with  Ustilago 
longissima,  U.  striaeformis,  Urocystis  anemones,  and  U.  cepnlae. 
Davis  (1924)  stored  spores  of  U.  striaeformis  in  the  laboratory  in 
a  damp  atmosphere  at  20°  C  for  about  240  days  before  he  could 
secure  germination.  About  265  days  were  required  if  the  material 
was  stored  out  of  doors.  Davis  was  able  to  hasten  after-ripening 
by  exposing  fresh  smut  spores  to  fumes  of  chloroform  for  1  min- 
ute, then  submerging  them  for  5  minutes  in  a  10° £  solution  of 
citric  acid,  and  washing  them  before  placing  them  in  storage. 

The  oospores  of  certain  Peronosporaceae,  for  example,  Plasmo- 
para  viticola  and  Sclerospora  graminicola,  and  the  teliospores  of 
certain  rusts  that  normally  hibernate  and  then  germinate  in  spring 
may  be  induced  to  germinate  during  the  preceding  autumn.  By 
floating  teliospores  on  water  or  by  alternate  wetting  and  drying, 
Maneval  ( 1922 )  was  able  to  secure  germination  during  November 
and  December.  As  the  season  advanced,  there  was  a  marked 
increase  in  the  percentage  germination  and  a  decrease  in  the  time 
necessary  for  germination  to  begin.  He  used  Puccinia  asparagi,  P. 
helianthi,  P.  menthae,  P.  peridermiospora,  P.  riielliae,  P.  sorghi,  P. 
sydowiana,  P.  windsoriae,  and  Phragmidium  potentillae.  Still 
other  species  appear  completely  to  lack  a  more  or  less  fixed  period 
of  dormancy.  Spaulding  and  Rathbun-Gravatt  (1925)  noted  that 
under  outdoor  conditions  one  collection  of  teliospores  of  Cvonav- 
tium  ri hi cola  from  Ribes  rotundifolium  retained  longevity  for  19 
days,  and  one  from  jR.  nigrum  for  87  days,  and  that  urediniospores 


HEREDITARY  FACTORS  AND  GERMINATION  215 

accompanying  the  teliospores  remained  viable  for  a  maximum 
period  of  59  days. 

Horner  (1921)  attempted  to  germinate  the  aeciospores  of  Puc- 
cinia  coronata  avenue  on  leaves  of  Rhamnus  kept  in  the  herbarium 
and  found  them  non-viable   167  days  after  collection,  whereas 
urediniospores  on  Avena  sativa,  under  the  same  conditions  of  stor- 
age, were  viable  87  days  after  collection.    He  also  placed  rust-in- 
fected oat  leaves  in  Petri  dishes  and  stored  them  as  follows:  Five 
collections  were  stored  outdoors  under  a  thick  covering  of  leaves 
and  snow,  at  a  temperature  range  of  27°  to  42°  F.    Two  of  these 
collections  showed  viable  urediniospores  after  44  days.    Of  four 
collections   placed   unprotected   outdoors,   none   showed   viable 
spores  after  22  days.    Both  of  the  collections  wrapped  in  paper 
and  stored  in  the  dark  at  temperatures  ranging  from  29°  to  86°  F 
had  viable  urediniospores  after  79  days.    Neither  of  two  collec- 
tions exposed  to  sunlight  at  29°  to  86°  F  had  viable  spores  after 
23   days.     The  urediniospores  of  this  species  kept  outdoors  in 
Arkansas  under  the  natural  variations  of  temperatures  and  humid- 
ity succumbed  in  15  days  [Rosen  and  Weetman  (1940)].    Under 
controlled  conditions  Rosen  and  Weetman  found  that  spores  were 
short-lived  at  relative  humidities  below  25%  or  above  50%,  irre- 
spective of  temperature.    At  higher  temperatures  and  humidities 
viability  was  lost  in  15  days,  and  at  lower  temperatures  and  hu- 
midities the  spores  survived  for  over  300  days.    These  results  with 
crown  rust  of  oats  and  other  similar  ones  with  Puccinia  graminis 
triticij  both  heteroecious  species,  have  an  important  bearing  on  the 
problem  of  the  source  of  inoculum  in  spring  for  infections  on 

these  cereals. 

Hart  (1926)  found  a  similar  relationship  between  temperature 
and  humidity  in  the  retention  of  viability  of  urediniospores  of 
Melampsora  lint.  They  retained  ability  to  germinate  for  almost 
3  months  at  favorable  temperature  and  humidity.  At  relative 
humidities  of  40%  and  60%  they  were  viable  longer  than  at  20% 
or  80%.  When  stored  at  high  temperatures,  they  lost  viability 
more  rapidly  than  when  kept  at  low  temperatures. 

Raeder  and  Bever  (1931)  recorded  that  urediniospores  of  Puc- 
cinia glumarum,  P.  graminis  phlei-pvatensis,  and  P.  graminis  tritici 
remained  germinable  88,  120,  and  128  days,  respectively,  when 
kept  at  a  relative  humidity  of  49%  and  at  a  temperature  range 
between  9°  and  13°  C.     At  the  same  relative  humidity  and  at 


216  GERMINATION  OF  SPORES 

temperatures  between  3°  and  11°  C,  P.  triticina  remained  viable 
124  days. 

Smut  fungi  are  known  to  retain  their  viability  for  long  periods. 
.McAlpine  found  Tolyposporium  bursum  on  kangaroo  grass  viable 
after  4  years1  storage  in  the  laboratory.  Long  ago  Brefeld  noted 
that  Tilletia  tritici,  when  kept  dry  in  the  herbarium  for  8% 
years,  was  still  germinable.  Urocystis  cepulae  is  reported  to  re- 
main viable  in  the  soil  for  at  least  5  years.  Many  root-invading 
pathogens  are  well  known  to  persist  in  the  soil  not  only  from  one 
year  to  the  next  but  also  for  a  term  of  years. 

It  has  been  indicated  that,  as  teliospores  of  certain  rusts  become 
older,  less  time  may  be  necessary  for  their  germination,  especially 
in  species  in  which  the  teliospores  constitute  the  overwintering 
stage.  The  converse  is  true  in  many  conidial  forms.  Brown 
(1922)  observed  that  6-week-old  conidia  of  Botrytis  cinerea,  for 
instance,  require  twice  as  long  to  germinate  as  do  10-dav-old  ones. 
On  the  other  hand,  a  larger  percentage  of  conidia  of  Phyllosticta 
solitaria  are  capable  of  germination  10  to  14  days  after  they  are 
of  mature  size  than  can  germinate  immediately  after  they  have 
attained  this  size  [Burgert  (1934)].  It  thus  appears  that  an  in- 
terval may  exist  between  morphological  and  physiological  ma- 
turity of  spores. 

The  retention  of  viability  by  spores  is  in  some  instances  mated 
to  their  separation  from  the  parent  cell  and  from  the  host  tissues 
and  to  their  isolation  from  each  other.  The  ascospores  of  bark- 
inhabiting  and  leaf-inhabiting  species  are  known  to  retain  their 
ability  to  germinate  for  a  longer  time  if  they  remain  within  the 
host  tissues  than  if  they  are  removed.  Similarly,  the  conidia  of 
Gloeosporium,  Colletotrichum,  Lecanosticta,  and  other  genera  in 
which  a  mucilaginous  matrix  holds  the  conidia  together  in  mucoid 
masses  succumb  much  more  quickly  after  they  have  been  dis- 
persed by  contact  with  water.  Desiccation  is  undoubtedly  the 
primary  cause  of  loss  of  viability  in  such  cases. 

The  studies  by  Goddard  ( 1935)  and  Goddard  and  Smith  (1938) 
constitute  an  interesting  approach  to  the  problem  of  dormancy 
in  spores.  Goddard  (1935)  induced  the  dormant  ascospores  of 
Xcuvospora  tetrasperma  to  germinate  by  heating  them  for  a  few 
minutes  at  temperatures  of  50°  C  or  higher.  Germination  occur- 
red within  2  or  3  hours  if  such  heat-treated  spores  were  placed 
in  water  at  room  temperature.     If  the  spores  were  stored  under 


HEREDITARY  FACTORS  AND  GERMINATION 


211 


anaerobic  conditions  for  a  few  hours  after  treatment  and  then 
placed  under  conditions  favorable  for  germination,  however,  they 
failed  to  grow.  Activation  and  deactivation  were  therefore  re- 
versible reactions.  In  later  work  Goddard  and  Smith  (1938) 
sought  to  explain  what  portion  of  the  respiratory  mechanism  is 
activated  by  heat  and  what  constitutes  the  respiratory  block  in 
dormant  spores.  By  subjecting  spores  to  various  partial  pressures 
of  oxygen  and  carbon  dioxide,  they  determined  that  the  respira- 
tory rates  are  not  limited  bv  permeability  of  the  spore  membranes 
to  passage  of  these  gases.  Under  anaerobic  conditions  carbon 
dioxide  was  not  evolved  by  dormant  spores,  an  observation  which 
led  Goddard  and  Smith  to  suggest  that  active  carboxylase  is  not 
present  in  such  spores.  On  heating,  however,  this  enzyme  is  re- 
versibly  activated.  They  interpreted  their  results  to  show  that 
two  qualitatively  different  respiratory  systems  are  present  in  the 
ascospores  of  N.  tetrasperma,  the  dormant  system  which  func- 


TABLE  17 

Viability  of  Spores  of  M1 

fXOMYCETES 

Germinated  at  Indicated 

Interval  after  Collection 

(approximate  number 

Species 

of  years) 

Stemonitis  favogenita 

5 

Fuligo  septica 

6 

Reticularia  lycoperdon 

10 

Lamproderma  violaceum 

13 

Trichia  favoginea 

16 

Enteridium  olivaceum 

17 

Badhamia  utricularia 

20 

Stemonitis  ferruginea 

21 

Dictydiaethalium  plumbeum 

22 

Badhamia  panicea 

23 

Trichia  botrytis 

26 

Lepidoderma  tigrinum 

26 

Physarum  straminipes 

26 

Trichia  scabra 

27 

Trichia  later  it  ia 

28 

Physarum  cinereum 

29 

Didymium  squamulosum 

30 

Fuligo  septica 

30 

Diachea  leucopoda 

30 

Hemitrichia  clavata 

32 

Stemonitis  ferruginea 

32 

218  GERMINATION  OF  SPORES 

tions  in  the  absence  of  the  enzyme  carboxylase,  and  a  second  sys- 
tem which  is  active  in  heated  spores.  Inactivity-  of  carboxylase 
thus  constitutes  the  respiratory  block. 

The  age  of  spores  of  Myxomycetes  has  been  shown  by  Smith 
(1929)  to  be  of  little  significance  in  germination.  Using  herbarium 
specimens,  he  secured  germination  in  spores  from  5  to  32  years 
after  collection,  as  is  shown  in  Table  17. 

WATER  RELATIONS  AFFECTING  GERMINATION 

Since  water  is  profoundly  important  in  all  vital  phenomena,  it 
may  be  anticipated  that  its  presence  is  a  primary  requirement  in 
initiating  spore  germination.  Spores,  like  seeds,  do  not  all  become 
wet  with  equal  facility,  an  observation  that  has  been  made  by 
everyone  who  has  attempted  to  suspend  spores  in  water  for  use  as 
inoculum.  Ziegenspeck  (1934)  has  clarified  the  physico-chemical 
principles  involved  in  the  problem  of  wetting  spores.  Wetting 
must  be  regarded  as  the  displacement  of  a  gas  film  at  the  surface 
of  a  solid  (spore)  by  a  liquid  (water).  It  implies  an  affinity  of  the 
solid  for  the  liquid  and  is  governed  by  solid-liquid,  solid-gas,  and 
liquid-gas  tensions.  The  resultant  forces  are  measurable  in  terms 
of  the  angle  of  contact  made  by  the  solid  with  the  liquid,  as 
Ziegenspeck  shows. 

An  examination  of  the  literature  on  moisture  requirements  for 
germinating  spores  shows  conflicting  results  concerning  whether 
a  film  of  water  is  necessary,  since  at  high  relative  humidity  a 
slight  decrease  in  temperature  causes  condensation.  Experimenta- 
tion becomes  difficult  if  the  effects  of  an  aqueous  film  and  of  hu- 
midity are  to  be  distinguished.  Far  too  little  careful  work  has 
been  done  on  this  problem. 

Doran  (1922,  pp.  334-335)  recorded  that  Sclerotinia  fructigena, 
Peronospora  pygmaea,  Phyllosticta  antirrhini,  Cylindrocladium 
scoparium,  and  urediniospores  of  Puccinia  coronata  germinate 
only  when  in  direct  contact  with  water.  On  the  other  hand,  his 
observations  show  that  aeciospores  of  Gy?tmosporangium  clavipes 
and  conidia  of  Alternaria  solani  and  Venturia  inaequalis  may  germ- 
inate in  moist  air.  Stock  (1931)  failed  to  secure  germination  of 
urediniospores  of  Puccinia  graminis  and  P.  coronata  when  the 
spores  were  dusted  on  glass  slides  at  relative  humidities  of  99% 
or  below. 


WATER  RELATIONS  AFFECTING  GERMINATION         219 

Hemmi  and  Abe  (1933)  controlled  humidity  by  exposure  over 
varying  concentrations  of  sulphuric  acid  with  the  results  shown 
in  Table  1 8  for  urediniospores  of  P.  glwnarum. 

TABLE  18 

Germination  of  Puccinia  glumarum  as  Modified  by  Various  Relative 

Humidities 


H2S04 

Number 

Percentage 

Relative 

{specific 

Condition 

of 

of 

Humidity 

gravity) 

of  Spores 

Spores 

Germination 

100 

1.0 

In  drops 

1247 

44.5 

100 

1.0 

Dry 

684 

12.4 

99 

1.020 

Dry 

646 

1.5 

95 

1.090 

Dry 

739 

0 

90 

1.158 

Dry 

904 

0 

Although  fungi  generally  respond  to  humidity  in  a  manner 
similar  to  that  shown  by  P.  glumarum  in  Table  18,  certain  of  them 
germinate  independently  of  the  moisture  content  of  the  surround- 
ing air.  The  conidia  of  Erysiphe  polygojii,  for  instance,  were 
found  by  Brodie  and  Neufeld  (1942)  to  germinate  through  a 
range  of  relative  humidity  from  approximately  zero  to  100%. 
These  observations  find  support  in  the  fact  that  powdery  mildews 
are  known  to  grow  luxuriantly  in  areas  where  low  relative  hu- 
midities prevail. 

By  means  of  apparatus  in  which  he  was  able  to  control  relative 
humidities  accurately,  Clayton  (1942)  found  that  the  mean  per- 
centage germination  of  urediniospores  of  Puccinia  coronata,  P. 
graminis  tritici,  and  P.  graminis  avenae  was  lower  at  a  relative 
humidity  of  100%  than  in  water,  was  considerably  less  at  99% 
relative  humidity,  and  was  practically  nonexistent  at  98%.  The 
conidia  and  ascospores  of  Venturia  inaequalis  germinated  on  dry 
glass  if  the  relative  humidity  was  99  to  100%.  When  chlamydo- 
spores  of  Ustilago  hordei  and  17.  nuda  were  similarly  placed  on 
dry  glass,  they  germinated  at  relative  humidities  of  95  to  100% 
but  not  at  93%  or  below.  Furthermore  he  was  able  to  germinate 
the  conidia  of  Erysiphe  polygoni  on  dry  glass  at  relative  humidi- 
ties of  zero  to  100%,  thus  verifying  the  results  of  Brodie  and 
Neufeld  (1942). 

Rippel  (1933)  presented  evidence  in  connection  with  his  studies 
on  the  germination  of  conidia  of  Cladosporium  fulvum  that  the 


220  GERMINATION  OF  SPORES 

humidity  gradient  between  the  air  and  the  spore  membrane  is  a 
more  decisive  factor  than  relative  humidity  in  influencing  germi- 
nation.  In  C.  fulvum  moisture  content  of  the  spores  is  low.  He 
concluded  that  the  higher  is  the  gradient,  the  better  are  the 
chances  of  germination. 

In  many  of  the  studies  concerned  with  germination  of  rusts, 
infected  host  tissues  or  the  spores  themselves  are  floated  on  water. 
Blackman  (1903)  noted  that  the  submerged  germ  tubes  (promy- 
celium)"of  Uromyces  fabae,  Fncchiia  graminis,  and  Phragnridium 
ruin  grew  to  considerable  length  with  the  protoplasm  collected 
near  the  apex  and  that  basidiospores  were  not  formed  unless  the 
tube  reached  the  air,  whereas  in  moist  air  the  tubes  were  short  and 
4-celled,  and  each  cell  possessed  a  sterigma  upon  which  a  basidio- 
spore  was  borne.  This  morphological  modification  in  type  of 
termination  is  now  known  to  be  related  to  the  fact  that  rusts 
forcibly  expel  their  basidiospores,  which  are  adapted  for  dispersal 
by  air. 

Evidently  alternate  wetting  and  drying  play  an  important  part 
in  the  spore  germination  of  some  species.  Jahn  ( 1905)  stated  this 
to  be  true  of  certain  slime  molds.  Alternate  wetting  and  drying, 
he  believed,  activated  the  glvcogen-cleaving  enzymes,  thus  caus- 
ing  glycogen  in  the  spore  to  be  converted  into  maltose  with  re- 
sultant  increase  of  osmotic  pressure.  This  explanation  may  well 
apply  to  other  kinds  of  fungi,  but  it  is  conceivable  that  modifica- 
tion of  the  spore  wall  itself  may  result  from  alternate  wetting  and 
drying  and  that  this  change  is  an  important  factor  in  germination. 

Little  is  known  concerning  the  application  of  findings  from 
laboratory  studies  on  the  relation  of  moisture  to  spore  germination. 
A  body  of  data  is  much  needed,  especially  on  the  relation  of  mois- 
ture to  germination  and  infection  by  plant  pathogens.  Observa- 
tional evidence,  which  is  insufficient  and  which  may  indeed  be 
misleading,  has  led  to  the  conclusion  that  outbreaks  of  some  plant 
diseases  are  caused  by  dry  weather,  others  by  wet  weather. 
Among  studies  of  this  kind  is  that  of  Jones  ( 1923 ),  who  attempted 
to  correlate  the  moisture-holding  capacity  of  the  soil  with  germi- 
nation by  Ustilago  avenae.  She  placed  chlamvdospores  on  agar 
between  filter  papers  and  then  placed  them  in  soils  containing  30, 
60,  or  80°  \  of  their  water-holding  capacitv.  At  favorable  temper- 
atures germination  was  highest  at  30  ,  slightly  less  at  60%,  and 
markedly  less  at  80%.    At  80     ,  which  is  also  unfavorable  for  in- 


EFFECTS  OF  TEMPERATURE  ON  GERMINATION  221 

fection,  lack  of  sufficient  oxygen,  as  Jones  points  out,  is  undoubt- 
edly a  controlling  factor. 

Heavy  water,  deuterium  oxide,  as  it  affects  germination  of 
conidia  of  Erysiphe  gravnms  tritici,  was  studied  by  Pratt  (1936). 
He  varied  the  concentrations  of  D20  from  0.02  to  100%,  with 
phosphates  as  buffers.  Conidia  germinated  in  all  concentrations, 
but  the  rate  of  elongation  of  the  germ  tube  and  its  final  length 
were  found  to  be  inversely  proportional  to  the  concentration  of 
DoO.  Deuterium  oxide  seems  to  limit  the  amount  of  solutes  and 
colloids  within  the  conidia  that  is  utilizable  in  growth. 

EFFECTS  OF  TEMPERATURE  ON  GERMINATION 

Temperature  is  known  to  be  one  of  the  factors  that  modify  the 
severity  of  plant  diseases.  It  may  also  be  the  limiting  factor  in  the 
prevalence  of  diseases  of  crop  plants  in  certain  areas.  As  examples 
it  may  be  recalled  that  apple  scab  and  late  blight  of  potatoes  are  of 
rare  occurrence  and  are  never  of  consequence  in  the  Coastal 
Plain  area  of  the  southeastern  United  States.  Anthracnose-free 
bean  seed  can  be  produced  in  portions  of  this  area  by  planting  at 
such  seasons  that  high  temperatures  will  prevail  at  the  critical 
period  during  maturing  of  the  crop.  Blue-staining  fungi  are  an 
important  cause  of  the  degrading  of  lumber  in  the  warmer  parts 
of  the  United  States. 

For  every  fungus  there  is  a  minimum,  an  optimum,  and  a  maxi- 
mum temperature,  the  cardinal  temperatures,  for  germination  and 
for  subsequent  growth  of  the  fungus.  The  metabolic  activities 
or  rate  of  reaction  of  each  species  increases  with  an  increase  of 
temperature  up  to  a  certain  limit.  These  cardinal  temperatures 
must  be  understood  to  mean  both  the  extreme  temperature  limits 
of  metabolic  activity,  all  other  factors  being  kept  constant,  and 
the  temperature  at  which  metabolism  proceeds  at  the  best  rate. 

The  effect  of  temperature  on  germination  of  urediniospores  of 
Puccinia  coronata  and  on  rate  of  qrowth  of  the  s^erm  tube  is  shown 
by  the  work  of  Melhus  and  Durrell  (1919),  the  rate  being  greatest 
at  the  optimum  temperature.  At  either  extreme,  there  is  no 
growth.  Rate  of  growth  may,  therefore,  be  regarded  as  a  direct 
function  of  (t  —  t°),  if  t  represents  any  particular  temperature, 
and  t°,  the  minimum  temperature.  In  some  instances,  as  could 
be  expected,  the  temperature  which  is  optimum  for  germination 


222 


GERMINATION  OF  SPORES 


of  spores  may  not  be  optimum  for  subsequent  development. 
These  adaptations  may  be  hereditary  and  may  account  for  the 
geographical  distribution  of  the  organisms  concerned  and  for 
their  seasonal  incidence. 

One  type  of  influence  of  temperature  upon  the  method  of  spore 
termination  was  shown  by  Melhus  (1915).  He  noted  that  the 
sporangia  of  Phytophthora  infestans  germinated  by  either  forma- 
tion of  a  tube  or  formation  of  swarm  spores.    A  temperature  of 


30 


0) 

to 
3 

|  20 

a 

c 
o 

I   10 


a 


1 

\ 
\ 

' 

4 

\ 

/ 

/             . 

\.      \ 

-    ^s\ — 

IS 

V 

'I 

// 

/  / 

1 

H\ 

\\ 

600  « 
c 
o 
E 
5 


400  g 

3 

s 

200  & 

O 

X. 

& 

c 

0       _3 


0 


30 


35 


5  8  13  17        20  25 

Temperature  (degrees  Centigrade) 

Fig.  39.  Effect  of  temperature  upon  percentage  of  germination  and  upon 
length  of  cjcrni  tubes  in  urediniospores  of  Viiccinia  coronata.  (After  Melhus 
and  Durrell.)     A.  Percentage  of  germination.    B.  Length  of  germ  tubes  in 

microns.     A  close  correlation  is  shown. 

23°  C  was  optimum  for  tube  formation  and  of  13°  C  for  produc- 
tion of  swarm  spores.  These  critical  temperatures,  as  given  by 
Crozier  (1933),  were  24°  C  and  12°  C,  respectively.  Other 
Peronosporales,  notably  Peronophmnopara  cnbensis,  are  known 
to  behave  similarly. 

Cardinal  temperatures  for  germination.  From  his  own  ob- 
servations and  those  of  other  workers,  Doran  (1922)  assembled  in 
tabular  form  data  on  the  influence  of  temperature  on  spore  germi- 
nation among  a  variety  of  pathogenic  fungi.  These  data  consti- 
tute the  bases  from  which  Table  19,  supplemented  by  more  recent 
observations,  has  been  prepared.  Xo  generalizations  appear  war- 
ranted from  these  data,  except  perhaps  that  the  temperatures 
which  normally  prevail  when  the  spores  of  these  species  are  be- 
in<T  dispersed  are  favorable  for  germination.  The  data  have  a 
direct  bearing,  however,  on  problems  that  concern  the  relation 


EFFECTS  OF  TEMPERATURE  ON  GERMINATION 


223 


TABLE  19 

Cardinal  Temperature  and  Spore  Germination 


Cardinal  Temperatures 


Organism 

Plasmodiophora  brassicae 
Plasmopara  viticola  (sporangia) 
Cysiopus  candidus  (sporangia) 
Phytophthora  injestans  (sporangia) 
(indirect  method) 
(direct  method) 
Peronospora  parasitica  (sporangia) 
Sclerospora  graminicola 

(sporangia)  [Tsaugi  (1933)] 
(oospores)  [Tsaugi  (1933)] 
Rhizopus  nigricans  [Ames  (1915)] 
Glo?nerella  rujormaculans 
Gymnosporangium  clavipes  (aeciospores) 
Gymnosporangium  juniperi-virginianae 
(teliospores) 
(teliospores) 
Cronartium  ribicola 
(aeciospores) 
(urediniospores) 
Melampsora  lini  (urediniospores)  [Hart  (1926)] 
Puccinia  antirrhini  (urediniospores) 
Puccinia  coronifera  (urediniospores)  [Stock  (1931)] 
Puccinia  coronata 
(urediniospores) 
(urediniospores) 
(urediniospores) 
(urediniospores)  [Stock  (1931)] 
Puccinia  dispersa  (urediniospores) 
Puccinia  graminis  (basidiospores) 
(urediniospores) 
(urediniospores)  [Stock  (1931)] 
(teliospores) 
Puccinia  malvacearum  (teliospores) 
Puccinia  phlei-pratensis  (urediniospores) 
Puccinia  rubigo-vera  (urediniospores) 

(urediniospores)  [Johnson  (1912)] 
Puccinia  sorghi  (urediniospores) 
Puccinia  triticina  (urediniospores)  [Stock  (1931)] 
Uromyces  caryophyllinus  (urediniospores) 
Uromyces  trifolii  (urediniospores) 
Ustilago  avenae  [Jones  (1924)] 
Ustilago  striaeformis  [Davis  (1924)] 
Urocystis  cepulae  [Walker  and  Wellman  (1926)] 
Urocystis  tritici  [Noble  (1923)] 
Urocystis  occulta  [Ling  (1940)] 
Alternaria  solani  [Doran  (1919),  p.  392] 
Colletotrichum  lagenarium 

Cylindrocladium  scoparium  [Doran  (1919),  p.  392] 
Phyllosticta  solitaria  [Burgert  (1934)] 
Monilia  fructigena  [Ames  (1917)] 
Cephalothecium  roseum  [Ames  (1917)] 
Penicillium  digitatum  [Ames  (1917)] 


r 

Mini- 

Opti- 

1 

Maxi- 

mum 

mum 

mum 

(°C) 

(°Q 

27-30 
25-35 

(°C) 

0 

10 

25 

2-3 

12-13 

24-25 

12-13 

24 

30 

8-12 

29 

5 

17.5 

33.5 

11.5 

20-23.5 

35 

5 

36 

5 

30 

8 

14 

25 

11 

15 

29 

7 

23-24 

29 

5 

12 

19 

8 

14 

25 

0 

6-23 

26 

5 

10 

20 

5 

14-25.5 

32.5 

18 

30 

7 

30 

1 

17-22 

35 

7-8 

12-17 

30     ' 

10-12 

18-20 
15-20 

25-27 

2 

31 

2-3 

5-20 

29-30 

9 

22 

23 

3 

14 

30 

18 

30 

2 

31 

2 

12-17 

30 

4 

14 

25 

2-3 

5-20 

29-30 

4 

14 

29 

16 

34 

4-5 

15-28 

29-30 

7 

22 

35 

9 

15-22 

29 

5 

24 

32 

5 

15 

30 

1-3 

26-28 

37-45 

7 

22-27 

8 

12-30 

36 

5 

23 

39 

0 

25 

5 

30 

0 

25 

224  GERMIXATIOX  OF  SPORES 

of  temperature  to  infection,  escape  from  infection,  resistance, 
and  cardinal  temperatures  of  the  host.  Such  matters  are  beside 
the  present  purpose  but  are  comprehensively  dealt  with  bv 
Lauritzen  (1919)  in  his  studies  of  Ascochyta  fagopyrum  on  buck- 
wheat, Colletotrichum  Undentuthianum  on  bean,  and  Pucc'mia 
grandnis  on  wheat.  It  may  be  mentioned,  how  ever,  that  tem- 
peratures permitting  spore  germination  generally  also  permit 
infection.  In  soil-borne  pathogens  and  smuts  that  infect  seed- 
lings, temperature  interacts  with  soil  moisture  and  soil  reaction, 
and  each  factor  is  interdependent. 

The  temperature  relations  of  those  fungi  that  produce  decay, 
especially  of  fruits  and  vegetables,  have  been  extensively  studied 
because  of  their  bearing  on  problems  of  storage  and  refrigeration. 
YVeimer  and  Harter  (1923)  determined  the  cardinal  temperatures 
of  several  species  of  Rhizopus,  all  of  which  cause  decay  of  sweet 
potatoes  in  storage,  to  be  as  shown  in  Table  20.    The  first  four 

TABLE  20 

Cardinal  Temperatures  of  Species  of  Rhizopus  Associated  with  Soft  Rot 

of  Sweet  Potatoes 

Temperature  {degrees  C) 


Species 

r 

Minimum 

Optimum 

Maximum 

R.  artocarpi 

1.5 

26-29 

33.5 

R.  nigricans 

1.5 

Zh-28 

33.0 

R.  reflex  us 

1.5 

30-32 

36.6 

R.  microsporus 

1.5 

26-28 

33.0 

R.  tritici 

1.5 

36-38 

44.0 

R.  delemar 

8.7 

36-38 

44.0 

R.  nodosus 

1.5 

36-38 

44.0 

R.  oryzae 

9.0 

36-38 

44.0 

R.  arrhizus 

1.5 

36-38 

43.6 

R.  chinensis 

10.0 

43-45 

51.0 

species  in  the  list  may  be  set  apart  as  a  low-temperature  group, 
R.  chinensis  is  a  high-temperature  species,  and  the  others  are 
intermediate. 

In  general,  the  studies  on  minimal  temperatures  that  prevent 
germination  and  growth  of  species  causing  decay  of  perishable 
foods  show  that  storage  temperatures  near  0°  C  must  be  main- 
tained if  losses  are  to  be  prevented.  Hoffman  ( 1860)  found  that 
conidia  of  Penicillium  glaucuvi,  Botrytis  vulgaris,  and  Trie  hot  he- 


EFFECTS  OF  TEMPERATURE  ON  GERMINATION  22$ 


chim  roseum,  all  essentially  omnivorous  species,  germinate  very- 
near  the  freezing  point.  In  similar  studies  Ames  (1915)  employed 
Glovierella  ntfomaculans  and  Cephalotheciwn  roseum  from  apple, 
Thielaviopsis  paradoxa  from  pineapple,  Fenicillhnn  digitatam  from 


be 

S 
c 
a> 
v 

- 

C 

o 

-t-> 
cs 

e 

■  <*-« 

6 

- 

O 


100 

90 

80 

70 

60 

50 

40 

30 

20 

10 
0 


s        s 
— _< * 

\ 

4 

/ 
/ 

f 

y  — 

t 

/ 
/ 

—  -i 

* 

s/ 

- -^    V 

4* 
* 

4 

/ 
/ 
y 

f 

4 

t 

/ 
/ 
/ 

/ 

f 

1 

/ 

t 

f 



/ 
i 

0 


8         10        12        14 
Time  (hours) 


16 


18        20 


22 


24 


Fig.  40.  Effect  of  storage  indoors  for  different  periods  on  germination  of 
teliospores  of  Cronartium  ribicola.  The  curves  are  based  on  3-hour  moving 
averages.  Solid  line,  from  teliospores  taken  from  Ribes  nigrum  and  stored 
for  5  days;  dash  line,  from  teliospores  taken  from  R.  americanum  and 
stored  for  15  days;  dot-dash  line,  from  teliospores  taken  from  R.  nigrum 
and  stored  for  25  days.     (After  Spaulding  and  Rathbun-Gravatt.) 

orange,  Rhizopus  nigricans  from  sweet  potato,  and  Monilia  fruc- 
ticola  from  plums  and  found  that  near-freezing  temperatures 
must  be  maintained  in  storage  if  germination  of  these  species  is 
to  be  prevented  and  development  of  decay  by  them  entirely 
avoided. 

The  most  extensive  data  on  cardinal  temperatures  among  Alyxo- 
mycetes  are  those  of  Smart  (1937).  He  germinated  the  spores 
of  70  species,  finding  that  the  range  22°  to  30°  C  is  optimum  for 
all.    At  10°  C  or  lower  and  above  30°  C  percentage  germination 


226  GERMINATION  OF  SPORES 

and  rate  of  germination  are  greatly  reduced.     The  temperature 
range  for  germination  extends  from  2°  to  36°  C. 

Thermal  death  point.  In  bacteriology  the  term  thermal 
death  point  or,  more  appropriately,  thermal  death  time  has  b'een 
employed  to  express  that  minimal  temperature  fatal  to  all  bac- 
teria after  exposure  for  10  minutes.  The  method  used  is  to  sub- 
ject a  suspension  of  bacteria  to  a  series  of  selected  temperatures 
and  at  definite  intervals  to  plant  out  portions  to  determine  the 
number  of  survivors.  If  the  operation  is  repeated  sufficiently 
often,  it  will  be  found  that  at  a  particular  temperature  all  organ- 
isms are  dead  after  an  exposure  of  10  minutes.  All  other  factors 
must  be  identical  in  thermal-death-time  measurements,  because 
age  of  organisms,  concentration  of  organisms,  and  pH  are  modi- 
fying factors.  Essentially  the  same  method,  using  suspensions  of 
spores,  may  be  employed  for  fungi.  Smith  (1923)  made  such  a 
study  with  conidia  of  Botrytis  cinerea  exposed  at  a  range  of  tem- 
peratures between  31°  and  50.3°  C.  When  he  plotted  the  propor- 
tion surviving  at  different  times  for  each  temperature,  he  got  a 
series  of  approximately  symmetrical  sigmoid  curves  all  exactly 
alike  except  for  the  rate  of  speed  of  killing  at  different  tempera- 
tures. If  the  observations  at  each  temperature  employed  by 
Smith  are  plotted,  they  will  be  seen  to  fall  closely  on  a  typical  fre- 
quency-distribution curve. 

Spores  retain  their  viability  at  higher  temperatures  when  sub- 
jected to  dry  heat  than  to  moist  heat.  These  differences  in  toler- 
ance become  greater  if  the  temperature  is  very  slowly  elevated 
during  dry  heating.  In  explanation  it  may  be  pointed  out  that 
heat  coagulates  proteins  more  readily  when  the  moisture  content 
is  high  than  when  a  small  percentage  of  water  is  present.  The 
observations  of  Tsaugi  (1933)  on  retention  of  germinabilitv  by 
oospores  of  Sclerospora  graviinicola  are  concerned  with  this  point. 
Those  subjected  to  dry  heat  at  50°  C,  55°  C,  and  60°  C  remained 
viable,  whereas  moist  heat  at  these  temperatures  was  lethal. 

Ames  (  1915)  determined  that  the  thermal  death  point  of  Thiela- 
viopsis  paradoxa  is  52.5°  to  53.5°  C,  of  Rhizopus  nigricans,  60°  C, 
of  Monilia  fructicola,  52.0°  to  52.5°  C,  of  Glomerella  rufomacu- 
lans,  53.0°  to  5  3.5°  C,  of  Cephalothecium  roseum,  47°  to  48°  C, 
and  of  Penicillin//;  digitatum,  58.0°  to  58.5°  C. 


EFFECTS  OF  TEMPERATURE  ON  GERMINATION  221 

The  tolerance  of  fungus  spores  to  low  temperatures  should  be 
subjected  to  study  by  methods  patterned  after  those  dealing  with 
thermal  death  points.  Such  studies  appear  not  to  have  been  ac- 
complished, except  for  relatively  few  species.  This  topic  is  sum- 
marized by  Luvet  and  Gehenio  (1941)  and  is  briefly  discussed 
in  Chapter  5.  Investigations  of  the  effects  of  cold  on  fungi,  espe- 
cially rusts,  have  been  largely  concerned  with  overwintering,  as 
related  to  the  source  of  inoculum  for  the  development  of  disease 
outbreaks.     Christman   (1905)    and  Horner   (1921)    are  among 


Fig.  41.    Effect  of  temperature  upon  survival  of  Botrytis  cinerea.    Percent- 
age surviving  plotted  against  time  in  minutes,  except  for  the  37°  C  curve, 
the  intervals  of  which  are  30  minutes.     (After  J.  H.  Smith.) 

those  who  have  investigated  survival  of  urediniospores  of  cereal 
rusts.  Ewert  (1910)  noted  that  a  small  proportion  of  conidia  of 
Psendopeziza  ribls  survived  the  winter  when  exposed  to  outdoor 
temperatures  as  low  as  —  22°  C.  Several  exposures  of  Fusicladhim 
dendriticum  and  F.  pirinum  to  freezing  greatly  reduced  their 
percentage  of  germination.  The  conidia  of  Mycosphacrella  sen- 
tinel, however,  artificially  subjected  to  alternate  freezing  at  tem- 
peratures as  low  as  -16°  C  and  thawing,  retained  germinability 
as  well  as  did  untreated  ones. 

Many  Ascomycetes  known  to  possess  a  conidial  stage  can  over- 
winter in  this  stage.    The  ascospores  of  others  are  mature  in  fall 


228  GERMINATION  OF  SPORES 

and  remain  dormant  throughout  winter.  The  ascogenous  stage  of 
a  third  group  develops  slowly  during  winter  and  matures  in 
spring.  In  any  event  the  overwintering  of  conidia  of  a  species 
not  known  to  possess  an  ascogenous  stage  is  not  a  criterion  upon 
which  to  predicate  the  possession  of  such  a  stage. 

Temperature  and  percentage  germination.  Obviously  the 
proportion  of  the  total  number  of  spores  of  a  given  species  which 
(terminate  is  correlated  with  temperature  and  with  time  as  external 
factors  of  primary  importance.  Temperature  as  a  correlated 
factor  in  percentage  germination  is  illustrated  by  the  observations 
of  Kaufmann  (1934),  presented  in  Table  21.     Germination  was 

TABLE  21 

Proportion  of  Spores  of  Certain  Basidiomycetes  That  Germinate  at 

Different  Temperatures 

Percentage  of  Germination  at 


Organism 

15°  C 

20°  C 

25°  C 

30°  C 

35°  C 

40°  C 

45°  C 

Coprinus  micaceus 

1.72 

3.30 

15.09 

15.05 

77.73 

39.54 

27.48 

Coprinus  comatus 

3.37 

6.72 

12.69 

17.18 

16.29 

14.38 

7.58 

Lepiota  cepae stipes 

0 

0 

3.39 

8.97 

2.71 

0 

0 

Cyathus  olla 

0 

2.59 

4.26 

10.52 

4.53 

0 

0 

Cyathus  striatus 

0 

1.99 

3.93 

7.65 

3.19 

0 

0 

relatively  poor  with  each  of  these  species,  so  that  the  relationship 
is  not  so  striking  as  may  have  been  desired.  Doran's  (1922)  re- 
sults with  a  series  of  trials  employing  conidia  of  Venturia  inaequa- 
lis  are  more  representative.  The  averages  of  his  tests  are  0%  at 
2°  C,  3%  at  5°  C,  21.5%  at  8°  C,  56.2°fat  10°  C,  76.5%  at  12°  C, 
100%  at  15°  C,  77.2%  at  18°  C,  56.5\  at  20°  C,  41.5%  at  24°  C, 
22.2%  at  28°  C,  11%  at  30°  C,  and  0%  at  32°  C 

Time  required  for  germination  at  different  temperatures. 
As  has  previously  been  stated,  the  spores  of  some  fungi  are  capable 
of  germination  as  soon  as  they  are  produced,  whereas  others  un- 
dergo a  period  of  dormancy.  In  any  event  temperature  is  a  factor 
correlated  with  the  time  required  for  spore  germination.  In  some 
species  germination  can  be  secured  within  an  hour;  at  the  opposite 
extreme,  others  may  require  exposure  for  several  weeks  to  condi- 
tions favoring  germination.  The  time-temperature  relationships 
in  spore  germination  are  illustrated  by  Ames's  (1915)  results  of 
studies  on  fruit-rottino-  funm  and  are  shown  in  Table  22. 


INFLUENCE  OF  REACTION  ON  GERMINATION  229 

TABLE  22 

Time  (Hours)  Required  for  Germination  of  Spores  at  Different 

Temperatures 


Fungus 

1°  C 

5°-6°  C  1 

0°-12°  ( 

:  15°  c 

20°  C 

25°  C 

30° 

Thielaviopsis  paradoxa 
Rhizopus  nigricans 
Monilia  jructigena  (jructicola) 
Penicillium  digitatum 

i 
i 

245 
120 

168 
168 
100 

48  * 

23 
43 

7 
15 

13 
36 

7 
8 

8 
16 

7 
8 

8 
13 

7 
8 

8 
16 

7 
8 

Glomerella  rujormaculans 

i 

174 

15 

8 

7 

7 

7 

Cephalothecium  roseum 

i 

i 

24 

15 

7 

7 

7 

1  Failed  to  germinate. 

INFLUENCE  OF  REACTION  ON  GERMINATION 

The  pH  which  limits  germination  has  been  determined  for  many 
species  of  fungi.  A  divergence  of  opinion  exists  concerning  the 
proper  appraisal  of  the  value  of  such  knowledge.  No  such  dis- 
agreement exists,  however,  regarding;  the  usefulness  of  data  in- 
volving  the  influence  of  reaction  on  mycelial  development  of 
fungi  in  cultures  or  in  soil  and  other  natural  habitats. 

Most  fungi  germinate  and  develop  best  in  acid  media.  The  kind 
of  nutrient,  however,  exerts  a  profound  influence  upon  the  re- 
sponse to  the  reaction  of  the  medium.  Webb  (1921)  made. a 
comparative  study  of  the  effects  of  hydrogen-  and  hydroxyl-ion 
concentration  upon  the  germination  of  B'otrytis  cinerea,  Asper- 
gillus niger,  Penicillium  italicum,  P.  cyclopium,  Lenzites  saepiaria, 
Puccinia  graminis,  Fusarium  sp.,  and  Colletotrichum  gossypii  in 
four  liquid  media,  namely,  solutions  of  mannite  and  of  peptone, 
Czapek's  nutrient,  and  sugar-beet  decoction.  All  except  Fusarium 
sp.  and  C.  gossypii  responded  favorably  to  successively  increasing 
concentrations  of  hydrogen  ions  in  all  media  within  the  range  pH 

7.0  to  3.0-4.0.  Colletotrichum  gossypii  responded  best  within  the 
alkaline  range.  Specificity  of  response  in  each  nutrient  is  illus- 
trated by  the  fact  that  Botrytis  cinerea  germinated  in  mannite 
from  pH  1.6  to  6.9,  but  did  best  at  pH  3.0;  in  Czapek's  nutrient 
from  pH  2.5  to  9.6,  but  best  at  pH  3.0  to  3.6;  in  peptone  from  pH 

2.1  to  8.7,  but  best  at  pH  4.0  to  5.3;  and  in  beet  decoction  from 
pH  2.0  to  9.8,  but  best  at  pH  4.0  to  7.0. 

Similar  studies  on  other  organisms  show  that  pH  6.86  is  opti- 
mum for  germination  of  Urocystis  occulta,  with  no  germination 


250  GERMINATION  OF  SPORES 

at  pH  3.80  and  sparse  germination  at  pH  8.95  [Ling  (1940)]. 
Tsau^i  (1933)  secured  best  germination  of  oospores  of  Sclero- 
spora  graminicola  at  pH  2.9  to  3.1,  with  very  little  germination  at 
pH  9.3.  Kaufmann  (1934)  found  pH  7.5  optimum  for  Coprimis 
mi  c  ace  us,  C.  comatus,  and  Cy  at  hits  olla,  pH  7.0  optimum  for 
Lepiota  cepaestipes,  and  pH  6.5  optimum  for  Armillaria  mellea. 
Smart  (1937)  made  a  study  involving  the  effect  of  reaction  on  the 
germination  of  70  species  of  slime  molds.  All  species  germinated 
within  the  range  pH  4.0  to  8.0.  Full  go  septic  a  germinated  within 
the  range  pH  2.0  to  10,  and  Fhysarum  serpula,  pH  2.0  to  8.5.  The 
optimum  pH  for  germination  in  all  species  was  4.5  to  7.0. 

INFLUENCE  OF  OXYGEN  ON  GERMINATION 

De  Bary  (1887)  noted  that  spores  in  a  drop  of  water  between 
the  cover  glass  and  slide  germinate  better  near  the  periphery  of 
the  cover  glass  than  near  the  center.  He  attributed  this  effect 
to  the  relative  amounts  of  air  available.  This  observation  has  been 
verified  by  everyone  who  has  attempted  to  repeat  the  experiment. 
Dus^ar  (1901)  gave  special  consideration  to  reduced  02  tension 
as  a  factor  in  retarding  germination.  Blackman  (1903)  pointed 
out  the  occurrence  of  morphological  differences  in  germination 
of  teliospores  in  water  and  in  air.  Melhus  and  Durrell  (1919) 
recorded  that  few  urediniospores  of  Puccima  coronata  germinate 
if  submerged  in  comparison  with  the  number  germinating  if 
they  float  at  the  surface.  Abundant  evidence  shows  that  a 
smaller  percentage  of  germination  is  secured  in  drops  of  water 
containing  many  spores  than  in  those  containing  few.  Oxygen 
relations  must  therefore  be  considered  in  studies  of  spore  germi- 
nation, and  they  may  be  expected  to  be  correlated  with  the  ability 
to  become  wet  and  with  the  specific  gravity  of  the  spores. 

The  absence  of  oxygen  may  not  inhibit  germination,  as  is 
shown  by  UppaFs  (1926)  studies  on  certain  Peronosporales. 
When  he  removed  the  oxygen  ( by  a  vacuum  pump  or  by  alkaline 
solutions  of  pvrogallic  acid)  from  the  environment  in  which 
sporangia  of  Phytophthora  colocasiae,  P.  infestans,  P.  parasitica, 
and  P.  pahmvora  were  placed  for  germination,  these  species  germi- 
nated by  formation  of  swarm  spores.  On  the  other  hand,  Albugo 
Candida,  Flasmopara  viticola,  and  Sclerospora  graminicola,  which 
germinate  in  the  same  manner,  require  the  presence  of  oxygen 


INFLUENCE  OF  LIGHT  ON  GERMINATION  231 

for  germination,  as  do  also  Peronospora  parasitica  and  P.  trifolio- 
rz/777,  which  germinate  by  formation  of  germ  tubes. 

INFLUENCE  OF  CARBON  DIOXIDE  ON  GERMINATION 

The  observations  of  Brown  (1922)  on  volatile  materials  pro- 
duced by  apples  and  potatoes  in  storage  led  him  to  conclude  that 
volatile  substances  may  have  considerable  influence  in  control 
of  organisms  which  produce  decay.  Ethyl  acetate,  a  common 
fruity  ester  evolved  by  apples,  exerted  either  a  stimulatory  or  an 
inhibitory  effect  on  the  germination  of  Botrytis  cinerea,  depend- 
ing upon  the  concentration.  Volatile  substances  from  leaves  of 
apple,  Ruta,  Eucalyptus  and  other  aromatic  plants  increased  germi- 
nation of  this  fungus,  whereas  vapors  from  potato  tubers  and 
onions  were  inhibitory.  Platz,  Durrell,  and  Howe  (1934)  con- 
cluded that  stimulation  of  germination  of  Ustilago  zeae  in  the 
presence  of  plant  tissues  is  the  result  of  increased  carbon  dioxide 
tension,  the  carbon  dioxide  being  generated  by  the  plant  tissues. 
The  presence  of  corn  leaves  in  their  germination  chambers  in- 
creased the  carbon  dioxide  content  to  15%,  the  optimum  for  ger- 
mination of  the  corn  smut.  Platz,  Durrell,  and  Howe  reported 
that  carbon  dioxide  acts  by  changing  the  reaction,  and  that  15% 
carbon  dioxide  in  the  air  produces  hydrogen-ion  concentrations 
ranging  from  pH  4.9  to  5.6,  which  is  optimum  for  U.  zeae. 

INFLUENCE  OF  LIGHT  ON  GERMINATION 

Too  little  is  known  regarding  the  effect  of  radiations  on  the 
germination  of  fungi,  and  published  reports  frequently  contain 
conflicting  conclusions.  De  Bary  [Doran  (1922),  p.  333]  and 
Farlow  [Doran  (1922),  p.  333]  state  that  light  inhibits  germina- 
tion of  spores  of  Oomycetes.  Melhus  (1915),  on  the  other  hand, 
found  that  light  does  not  inhibit  germination  of  sporangia  of 
Phytophthora  infestans.  Doran  (1922)  noted  that  Alternaria 
solani  and  conidia  of  Sclerotinia  fructigena  germinate  equally  well 
in  direct  light,  diffuse  light,  or  darkness.  Dillon-Weston  (1932) 
germinated  urediniospores  of  Puccinia  graminis  avenae,  P.  graminis 
tritici,  and  P.  coronata  under  standardized  Wratten  green  and  blue 
filters,  which  permit  the  passage  of  wavelengths  of  450  to  555  m^, 


232  GERMINATION  OF  SPORES 

but  ^Termination  was  inhibited  under  the  red,  orange,  yellow,  and 
purple  filters. 

INFLUENCE  OF  NUTRITION  ON  GERMINATION 

As  has  been  emphasized,  the  intake  of  water  by  the  spore  is  the 
sine  qua  11  on  for  the  initiation  of  germination.  Apparently,  how- 
ever, not  all  species  can  be  made  to  germinate  in  pure  water. 
Since  water  is  a  universal  solvent,  spores  do  not  come  in  contact 
with  pure  water  under  natural  conditions.  Whether  they  lodge 
on  living  plants  or  animals,  on  decaying  tissues,  on  the  soil,  or  in 
water,  thev  come  in  contact  with  soluble  organic  materials.  Ad- 
vantage may  be  taken  of  this  fact  in  germination  trials,  especially 
with  species  that  thus  far  have  proved  impossible  to  grow  in  arti- 
ficial culture,  for  example,  Peronosporaceae,  Erysiphaceae,  and 
Hvpodermataceae.  The  germination  of  some  species  in  those 
families  appears  to  be  hastened  by  the  presence  of  the  green  tissues 
of  their  appropriate  hosts.  Similar  experiences  have  also  been 
recorded  with  Rhytisma  acerinum,  Gnomonia  ulmea,  Cymadothea 
trifolii,  Diplocarpon  rosae,  and  Lhwspora  gleditsiae.  Germination 
of  the  spores  of  Merulius  lacrymans  is  hastened  by  the  presence 
of  urine.  In  general,  with  species  whose  germination  is  attended 
with  difficulty  in  potable  water,  an  attempt  should  be  made  to 
approximate  natural  conditions  of  germination. 

RESUME 

It  is  plainly  apparent  from  the  foregoing  discussion  that  both 
hereditarv  and  environmental  factors  influence  the  germination 
of  fungus  spores.  It  is  not  evident,  however,  that  anything  of 
fundamental  importance  is  likely  to  be  established  by  additional 
studies  of  this  sort  involving  either  these  same  species  or  other 
species.  Perhaps  attention  might  better  be  centered  on  determin- 
ing the  causes  of  dormancy  in  spores  and  the  means  whereby  dor- 
mancy may  be  broken.  Such  inquiries  are  likely  to  be  most  fruit- 
ful if  they  are  patterned  after  studies  on  the  germination  of  seed. 

Studies  involving  the  presence  of  growth  factors  to  hasten  or 
to  increase  germination  might  conceivably  yield  results  of  value, 
especially  with  species  that  require  the  given  growth  factor  for 


RESUME  233 


mycelial  development.    Conceivably  such  information  might  have 
a  bearing  on  problems  of  obligate  parasitism. 


LITERATURE  CITED 


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Ann.  Botany,  36:285-300,  1922a. 
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Trans.  Wis.  Acad.  Sci.,  IS:  98-107,  1905. 
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trolled humidity,"  Phytopathology,  32:921-943,  1942. 
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14:251-267,  1924. 
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wavelengths  in  the  visible  and  invisible  spectrum,"  Phytopath.  Z.,  4:  229- 

246,  1932. 
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spore  germination  in  some  Uredinales,"  Phytopathology,  9:  391-402,  1919. 
"Effect  of  external  and  internal  factors  on  the  germination  of  fungous 

spores,"  Bull.  Torrey  Botan.  Club,  49:  313-336,  1922. 
Duggar,  B.  M.,  "Physiological  studies  with  reference  to  the  germination  of 

certain  fungous  spores,"  Botan.  Gaz.,  31:  38-66,  1901. 
Ewert,  R.,  "Die  Uberwinterung  von  Sommerkonidien  pathogener  Ascomy- 

ceten  und  die  Widerstandfahigkeit  derselben  gegen  Kalte,"  Z.  Pflanzenk., 

22:  129-141,  1910. 
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Oliver  and  Boyd,  Edinburgh.     1930. 


234  GERMINATION  OF  SPORES 

Goddard,  D.  R.,  "The  reversible  heat  activation  inducing  germination  and 

increased    respiration   in    the    ascospores    of   Neurospora   tetrasperma," 

J.  Gen.  Physiol.,  19: 45-60,  1935. 
Goddard,  D.  R.,  and  P.  E.  Smith,  "Respiratory  block  in  the  dormant  spores 

of  Nettrospora  tetrasperma,"  Plant  Physiol.,  75:241-264,  1938. 
Hart,  Helen,  "Factors  affecting  the  development  of  flax  rust,  MeLvnpsora 

lini  (Pers.)  Lev,"  Phytopathology,  16:185-205,  1926. 
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of   urediniospores   of   some   species   of   Puccinia   parasitic   on   cereals," 

Forsch.  Gebiete  Pflanzenk.,  2: 1-10,  1933. 
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wiss.  Botan.,  2:  267-297,  1860. 
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of  Puccinia  coronata"  Botan.  Gaz.,  12:  173-177,  1921. 
Jahn,  E.,  "Mvxomycetenstudien  4.     Die  Keimung  der  Sporen,"  Ber.  dent. 

botan.  Ges.,  23:  489-497,  1905. 
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spores of  cereal  rusts   (abst.),"  Phytopathology,  2:47^8,  1912. 
Jones,  Edith  S.,  "Influence  of  temperature,  moisture,  and  oxygen  on  spore 

germination  of  Ustilago  avenae"  J.  Agr.  Research,  24:  577-590,  1923. 
Kauf.m ann,  F.  H.  O.,  "Studies  on  the  germination  of  the  spores  of  certain 

Basidiomycetes,"  Botan.  Gaz.,  96:  282-297,  1934. 
Lauritzen,  J.  I.,  "Relation  of  temperatures  and  humidity  to  infection  by 

certain  fungi,"  Phytopathology,  9:  7-35,  1919. 
Lin,  C.  K.,  "Germination  of  the  conidia  of  Sclerotinia  fructicola,  with  special 

reference  to  the  toxicity  of  copper,"   Cornell  Agr.  Expt.  Sta.  Mem., 

233:  1-33,  1940. 
"Nutrient  requirements  in  the  germination  of  the  conidia  of  Glomerella 

cingnlata,"  Am.  J.  Botany,  32:  296-298,  1945. 
Ling,  Lee,  "Factors  affecting  spore  germination  and  growth  of  Urocystis 

occulta  in  culture,"  Phytopathology,  30:  579-591,   1940. 
Luyet,  B.  F.,  and  P.  M.  Gehenio,  Life  and  death  at  low  temperatures.    341 

pp.    Biodvnamica,  Normandv,  Mo.     1941. 
M  \neval,  W.  E.,  "Germination  of  teliospores  of  rusts  at  Columbia,  Mis- 
souri," Phytopathology,  72:471-488,  1922. 
McCaj  i  an,  S.  E.  A.,  and  Frank  Wilcoxon,  "The  precision  of  spore-germi- 
nation tests,"  Contrib.  Boyce  Thompson  Inst.,  4:  233-243,  1932. 
Melhus,  I.  E.,  "Experiments  on  spore  germination  and  infection  in  certain 

species  of  Oomvcctes,"  Wis.  Agr.  Expt.  Sta.  Research  Bull.,  15:  25-91, 

1911. 
"Germination  and  infection  with  the  fungus  of  the  late  blight  of  potato," 

Wis.  Agr.  Expt.  Sta.  Research  Bull.,  57:64  pp.     1915. 
Mi  i  in  s.  1.  1  ..  and  I..  \V.  Dl  krell,  "Studies  on  the  crown  rust  of  oats,"  Iowa 

i   r.  Expt.  Sta.  Research  Bull.,  4(J:  115-144,  1919. 
Noble,  R.  J.,  "Studies  on  Urocystis  tritici  Koern.,  the  organism  causing  flag 

smut  of  wheat/'  Phytopathology,  13:  127-139,  1923. 
Platz,  G.  A.,  L.  W.  Durrell,  and  Mary  E.  Howe,  "Effect  of  carbon  dioxide 


LITERATURE  CITED  235 

upon  the  germination  of  chlamydospores  of   Ustilago  zeae    (Beckm.) 

Ung.,"  /.  Agr.  Research,  34:  137-147,  1927. 
Pratt,  R.,  "Growth  of  germ  tubes  of  Erysiphe  spores  in  deuterium  oxide," 

Am.  J.  Botany,  25:422-431,  1936. 
"The  influence  of  the  proportions  of  KH2P04,i\IgS04,  and  NaNCX   in 

the  nutrient  solution  on  the  production  of  penicillin  in  surface   cul- 
tures," Am.  J.  Botany,  32:  528-535,  1945. 
Raeder,  J.  M.,  and  W.  M.  Bever,  "Spore  germination  in  Puccinia  glumarum 

with  notes  on  related  species,"  Phytopathology,  27:767-789,  1931. 
Rippel,   K.,   "Untersuchungen   iiber   die   Abhangigkeit   der   Sporenkeimung 

vom    Wassergehalt    der    Luft    bei    Cladosporium    fulvwn    Cooke    und 

anderen  Pilzen,"  Arch.  Mikrobiol.,  4:  530-542,  1933. 
Rosen,  H.  R.,  and  L.  M.  Weetman,  "Longevity  of  urediospores  of  crown 

rust  of  oats,"  Ark.  Agr.  Expt.  Sta.  Bull.,  391:  3-20,  1940. 
Smart,  R.  F.,  "Influence  of  external  factors  on  spore  germination  in  the 

Mvxomycetes,"  Am.  J.  Botany,  24:  145-159,  1937. 
Smith,  E.  C,  "The  longevity  of  myxomycete  spores,"  My  col.,  27:321-323, 

1929. 
Smith,  J.  H.,  "The  killing  of  Botrytis  cinerea  by  heat,  with  a  note  on  the 

determination  of  temperature  coefficients,"  Ann.  Appl.  Biol.,  70:335- 

347,  1923. 
Spaulding,  P.,  and  A.  Rathbun-Gravatt,  "Longevity  of  the  teliospores  and 

accompanying  urediospores  of  Cronarthtm  ribicola  in   1923,"   /.  Agr. 

Research,  37:901-916,  1925. 
Stock,  F.,  "Untersuchungen  iiber  Keimung  und  Keimschluchwachstum  der 

Uredosporen  einiger  Getreideroste,"  Phytopath.  Z.,  3:231-280,  1931. 
Tsaugi,  H.,  "Studies  on  the  physiology  of  the  conidiospores,  conidia,  and 

oospores  of  Sclerospora  graminicola   (Sacc.)    Schroet.  on  the  Japanese 

millet  [Setaria  italica  (L.)  Beauv.],"  /.  Imp.  Agr.  Expt.  Sta.,  2:225-252, 

1933. 
Uppal,  B.  N.,  "Relation  of  oxvgen  to  spore  germination  in  some  species  of 

Peronosporales,"   Phytopathology,   16: 285-292,    1926. 
Walker,  J.  C,  and  F.  L.  Wellman,   "Relation  of  temperature  to  spore 

germination    and    growth    of    Urocystis    ceptdae"    J.    Agr.    Research, 

32:  133-146,  1926. 
Webb,  R.  W.,  "Studies  in  the  physiology  of  fungi.    XV.  Germination  of  the 

spores  of  certain  fungi  in  relation  to  hydrogen-ion  concentration,"  Ann. 

Mo.  Botan.  Garden,  8:  282-341,  1921.  ' 
Weimer,  J.  L.,  and  L.  L.  Harter,  "Temperature  relations  of  eleven  species 

of  Rhizopus,"  /.  Agr.  Research,  24:  1-39,  1923. 
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und  sagespanformigen  Samen,"  Biol.  Generalis,  10:615-656,  1934. 


Chapter   10 

HOST  PENETRATION 

The  production  of  disease  by  pathogenic  fungi  involves  the  fol- 
lowing sequential  processes:   inoculation,  incubation,  and  infec- 
tion, "in  the  first  process  is  included  distribution  of  the  pathogen 
bv  any  agencies  whatsoever  that  bring  into  contact  inoculum  and 
suscept.    The  inoculum  may  take  an  active  part  in  this  process,  as 
occurs  among  swarm  spores  of  certain  Phycomycetes  and  among 
ascospores  and  basidiospores  that  are  forcibly  expelled.     On  the 
other  hand,  the  inoculum  may  be  entirely  passive  and  therefore 
be  dependent  upon  water,  currents  of  air,  and  insects  or  other 
bioloo-ical  agencies.     In  incubation  are  included  penetration  of 
the  tissues  of  suscepts  by  germination  and  growth  of  the  inoculum 
to  set  up  the  parasitic  relationship.     Penetration  may  be  accom- 
plished by  entrance  through  natural  openings,  such  as  stomata, 
lenticels,  and  hvdathodes,  by  direct  passage  through  cuticle  and 
epidermal  walls,  or  bv  entrance  through  wounds.    Length  of  the 
incubation  stage  is  definite  for  each  specific  pathogen  and  termi- 
nates  when  symptoms   appear.     All   of  those   physiologic   and 
morphologic  responses  (symptoms)  that  express  the  interaction 
of  pathogen  and  suscept  are  infection  phenomena,  and  they  con- 
stitute a  "continuous  process.    It  may  be  impossible  to  determine 
when  the  incubation  stage  ends  and  the  infection  stage  begins,  the 
disturbances  being  imperceptible  when  first  initiated. 

In  the  present  instance  concern  centers  upon  the  beginning  of 
the  incubation  stage,  especially  upon  the  phenomena  of  penetra- 
tion and  the  subsequent  relationship  of  the  fungus  to  the  invaded 
tissues.  Numerous  studies  have  been  made  of  this  complex  prob- 
lem, beginning  with  those  by  de  Bary  (1886)  and  carried  forward 
by  Ward  (1888)  and  later  by  Blackman  and  by  Brown  and  his 
associates.     The  status  of  this  problem  has  been  summarized  by 

Blackman  (1924)  and  Brown  (1936). 

236 


DIRECT  PENETRATION  231 

DIRECT  PENETRATION 

Pioneer  work  on  the  initiation  of  attack  by  direct  penetration 
was  done  by  de  Bary  (1886)  in  a  study  dealing  with  invasion  by 
Sclerotinia  libertiana.  He  maintained  that,  when  he  applied  asco- 
spores  in  drops  of  nutrient  solution  to  suitable  intact  plant  tissues, 
they  were  able  to  penetrate  directly;  whereas,  if  ascospores  were 
placed  in  drops  of  water,  they  formed  organs  of  attachment  by 
means  of  which  they  intimately  applied  themselves  to  the  surface 
of  the  host.  These  organs  of  attachment  secreted  a  principle 
which  killed  the  underlying  cells,  and  in  consequence  nutrients 
diffused  from  the  dead  cells.  As  a  parasite,  therefore,  S".  libertiana 
was  able  to  penetrate  directly,  and  as  a  saprophyte  it  must  first 
kill  the  underlying  host  cells.  When  he  prepared  an  extract  from 
infected  tissues,  he  was  able  to  demonstrate  that  this  extract  could 
cause  the  cells  to  fall  apart,  that  is,  to  rot,  and  could  kill  the  proto- 
plasts. Boiling  destroyed  the  activity  of  the  extract;  from  this 
fact  he  concluded  that  rotting  was  caused  by  an  enzyme,  but  he 
was  unable  to  determine  the  nature  of  the  lethal  substance.  Al- 
though he  expressed  the  opinion  that  oxalic  acid  produced  by 
the  fungus  killed  the  cells,  he  did  not  know  whether  this  acid  was 
solely  responsible  for  the  death  of  the  tissues.  Several  reports 
have  subsequently  appeared,  the  authors  of  which  accepted  the 
de  Bary  hypothesis  that  parasitic  fungi  and  bacteria  secrete  a  fer- 
ment that  enables  them  to  penetrate  cell  walls.  Ward  (1888) 
expressed  this  opinion  regarding  Botrytis  cinerea,  the  cause  of  a 
disease  of  lilies. 

In  regard  to  the  cause  of  killing  in  advance  of  penetration, 
Smith  (1902)  found  in  connection  with  Botrytis  cinerea,  parasitic 
on  lettuce,  that  it  produced  a  thermostable  toxic  substance  and 
expressed  the  opinion  that  this  substance  was  oxalic  acid.  Peltier 
(1912),  on  the  other  hand,  in  a  study  involving  presumably  the 
same  fungus  on  pepper  and  lettuce,  concluded  that  the  toxic 
thermostable  substance  was  not  oxalic  acid  but  some  other  organic 
acid  or  acids.  Higgins  (1927)  demonstrated  production  by 
Sclerotinm  rolfsii  of  oxalic  acid  in  certain  nutrient  solutions. 
Considerable  quantities  of  oxalates  were  also  found  in  the  dead 
cells  underlying  the  holdfasts  of  soybeans  and  peppers,  but  none 
occurred  in  healthy  cells  of  the  same  hosts.     Moreover,  the  tox- 


238  HOST  PENETRATION 

icitv  of  filtrates  from  cultures  in  which  5.  rolfsii  had  been  grown 
became  greater  with  increase  in  oxalic  acid  content.  For  these 
reasons  Higgins  stated  that  the  evidence  appears  conclusive  in 
showing  that  oxalic  acid,  secreted  by  fungus  hvphae,  causes  death 
of  cells  in  advance  of  actual  penetration. 

Other  pertinent  evidence  was  presented  by  Brown  (1915)  from 
his  experiments  with  extracts  from  germ  tubes  of  Botrytis  cinerea. 
These  extracts  are  highly  active  in  decomposing  parenchymatous 
tissues  of  manv  kinds  of  vegetables  and  fruits.  Heating  to  60°  to 
70°  C  inactivated  this  extract,  and  he  was  unable  to  separate 
enzyme  from  toxic  principle.  Drops  of  extract,  when  placed  on 
delicate  rose  petals,  were  quite  innocuous,  provided  that  the  cu- 
ticle was  intact.  Brown  found  no  oxalic  acid  in  the  extract  and 
was  forced  to  conclude  as  follows:  (a)  that  the  only  active  con- 
stituent of  the  extract  was  pectinase,  and  (b)  that  he  had  failed 
to  extract  a  toxic  principle,  leaving  unfounded  the  killing  in  ad- 
vance of  penetration  described  by  de  Bary. 

In  early  stages  of  invasion  bv  Diplocarpon  rosae,  browning  of 
the  host  cells  has  been  observed  [Aronescu  (1934)1,  but  the  im- 
mediate cause  has  not  been  determined. 

When  Blackman  and  Welsford  (1916)  and  Boyle  (1921)  made 
cytoloeical  examination  of  tissues  attacked  bv  Botrytis  cinerea 
and  by  Sclerotinia  libertiana,  thev  noted  that  the  staining  reactions 
of  the  host  cell  beneath  the  germ  tube  were  early  modified  and 
that  a  very  slender  "infection  hvpha"  always  penetrated  the  cells 
in  advance  of  killing-.  Once  this  had  been  established,  Brown 
(1922)  determined  bv  conductivity  tests  that  rapid  exosmosis  of 
solutes  from  the  tissues  does  not  occur  unless  the  infection  hvphae 
have  penetrated,  and  thus  he  was  able  to  establish  with  some  de- 
gree of  finality  how  facultative  parasites  are  able  to  attack  host 
cells. 

The  role  of  appressoria.  Certain  pathogenic  fungi,  notably  of 
the  genera  Colletotrichum,  Gloeosporium,  and  Marssonia,  form  pe- 
culiar structures  called  appressoria,  which  function  in  penetration 
of  the  suscept.  Frank  (1883)  first  recognized  the  true  nature  of 
appressoria  in  connection  with  observations  on  Fusicladium  trevi- 
ulae,  Poly  stigma  nibrnm,  and  Colletotrichum  lindeinuthiamnn. 
He  interpreted  them  to  be  adhesion  disks  which  applied  them- 
selves closely  to  the  surface  to  be  penetrated  and  there  served  to 
anchor  the  pathogen  while  the  membranes  immediately  beneath 


DIRECT  PENETRATION  239 

were  being  pierced  by  the  infection  hypha.  Biisgen  (1893)  veri- 
fied Frank's  observations  and  concluded  that  appressorium  forma- 
tion results  in  response  to  contact  of  germ  tubes  or  hvphac  with 
a  solid  body.  In  hanging  drops  or  in  drops  of  liquid  on  glass 
slides,  appressoria  generally  form  as  soon  as  the  tube  emerges. 

Hasselbring  (1906)  noted  the  existence  of  appressoria  12  to  18 
hours  after  inoculation  in  Gloeosporhim  fructigenum,  Allen 
(1923)  on  the  day  after  inoculation  with  wheat  rust,  and  Aro- 
nescu  (1934)  as  early  as  the  ninth  hour  after  inoculation  with 
Diplocarpon  rosae.  Appressoria  become  separated  from  the  tube 
by  a  septum,  their  wall  thickens,  and  eventually  they  become  cir- 
cular in  outline,  being  flattened,  however,  on  the  side  in  contact 
with  the  solid  body.  These  characteristics  led  various  American 
workers  who  early  studied  the  organisms  causing  cotton  anthrac- 
nose,  apple  bitter-rot,  ripe-rot  of  grapes,  and  pepper  anthracnose 
to  regard  appressoria  as  secondary  spores.  Attention  was  directed 
to  this  error  and  to  their  true  function  among  anthracnose-pro- 
ducing  species  by  Hasselbring  (1906).  He  also  observed  that 
lack  of  food  is  a  factor  in  their  formation,  since  they  may  not 
develop  in  the  presence  of  a  supply  of  nutrients.  Similar  studies 
involving  appressoria  of  Collet otrichum  lindemathiamim  and  C. 
gloeosporioides  were  made  by  Dey  (1919,  1933).  His  evidence 
indicated  that  appressoria  can  withstand  drying  and  that  they  give 
rise  to  the  penetration  tube  only  when  nutrients  are  available. 
It  is  indicated  that  substances  diffuse  out  through  the  cuticle  to 
stimulate  germination. 

In  1886  de  Bary  described  organs  of  attachment  that  facilitated 
penetration  among  species  of  Sclerotinia.  Details  of  the  penetra- 
tion by  5.  libertiana  were  presented  by  Boyle  (1921).  When  this 
fungus  was  placed  on  bean  leaves,  appressoria  formed  near  the 
hypha  tips.  Thev  became  fixed  to  the  leaf  surface  by  means  of  a 
mucilaginous  sheath.  From  beneath  the  appressoria  a  very  slender 
"infection  hypha"  then  developed,  which  indented  the  cuticle  at 
the  point  of  contact.  There  was  no  evidence  of  dissolution  of 
the  cuticle,  but  eventually  the  infection  hypha  penetrated  this 
membrane  by  mechanical  pressure. 

Diplocarpon  rosae  pierces  rose  cuticle  wholly  by  mechanical 
pressure,  but  the  enlargement  of  the  infection  peg  into  an  infec- 
tion hyphae  is  interpreted  by  Aronescu  (1934)  to  indicate  that 
further  penetration  occurs  in  a  different  manner. 


240  HOST  PENETRATION 

Penetration  by  infection  hvphae  of  the  same  type  is  known 
among  other  pathogenic  fungi.  Blackman  and  Welsford  (1916) 
noted  that  Botrytis  cinerea  pierces  the  cuticle  of  Vic'ia  faba  by 
mechanical  pressure  exerted  on  a  narrow  outgrowth  from  the 
germ  tube.  Waterhouse  (1921)  recorded  the  occurrence  of  a 
mucilaginous  envelope  on  the  germ  tubes  of  sporidia  of  Puccinia 
graminis  germinating  on  leaves  of  Berberis  vulgaris.  The  muci- 
laginous matrix  fixed  the  sporidium  and  germ  tube  to  the  leaf. 
Penetration  of  the  cuticle  was  accomplished  by  mechanical  pres- 
sure exerted  upon  a  beak-like  outgrowth  from  beneath  the  spo- 
ridium or  upon  a  very  tenuous  style-like  hypha  beneath  the  germ 
tube.  After  penetration  the  tip  of  the  infection  tube  swells  into 
a  vesicle,  and  from  it  the  mycelium  forms. 

Penetration  by  boring  through  the  host-cell  membranes  has 
been  observed  and  described  in  several  Phycomycetous  species. 
Curtis  (1921)  noted  entrance  of  zoospores  that  had  come  to  rest 
and  of  young  zygotes  of  Synchytrhnn  endobiotiaim  into  potato 
tissues.  A  small  protuberance  develops  on  the  side  in  contact 
with  the  host,  which  eventually  perforates  the  wall.  The  tip  of 
the  tube  then  enlarges  into  a  vesicle  within  the  lumen  of  the  host 
cell,  into  which  the  entire  protoplast  flows,  leaving  the  empty 
wall  of  the  resting  cell  or  of  the  zygote  outside  the  host.  Similarly 
Tisdale  (1919)  noted  migration  of  the  content  of  erstwhile  zoo- 
spores of  Phy  so  derma  zeae-may  dis  through  narrow  bore  tubes 
into  the  epidermal  cells  of  corn.  Among  certain  higher  Phy- 
comycetes,  such  as  Peronospora  tabacina,  entrance  may  be  effected 
with  apparently  equal  facility  either  by  direct  penetration  or  by 
entrance  through  stomata. 

Among  hyperparasites  the  hvphae  of  the  one  species  may  pene- 
trate the  walls  of  a  second  and  grow  within  them,  and  others 
merely  entwine  themselves  closely  around  the  host  species.  An 
unusual  type  of  hyperparasite  and  of  direct  penetration  is  pre- 
sented in  Parasitella  (M/tcor)  parasiticus  and  in  Chaetocladium, 
both  of  which  are  parasitic  upon  other  Alucoraceae.  Burgeff 
( 1924)  described  this  relationship,  pointing  out  that  the  sequence 
of  events  is  as  follows:  The  hypha  tip  of  the  parasitic  species, 
after  contact  with  the  host  hypha,  cuts  off  a  buffer  cell.  The 
wall  between  this  buffer  cell  and  the  host  is  then  dissolved,  effect- 
ing a  direct  connection  between  them.  The  buffer  cell  then 
enlarges,  and  hypha  branches  are  developed  from  it.    Meanwhile 


DIRECT  PENETRATION 


241 


host  and  parasite  nuclei  and  protoplasm  freely  intermingle  with 
each  other. 

The  stimulus  causing  penetration.  The  observations  of 
Pfeffer  that  chemotropic  stimuli  are  responsible  for  the  migra- 
tion of  antherozoids  of  mosses  and  ferns  to  the  archegones  fur- 
nished the  stimulus  for  similar  studies  involving  the  proximate 
cause  of  penetration  by  fungi.  Miyoshi,  working  under  PfefTer's 
direction,  published  two  reports  (1894,  1895),  in  which  he  con- 


Fig.  42.  Stages  in  penetration  by  the  hyperparasite  Parasitella  (Mucor)  para- 
siticus into  the  hypha  of  Mucor.  The  buffer  cell  is  cut  off  in  B.  In  C  the 
wall  between  buffer  cell  and  host  has  been  dissolved,  permitting  direct 
protoolasmic  contact.    In  D  branches  are  developing  from  the  buffer  cell. 

(After  Burgeff.) 

eludes  that  membranes  are  penetrated  by  germ  tubes  or  hyphae 
only  when  a  certain  concentration  of  an  attractive  substance 
(chemical  attractant)  is  present  on  the  opposite  side.  According 
to  this  theory,  concentration  of  the  chemical  must  exceed  a  spe- 
cific threshold  value  if  it  is  to  attract;  but,  if  a  certain  maximum 
concentration  is  employed,  the  result  is  repellant  action.  He 
dealt  with  penetration  of  collodion  films,  parchment,  gold  leaf, 
cellulose  films,  and  the  epidermis  of  onion  scales.  The  spores  of 
the  various  species  used  were  placed  in  films  of  agar  that  were 
separated  from  the  chemical  to  be  tested  by  perforated  sheets  of 
mica.  He  also  injected  with  water  leaves  of  Begonia  and  Trades- 
cantia  to  which  spores  were  applied,  but  no  penetration  resulted, 
whereas  active  penetration  followed  injection  with  cane  sugar. 
Admittedly  his  conclusion  that  chemotropic  factors  are  funda- 
mental in  determining  whether  germ  tubes  oenetrate  is  supported 
by  quite  convincing  evidence. 


242  HOST  PEXETRATION 

A  different  point  of  view,  however,  results  from  the  experi- 
ments of  Fulton  (1906).  He  followed  the  same  techniques  as 
Mivoshi,  using  among  others  the  following  fungi:  Botrytis  vul- 
garis,  Penicillium  glaucum,  Sterigmatocystis  nigra,  Mucor  vm- 
cedo,  Monilia  sitophila,  M.  fructigena,  and  Sphaeropsis  malorwn. 
Fulton  postulated  a  negative  chemotropism,  resulting  from  meta- 
bolic staling  products  produced  by  the  fungus  itself.  The  germ 
tubes  showed  quite  as  much  turning  toward  pure  water  and  non- 
nutrient  solutions  as  toward  substances  that  were  presumed  to 
act  as  attractants. 

Graves  (1916)  reinvestigated  the  problem  of  chemotropism, 
usin^  reactions  of  germinating  spores  of  Rhizopns  nigricans  and 
Botrytis  cinerea.  Me  too  employed  the  perforated  mica-plate 
technique.  His  evidence  inclined  him  toward  the  negative- 
chemotropism  hvpothesis  of  Fulton  for  these  reasons:  (a)  the 
germ  tubes  and  hvphae  turn  away  from  the  layer  on  the  opposite 
side  of  the  mica  plate  if  it  is  already  well  occupied  by  hyphae 
or  already  contains  their  own  staling  products;  (b)  the  germ  tubes 
and  hyphae  turn  toward  the  layer  on  the  opposite  side  of  the  mica 
plate  if  it  is  free  of  hvphae  and  staling  products,  unless  it  con- 
tains some  other  substance  capable  of  evoking  a  negative  chemo- 
tropic  reaction;  (c)  the  germ  tubes  and  hyphae,  when  present  in 
equal  amounts  on  both  sides  of  the  mica  plate,  exhibit  no  turning 
from  one  side  to  the  other.  Nevertheless,  Graves  found  justifica- 
tion also  for  the  views  of  Miyoshi.  In  his  general  conclusion  he 
took  the  position  that  positive  chemotropism  is  to  be  regarded 
as  one  of  the  factors  that  govern  penetration,  but  that  negative 
chemotropism  is  the  major  factor. 

It  becomes  of  interest  to  follow  the  implications  that  logically 
follow  the  acceptance  of  these  conclusions.  Susceptibility  could 
be  attributed  to  the  possession  by  the  host  tissues  of  substances 
that  attract  and,  conversely,  resistance  to  substances  that  repel. 
A  specialized  pathogen,  then,  is  one  which  would  react  to  one 
particular  substance  onlv,  whereas  a  generalized  pathogen  would 
react  to  a  variety  of  substances.  That  such  is  not  the  situation  is 
shown  by  the  work  of  Johnson  (1932)  in  his  studies  with  Col- 
letotrichum  circinans.  He  found  that  this  organism  is  capable  of 
penetrating  such  widely  unrelated  species  as  buckwheat,  bean, 
cotton,  tomato,  cucumber,  tobacco,  cabbage,  castor  bean,  and 
morning  glory.    It  was  unable  to  produce  lesions,  to  be  sure,  but 


DIRECT  PENETRATION  243 

the  organism  could  be  isolated  from  the  interior  of  these  host 
species  several  days  after  inoculation.  Similarly  Young  (1926), 
using  Diplodia  zeaey  Cephalosporin?;?  acremormum,  Colletotrich- 
ium  nigrum,  Hefomnthosporium  gra???i??eu???,  and  other  fungi,  was 
able  to  produce  lesions  or  callosities  on  many  kinds  of  plants  not 
normally  infected  by  these  fungi.  Since  the  spores  of  a  multitude 
of  different  fungi  must  find  lodgment  at  the  surface  of  every 
green  plant,  it  is  reasonable  to  expect  that  their  hyphae  may  gain 
entrance  yet  be  unable  to  establish  a  pathogenic  relationship. 
That  this  occurs  is,  moreover,  attested  by  the  experiences  of 
everyone  who  has  attempted  to  isolate  fungi  by  using  bits  of  host 
tissues  as  inocula.  It  is  not  surprising,  therefore,  to  find  many  ad- 
herents to  the  viewpoint  voiced  by  Brown  (1934)  that  neither 
positive  chemotropism  nor  negative  chemotropism  plays  any  sig- 
nificant role  in  penetration. 

Further  examination  of  the  perforated  mica-plate  method  as 
a  working  model  to  represent  host  tissue  with  its  natural  openings 
appears  pertinent.  Without  the  arguments  being  followed  out, 
this  analogy  would  appear  to  be  in  the  same  category  as  the  sub- 
stitution of  glass  slides  sprayed  with  fungicides  for  the  surface  of 
leaves  and  fruits  in  tests  to  determine  the  value  of  fungicides. 
Studies  on  the  toxicity  of  Bordeaux  by  Yarwood  (1943)  show 
that  it  is  more  active  on  bean  leaves  against  the  urediniospores  of 
Uromyces  phase oli  than  it  is  on  glass  slides.  These  results  serve 
to  bring  into  sharp  perspective  the  differences  between  in  vitro 
and  i?i  vivo  tests  for  the  toxicity  of  fungicides. 

Brown  and  Harvey  (1927)  got  ready  penetration  by  germ  tubes 
of  Botrytis  cinerea  of  epidermis  from  onion  scales  and  of  Eucharis 
leaves,  either  inward  or  outward,  if  the  membranes  were  washed 
to  remove  diffusible  substances.  Similar  results  followed  the  sub- 
stitution of  membranes  made  of  paraffin.  These  results  and  a 
mass  of  similar  ones  by  other  workers  show  that  penetration  may 
be  independent  of  any  chemotropic  stimulus. 

Failure  to  establish  response  to  chemotropic  stimuli  as  a  satis- 
factory explanation  for  penetration  has  focussed  attention  on  the 
role  of  the  stimulus  of  contact,  haptotropism.  It  may  be  recalled 
that  certain  species  of  Botrytis,  Sclerotinia,  Colletotrichum,  Gloeo- 
sporium,  and  Marssonia  show  their  reaction  to  contact  by  form- 
ing attachment  organs.  The  best  evidence  in  favor  of  hapto- 
tropism as  a  factor  in  penetration  comes  from  experiments  with 


244 


HOST  PENETRATION 


species  that  produce  appressoria  or  other  means  of  attachment 
that  function  in  the  same  manner  as  appressoria.  Here  again  evi- 
dence and  opinion  are  divided,  since  some  workers  maintain  that 
the  penetration  tube  enters  only  in  conjunction  with  the  dissolu- 
tion of  the  cuticle  to  prepare  the  way,  and  others  that  the  cuticle 
is  pierced  by  a  mechanical  thrust.    Brown  (1915)  made  extracts 


Fig.  43.  Haustorial  tvpes.  A.  Branched  haustorium  of  Peronospora  calo- 
thecae.  (After  de  Barv.)  B.  Haustoria  of  Puccinia  adoxae.  A  sheath  partly 
invests  the  haustorium.  (After  Guttenberg.)  C.  A  bulbous  haustorium  of 
Erysiphe  communis.     (After  Smith.)     D.  Digitate,  sheathed  haustorium  of 

Erysiphe  graminis.     (After  Smith.) 

of  Botrytis  cinerea,  as  has  been  stated,  which  were  capable  of  di- 
gesting tissues  very  rapidly  when  injected  into  them,  but  which, 
if  placed  at  the  surface  of  delicate  rose  petals,  caused  no  injury 
within  a  period  of  approximately  24  hours.  His  lack  of  evidence 
of  solvent  effect  to  aid  penetration  is  substantiated  by  the  results 
of  Boyle  ( 1921 ),  Waterhouse  (1921),  Dey  (1919,  1933)  and  many 
others.  Instead  they  adhere  to  the  mechanical  theory  of  penetra- 
tion. In  the  experiments  of  Brown  and  Harvey  (1927)  cells  of 
Eucharis  and  other  plants  were  readily  penetrated  if  they  had 
previously  been  plasmolyzed,  but  no  penetration  took  place  if  the 
cells  were  turgid.  It  becomes  difficult  to  understand  how  rigid- 
ity  of  the  host  cells  could  inhibit  the  production  of  wall-dissolving 
enzymes. 


DIRECT  PENETRATION  245 

The  work  of  Link  and  his  associates  (1929)  involving  the  in- 
hibitory activity  of  specific  chemicals  is  of  special  interest.  They 
noted  that  white  onions  are  subject  to  attack  by  Collet otrichum 
(Vermicalaria)  circinans,  which  causes  the  disease  known  as 
smudge,  and  that  pigmented  onions  are  disease-free.  From  these 
onions  they  isolated  protocatechuic  acid,  which  was  found  to 
inhibit  the  growth  of  the  pathogen.  This  organic  complex,  fur- 
thermore, does  not  occur  in  white-scaled  onions.  Inhibition  of 
penetration  by  the  smudge  fungus  and  disease  resistance,  there- 
fore, are  caused  by  protocatechuic  acid.  Presumably  this  is  the 
first  chemical  substance  isolated  that  has  been  demonstrated  to 
render  plants  immune  from  infection. 

In  connection  with  mechanical  penetration  it  mav  be  recalled 
that  a  mucilaginous  matrix  aids  in  sticking  the  spore,  appressorium. 
or  germ  tube  to  the  cuticle,  thus  providing  anchorage  against 
the  force  of  the  thrust  required  to  pierce  the  cuticle.  The  small 
diameter  of  the  infection  hypha  minimizes  this  required  force, 
which  attempts  have  been  made  to  measure  by  mechanical  de- 
vices. Hawkins  and  Harvey  (1919)  studied  penetration  of  potato 
by  the  rot-producing  fungus,  Fythium  de  baryamnn.  They  em- 
ployed a  modified  Joly  balance  with  a  needle  having  a  point  of 
definite  area  to  test  resistance  of  potato  tissues  to  puncture.  Po- 
tatoes of  the  McCormick  variety,  resistant  to  attack  by  this 
organism,  were  found  to  require  more  pressure  to  puncture  than 
was  required  for  Bliss  Triumph  or  Green  Mountain,  varieties  sus- 
ceptible to  decay.  Rosenbaum  and  Sando  (1920),  using  the  same 
appliance,  correlated  resistance  of  tomatoes  to  puncture  with  re- 
sistance to  penetration  by  Meter ospor'mm  tomato.  Certain  of  their 
data  are  presented  in  Table  23.  These  data  show  that,  as  tomato 
fruits  increase  in  age,  they  also  increase  in  ability  to  inhibit  pene- 
tration and  consequent  infection  bv  this  fungus.  Thickness  of 
the  cuticular  layer  also  increases  with  the  age  of  the  tomato  fruit, 
but,  as  Rosenbaum  and  Sando  point  out,  these  results  do  not  prove 
that  inhibition  of  penetration  is  purely  a  matter  of  resistance  to 
mechanical  pressure. 

Epidermal  resistance  of  barberry  to  puncture  was  measured 
with  a  mechanical  device  by  Melander  and  Craigie  (1927),  and 
they  correlated  their  measurements  with  resistance  to  penetration 
by  germinating  basidiospores  of  Puccinia  grcmrinis.     They  con- 


246 


HOST  PENETRATION 


TABLE  23 

Relation  of  Resistance  of  Tomato  Fruits  to  Puncture  and  to  Penetration 

by  Macros  porium  tomato 


Diameter 

Average  Pressure 

Infection 

e  of  Fruit 

of  Fruit 

Xccessary  to 

of  Fruit 

{days) 

{centimeters) 

Puncture  {grams) 

{percentage) 

7 

0.70 

0.97 

100 

14 

2.30 

2.99 

100 

21 

5.18 

4.21 

85 

28 

5.40 

4.90 

49 

35 

5.46 

5.08 

23.3 

41 

6.55 

5.96 

0 

48 

6.92 

6.74 

0 

55 

5.56 

0 

eluded  that  species  of  Berberis  which  are  resistant  to  puncture  are 
usually  resistant  to  rust,  but  the  converse  is  not  usually  true. 

Pioneer  work  on  the  correlation  of  structure  of  plant  tissues  and 
inhibition  of  penetration  by  fungi  into  plant  tissues  was  instituted 
by  Yalleau  (1915).  Thickness  of  the  skin  of  plums  was  found 
correlated  with  resistance  to  the  brown-rot  fundus.  Yalleau  also 
found  that  the  cells  lining  substomatal  cavities  possessed  corky 
walls  and  that  the  stomata  were  very  commonly  completely 
occluded  with  corky  cells.  By  and  laroe,  Curtis  (1928)  verified 
Valleau's  findings  but  believed  that  cuticular  resistance  to  pene- 
tration by  the  brown-rot  pathogen  was  equally  as  important  as 
the  presence  of  corky  tissue  in  natural  openings,  if  not  more  im- 
portant. It  might  be  expected  that  varieties  of  stone  fruits  lack- 
ing stomata  or  lenticels  would  be  immune.  Curtis  did  not  find 
this  to  be  true,  however,  since  in  the  varieties  which  he  investi- 
gated the  germ  tubes  entered  through  the  stomata  in  plums, 
through  the  cuticle  in  cherries,  and  down  the  hair  sockets  in 
peaches,  and  penetrated  cither  through  the  cuticle  or  the  stomata 
in  apricots. 

In  varieties  of  tobacco  resistant  to  invasion  by  the  black  root-rot 
fungus,  Thielaviopsis  basicola,  Conant  (1927)  found  that  resist- 
ance to  infection  is  correlated  with  the  ability  of  the  host  rapidly 
to  develop  a  corky  layer  to  inhibit  the  spread  of  the  pathogen. 

The  short  period  of  time  required  for  penetration  of  the  cell 
wall  by  Pythiitui  de  baryamtm  [Hawkins  and  Harvev  (1919)] 
also  constitutes  evidence  of  mechanical  puncture.    They  observed 


DIRECT  PENETRATION 


241 


penetration  to  be  accomplished  within  approximately  5  minutes. 
They  also  found  the  hvphae  to  possess  an  osmotic  pressure  suffi- 
cient to  penetrate  turgid  potato  cells.  Few  measurements  of 
osmotic  pressure  in  fungi  have  been  made;  thev  might  be  found 
valuable  in  an  interpretation  of  factors  concerned  in  penetration. 
Studies  of  this  type  were  conducted  bv  Thatcher  (1939,  1942). 
He  used  the  plasmolvtic  method  in  osmotic  pressure  and  permea- 
bility determinations  and  was  able  to  show  that  certain  parasitic 
funs^i  increase  the  permeability  of  the  plasma  membrane  of  the 
host  cells.  His  measurements  of  the  osmotic  pressure  of  parasite 
and  host  are  shown  in  Table  24.     In  each  fungus  the  osmotic 


TABLE  24 

rs   of   Measurements 

of   Osmotic   P 

ressure   in   Parasite   and   H 

Average 

Average 

Osmotic 

Osmotic 

Pressure 

Pressure 

Parasite 

{atmospheres) 

Host 

{atmospheres') 

Uromyces  jabae 

Pis  urn  sativum 

germ  tubes 

44.25 

leaf 

9.15 

haustoria 

21.90 

petiole 

10.10 

Uromyces  caryophyllinus 

Dianthus 

haustoria 

18.6 

leaf  base 

11.2 

Puccinia  graminis 

Mindum  wheat 

haustoria 

18.9 

leaf 

9.4 

Erysiphe  polygoni 

Brassica 

hvphae 

18.0 

leaf 

10.6 

Botrytis  cinerea 

Apium  graveolens 

hvphae 

29.8 

petiole 

8.3 

Sclerotinia  sclerotiorum 

Apium  graveolens 

hvphae 

23.5 

petiole 

13.4 

Phoma  lingam 

Brassica 

hvphae 

41.3 

root 

11.3 

pressure  of  the  parasite  is  greater  than  that  of  its  host.  Moreover, 
Thatcher  was  able  to  demonstrate  an  increased  permeability  in 
diseased  tissues  over  healthy  tissues,  indicating  that  the  parasite 
causes  certain  substances  to  leach  from  the  host  cells  and  thus  to 
lower  their  osmotic  pressure. 

Although  these  data  as  a  whole  have  a  bearing  on  the  problem 
of  penetration  and  might  be  taken  to  prove  that  penetration  is 
the  result  of  mechanical  pressure  in  certain  species  of  fungi,  it 
does  not  necessarily  follow  that  all  species  which  effect  their  own 


248  HOST  PEXETRATIOX 

entrance  do  so  by  the  same  means.  Aronescu  ( 1934)  concluded 
that  both  chemical  action  and  mechanical  pressure  are  necessary 
for  penetration  bv  the  fungus  causing  black  spot  of  roses.  There 
may  exist  only  the  two  general  means  of  penetration  that  have 
been  discussed,  but  perhaps  each  pathogen  has  made  such  modifi- 
cations and  adaptations  as  are  suited  to  its  own  requirements. 

STOMATAL  PEXETRATIOX 

Stomata  constitute  normal  portals  for  entrance  by  a  large  num- 
ber of  pathogenic  species.  Observations  on  penetration  through 
stomata  have  been  recorded  for  many  different  fungi.  Such  ob- 
servations may  be  made  by  one  of  three  methods:  (a)  epidermal 
stripping,  (b)  sections  of  fixed,  embedded  material,  and  (c)  use 
of  a  stomatoscope.  Certain  advantages  and  disadvantages  attend 
the  use  of  each. 

If  spores  are  sown  in  drops  of  water  on  leaves  and  chalk  is  added 
to  indicate  the  site  of  the  drops,  it  is  not  difficult  to  strip  off  epi- 
dermis in  the  areas  marked  by  deposits  of  chalk,  mount  it  in  water 
with  the  exterior  surface  upward,  and  examine  it  under  the  micro- 
scope. With  a  little  practice  the  investigator  can  learn  to  tear  the 
leaf  and  thus  strip  off  the  epidermis,  or  to  cut  it  off  by  holding 
the  leaf  taut  over  the  end  of  the  finger  and  slicing  parallel  to  the 
leaf  surface.  Bv  this  method  many  examinations  can  be  made  in  a 
comparatively  short  time,  and  the  time  interval  involved  in  pene- 
tration can  thus  be  determined.  Mounting  specimens  in  cotton 
blue  *  instead  of  water  may  aid  in  differentiating  the  hyphae  and 
in  clearing  the  host  tissues. 

The  merit  of  fixing,  at  known  intervals  after  inoculation,  tissues 
which  have  had  spores  applied  to  their  surfaces  has  the  feature  of 
permanency  to  recommend  its  use.  These  tissues  may  be  em- 
bedded, sectioned,  stained,  and  examined  whenever  time  is  avail- 
able and  may  be  kept  indefinitely.  This  method,  however,  is 
obviously  both  laborious  and  time-consuming. 

Direct  examination  with  an  apparatus  known  as  the  stomato- 
scope requires  familiarity  with  the  operation  of  an  apparatus  that 
has  been  available  to  only  a  few  investigators.  Pool  and  McKay 
(1916)  used  such  an  appliance  in  their  studies  of  penetration  of 

'Use  0.1%  cotton  blue  in  lactophcnol,  which  contains  equal  parts  of 
phenol,  lactic  acid,  glycerin,  and  distilled  water. 


STOMATAL  PENETRATION 


249 


Fig.  44.  Types  of  appressoria.  A.  Appressorium  of  urediniospore  at  stomatal 
aperture.  B,  C,  and  D.  Appressoria  formed  by  one  of  the  anthracnoses,  as 
an  early  stage  in  germination.  B.  In  culture  a  hypha  arises  from  the  appres- 
sorium. C.  In  the  host  the  appressorium  anchors  the  organism,  and  the 
slender  penetration  tube  arises  from  beneath  the  appressorium.  E  and  F. 
Appressoria  formed  by  Diplocarpon  rosae.     (After  Aronescu.) 


250  HOST  PENETRATION 

sugar-beet  leaves  by  germ  tubes  of  Cercospora  beticola.  They 
observed  that  this  organism  is  unable  to  penetrate  at  night  when 
stomata  are  closed  but  can  do  so  during  daytime  when  the  open- 
ing of  the  stomata  permits  the  entrance  of  germ  tubes  into  sub- 
stomatal  cavities.  No  doubt  many  fungi  among  those  that  pene- 
trate through  natural  openings  are  able  to  do  so  only  during  day- 
light hours.  This  factor  must  be  borne  in  mind  in  tests  involving 
the  pathogenicity  of  a  given  fungus. 

The  germ  tubes  of  aeciospores  and  urediniospores  of  rusts  very 
commonly  enter  through  stomata,  although  the  germ  tubes  of  the 
basidiospores  of  these  same  species  may  penetrate  directly.  Pady 
( 1935)  noted  that  germinating  aeciospores  of  Gymnoconia  inter- 
stitialis  enter  blackberry  leaves  not  through  the  stomata  but  by 
direct  penetration.  The  urediniospores  of  many  species  are 
known  to  produce  a  special  appressorium,  which  functions  in  the 
mechanism  of  entrance.  The  sequence  of  events  in  penetration 
is  as  follows:  When  the  tip  of  the  germ  tube  comes  to  lie  imme- 
diately above  a  stoma,  the  protoplasm  accumulates  in  the  tip. 
This  apical  region  then  swells,  and  the  end  cell  is  delimited  by  a 
cross-septum  to  become  the  appressorium.  By  nuclear  division 
two  or  more  pairs  of  nuclei  form  within  the  appressorium.  Then 
a  hypha  develops  from  the  lower  side  of  the  appressorium  and 
forces  its  way  between  the  guard  cells  into  the  substomatal  cavity; 
once  inside,  its  tip  swells  to  form  a  vesicle  into  which  the  proto- 
plast of  the  appressorium  migrates.  Meanwhile  more  conjugate 
nuclear  divisions  occur,  and  hvphae,  whose  cells  contain  paired 
nuclei,  grow  radiately  from  this  substomatal  vesicle.  These  hy- 
phae  course  between  the  host  cells  and  establish  intimate  contact 
with  them  by  forming  haustoria. 

Opinions  differ  as  to  whether  the  appressoria  of  rusts  adhere 
by  means  of  a  mucilaginous  matrix.  Rice  (1927)  saw  no  evidence 
of  such  a  matrix  in  Fuccinia  sorghi. 

Study  of  penetration  by  Fuccinia  graminis  tritici  into  resistant 
Khapli  emmer  by  Allen  (1926)  indicates  that  the  appressoria  se- 
crete a  toxin  upon  the  guard  cells.  This  observation  led  her  to 
opine  that  ".  .  .  the  appressorial  secretion  is  a  survival  from  an 
earlier  period  in  the  evolution  of  the  fungus  when  it  did  dissolve 
its  way  into  the  host." 

The  time  required  for  penetration  is  correlated  with  tempera- 
ture, as  has  been  capably  shown  by  Peltier  in  studies  with  Fuccinia 


PENETRATION  THROUGH  WOUNDS  251 

graminis  tritici.  When  he  inoculated  7-dav-old  wheat  seedlings 
with  urediniospores  within  the  range  optimum  for  germination, 
he  found  that  maximum  infection  required  at  least  36  hours  |  Pel- 
tier (1925)].  This  period  was  determined  by  use  of  a  series  of 
plants  inoculated  at  the  same  time  by  a  suspension  of  uredinio- 
spores. After  definite  intervals  the  surfaces  of  some  of  the  plants 
were  permitted  to  become  dry.  An  arbitrary  scale  to  show 
severity  of  infection  was  then  employed  as  a  basis  of  comparison. 
Leaves  on  which  5  or  fewer  rust  pustules  developed  were  regarded 
as  in  class  1;  those  with  6  to  10,  in  class  2;  and  those  with  1 1  to  25, 
in  class  3.    Certain  of  Peltier's  data  are  shown  in  Table  25.    Ap- 

TABLE  25 

Time  Required  for  Infection  by  Puccina  graminis  tritici 

Definite  Intervals  Plants  Severity  of 

after  Which  Leaves  Infected  Infection 

Dried  {hours)  {percentage)  {class) 

2  0  0 

3  1.7  1 
6                                17.0  1 

12  28.0  1 

16  33.0  1 

20  59.0  1 

24  89.0  2 

30  98.0  2 

36  100.0  3 

parentlv  the   minimum  time   required   by  the   wheat  stem-rust 

fungus  for  actual  entrance  through  the  stomatal  aoerture  is  he- 
ir ^ 

tween  2  and  3  hours. 

PENETRATION  THROUGH  WOUNDS 

There  is  a  large  group  of  facultative  parasites  that  lack  ability 
to  produce  disease  or  decay  in^  intact  tissues  but  can  establish 
themselves  in  wounds  and  thence  spread  to  normal  tissues.  The 
heartwood  and  sapwood  rots  of  trees  are  notable  in  this  respect. 
Many  of  these  fungi  gain  entrance  through  branch  stubs  or  scars 
left  in  pruning,  through  fire  scars,  through  abrasions  from  contact 
of  limbs,  or  through  injuries  by  other  fungi,  insects,  or  rodents. 

Little  is  known  about  the  fundamental  differences  between  these 
so-called  facultative  parasites  and  true  parasites  or  about  actual 


252  HOST  PENETRATION 

changes  in  aggressiveness  or  pathogenicity  which  they  may  un- 
dergo as  the'result  of  growth  on  wounded  tissues.  This  matter 
has'been  the  subject  of  experimentation  and  speculation  by  many 
students  of  fungi.  Salmon  ( 1905)  made  the  observation  that  races 
of  Erysiphe  graminis  occurring  on  various  genera  of  grasses  are 
morphologically  indistinguishable  yet  cannot  be  made  to  infect 
reciprocally  when  cross-inoculated  from  one  genus  to  another. 
If,  however,  he  wounded  the  leaf  by  cutting  away  a  small  piece  of 
tissue  or  by  applying  a  hot  needle  to  its  surface  and  then  placed 
the  spores  on  the  surface  opposite  the  wound,  ready  infection 

resulted. 

Many  have  concerned  themselves  with  what  may  be  a  closely 
related  problem  in  trving  to  account  for  the  inability  among  het- 
eroecious  rusts  of  basidiospores  to  infect  the  telial  host.  The  mere 
oeneralization  that  aggressiveness  is  enhanced  or  rejuvenated  by 
sexuality  does  not  appear  to  constitute  a  satisfactory  explanation. 

HAUSTORIA  AND  THEIR  SIGNIFICANCE 

Penetration  of  tissues  by  fungi  is  also  concerned  with  host- 
parasite  relations  after  the  pathogen  has  pierced  the  cuticle  or 
epidermis,  the  first  line  of  defence.  Some  species  remain  entirely 
intercellular;  others  are  intercellular  but  possess  intracellular  haus- 
toria;  and  in  others  the  mycelium  itself  courses  intracellularly  from 
cell  to  cell.  Our  immediate  interest  is  in  the  haustorium-forming 
species.  This  group  includes  such  obligate  parasites  as  the  downy 
mildews,  powderv  mildews,  rusts,  and  smuts  but  is  not  confined 
to  obligate  parasites,  since  haustoria  have  been  observed  in  Coc- 
ci >mvces,  Diplocarpon,  and  other  genera.  Among  the  rusts,  in- 
tracellular mycelium  has  been  observed  in  one  species  only, 
namely,  the  short-cycled  form  of  Gymnoconia  interstitialis.  In 
this  species,  which  is  systemic,  Pady  (1935)  described  peculiar 
intracellular  elements  which  functioned  to  establish  the  fungus 
in  the  host.  They  were  therefore  interpreted  as  being  haustoria! 
in  nature.  An  elaborate  account  by  Rice  (1927),  dealing  espe- 
cially  with  haustoria  of  rusts,  contains  much  of  value  regarding 
the  structure  and  function  of  haustoria  in  general. 

Haustoria  vary  in  form  among  the  different  species  of  fungi, 
bein^  spherical  in  the  simplest  forms  and  variously  branched  and 
tabulate  in  the  most  complex  ones.    Their  size  indicates  conform- 


PENETRATION  BY  ECTOPARASITES  253 

ity  to  that  necessary  to  maintain  a  delicate  nutritional  balance. 
Haustoria  mav  be  uninucleate,  may  contain  a  pair  of  nuclei,  or 
may  be  multinucleate.  They  possess  a  conspicuous  sheath  that  is 
deposited  by  and  is  continuous  with  the  host-cell  wall,  as  generally 
believed.  In  Diplocarpon  rosae  the  sheath  does  not  extend  com- 
pletely around  the  haustorium  [Aronescu  (1934)1,  as  has  been 
described  for  many  parasitic  fungi.  In  Erysiphaceae,  however, 
staining  reactions  indicate  that  haustorial  sheaths  are  chitinous. 
More  should  be  known  regarding  the  chemical  nature  of  the 
sheath  as  an  aid  in  understanding  how  the  sheath  modifies  absorp- 
tion and  passage  of  food. 

Haustoria  are  always  connected  with  the  intercellular  hyphae 
by  narrow  tubes  of  a  length  slightly  in  excess  of  the  thickness 
of  the  host-cell  membrane.  These  constrictions  facilitate  pene- 
tration. Presumably  both  mechanical  pressure  and  dissolution  of 
the  wall  are  involved  in  haustorial  penetration.  Allen  (1923) 
found  no  evidence  of  enzyme  secretion  in  connection  with  haus- 
torial penetration  by  Puccinia  graminla  tritici,  but  the  walls  be- 
neath the  appressoria  appeared  to  be  altered  during  initiation  of 
infection. 

PENETRATION  BY  ECTOPARASITES 

Several  distinct  types  of  host-parasite  relationships  occur  among 
fungi  possessing  mycelium  which  remains  wholly  external  to  the 
infected  plant  organs.  One  type  is  represented  by  the  powdery 
mildews,  all  of  which,  except  Fhyllactinia  cor y  lea  and  Leveillula 
(Erysiphe)  taurica,  are  ectophytic.  In  P.  cor y lea  both  internal 
and  external  mycelium  is  produced;  in  L.  taurica  the  mycelium  is 
wholly  internal,  an  adaptation  to  xerophytic  environment.  All 
parts  of  all  other  powdery  mildews,  except  the  haustoria,  are 
borne  externally. 

A  very  unusual  type  of  ectoparasitism  is  exhibited  by  Cerco- 
sporella  rubi,  the  cause  of  rosette  and  double  blossom  of  blackber- 
ries and  dewberries.  Plakidas  (1937)  found  that  the  mycelium 
of  this  fungus  occurs  in  buds  between  the  embryonic  leaves.  If 
the  buds  are  opened  at  any  time  during  summer,  fall,  winter,  or 
early  spring,  a  delicate  arachnoid  weft  will  be  observed  to  be  pres- 
ent between  the  young  leaves.  The  fungus  at  no  time  actually 
penetrates  the  young  branch  buds  and  flower  buds  but  absorbs 
its  nourishment  directly  through  the  thin  walls  of  the  embryonic 


254  HOST  PENETRATION 

cells.  Transfer  of  food  from  host  to  parasite  does  not  require,  in 
this  species,  the  production  of  specialized  organs  of  penetration. 

A  third  type  of  ectoparasitism  is  exhibited  by  the  Meliolaceae 
and  Capnodiaceae,  which  apply  themselves  to  the  surface  of  plant 
tissues  by  means  of  hyphopodia.  Graff  (1932)  found  that,  al- 
though some  species  of  Meliola  form  haustorial  vesicles  within  the 
epidermal  cells,  M.  civ  ductus  is  entirely  superficial.  Its  cell  walls 
are  in  intimate  contact  with  the  host  epidermis  and  are  thinner 
wherever  contact  is  maintained.  The  epidermal  cell  walls  are 
more  or  less  corroded  at  these  points  of  contact,  and  evidence  of 
defeneration  products  was  noted  within  them. 

Internal  mycelium  is  wanting  or  scanty  in  many  Microthy- 
riaceae  and  Hemisphaeriaceae.  Luttrell  (1940)  concluded  that 
Morejioclla  quercina,  one  of  the  Microthyriaceae,  absorbs  its  nu- 
trients through  the  intact  host  cuticle  at  first,  and  later  certain 
hyphae  penetrate  only  to  the  extent  of  becoming  subcuticular. 

IMPLICATIONS 

Problems  of  host  penetration  remain  of  utmost  importance  in 
spite  of  the  large  number  of  studies  that  have  been  devoted  to  this 
phenomenon  and  in  spite  of  the  conflict  among  observations  and 
the  interpretations  of  them.  They  should  continue  to  receive  un- 
stinted attention  because  of  their  bearing  on  matters  of  tolerance 
or  resistance  to  disease,  on  studies  involving  the  causes  of  natural 
immunity,  and  on  production  of  races  of  disease-resistant  crop 
plants. 

LITERATURE  CITED 

Vi.i.en,  Ruth  F.,  "A  cvtolomcal  study  of  infection  of  Baart  and  Kanrcd 
wheats  bv  Puccinia  graminis  tritici,"  J.  Agr.  Research,  23:  131-151,  1925. 
"Cvtological  studies  of  forms  IX,  XXI,  XXVII  of  Puccinia  grarmnis  tritici 
on  Khalpi  emmer,"  /.  Agr.  Research,  52:701-725,  1926. 

Arones<  u,  Ai  ice,  "Diplocarpon  rosae:  from  spore  germination  to  haustorium 
formation,"  Bull.  Torrey  Botan.  Club,  57:291-329,  1934. 

Barn.  A.  i>i  .  "(her  einige  Sclerotinicn  und  Sclerotienkrankheitcn,"  Botan. 
Z.,  44:  377-387,  393-404,  409-126,  433-441,  449-461,  465-474,  1886. 

Blackman,  V.  H.,  "Physiological  aspects  of  parasitism,"  Proc.  Brit.  Assoc. 
Bot.  Toronto,  23  3-246,  1924. 

Bi..\(  KMAN,  y.  H.,  and  I".  J.  Wl  lsford,  "Studies  in  the  physiology  of  para- 
sitism. II.  Infection  by  Botrytis  ciuerea"  Ann.  Botany,  50:389-398, 
1916. 


LITERATURE  CITED  255 

Boyle,  C,  "Studies  in  the  physiology  of  parisitism.    VI.  Infection  by  Sclero- 

tinia  libertiana"  Ann.  Botany,  35:117-147,  1921. 
Brown,  W.,  "Studies  on  the  physiology  of  parasitism.     I.  The  action  of 
Botrytis  cinerea"  Ann.  Botany,  22:313-348,  1915. 
VIII.  "On  the  exosmosis  of  nutrient  substances  from  the  host  tissue  into 

the  infection  drop,"  Ann.  Botany,  36:  285-300,  1922. 
"Mechanism   of   disease   resistance   in   plants,"   Trans.  Brit.  Mycol.  Soc, 

19:  11-33,  1934. 

"The  physiology  of  host-parasite  relation,"  Botan.  Rev.,  2:236-281,  1936. 

Brown,  W.,  and  C.  C.  Harvey,  "Studies  in  the  physiology  of  parasitism. 

X.  On  the  entrance  of  parasite  fungi  into  the  host  plant,"  Ann.  Botany, 

41:641-662,  1927. 

Burgeff,   H.,   "Untersuchungen  liber   Sexualitat  und   Parasitismus  bei   den 

Mucorineen,"  Botan.  Abhandl.  (Herausgeg.  von  Goebel),  4:  1-135,  1924. 

Busgen,  M.,  "Uber  einige  Eigenschaften  der  Keimlinge  parasitischer  Pilze," 

Botan.  Z.,  51:51-72,  1893. 
Conant,  G.  H.,  "Histological  studies  of  resistance  in  tobacco  to  Thielavia 

basicola,"  Am.  J.  Botany,  14:  457-480,  1927. 
Curtis,  K.  M.,  "The  life  history  and  cytology  of  Synchytrium  endobio- 
ticnm,"  Phil.  Trans.  Roy.  Soc.  London,  Ser.  B,  270:409-478,  1921. 
"The  morphological  aspect  of  resistance  to  brown  rot  in  stone   fruit," 
Ann.  Botany,  42: 39-68,  1928. 
Dey,  P.  K.,  "Studies  in  the  physiology  of  parasitism.    V.  Infection  by  Col- 
let otrichum  lindemiithianwn"  Ann.  Botany,  53:305-312,  1919. 
"Studies    in    the    physiology    of    the    appressorium    of    Collet  otrichum 
gloeosporioides"  Ann.  Botany,  47:305-312,  1933. 
Frank,  A.  B.,  "Uber  einige  neue  und  weniger  bekannte  Pflanzenkrankhei- 

ten,"  Ber.  dent,  botan.  Ges.,  7:29-34,  58-63,  1883. 
Fulton,  H.  R.,  "Chemotropism  of  fungi,"  Botan.  Gaz.,  47:81-108,  1906. 
Graff,  P.  W.,  "The  morphological  and  cytological  development  of  Meliola 

circinans,"  Bull.  Torrey  Botan.  Club,  59:  241-266,  1932. 
Graves,  A.  H.,  "Chemotropism  in  Rhizopus  nigricans"  Botan.  Gaz.,  62:  337— 

369,  1916. 
Hasselbring,  H.,  "The  appressoria  of  the  anthracnoses,"  Botan.  Gaz.,  42:  135- 

142,  1906. 
Hawkins,  L.  A.,  and  R.  B.  Harvey,  "Physiological  study  of  the  parasitism  of 
Yythium  de  Baryanum  Hesse  on  the  potato  tuber,"  /.  Agr.  Research, 
18:  275-297,  1919. 
Higgins,  B.  B.,  "Physiology  and  parasitism  of  Sclerotimn  rolfsii,"  Phyto- 
pathology, 77:417-448,  1927. 
Johnson,  Burt,  "Specificity  to  penetration  of  the  epidermis  of  a  plant  by 

the  hyphae  of  a  pathogenic  fungus,"  Am.  J.  Botany,  19:  12-31,  1932. 
Link,  K.  P.,  H.  R.  Angell,  and  J.  C.  Walker,  "The  isolation  of  proto- 
catechuic  acid  from  pigmented  onion  scales  and  its  significance  in  rela- 
tion to  disease  resistance  in  onion,"  /.  Biol.  Cheni.,  SI:  369-375,  1929. 
Luttrell,  E.  S.,  uMoroenoella  quercina,  cause  of  leaf  spot  of  oaks,"  Mycol., 
32:652-666,  1940. 


256  HOST  PENETRATION 

Melander,  L.  W.,  and  J.  H.  Craigie,  "Nature  of  resistance  of  Berberis  spp. 

to  Puccinia  graminis,"  Phytopathology,  77:95-114,  1927. 
Miyoshi,  M.,  "Uber  Chemotropismus  der  Pilze,"  Botan.  Z.,  52:  1-28,  1894. 
"Die  Durchbohrung  von  Membranen  durch  Pilzfaden,"  Jahrb.  iviss.  Botan., 
28:  269-289,  1895. 
Pady,  S.  M.,  "Aeciospore  infection  in  Gymnoconia  interstitialis  by  penetra- 
tion of  the  cuticle,"  Phytopathology,  25:453-474,  1935. 
"The  role  of  intracellular  mycelium  in  systemic  infections  of  Rubus  with 
the  orange  rust,"  Mycol.,  27:618-637,  1935a. 
Peltier,  G.  L.,  "A  consideration  of  the  physiology  and  life  history  of  a 
parasitic  Botrvtis  on  pepper  and  lettuce,"  Mo.  Botan.  Garden  Rept., 
25:41-74,  1912. 
"A  studv  of  the  environmental  conditions  influencing  the  development 
of  stem  rust  of  wheat  in  the  absence  of  an  alternate  host,"  Nebr.  Agr. 
Expt.  Sta.  Research  Bull,  35.     11  pp.     1925. 
Plakidas,  A.  G.,  "The  rosette  disease  of  blackberries  and  dewberries,"  /.  Agr. 

Research,  54:  275-303,  1937. 
Pool,  V.  W.,  and  M.  B.  McKay,  "Relation  of  stomatal  movement  to  infec- 
tion bv  Cercospora  beticola,"  J.  Agr.  Research,  5:  1011-1038,  1916. 
Rice,  Mabel  A.,  "The  haustoria  of  certain  rusts  and  the  relation  between  host 

and  pathogene,"  Bull.  Torrey  Botan.  Club,  54:  63-153,  1927. 
Rosenuaum,  J.,  and  C.  E.  Saxdo,  "Correlation  between  size  of  the  fruit  and 
the  resistance  of  the  tomato  skin  to  puncture  and  its  relation  to  infection 
with  Macrosporiwn  tomato  Cooke,"  Am.  J.  Botany,  7:  78-82,  1920. 
Salmon,   E.   S.,    "Cultural    experiments   with   biologic    forms   of   the   Ery- 

siphaceae,"  Phil.  Trans.  Roy.  Soc,  Ser.  B,  191:  107-122,  1905. 
Smith,  R.  E.,  "The  parasitism  of  Botrytis  cinerea,"  Botan.  Gaz.,  25:421-436, 

1902. 
Thatcher,  F.  S.,  "Osmotic  and  permeability  relations  in  the  nutrition  of 
fungus  parasites,"  Am.  J.  Botany,  26:  849-858,  1939. 
"Further   studies   of   osmotic    and   permeability   relations   in   parasitism," 
Can.  J.  Research,  20:283-311,  1942. 
Tisdale,  \Y.  H.,  "Physoderma  disease  of  corn,"  /.  Agr.  Research,  16:  137- 

154,  1919. 
Valleau,  W.  D.,  "Varietal  resistance  of  plums  to  brown  rot,"  /.  Agr.  Re- 
search, 5:365-396,  1915. 
Ward,  H.  Marshall,  "A  lily  disease,"  Ann.  Botany,  2:  319-382,  1888. 
Waterhouse,  W.  L.,  "Studies  in  the  physiology  of  parasitism.     VII.  Infec- 
tion   of    Berberis    vulgaris    by    sporidia    of    Puccinia    graminis"    Ann. 
Botany,  55:557-564,  1921. 
Yarwood,  C.  E.,  "The  function  of  lime  and  host  leaves  in  the  action  of 

Bordeaux  mixture,"  Phytopathology,  33:  1146-1156,  1943. 
Young,  P.  A.,  "Penetration  phenomena  and  facultative  parasitism  in  Alter- 
naria,  Diplodia,  and  other  fungi,"  Botan.  Gaz.,  SI:  258-279,  1926. 


Chapter  11 

PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

AMONG  FUNGI 

The  concept  that  physiological  differences  exist  between  the 
members  that  together  constitute  a  given  species  of  fungus  prob- 
ably has  its  origin  in  bacteriology.  In  the  early  years  of  bacteri- 
ology there  were  two  opposing  schools  of  thought,  one  of  which 
held  to  the  monomorphic  hypothesis  and  the  other  to  the  poly- 
morphic or  pleomorphic  hypothesis.  Adherents  of  the  mono- 
morphic hypothesis  believed  in  fixity  and  immutability  of  species; 
adherents  of  the  polymorphic  hypothesis,  in  variability  in  mor- 
phological and  physiological  characteristics.  Billroth  (1874), 
representing  an  extreme  of  the  polymorphic  group,  for  example, 
believed  that  only  one  species  of  bacteria,  "Coccobacteria 
septica"  existed. 

To  the  person  who  compares  a  considerable  number  of  isolates 
of  any  one  fungus,  especially  when  grown  on  artificial  media,  it 
quickly  becomes  apparent  that  the  species  is  variable  and  that 
differences  exist  between  the  several  isolates.  Although  these  dif- 
ferences may  be  so  minute  as  to  be  morphologically  indistinguish- 
able, they  are  none  the  less  real  and  of  tremendous  importance, 
especially  as  they  concern  pathogenic  species.  In  fact,  problems 
of  virulence  of  species,  of  their  aggressiveness,  of  the  outbreak 
of  epidemics,  and  of  the  breeding  of  crop  plants  that  are  resistant 
or  immune  to  attack,  all  hinge  upon  the  fact  that  these  differences 
are  meaningful  and  must  be  taken  into  account.  Questions  con- 
cerning  the  origin  of  these  differences  have  been  regarded  too 
largely  as  of  only  academic  interest.  Actually  no  useful  purpose 
is  served  by  assigning  them  to  the  academician. 

Definition  of  terms.  The  concept  embodied  in  the  term 
physiologic  species  has  changed  since  Schroeter  (1879)  first  sug- 
gested that  physiologic  specialization  in  fungi  exists.  He  observed 
that  Paccinia  graminis,  growing  on  wheat,  failed  to  produce  in- 

257 


258        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

f ection  if  inoculated  onto  other  grass  hosts,  such  as  rye,  oats,  timo- 
thv,  and  blue  grass,  whereas  under  the  same  environmental  condi- 
tions  wheat  readily  became  infected.  Similarly  Fuccinia  graminis 
from  any  of  the  other  grasses  produced  infection  on  the  host 
species  from  which  the  inoculum  was  taken,  but  reciprocal  inocu- 
lations always  failed  to  cause  infection.  Further  work  of  the  same 
nature  by  Eriksson  (1894)  led  to  the  division  of  Puccinia  graminis 
into  the  following  groups,  which  he  called  "formae  speciales": 
Fuccinia  graminis  tritici,  P.  graminis  secalis,  P.  graminis  avenae, 
P.  graminis  phlei-pratensis,  P.  graminis  agrostidis,  and  P.  graminis 
poae.  He  also  showed  that  subdivisions  can  similarly  be  made  of 
P.  ghimavum,  P.  dispersa,  and  P.  coronata.  He  recognized  five 
specialized  forms,  tritici,  secalis,  elymi,  agropyri,  and  hordei,  of 
P.  ghimavum.  Four  specialized  forms,  secalis,  agropyri,  bromi  and 
tritici,  comprise  P.  dispersa;  and  P.  coronata  consists  of  six,  avenae, 
alopecnri,  festucae,  lolii,  calamagrostis,  and  vielicae.  To  these 
groupings  within  the  species  the  terms  biologic  forms,  biologic 
races,  physiologic  forms,  biologic  species,  physiologic  species, 
physiologic  races,  parasitic  strains,  sister  species,  and  specialized 
varieties  have  been  applied.  They  are  now  generally  regarded 
as  varieties,  and  many  workers  designate  them  as  of  varietal  rank. 
Their  pathogenic  behavior  thus  serves  as  the  basis  for  the  varietal 
separations.  Within  the  past  25  years  it  has  been  found  that  many 
parasitic  strains  or  biotypes  comprise  a  given  variety  and  that 
some  of  these  strains  can  be  isolated  by  their  pathological  effects 
on  appropriate  suscept  species,  and  others  by  cultural  character- 
istics. It  is  to  these  strain  groupings  that  the  term  physiologic 
specialization  is  properly  applied. 

Some  mycologists  maintain  that  it  is  impossible  to  establish 
varieties  among  pathogenic  fungi,  as  in  Fuccinia  graminis,  on  the 
basis  of  morphologic  differences.  If  this  be  true,  there  is  little 
justification  for  the  use  of  varietal  names.  Minute  yet  recogniz- 
able differences  are  indicated  by  others  to  exist,  and  they  there- 
fore  find  it  convenient  to  employ  varietal  names.  Without  the 
threadbare  problem  of  what  constitutes  a  variety  or  physiologic 
species  being  raised  again,  it  is  clearly  established  by  students 
of  rusts  and  smuts  that  secondary  groupings  within  the  variety 
may  be  made  on  the  basis  of  pathogenicity  on  selected  suscepts. 
These  secondary  groupings  are  called  physiologic  strains.    They 


WHAT  FUNGI  HAVE  PHYSIOLOGIC  SPECIALIZATION?      259 

are  not  sufficiently  distinct  morphologically  to  entitle  them  to 
specific  rank  but  must  be  distinguished  from  each  other  by 
pathogenic  reactions. 

If  the  worker  is  dealing  with  fungi  that  can  be  cultivated  on 
artificial  media,  he  may  employ  differences  in  cultural  character- 
istics, for  example,  in  color  of  mycelial  mat,  shape  of  colonies, 
surface  markings,  size  of  colonies,  branching  of  hyphae,  and 
abundance  of  conidia,  to  distinguish  physiologic  forms.  This 
situation  is  typified  by  the  cultural  differences  noted  by  Chris- 
tiansen (1932)  in  the  15  races  of  Pestalozzia  fwierea  that  he  iso- 
lated from  needles  of  longleaf  pine.  These  races  differed  in 
abundance,  color,  and  zonation  of  surface  and  aerial  mycelium,  in 
abundance,  distribution,  and  size  of  acervuli,  and  in  size,  shape,  and 
color  of  spores. 

Several  other  terms,  including  variation,  mutation,  saltation,  and 
dissociation,  have  been  more  or  less  loosely  used  in  connection 
with  the  phenomenon  of  differences  among  the  members  that 
comprise  a  given  species  of  fungi.  For  clarity  these  terms  may 
at  this  point  be  defined.  Variation  is  applied  to  divergences, 
whether  morphological  or  physiological,  from  the  observed  char- 
acteristics of  the  usual  or  normal  condition.  They  are  regarded 
as  non-hereditary.  Variation  is  usually  regarded  as  svnomvmous 
with  dissociation.  Mutation,  as  originally  employed  by  de  Vries, 
refers  to  sudden  variations,  the  offspring  differing  from  the  par- 
ents in  one  or  more  clearly  defined  characteristics.  Mutation  is 
to  be  distinguished  from  gradual  variation,  such  as  may  occur 
during  the  course  of  countless  generations.  Furthermore  muta- 
tions are  hereditary,  since  once  they  appear,  they  can  be  trans- 
mitted to  the  progeny.  Saltation  may  be  defined  as  a  type  of  mu- 
tation that  appears  in  artificial  cultures.  Saltations  may  be  main- 
tained indefinitely  in  subcultures  if  conidia  or  hyphae  are  used  in 
transplantation.  Sports,  as  the  term  is  applied  to  seed  plants  that 
can  be  propagated  by  cutting  or  other  vegetative  structures,  cor- 
respond to  saltants  among  fungi. 

In  what  fungi  has  physiologic  specialization  been  observed? 
Numerous  species  of  pathogenic  fungi  are  known  to  consist  of 
many  physiologic  forms.  Presumably  all  do.  At  least,  it  would 
be  scientific  news  if  after  extensive  study  one  was  found  that  was 
not  comprised  of  numerous  physiologic  forms. 


260        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 


TABLE  26 
Fungi  Reported  to  Exhibit  Physiologic  Specialization 


Name  of  Fungi 

Rhizopus  nigricans 
Albugo  Candida 
Albugo  ipomoeae-panduranae 
.  llbugo  tragopogonis 
Phvtophthora  parasitica  var.  rhei 
Pcronospora  spp. 
Erysiphe  communis 
Erysiphe  graminis 
Erysiphe  graminis  hordei 
Erysiphe  graminis  tritici 
Erysiphe  horridula 
Phyllactinia  guttata 
Sphaerotheca  hamuli 
Claviceps  purpurea 
Pleospora  spp. 
Plonrightia  morbosa 
Puccinia  a  no  mala 
Puccinia  coronata  avenae 
Puccinia  glumarum 

Puccinia  graminis  avenae 


Puccinia  graminis  secalis 
Puccinia  graminis  tritici 


Puccinia  rubigo-vera  tritici 


Puccinia  sorghi 
Sphacelotheca  sorghi 

Sorosporium  reilianum 
Tilletia  laevis,  T.  tritici 

Ustilago  avenae,  U.  levis 


Vstilago  hordei 
Ustilago  tritici 
Ustilago  violacea 
Ustilago  zeae 

:oria  >pp. 
Pestalozzia  guepini 
Pestalozzia  fit  nerea 
Co lletotrich u  m  li ndem uth ia n u m 

Helminthosporium  gramineum 

Helminthos porium  sativum 
Polyspora  lini 
Fusarium  lini 

Rhizoctonia  solani 


Authority  for  Report 

Harter  and  Weimer  (1923) 

Toeashi  and  Shibasaki  (1934) 

Citerri  (1928) 

Pfister  (192") 

Leonian  (1926) 

Gaumann  (1923) 

Hammarlund  (1925) 

Reed  (1918),  Salmon  (1904),  Marchal  (1903) 

Mains  and  Dietz  (1930) 

Mains  (1933) 

Blumer  (1922) 

Hammarlund  (1925) 

Steiner  (1908) 

Stager  (1903),  Stakman  (1926) 

Diedicke  (1902) 

Gilbert  (1913) 

Mains  (1933a),  Hev  (1931) 

Hoerner  (1919),  Peturson  (1930),  Frenzel  (1930) 

Eriksson   (1894),  Allison  and  Isenbeck   (1930), 

Wilhelm  (1931) 
Eriksson  (1894),  Stakman,  Levine,  and  Bailey 
(1923),    Bailey    (1925),    Waterhouse    (1929), 
Gordon  (1933) 
Cotter  and  Levine  (1932) 

Eriksson  (1894),  Stakman  and  Piemeisel  (1917), 
Stakman    and    Levine    (1922),    Waterhouse 
(1929),  Stakman,  Levine,  and  Hines  (1934), 
Newton  and  Johnson  (1927) 
Mains  and  Jackson  (1926),  Waterhouse  (1929), 
Johnson  and  Mains  (1932),  Mains  (1933),  Ra- 
dulescu  (1932) 
Stakman  et  al.  (1928) 
Tisdale,  Melchers,  and  Clemmer  (1927),  Melch- 

ers,  Fricke,  and  Johnston  (1932) 
Reed,  Swabev,  and  Kolk  (1927),  Stakman  (1926) 
Rodenheiser  and  Stakman  (1927),  Reed  (1928), 
Gaines  (1928),  Holton  (1931),  Bressman  (1931) 
Reed    (1924,    1927,    1929,    1940),    Reed    and 
Stanton  (1932),  Aamodt  (1931),  Flor  (1933), 
Melchers  (1934) 
Faris  (1924) 

Stakman  (1926),  Grevel  (1930) 
Zillig  (1921),  Goldschmidt  (1928) 
Christiansen  and  Stakman  (1926),  Stakman  et  al. 

(1929) 
Beach  (1919) 

LaRue  and  Bartlett  (1922) 
Christiansen  (1932) 

Barrus  (1918),  Burkholder  (1923),  Leach  (1922), 
Budde  (1928),  Penser  (1931),  Schreiber  (1932) 
Christiansen  and  Graham  (1934) 
Christiansen  (1922) 
Stakman  (1926) 
Stakman  (1926) 
Matsumoto  (1921),  Briton-Jones  (1924) 


PATHOGENICITY  TESTS 


261 


Although  the  list  in  Table  26  is  by  no  means  complete,  it  indi- 
cates that  physiologic  specialization  occurs  among  all  the  major 
groups  of  fungi.  A  survey  of  accounts  from  which  this  list  was 
compiled  shows  that  in  the  recognition  of  physiologic  forms  four 
criteria  were  employed:  (a)  pathogenicity  on  special  hosts,  (b) 
differences  in  artificial  culture,  (c)  minor  morphological  differ- 


40 


30 


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E=  20 


Hi 


10 


0 


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V 

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A 

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22        26        30 
Length  of  spores  (microns) 


34 


38 


Fig.  45.     Variation  in  length  of  spores  of  six  strains  of  Pestalozzia  guepini, 
plotted    as   length    of   spores    in    microns    against   percentage    of   the   total 

number  measured.     (After  LaRue.) 

ences,  and  (d)  physico-chemical  reactions.     Each  will  be  given 
further  consideration. 

Pathogenicity  tests.  Concerning  the  pathogenic  potentialities 
of  disease-producing  fungi,  two  diametrically  opposed  theories 
have  been  advanced.  One  is  that  disease-producing  potentialities 
are  inherent  in  the  fungus  itself  and  therefore  are  hereditary. 
The  other  is  that  the  pathogens  become  adapted,  modified,  or 
"educated"  under  the  influence  of  the  host  or  of  other  environ- 
mental factors.  According  to  the  first  view,  the  physiologic 
forms  are  true-breeding  entities  that  maintain  a  uniform  potential- 
ity to  produce  disease  throughout  many  generations  or  over  a 
long  period  of  years.  The  weight  of  evidence  in  recent  years 
favors  this  viewpoint,  since  physiologic  characteristics  appear  to 


262        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

be  governed  bv  genetic  factors  in  the  same  way  as  morphologic 
characteristics  are  governed.  Nevertheless  the  idea  of  adaptation 
is  maintained  to  be  operative,  and  it  has  the  support  of  a  certain 
oroup  who  believe  in  evolution  through  adaptative  modifications. 
Attention  was  directed  to  this  point  of  view  bv  the  results  of 
Ward  (1903)  on  Puccinia  dispersa  on  brome  grasses  and  of  Sal- 
mon (1904)  on  various  powdery  mildews,  especially  Erysiphe 
graminis  on  grasses.  Ward  maintained  that  this  rust  could  acquire 
the  ability  to  attack  a  resistant  host  if  it  were  first  transferred  to 
another  host  with  lesser  resistance.  After  repeated  transfers  on 
this  less  resistant  host,  it  acquired  the  ability  to  attack  the  resist- 
ant one.  The  less  resistant  variety,  therefore,  served  as  a  "bridge." 
Similarly,  Salmon  maintained  that  E.  graminis  from  barley  could 
not  infect  wheat  unless  the  leaves  were  injured.  When  grown 
on  injured  wheat  leaves  for  several  transfers,  it  acquired  the  ability 
to  infect  intact  ones.  From  this  type  of  results  he  concluded, 
"The  restriction  in  power  of  infection  characteristic  of  biologic 
forms  breaks  down  if  the  vitality  of  the  leaf  on  which  the  conidia 
are  sown  is  interfered  with  in  certain  ways."  He  also  noted  that 
the  powdery  mildew  from  Brovnis  racemosus  did  not  infect  B. 
comrnutatus  in  12  trials,  but  that  it  infected  B.  hordeaceus  in  each 
of  36  trials.  Furthermore  failure  of  infection  resulted  in  36  at- 
tempts when  conidia  from  B.  comrnutatus  were  applied  to  B.  race- 
7/iosus,  and  infection  occurred  in  40  out  of  49  trials  in  which 
conidia  from  B.  hordeaceus  were  applied  to  B.  comrnutatus.  From 
these  experiments  B.  hordeaceus  was  concluded  to  act  as  a  bridg- 
ing species  for  powdery  mildews  on  B.  racemosus  and  B.  com- 
rnutatus. 

Hammarlund  (1925)  attempted  to  repeat  Salmon's  work,  using 
Erysiphe  comimniis  tritici  cultivated  for  37  generations  on 
wounded  leaves  of  Hordeum  europaeuvu  with  the  result  that 
there  was  no  increasing  tendency  to  become  adapted  to  barley. 
He  also  employed  E.  graminis  tritici  cultivated  on  wounded  leaves 
of  Hordeum  vulgare  for  128  generations.  In  this  experiment  like- 
wise there  was  no  evidence  at  the  end  that  the  powdery  mildew 
had  acquired  the  ability  to  infect  intact  barley  leaves. 

Stakman  and  his  associates  (1926)  attempted  to  adapt  Erysiphe 
graminis  tritici  to  grow  on  barley,  rye,  and  oats.  They  subjected 
the  plants  to  "every  conceivable  form  of  torture,"  but  all  refused 
to  become  infected. 


DIFFERENCES  IN  ARTIFICIAL  CULTURE 


263 


The  existence  of  adaptation  and  "bridging"  among  pathogens 
remains  questionable  in  the  light  of  these  experiments.  That  the 
pathogenicity  of  specialized  races  is  hereditary  and  therefore  con- 
stant, on  the  other  hand,  has  volumes  of  evidence  in  its  support. 
Those  who  have  studied  the  rusts  over  a  period  of  years,  as  have 


H.  hordeaceus 


H.  secalinus 


H.  arduennensis 


H.  interruptus 


H.  commutatus 


H.  racemosus 

Fig.  46.  Reciprocal  inoculation  of  species  of  Hordeum  with  conidia  of 
powdery  mildew.  Solid  lines  show  successful  transfer  with  resultant  in- 
fection in  direction  indicated  bv  arrow;  broken  lines,  failure  of  infection 
after  transfer  of  conidia.  The  numerator  indicates  the  number  of  successful 
trials;  the  denominator,  the  number  of  attempts  made  to  secure  infection. 
The    species    hordeaceus   is    a    "bridging    species"    for   Erysiphe    gram'inis. 

(After  Salmon.) 

Stakman  and  his  associates,  or  the  smuts,  as  have  Reed  and  his 
associates,  are  able  to  isolate  the  same  physiologic  forms  year 
after  year.  These  identical  forms  may  range  widely  in  one  area 
or  country  or  may  even  be  found  in  different  continents. 

Differences  in  artificial  culture.  Macroscopic  or  micro- 
scopic differences  between  strains  isolated  from  monosporous  cul- 
tures have  been  reported  for  numerous  species  of  fungi.  From 
our  knowledge  of  genetics  these  strain  differences  may  have  arisen 
either  through  hybridization  or  through  mutation. 

From  the  voluminous  literature  on  plus  and  minus  strains  within 


264        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

a  s;iven  species,  it  would  be  anticipated  that  new  forms  are  being 
produced  constantly.  There  is  abundant  evidence  that  this  is  the 
situation,  especially  among  rusts  and  smuts  [Christiansen  and  Stak- 
man  (1926),  Newton  and  Johnson  (1927),  Christiansen  (1929), 
Flor  (1932)]. 

Sectoring.  Sometimes  differences  appear  as  sectors  in  the  col- 
onies on  Petri  dishes.  These  sectors  may  appear  as  wedge-shaped 
areas  of  different  color,  of  different  compactness  of  mycelial 
growth,  with  less  profuse  sporulation,  or  of  some  other  very 
marked  difference.  Christiansen  and  Stakman  (1926)  and  Stak- 
man,  Tyler,  and  Hafstad  ( 1933)  noted  sectoring  in  Ustilago  zeae. 
In  their  report  Stakman,  Tyler,  and  Hafstad  (1933)  recorded  the 
isolation  of  14  variant  lines  of  U.  zeae  from  a  single  monosporidial 
cell  that  sectored  in  culture.  Each  line  maintained  distinctive 
cultural  characteristics  for  5  years.  Evidently  each  was  a  distinct 
biotype,  and  each  arose  as  a  mutation. 

Dod^e  ( 1931)  isolated  an  albino  strain  of  Nenrospora  sitophila 
that  produced  few  conidia.  Johnson  and  Yalleau  (1935)  isolated 
from  a  sector  an  albino  strain  of  Thielaviopsis  basicola.  Leonian 
(1930)  observed  sectoring  in  Fusarium  moniltforvie,  and  it  appears 
to  be  of  rather  common  occurrence  among  Fusaria  in  the  section 
Elegans.  Hansen  and  Smith  (1932)  recorded  sectoring  in  Botrytis 
cinerea,  and  Wolf  and  Wolf  (1939)  in  Botryosphaeria  ribis.  Pes- 
talozzia  funerea  sectored,  giving  rise  to  conidia  with  only  a  single 
seta  [Christiansen  (1932)],  which  is  characteristic  of  the  genus 
Monochaetia. 

The  occurrence  of  dissociation  with  the  production  of  albinistic 
mutants  has  been  noted  in  Brachysporhnn  trifolii  [Bonar  (1922)] 
and  among  sclerotia  in  Botrytis  cinerea. 

Brierlev  (1920)  and  Christiansen  (1922)  secured  evidence  that 
some  of  the  mutations  of  Helminthosporiwn  sativum  were  more 
virulent,  and  others  less  virulent,  than  their  parents.  Ustilago 
zeae  from  purplish  sectors  was  more  virulent  than  that  from  tan 
sectors  [Christiansen  and  Stakman  (1926)].  Newton  and  John- 
son (1927)  isolated  a  bright  orange  and  a  greyish  strain  of  Pnc- 
cinia  graminis  tritici  from  form  species  9.  Both  seemed  identical 
in  pathogenecity,  however,  with  the  normal  form. 

Sectoring  among  fungi  has  been  compared  with  "bud  sporting" 
among  seed  plants.  The  causes  of  sectoring  are  not  understood, 
although  certain  factors  are  known  to  exert  an  influence.    These 


SECTORING  265 

include  kind  and  amount  of  nutrients,  temperature,  light  and  other 
radiations,  pH,  staling  products,  and  the  addition  of  certain  salts 
and  toxic  substances,  a  subject  brief! v  summarized  by  Christian- 
sen (1940). 

Sectoring  could  be  expected  to  take  place  among  fungi  in  which 
hvphal  fusions  occur  or  in  those  with  multinucleate  spores,  as  in 
Botrytis  cinerea.  Hansen  and  Smith  (1932)  have  shown  that  the 
propagative  elements  of  this  fungus  are  heterocaryotic,  resulting 
from  anastomoses  that  permit  the  migration  of  nuclei  from  one 
cell  to  another.  In  Botryosphaeria  ribis,  which  has  multinucleate 
ascospores  and  conidia,  however,  all  the  nuclei  within  anv  asco- 
spore  or  conidium  have  the  same  origin  and  hence  are  homo- 
caryotic  [Wolf  and  Wolf  (1939)].  The  causes  of  sectoring  in 
this  species  are  unknown,  and  the  phenomenon  may  be  wholly 
spontaneous. 

Normally  when  a  culture  originates  from  a  single  conidium  it 
is  regarded  as  clonal  and  is  presumed  to  be  genetically  pure. 
Variations  occur  in  the  colonies  from  these  clones,  as  has  been 
shown  by  LaRue  (1922)  in  Festalozzia  guepiiii,  by  Christiansen 
(1932)  in  Festalozzia  funerea,  and  by  Leonian  (1929)  in  many  spe- 
cies and  varieties  of  Fusarium.  Sometimes  the  variants  in  subcul- 
tures of  Fusarium  remained  different  from  the  parent  type  and 
that  of  the  variant  biotype  that  arose  by  sectoring.  Leonian 
(1929)  concluded,  "The  presence  of  distinct  strains  and  variants 
within  the  same  species  and  their  decidedly  different  reactions  (to 
various  acids  and  toxic  substances)  seem  to  indicate  that  the  con- 
cept of  the  species  must  not  be  that  of  a  single  organism  but  that 
of  a  group  of  many  organisms  having  in  general  the  same  principal 
characters." 

Brierley  (1929)  summarized  his  observations  on  variation  of 
fungi  in  cultures,  especially  of  Botrytis  cinerea,  by  stating  that  his 
distinct  monosporial  isolates  of  B.  cinerea  remained  stable  for  long 
periods  of  time  when  cultivated  under  different  nutritional  and 
environmental  conditions,  both  in  vitro  and  in  vivo.  When  the 
different  isolates  were  then  brought  back  to  the  common  stand- 
ardized environment,  all  immediately  reverted  in  their  conidial 
dimensions  to  a  common  original  condition.  This  phenomenon 
shows  genotypic  fixity  within  the  species,  which  has  been  re- 
peatedly demonstrated  to  occur  in  other  organisms. 


266        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

Four  variant  strains  of  Hypomyces  ip07?weae—purp\e,  alba,  con- 
voluta,  and  reverta— were  isolated  by  Dimock  (1939).  They 
originated  by  gene  mutations.  None  of  them  appeared  to  be 
capable  of  perpetuating  themselves  in  competition  with  the 
normal  type,  because  all  had  growth  rates  slower  than  the  normal, 
produced  conidia  less  abundantly,  and  were  quite  incapable  of 
inbreeding. 

The  causes  underlying  these  variational  phenomena  are  un- 
doubtedly diverse.  In  some  cases  they  have  been  shown  to  be 
frenetic,  but  in  others  a  different  explanation  must  be  sought. 
Dodge  (1942)  noted  increased  vigor  of  growth  and  production  of 
conidia  in  Neurospora  tetrasperma  when  he  crossed  a  dwarf 
race  of  this  fungus  with  a  normal  one  of  opposite  sex  or  else 
with  one  of  the  same  sex  with  resultant  mycelial  fusions.  The 
cells  of  these  mvcelia,  containing  nuclei  of  both  races,  grew  two 
or  three  times  as  fast  as  those  of  normal  ones.  He  ascribed  in- 
creased vigor  to  synthesis  of  vitamins  by  the  heterocaryotic  my- 
celium. 

Hybridization.  Stakman,  Levine,  and  Cotter  (1930)  crossed 
Fuccinia  gr avium  tritici  form  36  with  Puccinia  graminis  agrostidis. 
When  segregation  occurred  in  the  progeny,  3  new  form  species 
were  isolated  that  had  previously  not  been  encountered  among 
the  numerous  form  species  of  tritici..  Stakman,  Levine,  Cotter, 
and  Hines  (1934)  segregated  over  20  different  races  of  wheat- 
stem  rust  from  aecial  collections  and  80  from  uredinial  collections. 
In  the  Mississippi  Valley,  where  barberry  occurs,  there  is  ample 
opportunity  for  hybridization  to  occur,  whereas  in  Australia, 
where  barberry  is  absent,  as  was  pointed  out  by  Waterhouse 
(1929),  there  are  few  races  of  wheat-stem  rust.  In  consequence, 
an  abundance  of  races  can  exist,  and  new  ones  can  continue  to 
arise  naturally  by  segregation  and  recombination  of  factors  for 
differences  in  pathogenicity  wherever  the  barberry  host  thrives. 
Emphasis  was  also  placed  on  hybridization  as  a  means  of  securing 
new  races  of  stem  rust  by  Craigie  (1940)  in  his  summary  of 
studies  conducted  at  the  Dominion  Rust  Research  Laboratory, 
Winnepeg,  Canada. 

Similarly  Tisdale,  Alelchers,  and  Clemmer  (1927)  found  in 
Kansas,  New  .Mexico,  and  Texas  a  new  kernel  smut  that  infects 
milo  :md  hegari  but  is  non-infectious  to  feteretia,  and  presented 
evidence  that  it  arose  as  a  hybrid  between  Sphacelotheca  sorghi 


MORPHOLOGICAL  DIFFERENCES  261 

and  5".  cruerita.  The  phenotypes  obtained  had  characters  common 
to  both  parents.  Other  interspecific  smut  hybrids,  such  as  those 
between  Ustilago  avenae  and  U.  levis,  and  between  U.  hordei  and 
U.  medians,  have  been  produced  that  are  intermediate  in  the  Fi 
generation  but  segregate  in  the  F2  generation.  The  status  of 
present  knowledge  of  genetic  factors  as  applied  to  hybridization 
in  smuts,  and  especially  to  the  origin  of  physiologic  races  by  this 
means,  is  summarized  by  Rodenheiser  (1940).  New  specialized 
races  of  smuts  are  known  to  arise  in  nature,  presumably  by  hy- 
bridization. Reed  (1935)  isolated  from  a  collection  of  loose  smut 
of  oats  from  Texas  two  distinct  new  races,  one  capable  of  infect- 
ing Red  Rustproof  oat  and  the  other  Fulgum  oat. 

It  should  be  recalled  that  in  some  species  of  smuts  infection  and 
production  of  chlamydospores  occur  only  if  there  has  been  fusion 
of  lines  of  opposite  sex.  In  such  species  hybridization  between 
biotypes  undoubtedly  is  of  common  occurrence.  Moreover,  inter- 
specific hybrids  between  Ustilago  hordei  and  U.  medians,  U.  levis 
and  U.  avenae,  Tilletia  levis  and  T.  tritici,  and  Sphacelotheca 
omenta  and  S.  sorghi  have  been  produced.  Certain  intergeneric 
crosses,  as  between  Sorosporiwn  reilianum  X  Sphacelotheca 
sorghi,  and  Sorosporhtm  reilianum  X  Sphacelotheca  omenta,  have 
also  been  effected  [Tyler  and  Shumway  (1935),  Christiansen  and 
Rodenheiser  (1940)]. 

Morphological  differences  between  physiologic  species.  It 
has  been  pointed  out  that  minor  morphologic  differences  have 
been  noted  between  urediniospores  of  varieties  of  Pnccinia  granii- 
nis.  This  observation  has  led  to  a  search  for  distinctive  differences 
by  means  of  which  to  separate  specialized  races  of  this  rust  as  it 
occurs  on  wheat.  The  outstanding  of  these  attempts  is  that  of 
Levine  (1928),  who  by  the  aid  of  biometrical  methods  was  able 
to  show  minor  differences  in  size  and  shape  of  spores  between 
the  several  physiologic  forms.  Newton  and  Johnson  (1927) 
were  able  to  show  that  a  bright  orange  form  species  and  a  greyish 
brown  one  can  be  distinguished  from  the  normal  form  9  of  P. 
graminis  tritici.  Similar  segregation  of  species  followed  from 
monographic  studies  on  Peronospora  by  Gaumann  (1923).  By 
making  numerous  measurements  of  the  lengths  and  widths  of 
sporangia  of  Peronospora  parasitica  and  then  plotting  these  data 
as  population  curves,  he  was  able  to  separate  the  species  into  a 
number  of  distinct  groups. 


268        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

Savulescu  and  Ravss  (1930)  found  minor  differences  in  the 
sporangia  of  Albugo  Candida  and  used  them  as  a  basis  to  divide  it 
into  8  form  species.  Togashi  and  Shibasaki  (1934)  were  able,  by- 
means  of  a  large  series  of  measurements  of  sporangia,  to  divide  this 
species  into  2  varieties,  microspora  and  macrospora,  and  then  to 
separate  microspora  into  3  form  species  and  macrospora  into  2 
form  species. 

Leonian  (1925)  isolated  from  Phytophthora  parasitica  rhei  5 
tvpes  of  colonies  that  were  so  different  no  one  would  regard  them 
as  members  of  the  same  species.  For  a  long  time  mycologists  have 
placed  great  emphasis  upon  the  host  species  as  an  aid  in  identifying 
rusts,  smuts,  downy  mildews,  powdery  mildews,  and  other  obli- 
gate parasites.  Undoubtedly  some  so-called  species  are  in  reality 
only  form  species.  The  converse  may,  of  course,  be  found  to  be 
equally  true,  with  changes  in  concepts  of  what  constitutes  the 
species. 

Physico-chemical  differences  among  specialized  races.  In 
the  light  of  statements  already  made,  it  would  seem  possible  to 
isolate  races  that  possessed  more  marked  ability  than  other  isolates 
to  produce  a  given  by-product  as  the  result  of  their  metabolic 
activity.  This  is  true  in  the  case  of  the  groups,  baker's  yeasts 
and  brewer's  yeasts,  that  have  been  selected  from  the  complex 
known  as  Sac  char  omyces  cerevisiae.  Growth  of  the  baker's 
yeasts  is  inhibited  in  wort  in  which  the  alcohol  content  has  ac- 
cumulated to  a  concentration  of  4  to  50/0,  and  of  the  brewer's 
yeast,  at  an  alcohol  concentration  of  14  to  17%.  Similarly  races 
of  molds,  especially  of  Penicillium,  Rhizopus,  and  Aspergillus, 
differing  in  fermentative  ability  in  the  formation  of  oxalic  acid, 
acetic  acid,  lactic  acid,  and  other  products,  have  been  isolated.  It 
would  seem  that  these  races  are  merely  selections  within  the 
species.  This  interpretation  has  direct  bearing  on  the  "species 
concept."  The  degree  of  difference  requisite  in  separating  species 
and  varieties,  and  sometimes  genera,  of  funsri  is  not  fixed.  Alor- 
phology  is  agreed  to  be  the  primary  basis  of  specific  distinctions. 
In  some  genera,  such  as  Botrytis,  Fusarium,  and  Phytophthora, 
morphologic  differences  are  either  minute  or  non-existent  and 
hence  a  source  of  confusion.  Physiologic  differences  amongr 
them  are,  therefore,  employed  as  a  convenient  basis  for  specific 
taxonomic  units.  If  physiologic  differences  were  employed 
among  rusts,  precise  means  of  cleaving  species  exist  that  are  more 


INFLUENCE  OF  ENVIRONMENTAL  FACTORS  269 

distinctive  than  morphologic  differences  between  accepted  spe- 
cies in  certain  other  genera.  Similarly  constant  physico-chemical 
differences  amonsj  funoi  can  be  demonstrated  to  exist.  Their 
taxonomic  value,  like  that  of  other  bases,  however,  remains  a 
matter  of  dispute. 

Influence  of  environmental  factors  on  physiologic  species. 
The  pathogenic  potentialities  of  fungi  are  modified  by  environ- 
mental factors,  as  has  been  demonstrated  to  the  satisfaction  of 
everyone  who  has  worked  with  plant  pathogens.  There  is  evi- 
dence also  that  the  specialized  races  that  together  constitute  a 
species  respond  differently  to  a  single  factor.  For  example, 
Waterhouse  (1929)  has  shown  that  certain  physiologic  forms  of 
Fiiccinia  graminis  tritici,  P.  gramims  avenue,  P.  triticina,  and  P. 
simplex  are  pathogenic  to  a  particular  host  variety  in  summer  but 
not  in  winter.  Waterhouse  reported  that  P.  simplex  was  capable 
of  infecting  14  varieties  of  barley  equally  potently  in  winter  and 
in  summer,  but  8  varieties  were  resistant  under  winter  weather 
conditions  and  susceptible  in  summer.  A  similar  response  to 
weather  was  noted  by  Peturson  (1930)  in  P.  coronata  avenae.  At 
57°  F  Red  Rust-proof  oats  were  resistant,  but  at  70°  F  or  higher 
this  variety  was  susceptible.  Ruakura  oats  were  resistant  within 
the  range  57°  to  77°  F,  whereas  the  varieties  Green  Mountain, 
White  Tartar,  and  Green  Russian  were  susceptible  within  this 
range.  Susceptibility  to  form  species  21  of  P.  gramims  tritici  was 
dominant  at  high  temperature  in  the  cross  between  Marquillo  and 
Marquis  wheat,  but  at  low  temperature  resistance  was  dominant 
[Harrington  (1931)].  Presumably  these  effects  of  temperature, 
representative  of  similar  observations  on  other  pathogenic  fungi, 
involve  the  metabolic  activities  of  both  interacting  organisms  and 
are  to  be  regarded  as  quantitative  rather  than  qualitative. 

It  is  well  known  that  certain  diseases  involve  only  mature  plants 
or  plant  parts,  whereas  others  are  limited  to  seedlings  or  to  young 
tissues.  Fomes  pini,  for  example,  causes  disease  of  mature  conifers 
and  becomes  a  very  important  cause  of  decay  in  overmature  stands. 
Again,  the  leaves  and  fruits  of  grapefruit  and  orange  are  subject 
to  melanose,  caused  by  Diaporthe  citri,  and  to  scab,  caused  by 
Sphaceloma  faivcetti,  in  the  period  of  4  to  6  weeks  after  the  petals 
have  fallen  but  become  highly  resistant  thereafter.  The  funda- 
mental causes  of  differences  between  young  and  old  tissues  in 
susceptibility  to  infection  by  fungi  are  little  understood.    Further- 


270        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

more,  that  such  differences  may  be  correlated  with  the  existence 
of  physiologic  races  of  the  particular  species  is  shown  by  the 
experiments  of  Goulden,  Newton,  and  Brown  (1930).  Among 
the  16  form  species  of  Puccinia  graminis  tritici  that  they  used 
some  were  more  pathogenic  on  wheat  in  the  seedling  stage  than  on 
the  same  variety  in  the  mature  condition. 

Environmental  factors  and  variation  among  saprophytes. 
Variations  among  saprophytic  fungi,  in  relation  to  their  produc- 
tion by  such  factors  as  temperature,  chemicals,  kind  and  amount 
of  food,  and  effects  of  radiations,  have  also  been  given  due  con- 
sideration. An  appreciation  of  the  influence  of  environmental 
factors  is  shown  in  the  report  by  Barnes  (1936).  In  it  he  states 
that  Hansen,  in  his  work  with  yeasts  in  1883,  was  the  first  to  in- 
duce variation  in  a  fungus.  He  secured  an  anascosporous  yeast 
by  use  of  high  temperature.  In  Barnes'  own  studies,  involving 
Eurotium  herbariorum,  Botrytis  cinerea,  and  Thamnidium  elegans, 
he  secured  variants  by  exposure  to  temperatures  just  insufficient 
to  kill.  These  variations  were  manifest  by  reduced  fertility  or 
less  vigorous  vegetative  development.  Barnes  judiciously  indicates 
the  need  for  distinguishing  between  modifications  that  are  tempo- 
rary in  nature  and  variants  characterized  by  permanency.  Both 
modificatory  types  appeared  in  his  own  experiments  and  in  those 
of  certain  others.  Barnes'  (1936)  discussion  involves  the  possibil- 
ity that  wounding  which  results  from  breaking  the  hyphae  while 
making  transfer  from  one  medium  to  another  may  induce  varia- 
tion.  He  would  not  attribute  all  variation  to  nuclear  changes, 
since  physiological  processes  might  conceivably  be  deranged 
without  nuclear  derangement.  Barnes  concludes  by  saying, 
"Variants  are  damaged  versions  of  the  normal  stocks  .  .  .  and  the 
evolutionary  process  may  depend  in  part  on  the  running  down 
of  the  biological  machine." 

Evidence  presented  by  Barnes  (1928,  1930)  shows  that  variation 
can  be  induced  in  Eurotium  herbariorum  and  Botrytis  cinerea  by 
subjecting  the  spores  to  high  temperatures.  In  E.  herbariorum 
these  variations  are  manifest  by  differences  in  amount  of  aerial 
mycelium,  density  of  growth,  color  of  conidia,  and  abundance 
of  perithecial  formation;  in  B.  cinerea,  by  the  change  in  color 
and  density  of  the  mycelium  and  by  abnormalities  in  abundance 
of  conidia  and  sclerotia.  Certain  variants  that  arose  by  high-tem- 
perature treatment  seemed  capable  of  retaining  these  characteristic 


PHYSIOLOGIC  SPECIALIZATION  AND   VARIATION        211 

differences  even  after  repeated  transfer,  whereas  others  reverted 
to  the  normal. 

Importance  of  physiologic  specialization  and  variation. 
Thus  far  emphasis  has  been  placed  upon  the  fact  that  specialized 
races  exist,  and  their  possible  origin  has  been  considered.  The 
significance  and  practical  application  of  these  facts  and  theories 
cannot  have  been  kept  from  mind  during  the  perusal  of  this  dis- 
cussion. Their  importance  in  the  field  of  plant  pathologv  is  not 
believed  to  be  properly  appreciated;  indeed,  it  can  scarcely  be 
overestimated.  For  a  period  of  years  these  problems  have  engaged 
the  attention  of  many  students  of  the  rusts  and  smuts,  especially 
Stakman  and  his  associates.  In  a  report  Stakman  (1936)  has  sum- 
marized them  in  their  application  to  the  need  for  plant  quaran- 
tines and  to  the  breeding  of  varieties  resistant  to  disease. 

Investigations  at  the  Minnesota  Agricultural  Experiment  Sta- 
tion, at, the  Dominion  Rust  Research  Laboratory,  and  in  Australia 
[Waterhouse  (1929)]  are  in  accord  in  showing  the  relationship 
between  the  presence  of  barberry  and  the  existence  of  numerous 
races  of  Puccinia  graminis  tritici.  Race  34  seems  to  be  the  only 
one  present  in  quantity  in  Australia,  whereas  in  the  wheat-grow- 
ing belt  of  North  America  approximately  150  races  are  known 
to  exist.  In  addition,  new  races  are  continuously  being  developed 
as  the  result  of  hybridization  on  the  barberry.  The  unrestricted 
introduction  of  the  North  American  races  into  Australia  or  other 
continents  might  easily  result  in  epidemics  of  rust  on  varieties  of 
wheat  that  are  highly  resistant  to  races  of  rusts  already  present  in 
these  countries.  This  supposition  is  supported  by  Stakman's 
(1936)  observations  on  the  rust  epidemic  on  the  varieties  Ceres 
and  Thatcher  in  1935.  Both  had  previously  rather  uniformly  re- 
sisted rust  for  a  term  of  years.  It  should  be  added  that  in  1935 
no  races  of  rust  capable  of  infecting  Vernal  emmer  were  isolated 
from  uredinial  collections  made  in  reoions  where  barberries  are 
absent,  whereas  three  capable  of  infecting  this  variety  of  emmer 
were  isolated  from  barberries  or  from  grain  growing  near  them. 
Several  of  the  races  isolated  that  year  from  barberries  were  new 
biotypes,  showing  that  hybridization  and  segregation  in  rusts  are 
taking  place  in  nature.  Experiences  of  this  sort  should  convince 
the  most  hard-headed  unbeliever  that  barberries  should  be 
eradicated. 


272        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

The  recent  work  of  Reed  (1940)  serves  to  emphasize  the  im- 
portance of  physiologic  races  in  the  breeding  of  oats  resistant  to 
smuts.  He  differentiated  29  races  of  Ustilago  avenae  and  14  of 
U.  levis  by  their  pathogenic  behavior  on  strains  and  varieties  of 
9  species  of  Avena.  Avena  bar  bat  a  was  susceptible  to  all  races  of 
smuts.  The  variety  Canadian  was  susceptible  to  all  physiologic 
races  of  these  smuts  except  one  of  each.  The  varieties  Markton, 
Victoria,  and  Navarro  proved  to  be  highly  resistant  to  many  races 
of  both  loose  and  covered  smuts. 

Literature  on  plant  pathology  contains  many  accounts  of  varie- 
ties of  crop  plants  that  are  resistant  to  a  specific  pathogen  when 
grown  in  one  region  but  are  susceptible  when  grown  in  another 
region.  Of  course  this  apparent  breakdown  of  resistance  cannot 
be  attributed  to  one  cause  in  every  case,  but  the  existence  of  dif- 
ferent specialized  races  in  different  regions  is  no  doubt  frequently 
the  primary  cause.  For  example,  it  is  a  common  observation  that 
durum  wheats  in  the  United  States  are  more  resistant  to  stinking 
smut  than  are  vulgare  wheats.  The  opposite  situation  has  been 
observed  in  Palestine.  Abundant  evidence  is  now  at  hand  that 
these  conflicting  observations  can  be  explained  by  the  existence 
of  different  physiologic  races  of  Tilletia  tvitici  and  T.  levis  in  these 
two  regions.  It  is  to  be  expected  that  hybridization  is  less  im- 
portant in  breeding  crops  resistant  to  smuts  if  the  smuts  belong 
to  the  group  in  which  the  promycelium  or  its  branches  directly 
penetrate  the  host  tissues.  Even  in  these  species  fusions  between 
different  promvcelia  could  occur,  and  new  races  could  be  formed. 

From  the  numerous  examples  of  interracial  and  interspecific 
hybridization  and  of  variation  by  sectoring  that  have  been  oh- 
served,  it  is  apparent,  as  has  been  indicated,  that  new  forms  are 
continuously  being  produced  in  nature.  The  plant  pathologist 
must  therefore  first  know  the  pathogen  thoroughly,  if  the  breed- 
ing or  selecting  ot  resistant  host  varieties  is  to  be  successful. 

LITERATURE  CITED 

A  \.\iodt,  O.  S.,  "Varietal  trials,  physiologic  specialization,  and  breeding 
spring  wheats  for  resistance  to  Tilletia  tvitici  and  T.  levis"  Can.  J.  Re- 
search, 5: 501-528,  1931. 

Allison,  C.  C,  and  K.  [senbeck,  "Biologisches  Spccialisicrung  von  Puccinia 
glumarum  tritici  Eriksson  and  Henning,"  Phytopath.  Z.,  2:87-98,  1930. 


LITERATURE  CITED  213 

Bailey,  D.  L.,  "Physiologic  specialization  in  Puccinia  graminis  avenae  Erikss. 
and  Henn.,"  Minn.  Agr.  Expt.  Sta.  Tech.  Bull.,  35:  36  pp.  1925. 

Barnes,  B.,  "Variations  in  Eurotium  herbariorum  (Wigg)  Link,  induced  by 
the  action  of  high  temperatures,"  Ann.  Botany,  42:783-812,  1928. 
"Variations  in  Botrytis  cinerea  Pers.,  induced  by  the  action  of  high  tem- 
peratures," Ann.  Botany,  44:  825-858,  1930. 
"Induced  variation,"  Trans.  Brit.  Mycol.  Soc,  20:  17-32,  1936. 

Barrus,  M.  F.,  "Varietal  susceptibility  of  beans  to  strains  of  Colletotrichum 
lindemuthianum  (Sacc.  et  Magn.)  B.  and  C,"  Phytopathology,  8:  589- 
614,  1918. 

Beach,  W.  S.,  "Biologic  specialization  in  the  genus  Septoria,"  Am.  J.  Botany, 
6:  1-33,  1919. 

Billroth,  T.,  Untersuchungen  iiber  die  V  egetationsformen  von  Cocco-bak- 
teria  septic  a.    Berlin.     1874. 

Blumer,  B.,  "Beitrage  zur  Specialisation  der  Erysiphe  horriduhx  Lev.  auf 
Boraginaceen,"  Zentr.  Bakt.,  Parasitenk.,  II  Abt.,  55:480-506,  1922. 

Bonar,  L.,  "An  albino  mutation  of  the  dematiaceous  fungus  Brachysporium 
trifolii,"  Science,  56:226-221,  1922. 

Bressman,  E.  N.,  "Varietal  resistance,  phvsiologic  specialization,  and  inheri- 
tance studies  in  bunt  of  wheat,"  Ore.  Agr.  Expt.  Sta.  Bull.,  281:  1-44, 
1931. 

Brierley,  W.  B.,  "On  a  form  of  Botrytis  cinerea  with  colorless  sclerotia," 
Phil.  Trans.  Roy.  Soc.  London,  Ser.  B,  220:  83-114,  1920. 
"Variation  in  fungi  and  bacteria,"  Proc.  Intern.  Congr.  Plant  Sci.  Ithaca, 

2:  1629-1654,  1929. 
"Biological  races  in  fungi  and  their  significance  in  evolution,"  Ann.  Appl. 
Biol,  18:  420-434,  1931. 

Briton-Jones,  H.  R.,  "Strains  of  Rhizoctonia  solani  (Corticium  vaginn  Berk 
and  Curt.),"  Trans.  Brit.  Mycol.  Soc,  9:  200-210,  1924. 

Budde,  A.,  "Uber  Rasenbildung  parasitischer  Pilze  unter  besonderer  Beriick- 
sichtigung  von  Colletotrichum  lindemuthianum  (Sacc.  et  Magn.)  Bri. 
et  Cav.  in  Deutschland,"  Forsch.  Gebiete  Pflanzenkr.  Immunitat  im 
Pflanzenreich,  5:  115-147,  1928. 

Burkholder,  W.  H.,  "The  gamma  strain  of  Colletotrichum  lindemuthianum 
(Sacc.  and  Magn.)  B.  and  C,"  Phytopathology,  13: 316-323,  1923. 

Christiansen,  C,  "Cultural  races  and  the  production  of  variants  in  Pesta- 
lozzia  funerea,"  Bull.  Torrey  Botan.  Club,  59:  525-544,  1932. 

Christiansen,  J.  J.,  "Studies  on  the  parasitism  of  H ' elminthosporium  sati- 
vum," Minn.  Agr.  Expt.  Sta.  Tech:  Bull.,  11:  3—42,  1922. 
"Mutation  and  hvbridization  in  Ustilago  zeae.    Part  II.     Hvbridization," 

Minn.  Agr.  Expt.  Sta.  Tech.  Bull.,  65:  85-108,  1929. 
"Studies  on  the  genetics  of  Ustilago  zeae,"  Phytopath.  Z.,  4:  129-188,  1931. 
"The  origin  of  parasitic  races  of  phvtopathogenic  fungi  through  muta- 
tion," Genetics  of  Pathogenic  Organisms,  Am.  Assoc.  Adv.  Sci.,  77-82, 
1940. 

Christiansen,  J.  J.,  and  T.  W.  Graham,  "Phvsiologic  specialization  and  vari- 
ation in  H elminthosporhnn  graminenm  Rab.,"  Minn.  Agr.  Expt.  Sta. 
Tech.  Bull.,  95:  1-10,  1934. 


214        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

Christiansen,  J.  J.,  and  H.  A.  Rodenheiser,  "Physiologic  specialization  and 

genetics  of  the  smut  fungi,"  Botan.  Rev.,  6:  389-425,  1940. 
Christiansen,  J.  J.,  and  E.  C.  Stakman,  "Physiologic  specialization  and  mu- 
tation in  Ustilago  zeae"  Phytopathology,  16:  979-999,  1926. 
Ciferri,  R.,  "Osservasioni  sulla  specializzazione  dell  Albugo  ipomoeae-pan- 

duranae  (Schw.)  S\v.,  Nuov.  giorn.  ltd.,  35:  112-134,  1928. 
Cotter,  R.  U.,  and  M.  N.  Levine,  "Physiologic  specialization  in  Puccinia 

graminis  secalis,"  J.  Agr.  Research,  45:297-315,  1932. 
Craic;ie,  J.  H.,  "The  origin  of  physiologic  races  of  rust  fungi  through  hy- 
bridization," Genetics  of  Pathogenic  organisms,  Am.  Assoc.  Adv.  Sci., 

66-72,  1940. 
Diedicke,  H.,  "Uber  den  Zusammengehang  zwischen  Pleospora  und  Helmin- 

thosporium-artcn,"  Zentr.  Bakt.,  Parasitenk.,  II  Abt.,  9:  317-329,  1902. 
Dimock,  A.  W.,  "Studies  of  ascospore  variants  of  Hypomyces  ipomoeae," 

My  col.,  57:709-727,  1939. 
Dodge,  B.  O.,  "Inheritance  of  the  albinistic  non-conidial  character  in  inter- 
specific hybrids  in  Neurospora,"  My  col.,  23:  1-50,  1931. 
"Heterocarvotic  vigor  in  Neurospora,"  Bull.  Torrey  Botan.  Club,  69:  75- 

91,  1942.  ' 
Eriksson,  J.,  "Uber  die  Specialisierung  des  Parasitismus  bei  den  Getreiderost- 

pilzen,"  Ber.  dent,  botan.  Ges.,  12:  292-331,  1894. 
Faris,  J.  A.,  "Physiologic  specialization  of  Ustilago  hordei"  Phytopathology , 

1 4:  537-557,  1 924. 
"Factors  influencing  infection  of  Hordeum  sativum  by  Ustilago  hordei" 

Am.  J.  Botany,  11:  189-214,  1924a. 
Flor,  H.  H.,  "Heterothallism  and  hybridization  in  Tilletia  tritici  and   T. 

levis"  J.  Agr.  Research,  44:  49-58,  1932. 
"Studies  on  physiologic  specialization  in  Tilletia  tritici  and  T.  levis  in  the 

Pacific  Northwest,"  /.  Agr.  Research,  41:  193-213,  1933. 
Frenzel,  H.,  "Beitrage  zur  Spezialisierung  des  Haferkronenrostes  Puccinia 

coroiiifera,  f.  sp.,  avenae  Kleb,"  Arb.  biol.  Reichs.  Land-u.  Forstw.  Berlin- 

Dahlem,  18:  153-176,  1930. 
Gaines,  E.  F.,  "New  physiological  forms  of  Tilletia  levis  and  T.  tritici,'"' 

Phytopathology,  18:  579-588,  1928. 
Gaumann,  E.,  "Beitrage  zu  einer  Monographic  der  Gattung  Peronospora 

Corda,"  Beitr.  Kryptogainenflora,  5:  1-360,  1923. 
Gilbert,  E.  AI.,  "Biologic  forms  of  black  knot,"  Phytopathology,  5:246-247, 

1913. 
Goldschmidt,   V.,   "Vererbungsversuche    mit   den   biologischcn   Arten    der 

Antherenbrandes  (Ustilago  violacea  Pers.),"  Z.  Botan.,  21:  1-90,  192s. 
Gordon,  \V.  L.,  "Effect  of  temperature  on  host  reaction  to  physiologic  forms 

of  Puccinia  graminis  avenae  Erikss.  and  Henn.,"  Sci.  Agr.,  11: 95-103, 

1930. 
'  \    suulv    of   the    relation   of   environment   to    the    development   of   the 

uredinial  and  telial  stages  of  the  physiologic  forms  of  Puccinia  graminis 

avenae  Erikss.  and  Henn.,"  Sci.  Agr..  14:  184-237,  1933. 
Goulden,  C.  H.,  M.  Newton,  and  A.  AI.  Brown,  "The  reaction  of  wheat 


LITERATURE  CITED  215 

varieties   at  two   stages   of   maturity   to   sixteen   physiologic   forms   of 
Puccinia  graminis  tritici"  Sci.  Agr.,  11:9-25,  1930. 

Grevel,  F.  Km  "Untersuchungen  iiber  das  Vorhandensein  biologischer  Ras- 
sen  des  Flugbrandes  des  Weizens  (Ustilago  tritici) ,"  Phytopath.  Z., 
2:209-234,  1930. 

Hammarlund,  C,  "Zur  Genetik,  Biologie,  und  Physiologie  einiger  Erysiph- 
aceen,  Hereditas,  6:  1-126,  1925. 

Hansen,  H.  N.,  and  R.  E.  Smith,  "The  mechanism  of  variation  in  imperfect 
fungi:  Botrytis  cinerea"  Phytopathology,  22:953-964,  1932. 

Harrington,  J.  B.,  "The  effect  of  temperature  on  the  expression  of  factors 
governing  rust  reaction  in  a  cross  between  two  varieties  of  Triticum 
vulgare,"  Can.  J.  Research,  5:200-207,  1931. 

Harter,  L.  L.,  and  J.  L.  Weimer,  "Some  physiological  variations  in  strains 
of  Rhizopus  nigricans"  J.  Agr.  Research,  25:363-371,  1923. 

Hey,  A.,  "Beitrage  zur  Spezialisierung  des  Gerstenzwergrostes,  Puccinia 
simplex  Eriksson  et  Henning,"  Arb.  biol.  Reichs.  Land-u.  Forstiv.  Ber- 
lin-Dahlem,  19:227-261,  1931. 

Hoerner,  G.  R.,  "Biologic  forms  of  Puccinia  corojiata  on  oats,"  Phyto- 
pathology, .9:309-314,  1919. 

Holton,  C.  S.,  "The  relation  of  physiologic  specialization  in  Tilletia  to  re- 
cent epiphvtotics  of  bunt  in  Durum  and  Marquis  wheats,"  Phyto- 
pathology,21:  687-694,  1931. 

Johnson,  C.  O.,  "An  aberrant  physiologic  form  of  Puccinia  triticina  Erikss.," 
Phytopathology,  20:  609-620,'  1930. 

Johnson,  C.  O.,  and  E.  B.  Mains,  "Studies  on  physiologic  specialization  in 
Puccinia  triticina;'  U.  S.  Dept.  Agr.  Tech.  Bull.,  313:  1-23,  1932. 

Johnson,  E.  M.,  and  W.  D  Valleau,  "Cultural  variations  of  Thielaviopsis 
basicola,"  Phytopathology,  25:1011-1018,  1935. 

LaRue,  C.  D.,  "The  results  of  selection  within  pure  lines  of  Pestalozzia 
guepini"  Genetics,  7:  142-183,  1922. 

LaRue,  C.  D.,  and  H.  H.  Bartlett,  "A  demonstration  of  numerous  distinct 
strains  within  the  nominal  species  Pestalozzia  guepini  Desm.,"  Am.  J. 
Botany,  9:  79-92,  1922. 

Leach,  J.  G.,  "The  parasitism  of  Colletotrichum  lindemuthiammt"  Minn. 
Agr.  Expt.  Sta.  Tech.  Bull.,  14: 39  pp.    1922. 

Leontan,  L.  H.,  "Physiological  studies  on  the  genus  Phytophthora,"  Am.  J. 
Botany,  12: 444-498,  1925. 
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Phytopathology,  16:723-731,  1926.  " 
"Studies    on    the    variability    and    dissociation    in    the    genus    Fusarium," 

Phytopathology,  19:  753-868,  1929. 
"Attempts  to  induce  'mixochimaera'  in  Fusarium  monilifonne;''  Phyto- 
pathology, 20:895-901,  1930. 

Levine,  M.  N.,  "Biometrical  studies  on  the  variation  of  physiologic  forms 
of  Puccinia  graminis  tritici  and  the  effects  of  ecological  factors  on  the 
susceptibility  of  wheat  varieties,"  Phytopathology,  18:  7-126,  1928. 

Mains,  E.  B.,  "Host  specialization  of  barley  rust,  Puccinia  anomala"  Phyto- 
pathology, 20:  875-882,  1930. 


216        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

.Mains,  E.  B.,  "Host  specialization  of  Erysiphe  graviinis  tritici"  Proc.  Nat. 
Acad.  Sci.,    1 9:  49-53,  1933. 
"Host  specialization   in   the   leaf   rust   of  grasses,  Puccinia  rubigo-vera" 
Mich.  Acad.  Sci.  Papers,  77:289-394,  1933a. 
.Mains,  E.  B.,  and  S.  .M.  Dietz,  '"Physiologic  forms  of  barley  mildew,  Ery- 
siphe graminis  hordei  Marchal,"  Phytopathology,  20:229-239,  1930. 
.Mains,  E.  B.,  and  H.  S.  Jackson,  "Physiologic  specialization  in  the  leaf  rust 
of  wheat,  Puccinia  graviinis  Erikss.,"  Phytopathology,  16:  89-120,  1926. 
Marchal,  E.,  "De  la  specialization  du  parasitisme  chez  V Erysiphe  graminis 

DC,"  Comp.  rend.,  755:210-212,  1902;  136:  1280-1281,  1903. 
Matsumoto,  T.,  "Studies  in  the  physiology  of  fungi.     XII.  Physiological 
specialization  in  Rhizoctonia  solani  Kiihn,"  Ann.  Mo.  Botan.  Garden, 
8:  1-62,  1921. 
.Melchers,  L.  E.,   "Investigations   on   physiologic   specialization   of   Tilletia 

laevis  in  Kansas,"  Phytopathology,  24:  1203-1226,  1934. 
.Melchers,  L.  E.,  C.  H.  Fricke,  and  C.  O.  Johnston,  "A  study  of  physiologic 
forms  of  kernel  smut  (Sphacelotheca  sorghi)  of  sorghum,"  /.  Agr.  Re- 
search, 44:  1-11,  1932. 
Newton,  .M.,  and  T.  Johnson,  "Color  mutations  in  Puccinia  graviinis  tritici 
(Pers.)  Erikss.  and  Henn.,"  Phytopathology,  77:711-725,  1927. 
"Specialization  and  hybridization  of  wheat-stem   rust,  Puccinia  graviinis 
tritici,  in  Canada,"  Dom.  Canada  Dept.  Agr.  Bull.,  160:  1-60,  1932. 
Newton,  .M.,  T.  Johnson,  and  A.  .M.  Brown,  "A  preliminary  study  of  the 
hybridization  of  physiologic  forms  of  Puccinia  graviinis  tritici"  Sci. 
Agr.,  70:721-731,  1930. 
Penser,    H.,    "Fortgesetzte    Untersuchungen    iiber   das   Vorkommen   biolo- 
gischer  Rassen  von  Colletrotrichuvi  lindevmthianuvi   (Sacc.  et  .Magn.) 
Bri.  et  Cav.,"  Phytopath.  Z.,  4:  83-112,  1931. 
Peturson,  B.,  "Effect  of  temperature  on  host  reactions  to  physiologic  forms 

of  Puccinia  corovata  avenae,"  Sci.  Agr.,  11:  104-110,  1930. 
Pfister,  R.,  "Zur  Biologie  von  Cystopus  tragopogonis  Pers,"  Zentr.  Bakt., 

Parasitenk.,  II  Abt.,  77:  312-313,  1927. 
Radulescu,  E.,  "Zur  phvsiologischen  Spezialisierung  des  Weizenbraunrostes 

{Puccinia  triticina  Erikss.),"  Kiihn- Arch.,  33:  195-205,  1932. 
Reed,    G.    M.,    "Physiological   specialization   of   parasitic   fungi,"    Brooklyn 
Botan.  Garden  Mevi~.,  7:348-409,  1918. 
"Physiologic  races  of  oat  smuts,"  Am.  J.  Botany,  77:483-492,  1924. 
"Further  evidence  of  physiologic  races  of  oat  smuts,"  My  col.,  79:21-28, 

1927. 
"Physiologic  races  of  bunt  of  wheat,"  Am.  J.  Botany,  15:  157-170,  1928. 
"New   physiologic  races  of  oat  smuts,"  Bull.  Torrey  Botan.  Club,  56:  449- 

470,  1929. 
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1935. 
"Physiologic  races  of  oat  smuts,"  Am.  J.  Botany,  21:  135-143,  1940. 
Reed,  G.  .M.,  and  T.  R.  Stanton,  "Physiologic  races  of  Ustilago  levis  and 
U.  avenae  on  red  oats,"  /.  Agr.  Research,  44:  147-153,  1932. 


LITERATURE  CITED  211 

Reed,  G.  M.,  Marjorie  Swabey,  and  Laura  A.  Kolk,  "Experimental  studies 

of  head  smut  of  corn  and  sorghum,"  Bull.  Torrey  Botan.  Club,  54:  295- 

310,  1927. 
Rodenheiser,    H.    A.,    "Physiologic    specialization    in   some    cereal    smuts," 

Phytopathology,  i#:  955-1003,  1928. 
"The  origin  of  physiologic  races  in  the  smut  fungi  by  hybridization," 

Genetics  of  Pathogenic  Organisms,  Am.  Assoc.  Adv.  Sci.,  73-76,  1940. 
Rodenheiser,   H.   A.,   and   E.   C.   Stakman,    "Physiologic   specialization    in 

Tilletia  levis  and  Tilletia  tritici,"  Phytopathology,  11:  247-253,  1927. 
Salmon,  E.  S.,  "On  Erysiphe  graminis  DC,  and  its  adaptive  parasitism  within 

the  genus  Bromus,"  Ann.  My  col.,  2:255-267,  307-343,  1904. 
"Cultural   experiments  with   biologic   forms   of  the   Erysiphaceae,"   Phil. 

Trans.  Roy.  Soc.  Lo?idon,  Ser.  B.,  191:  107-122,  1904a. 
"Recent  researches  on  the  specialization  of  parasitism  in  the  Erysiphaceae," 

New  Phytopathologist,  3:  55-60,  1904. 
Savulescu,  T.,  and  T.  Rayss,  "Contribution  a  la  connaissance  des  Pero- 

nosporacees  de  Roumaine,"  Ann.  Mycol.,  28:  297-320,  1930. 
Schreiber,  F.,  "Resistenzziichtung  bei  Phaseolus  vidgaris,"  Phytopath.  Z., 

4:415-454,  1932. 
Schroeter,  J.,  "Entwickelung  einiger  Rostpilze,"  Beitr.  Biol.  Pflanzen,  3:  69- 

70,  1879. 
Stager,    R.,    "Infectionsversuche    mit    Gramineen-bewohnenden    Claviceps- 

arten,"  Botan.  Z.,  61:  111-158,  1903. 
Stakman,   E.   C,   "Physiologic   specialization   in   pathogenic   fungi,"   Proc. 

Intern.  Congr.  Plant  Sci.  Ithaca,  2:  1312-1330,  1926. 
"The  problem  of  specialization  and  variation  in  phytopathogenic  fungi," 

Genetica,  18: 372-389,  1936. 
Stakman,  E.  C,  J.  J.  Christiansen,  and  H.  E.  Brewbaker,  "Physiologic 

specialization  in  Puccinia  sorghi,"  Phytopathology,  18: 345-354,  1928. 
Stakman,  E.  C,  J.  J.  Christiansen,  C.  J.  Eide,  and  B.  Peturson,  "Mutation 

and  hybridization  in  Ustilago  zeae,"  Minn.  Agr.  Expt.  Sta.  Tech.  Bull., 

65:  108  pp.     1929. 
Stakman,  E.  C,  and  M.  N.  Levine,  "The  determination  of  biologic  forms 

of  Puccinia  graminis  on  Triticum  spp.,"  Minn.  Agr.  Expt.  Sta.  Tech. 

Bull.,  8:  1-10,  1922. 
Stakman,  E.   C,  M.  N.  Levine,  and   D.   L.  Bailey,   "Biologic   forms   of 

Puccinia  graminis  on  varieties  of  Avena  spp.,"  /.  Agr.  Research,  24:  1013- 

1018,  1923. 
Stakman,  E.  C,  M.  N.  Levine,  and  R.  U.  Cotter,  "Origin  of  physiologic 

forms  of  Puccinia  graminis  through  hybridization  and  mutation,"  Set. 

Agr.,  10:  707-720,  1930. 
Stakman,  E.  C,  M.  N.  Levine,  R.  U.  Cotter,  and  L.  Hines,  "Relation  of 

barberry  to  the  origin  and  persistence  of  physiologic  forms  of  Puccinia 

graminis?  J.  Agr.  Research,  48:953-969,  1934. 
Stakman,  E.  C,  M.  N.  Levine,  and  L.  Hines,  "Relation  of  barberry  to  the 

origin  and  persistence  of  physiologic  forms  of  Puccinia  graminis?  J. 

Agr.  Research,  48:951-969,  1934. 


218        PHYSIOLOGIC  SPECIALIZATION  AND  VARIATION 

Stakman,  E.  C,  and  F.  J.  Piemeisel,  "A  new  strain  of  Pucc'inia  graminis" 
Phytopathology,  7:  73,  1917. 

Stakman,  E.  C,  L.  J.  Tyler,  and  G.  E.  Hafstad,  "The  constancy  of  cul- 
tural characters  and  pathogenicity  in  variant  lines  of  Ustilago  zeae" 
Bull.  Torrey  Botan.  Club,  60:  565-572,  1933. 

Steiner,  J.  A.,  "Die  Specialization  der  Alchenillen-bewohnenden  Sphaero- 
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736,  1908. 
Tisdale,  W.  H.,  L.  E.  Melchers,  and  H.  J.  Clemmer,  "Strains  of  kernel 

smuts  of  sorghum,  Sphacelotheca  sorghi  and  S.  cruenta,"  J.  Agr.  Re- 
search, 34:  825-838,  1927. 
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Candida  (Pers.)  O.  Kuntze,  in  connection  with  its  specialization,"  Imp. 

Coll.  Agr.  Forestry,  Morioka,  Bull,  IS:  1-88,  1934. 
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cruenta  and  Sorosporiwn  reiliammi"  Phytopathology,  25:  375-376,  1935. 
Ward,  H.  .Marshall,  "Further  observations  on  the  brown  rust  of  bromes, 

Puccinia  dispersa  (Erikss.),  and  its  adaptive  parasitism,"  Ann.  My  col., 

1:  132-151,  1903. 
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Australian  phvsiologic  forms  of  Puccinia  graminis  tritici,"  Proc.  Lin- 

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Chapter  12 
ASSOCIATIVE  EFFECTS  AMONG  FUNGI 

In  this  chapter  it  is  proposed  to  consider  those  phenomena 
manifest  as  a  result  of  different  species  of  fungi  living  together 
in  close  proximity.  It  is  essentially  an  ecological  study  of  fungi 
and  corresponds  in  some  measure  to  a  consideration  of  associations 
among  seed  plants.  Of  course,  a  great  deal  has  been  learned  re- 
garding the  influence  of  one  species  of  seed  plant  upon  another 
growing  in  close  juxtaposition.  Our  knowledge  of  similar  asso- 
ciative relationships  among  fungi  is  strikingly  much  more  meager 
and  fragmentary,  and  the  data  are  rather  widely  dispersed  in  the 
literature.  Such  facts  regarding  fungi  appear  none  the  less  im- 
portant, however,  and  they  may  be  found  to  possess  interesting 
applications  and  economic  potentialities. 

For  convenience,  the  effects  of  interaction  of  fungi,  one  upon 
the  other,  may  be  divided  into  the  following  categories:  antibiotic, 
symbiotic,  and  synergetic.  The  associative  relationships  have 
been  designated  antagonism,  symbiosis,  and  synergism,  respec- 
tively. In  antibiotic  effects  are  included  those  antagonistic,  com- 
petitive, or  harmful  effects  that  result  to  organisms  from  their 
growth  in  close  proximity.  Effects  resulting  from  parasitism  are 
among  those  included  in  this  classification.  In  symbiotic  effects 
are  included  mutualistic  advantages  that  result  from  the  living  to- 
gether of  two  or  more  species.  In  synergetic  effects  are  included 
those  in  which  two  or  more  species  through  their  combined  action 
produce  effects  or  changes  that  neither  could  produce  alone. 

It  becomes  apparent  immediately  that  these  categories  are  arbi- 
trary, and  that  evidence  might  be  found  to  show  that  they  inter- 
grade.  Indeed,  such  evidence  is  at  hand.  Among  the  factors 
studied  that  have  to  do  with  inter£radation  and  with  associative 
effects  generally  are  competition  for  food,  modification  of  food 
supply  by  the  metabolism  of  one  or  the  other  of  the  associated 
species,  relative  availability  of  food  constituents,  changes  in  re- 

219 


280  ASSOCIATIVE  EFFECTS  AMONG  FUNGI 

action  of  the  medium,  production  of  inhibitory  toxic  products, 
production  of  stimulatory  or  growth-controlling  substances,  such 
as  vitamins,  auxins  and  hormones,  and  variation  in  temperature 
and  in  02  tension.  These  matters,  as  they  apply  to  associative 
effects,  have  been  capablv  reviewed  bv  Waksman  (1937),  Porter 
and  Carter  (1938),  Weindling  (1938),  D'Aeth  (1939),  and 
Waksman  (1941),  each  of  whose  summaries  should  be  carefully 
perused. 

ANTAGONISM 

In  our  social  organization  the  human  race  may  be  spoken  of  as 
constituted  of  two  groups,  producers  and  consumers,  and  if  this 
analogy  is  applied  to  fungi,  all  of  them,  by  virtue  of  their  lack  of 
chlorophyll,  are  perforce  in  the  consumer  grouping.  They  not 
only  are  largely  dependent  upon  other  organisms,  living  or  dead, 
as  sources  of  food,  but  also  the  "struggle  for  existence"  is  just  as 
acute  among  them,  with  resultant  "survival  of  the  fittest,"  as  it  is 
among  anv  other  tvpe  of  organism.  This  associative  interaction 
exists  not  only  among  the  fungi  themselves  but  between  bacteria 
and  fungi,  slime  molds  and  fungi,  actinomycetes  and  fungi,  proto- 
zoa and  fungi,  and  also  various  other  organisms  and  fungi.  In  fact, 
it  is  doubtful  if  anv  chlorophyll-bearing  species  of  plant  is  free 
from  attack  bv  fungi,  and,  moreover,  records  of  hyperparasitism 
among  fungi  are  not  infrequent. 

Evidence  of  antagonism  from  cultures.  One  of  the  essential 
techniques  in  the  study  of  fungi  is  their  isolation  in  pure  culture. 
These  procedures  are  based  upon  the  use  of  semisolid  media,  first 
utilized  by  Koch  to  isolate  bacteria  in  pure  culture.  All  mycolo- 
gists have  come  to  place  enormous  importance  upon  the  use  of 
pure  cultures,  although  they  know  full  well  that  in  nature  pure 
cultures  are  either  non-existent  or  else  occur  as  miraculous  oddi- 
ties. In  consequence  of  insistence  upon  use  of  pure  cultures,  too 
little  attention  has  been  given  to  studies  of  known  mixtures  of 
fungi  [Fawcett  (1931)]. 

It  has  long  been  known  that  microorganisms  in  culture  produce 
substances  that  limit  their  own  period  of  growth.  As  evidence 
the  production  of  alcohol  by  yeasts,  of  citric  acid  by  Aspergillus 
niger,  and  of  lactic  acid  by  Rhizopus  sp.  may  be  cited.  These 
growth-inhibiting  substances  have  been  regarded  as  aids  in  the 
struggle  for  existence  of  microorganisms. 


ANTAGONISM  281 

All  who  have  studied  microorganisms  on  artificial  media  have 
noted  evidence  of  this  antagonism  between  the  colonies  of  differ- 
ent species.  An  explanation  for  this  phenomenon  was  first  sought 
by  Raulin  in  1869  [D'Aeth  (1939)1  in  experiments  involving  the 
growth  of  A.  niger  on  liquid  synthetic  media.  He  removed  the 
mycelial  mat  by  filtration  at  intervals  of  3  days  and  determined  the 
amount  of  growth  during  each  successive  3 -day  period.  Most 
growth  occurred  in  the  first  period,  with  less  in  each  period  there- 
after. From  these  results  it  was  concluded  that  growth-affecting 
substances  are  excreted  by  A.  niger  and  that  they  remain  in  the 
filtrate.  The  reciprocal  influence  of  the  simultaneous  production 
of  such  substances  upon  paired  organisms  in  the  same  culture  was 
first  studied  by  Reinhart  in  1892  [D'Aeth  (1939)].  Since  then 
similar  studies  have  been  made  by,  among  others,  Zeller  and 
Schmitz  (1919),  Porter  (1924),  Sanford  and  Broadfoot  (1931), 
Endo  (1931,  1932,  1932a),  Weindling  (1932),  Broadfoot  (1933), 
and  Arrillaga  (1935). 

Porter  (1924)  used  80  species  of  fungi  and  bacteria  grown  in 
pairs  on  corn-meal  agar.  The  fungi  employed  included  Penicil- 
lium  glaucum,  P.  italicum,  Rhizopus  nigricans,  Fnsariiim  lini,  F. 
culmonem,  F.  coeruleum,  Gloeosporinm  piperatum,  Colleto- 
trichum  nigrum,  C.  lindemiithianum,  and  Helminthosporinm 
sativum.  He  classified  their  interactions  into  five  groups,  four  of 
which  are  antagonistic,  showing  differences  in  degree  of  inhibitory 
action  as  follows: 

1.  One  species  overgrows  and  inhibits  the  other. 

2.  Each  member  of  the  pair  exerts  a  slight  mutual  inhibition. 

3.  One  of  the  pair  grows  close  to  but  around  the  other. 

4.  Mutual  inhibition  is  exhibited  at  a  considerable  distance,  and 
the  two  remain  separate. 

Endo  (1931,  1932,  1932a)  found  that  Hypochnns  centrifugus, 
H.  sasakii,  and  Sclerotium  oryzae-sativae,  causing  root-rot  diseases 
of  rice,  are  indifferent  to  certain  other  fungi,  and  antagonism  was 
exhibited  in  other  combinations. 

Broadfoot  (1933)  studied  the  interaction  of  66  species  of  micro- 
organisms, many  of  them  bacteria,  with  special  consideration  to 
their  antagonisms  toward  Ophiobolns  graminis.  Among  the  fungi 
that  he  found  to  be  antagonistic  to  O.  graminis  are  Ascochyta 
graminis,  Botrytis  cinerea,  Helminthosporium  sativum,  Lepto- 


282  ASSOCIATIVE  EFFECTS  AMONG  FUNGI 

sphaeria  herpotrichoides,  Flenodomus  7/ielilotiy  and  Wofnoimda 
grandnis. 

Arrillaga  (1935)  made  all  possible  combinations  on  potato  dex- 
trose agar  of  12  species  of  fungi  associated  with  disease  or  decay 
of  Citrus  fruits,  with  the  result  that  Diaporthe  cirri  checked  the 
growth,  especially  of  Phytophthora  parasitica  and  P.  citrophthora. 

Causes  of  antagonism.  It  is  apparent  from  the  reports  of 
these  studies  that  the  range  of  interaction  between  fungi  extends 
from  complete  indifference  of  both  members  of  the  pair  on  the 
one  extreme  to  very  active  inhibition  on  the  other.  Since  these 
effects  are  manifest  indifferently  between  members  of  all  classes 
of  fungi,  it  appears  improbable  that  one  and  the  same  proximate 
cause  is  responsible  for  all.  Instead  a  variety  of  causes  has  been 
suggested,  and  evidence  in  their  support  has  been  submitted.  Some 
of  these  causes  are  exhaustion  of  nutrients,  modification  of  their 
balance  or  concentration,  differential  in  optimal  pH,  which  may 
be  the  result  of  metabolic  products  formed  by  one  of  the  species, 
differential  in  optimal  temperature,  production  of  excretory  prod- 
ucts, which  cause  staling,  production  of  toxic  substances,  and 
aversion.  Not  all  need  be  considered  in  this  discussion,  nor  need 
evidence  in  their  support  be  reviewed. 

The  term  staling  is  applied  to  the  well-known  phenomenon  in 
which  the  growth  rate  of  a  fungus  on  an  artificial  medium  grad- 
ually decreases  and  eventually  ceases.  This  phenomenon  is  not 
the  result  of  an  exhaustion  of  nutriment  but  of  the  presence  of  a 
progressive  increase  in  amount  of  products  of  metabolism.  Niki- 
tinsky  ( 1904)  grew  on  liquid  media  repeated  crops  of  Pemcillhim 
glaucum,  P.  griseim?,  Mucor  stolonifer,  Aspergillus  flavzis,  Sac- 
charomyces  cerevisiae,  and  S.  rosaceus.  At  intervals  the  mycelial 
mat  was  removed  by  filtration,  dried,  and  weighed.  The  medium 
was  then  sown  with  the  same  or  a  different  species,  and  the  mat 
was  again  removed.  This  procedure  was  repeated  until  the  me- 
dium would  no  longer  support  growth.  He  observed  that,  when 
ammonium  chloride  was  used  as  the  source  of  nitrogen,  the  inhibi- 
tion set  in  quickly,  and  the  medium  became  increasingly  more 
acid.  To  such  media  he  then  added  alkali,  and  the  media  again 
supported  good  growth.  When  he  employed  ammonium  tartrate 
as  the  source  of  nitrogen,  the  medium  became  stale  less  quickly, 
the  XHS  being  used  as  the  source  of  nitrogen  and  the  tartrate  radi- 
cal  as  the  source  of  carbon.    When  peptone  was  used,  the  media 


ANTAGONISM  283 

quickly  became  alkaline,  and  good  growth  could  again  be  pro- 
moted by  the  addition  of  acid. 

From  similar  studies  with  Aspergillus  niger,  Botrytis  cinerea, 
Cladosporhim  herbarum,  Fusarium  solani,  Mucor  mncedo,  Peni- 
cillium  glaucwn,  and  Rhizopus  nigricans  Lutz  (1909)  concluded 
that  a  variety  of  materials  cause  staling.  Although  he  was  unable 
to  indentify  any  of  them,  he  determined  that  some  filtrates  were 
free  from  growth-inhibiting  substances  after  passage  through  a 
porcelain  filter,  whereas  in  others  the  staling  products  passed  read- 
ily through  such  filters.  In  some  instances,  moreover,  heating  to 
80°  C  destroyed  the  inhibitory  properties,  indicating  a  relation- 
ship to  enzymes.  Even  after  dilution  with  20  volumes  of  water 
the  filtrates  still  greatly  inhibited  growth. 

Boyle  (1924)  grew  Botrytis  cinerea  and  Fusarium  sp.,  isolated 
from  apple,  on  Richards'  solution,  potato  extract,  and  apple  ex- 
tract. On  each  medium  these  organisms  caused  increased  alka- 
linity,  which  if  eliminated  in  slightly  stale  media  by  addition  of 
acid,  caused  growth  to  be  restored.  At  a  later  stage  of  staling, 
however,  adjustment  of  reaction  did  not  correct  conditions.  He 
concluded  from  these  results  that  change  in  reaction  is  not  per  se 
the  limiting  factor  but  that  it  accompanies  the  accumulation  of 
other  inhibitory  metabolic  products.  Filtration  through  a  col- 
lodion membrane  removed  part  of  the  inhibitory  properties. 
Boiling  of  the  staled  medium  also  resulted  in  improved  growth 
but  indicated  that  both  thermolabile  and  thermostable  products 
were  present. 

Pratt  (1924,  1924a),  using  a  species  of  Fusarium  that  rapidly 
staled  Richards'  solution  and  Botrytis  cinerea,  which  had  little 
staling  properties,  noted  that  hydrogen  peroxide  added  to  the 
staled  medium  removes  staleness,  as  does  charcoal  also,  provided 
that  the  alkalinity  is  first  removed.  Her  chemical  tests  of  media 
staled  by  Fusarium  indicate  that  ammonia,  alcohol,  and  salts  of 
acetic,  propionic,  butyric,  valeric,  and  lactic  acids  are  produced. 
Her  general  conclusion  is  that  alkaline  staling  is  caused  by  the  pro- 
duction of  bicarbonates  from  the  carbon  dioxide  of  respiration 
whenever  basic  radicals  are  set  free. 

From  the  foregoing  accounts  it  is  clear  that  a  variety  of  inhibi- 
tory staling  products  are  elaborated  and  that  different  species  of 
fungi  may  produce  different  products.  Some  of  them  may  be 
either  simple  or  complex,  some  either  heat-labile  or  heat-stable, 


284  ASSOCIATIVE  EFFECTS  AMONG  FUNGI 

some  either  filterable  or  non-filterable.  There  may  also  exist 
inter^radations  between  slight  inhibition  of  growth  and  marked 
toxic  action,  and  in  consequence  it  becomes  practically  impossible 
to  separate  staling  products  from  toxic  products.  Much  has 
been  written  regarding  these  toxins,  since  they  have  been  em- 
ployed to  explain  the  proximate  cause  of  wilting  by  pathogenic, 
vascular-tissue-invading  species  of  Fusarium.  The  chemical  con- 
stitution of  many  definitely  toxic  products  has  been  determined. 
Some  appreciation  of  the  extent  of  our  knowledge  on  this  matter 
may  be  gained  from  the  excellent  summaries  of  Raistrick  (1932, 
1938).  Clutterbuck,  Lowell,  and  Raistrick  (1932)  isolated  one 
such  toxic  substance,  a  yellow  pigment,  chrysogenin,  with  the 
empirical  formula  C8Ho2b(1.  It  is  formed  by  one  of  the  Penicil- 
lium  chrysogemnn  group  on  a  svnthetic  medium  containing  glu- 
cose. Tests  showed  it  to  possess  very  powerful  antibacterial  prop- 
erties, especially  against  the  pyogenic  cocci  and  the  diphtheria 
group,  but  it  was  ineffective  against  the  colon-typhoid  organisms. 
Weindlinc;  and  Emerson  (1936)  isolated  a  proteinaceous  toxin 
with  the  formula  C14H1CN2S2O4  from  Gliocladium  fimbriatum, 
whereas  Dutcher  (1941)  determined  its  formula  to  be  Ci3Hi4- 
04N2S2.  In  concentration  of  2.5  mg  per  milliliter  it  was  bac- 
tericidal to  Staphylococcus  albus,  and  of  1.0  mg  per  milliliter  to 
5.  aureus  and  Streptococcus  viridans. 

Recently  Abraham  and  associates  (1941)  isolated  penicillin, 
presumably  from  Penicillium  uotatum,  finding  that  it  was  very 
potent  against  several  species  of  bacteria  pathogenic  to  man.  Peni- 
cillin appears  to  have  therapeutic  value  when  used  in  place  of  sul- 
fonamides, as  is  indicated  in  Chapter  4.  In  some  cases  the  toxic 
principles  appear,  from  their  extractability  by  ether  or  chloroform, 
to  be  lipoidal  in  nature. 

A  very  different  type  of  antagonism,  in  which  the  cause  is  asso- 
ciated with  sex,  has  been  encountered  among  all  the  principal 
groups  of  fungi.  It  has  been  widely  studied  in  connection  with 
the  phenomenon  of  heterothallism,  which  need  not  be  discussed 
at  this  time.  Suffice  it  to  say  that,  when  the  mycelia  of  mono- 
sporic  cultures  are  grown  in  the  same  Petri-dish  culture,  mutual 
aversion  may  be  manifest  by  sexual  incompatibility.  Cayley 
(1923,  1931)  has  given  special  consideration  to  aversion,  pri- 
marily as  it  concerns  Diaporthe  permc'wsa,  the  cause  of  wilt  of 
plums  in  Europe.    In  cultures  of  this  organism,  the  isolates  may 


ANTAGONISM  285 

exhibit  mutual  aversion  at  their  line  of  contact,  evidenced  by  kill- 
ing of  the  hvphal  tips.  This  property  is  heritable  but  is  not 
influenced  by  sex.  Hoppe  (1936)  noted  a  similar  aversion  in  the 
conidial  fungus,  Diplodia  zeae,  pathogenic  to  maize,  and  the  prop- 
erty remained  fixed  as  shown  by  repeated  inoculation  into  the 
living  host  and  reisolation. 

Evidence  of  antagonism  from  growth  in  host  tissues.  Clear- 
cut  evidence  of  antagonism  between  microorganisms  when  associ- 
ated within  green  host  plants  is  lacking  or  meager.  Bamberg 
(1931)  found  that  several  species  of  unidentified  bacteria  reduced 
the  virulence  of  Ustilago  zeae  and  prevented  the  formation  of  smut 
galls  when  injected  into  maize  coincidentally  with  smut  sporidia 
or  even  3  days  later.  After  smut  galls  %  in.  in  diameter  had  de- 
veloped, injection  of  bacteria  was  followed  by  disintegration  of 
the  gall  and  failure  of  chlamydospores  to  form.  Johnson  (1931) 
found  that  certain  bacteria  produced  enzymes  capable  of  dissolv- 
ing the  cell  walls  of  sporidia  of  several  smuts  and  that  others  with 
the  same  enzymes  were  unable  to  attack  the  sporidia.  From  these 
results  she  concluded  that  the  antagonistic  principle  was  not  an 
enzyme. 

Savastano  and  Fawcett  (1929)  inoculated  citrus  fruits  with 
combinations  of  various  fungi  normally  associated  with  decays 
of  such  fruit.  In  some  combinations  the  rate  of  decay  was  slower 
than  that  produced  by  the  slower-growing  component  by  itself. 
These  investigators  conclude  that  the  cause  of  modification  of 
rate  of  decay  is  correlated  with  specific  food  requirements  of  the 
respective  species  and  with  the  competition  for  these  foods  that 
must  occur.  The  two  common  molds,  Penicillium  italicum  and 
P.  digitatum,  that  attack  citrus  fruits  are  antagonistic,  P.  digitatum 
being  able  to  grow  with  greater  rapidity  and  to  surround  the  area 
decayed  by  P.  italicum. 

Perhaps  the  best  evidence  in  hand  of  antagonism  between  fungi 
is  exhibited  by  the  numerous  instances  of  hyperparasitism  familiar 
to  every  mycologist.  Among  the  better  known  are  Cicinnobolus 
cesatii,  parasitic  on  various  Ervsiphaceae,  Darhica  filum  on  the 
uredinia  and  telia  of  rusts,  Tuber cidina  maxima  on  the  pycnia  and 
aecia  of  various  blister  rusts,  including  Cronartium  ribicola,  Myco- 
gyne  pemiciosa  on  mushrooms,  Hypomyces  sp.  on  Russula,  Lac- 
tarius,  and  other  Hymenomycetes,  and  Sclerotinia  fructicola  on 
hypertrophies  induced  by  Taphrina  mirabilis. 


286  ASSOCIATIVE  EFFECTS  AMONG  FUNGI 

Buller  (1924)  has  compiled  a  list  of  hyperparasites  of  more  than 
50  species.  They  include  members  in  the  Chytridiaceae,  Alucor- 
aceae,  Pyrenomycetes,  Agaricaeae,  Polyporaceae,  and  Fungi  Im- 
perfecti.  Little  of  a  fundamental  nature  is  known  about  the  an- 
tagonisms in  any  of  them. 

Evidence  of  antagonism  between  fungi  in  soils.  The  soil 
constitutes  the  normal  habitat  of  many  species  of  fungi.  Such 
factors  as  texture,  organic  content,  acidity,  moisture,  temperature, 
and  character  of  the  vegetational  cover,  are  known  to  influence 
the  presence  or  absence  of  a  particular  species  and  its  relative 
abundance.  How  these  interrelated  factors  influence  competi- 
tion between  soil  fungi  remains  largely  unknown,  but  undoubt- 
edly the  fungus  flora  is  never  in  equilibrium.  The  type  of  ob- 
servations that  have  been  made  on  these  problems  is  indicated  in 
the  following  discussion.  Millard  and  Taylor  (1927)  observed 
that  potato  scab,  caused  by  Actinomyces  scabies,  was  eliminated 
in  fields  containing  large  amounts  of  organic  matter  resulting  from 
green  manuring.  Under  these  conditions  the  development  of  a 
saprophytic  species,  A.  precox,  was  favored,  and  it  was  able  to 
suppress  the  pathogen.  A  proximate  cause  appears  from  the 
studies  by  Sanford  ( 1926).  He  noted  in  cultures  that  the  limiting 
acidity  for  germination  of  A.  scabies  was  about  pH  5.3  and  that 
the  optimum  reaction  was  pH  8.5.  From  these  results  it  may  be 
anticipated  that  acidity  from  decomposition  of  green  crops  that 
have  been  plowed  under  would  be  unfavorable  for  the  scab  patho- 
gen but  might  be  favorable  for  other  microorganisms  to  the  ex- 
tent that  they  would  predominate  and  manifest  their  antibiosis. 

Fungi  causing  root  rots  are  known  to  survive  in  the  soil  for 
varying  periods  in  the  absence  of  their  host  plants.  Supposedly 
they  live  under  these  conditions  as  saprophytes.  Hence  it  follows 
that  the  incorporation  of  organic  matter  should  increase  their 
incidence,  but  this  anticipated  result  is  not  invariable.  Other  soil- 
inhabiting  species  have  been  shown  to  modify  prevalence  of  the 
root-invading  pathogens,  as  the  work  of  Sanford  and  Broadfoot 
(1931,  1934)  on  Ophiobolus  gr  ami  iris,  Helminthosporiitm  sativum, 
and  Fusarium  culmorum  illustrates.  Not  only  were  soil-inhabit- 
ing saprophytes  able  to  modify  pathogenicity  in  their  pot  cul- 
tures but  also  similar  effects  were  secured  by  the  use  of  filtrates 
from  cultures  of  the  saprophytes.  Presumably  toxic  products 
caused  this  inhibitory  action  against  the  pathogens.     Similarly 


STIMULATION  BY  ASSOCIATIVE  INTERACTION  281 

Greaney  and  Machacek  (1935)  were  able  to  demonstrate  that 
Cephalothecium  roseum  inhibits  Helminthosporiwn  sativum. 

Garrett  (1936)  explains  somewhat  differently  the  relative  inci- 
dence of  Ophiobolus  graminis  in  soils.  His  observations  led  him 
to  conclude  that  O.  graminis  increases  in  amount  only  so  long  as 
there  are  living  host  roots,  along  which  it  spreads.  Its  rate  of 
spread  is  hypothesized  to  be  related  to  the  carbon  dioxide  content 
arising  from  respiratory  processes  in  the  microclimate  along  the 
root.  The  presence  of  alkaline  receptors  for  carbon  dioxide  in  the 
soil  stimulates  spread  of  the  pathogen.  Decline  of  O.  graminis 
occurs  in  its  saprophytic  phase  at  which  time  the  mycelium  is  be- 
ing decomposed  by  other  soil-inhabiting  species. 

Recently  Weindling  (1932,  1934,  1938)  found  that  Tricho- 
dervia  lignorwn  and  Gliocladium  fimbriatum  penetrate  the  hyphae 
of  such  soil-borne  parasites  of  seed  plants  as  Rhizoctonia  solani, 
Sclerothtm  rolfsii,  and  Phytophthora  parasitica.  Undoubtedly 
antagonisms  of  this  sort  are  not  uncommon  in  the  fungus  flora  of 
soil,  and  such  relationships  are  factors  in  the  control  of  diseases 
of  cultivated  plants.  Evidence  in  support  of  this  type  of  antago- 
nistic action  by  Trichoderma  against  fungi  that  cause  damping-off 
of  cucumber  seedlings  is  derived  from  the  experiments  of  Allen 
and  Haenseler  (1935).  They  applied  cultures  of  Trichoderma 
to   the   soil  with  the   result  that   damping-off  was   apparently 

checked. 

It  would  appear  to  be  feasible  to  evaluate  the  several  factors 
previously  mentioned  that  are  known  to  influence  the  incidence 
of  fungi  in  soil  generally.  This  field  of  research  certainly  offers 
many  possibilities.  As  is  indicated  by  the  rate  at  which  invasion 
of  heat-sterilized  soils  is  accomplished,  for  example,  by  Pyronema 
confluens,  more  attention  should  be  devoted  to  such  problems  as 
they  relate  to  culture  of  plants  in  cold  frames,  hotbeds,  and 
greenhouses. 

STIMULATION  BY  ASSOCIATIVE  INTERACTION 

Apparently  one  fungus  may  be  stimulated  by  the  presence  of 
another  in  either  of  two  ways:  increased  assimilatory  or  vegetative 
activity  or  else  reproductive  activity.  The  proximate  cause  of 
these  responses  need  not  be  the  same  metabolic  product  but  may 
be  different  specific  entities.     Much  interest  in  recent  years  has 


288  ASSOCIATIVE  EFFECTS  AMONG  FUNGI 

centered  around  the  complex  problem  of  factors  regulating 
growth  and  reproduction  in  plants  and  animals.  The  terms  auxins, 
hormones,  and  vitamins,  applied  to  stimulatory  and  regulatory 
substances,  are  commonly  used  not  only  by  the  biologist  but  also 
by  the  man  in  the  street. 

Stimulation  of  vegetative  activity.  Wildiers  (1901)  first 
established  that  Sacchacomyces  cerevisiae  will  not  grow  in  a  syn- 
thetic medium  consisting  of  ammonium  chloride  and  sugar  unless 
some  substance  essential  for  growth  is  added.  This  result  revived 
an  old  controversy  that  existed  years  before  between  Pasteur  and 
Liebig.  Pasteur  claimed  that  yeasts  made  abundant  growth  on  a 
nutrient  medium  containing  sugar,  ammonium  salts,  and  the  ashes 

DO7 

of  yeast.  Liebig  was  unable  to  grow  yeast  successfully  on  this 
formula,  whereupon  Pasteur  offered  to  produce  for  him  "all  the 
yeast  he  could  require."  Liebig  declined  the  challenge,  and  in 
consequence  Pasteur  was  considered  to  have  won  the  scientific 
argument.  Wildiers  noted  that,  when  he  placed  a  single  yeast 
cell  or  a  few  cells  only  in  this  medium,  little  or  no  growth  took 
place.  If,  however,  he  introduced  as  many  yeast  cells  as  were 
contained  in  two  drops  of  beer  wort  from  a  vat  in  which  yeast 
was  being  grown,  abundant  growth  resulted.  He  also  induced 
growth  by  the  addition  of  a  few  cubic  centimeters  of  boiled  yeasts. 
His  results  were  so  striking  that  he  assumed  some  hypothetical  sub- 
stance that  he  called  "bios"  to  be  essential  for  growth.  He  ex- 
tracted this  bios  from  yeasts  by  boiling.  It  was  dialyzable  from  a 
watery  extract;  it  was  not  present  in  yeast  ashes.  Of  course,  the 
results  of  Wildiers  attracted  wide  attention  and  were  sharply 
criticized.  They  were  substantiated,  however,  and  with  the  dis- 
covery of  vitamins  and  the  flood  of  investigation  that  followed,  it 
became  apparent  that  bios  and  vitamins  are  similar.  In  fact,  bios 
is  now  known  to  be  a  complex  consisting  of  a  number  of  compo- 
nents identified  as  vitamin  Bi  (thiamin),  biotin,  /-inositol,  and 
additional  factors  [Eastcott  (1928)]. 

Conflicting  evidence  exists  regarding  the  necessity  of  the  addi- 
tion of  growth  factors  to  culture  media  used  to  grow  other  fungi. 
Kogl  and  Fries  (1937)  have  shown  that  Polystictas  adustiis  grown 
on  a  synthetic  medium  requires  the  addition  of  thiamin,  and 
Nematospora  gossypii  requires  biotin.  Polystictus  adustus  is 
capable  of  producing  biotin,  and  N.  gossypii  thiamin,  so  that  they 
can  supply  their  mutual  needs  when  they  are  grown  in  association. 


STIMULATION  BY  ASSOCIATIVE  INTERACTION  289 

These  two  growth  factors  appear  to  be  necessary  for  a  large  num- 
ber of  fungi,  as  is  indicated  by  rather  numerous  reports  of  trials. 

Schopmeyer  and  Fulmer  (1931)  indicated  that  bios  is  produced 
by  Aspergillus  niger,  A.  clavatus,  and  Trichoderma  lignorum,  as 
judged  by  the  ability  to  stimulate  the  growth  of  yeast.  On  the 
other  hand,  Williams  and  Honn  (1932)  have  shown  distinct  stim- 
ulation in  growth  by  the  addition  of  yeast  extract  to  media  on 
which  Aspergillus  niger,  Mucor  racemosus,  Microsporum  fulvum, 
Monilia  metalondinensis ,  and  M.  macedoniensis  were  grown. 
They  called  these  stimulatory  substances  "nutrilites."  A  recent 
summary  by  Williams  (1941)  reviews  pertinent  literature  on  nu- 
trilites, which  have  been  identified  as  biotin,  inositol,  pantothenic 
acid,  pyridoxin,  and  thiamin. 

Leonian  and  Lilly  (1940)  have  shown  that  certain  thiamin- 
requiring  fungi  are  greatly  influenced  by  specific  amino  acids  and 
by  zinc,  iron,  and  other  minor  elements. 

Extracts  from  different  fungi  and  from  bacteria  have  been  used 
experimentally  to  stimulate  the  growth  of  fungi,  but  in  most  cases 
little  is  known  of  the  nature  and  properties  of  the  extracted  sub- 
stances. Such  studies  are  worth  while,  but  the  value  of  similar 
investigations  will  be  greatly  enhanced  if,  in  the  future,  more 
attention  is  devoted  to  analyses  to  determine  the  identities  of  the 
extracted  materials.  Evidence  is  given  in  one  study  [du  Vigneaud 
et  al.  (1940)  ]  of  the  identity  of  biotin  and  vitamin  H. 

Both  growth-stimulating  and  growth-inhibiting  factors  would 
be  expected  to  be  present  in  extracts  from  fungi.  Such  a  situation 
was  encountered  by  Satoh  (1931)  with  Ophiobolus  miyabeamis. 
When  the  liquid  on  which  this  fungus  had  been  grown  was  passed 
through  a  Chamberland  (F)  filter,  a  material  stimulatory  to 
Aspergillus  niger  was  contained  in  the  filtrate,  and  one  inhibitory 
to  the  same  fungus  was  retained  on  the  filter.  The  stimulatory 
component  proved  to  be  thermostable  and  the  inhibitory  one 
thermolabile. 

Stimulation  of  reproductive  activity.  The  opinion  was 
long  ago  voiced  that  some  chemical  attractant  aids  in  bringing 
together  plant  sex  cells  of  opposite  potentialities.  De  Bary  (1881) 
supposed  that  this  was  true  of  fungi  and  also  that  such  substances 
were  operative  in  stimulating  the  production  of  antheridial  and 
oogonial  branches  among  certain  Phycomycetes.  Ever  since  the 
discovery  of  heterothallism  the  same  opinion  has  been  entertained 


290  ASSOCIATIVE  EFFECTS  AMONG  FUNGI 

generally  in  connection  with  reproductive  activities  among  hetero- 
thallic  fungi.  Recently  .Moreau  and  Aloruzi  (1931)  claimed  that 
perithecia  of  Neurospora  are  produced  if  two  strains  are  grown 
in  opposite  ends  of  a  U-tube,  and  that  this  response  is  the  result 
of  diffusion  of  a  hypothetical  hormone  through  the  medium  from 
one  arm  of  the  tube  to  the  other.  Dodge  (1931)  attempted  to 
repeat  their  experiments  with  Neurospora  sitophila  and  N.  tetra- 
sperma  but  did  not  succeed  in  obtaining  perithecia  unless  and 
until  the  hyphae  of  opposite  colonies  were  in  contact.  Raper 
(1939,  1939a,  1940)  presented  evidence  that  the  sexual  reactions 
in  Achlya  bisexualis  and  A.  ambisexualis  are  controlled  by  four 
specific  substances,  two  produced  by  the  male  mycelia  and  two  by 
the  female.  Responses  are  evident  when  the  mycelia  are  6  mm 
apart,  if  mated  on  agar.  Both  sex  strains  are  activated  when 
grown  on  opposite  sides  of  a  cellophane  membrane.  Male  plants 
form  antheridial  branches  when  placed  in  water  in  which  female 
plants  have  previously  been  grown.  Furthermore,  female  plants 
produce  oogonial  initials  when  placed  in  water  in  which  male 
plants  have  been  grown  and  have  formed  antheridial  branches, 
although  there  is  no  such  activation  in  water  in  which  a  vegetative 
male  has  been  grown.  Of  the  two  hormones  produced  by  the 
female  plant,  one  initiates  the  formation  of  antheridial  branches, 
and  the  other,  in  connection  with  a  thigmotropic  response,  in- 
duces the  delimitation  of  antheridia.  Of  the  two  hormones  pro- 
duced by  the  male  plant,  one  initiates  the  formation  of  oogonial 
branches,  and  the  other  brings  about  the  delimitation  of  the 
oogonium.  The  chemical  constitution  of  none  of  the  hormones 
is  yet  known. 

The  filtrate  of  old  cultures  of  Aspergillus  niger  contains  a  prin- 
ciple that  promotes  conjugation  of  Zygosaccharomyces  acld'i- 
jaciens  [Nickerson  and  Thimann  ( 1943)  ].  This  principle,  on  be- 
ing fractionated,  appears  to  consist  of  an  organic  acid  and  a  mem- 
ber of  the  vitamin  B  complex,  neither  fraction  having  much 
activity  by  itself.  Nickerson  and  Thimann  were  unable  to  iden- 
tify these  constituents  with  certainty,  but  when  they  imitated  the 
principle  by  a  mixture  of  glutaric  acid  and  riboflavin,  conjugation 
was  promoted. 

Synergetic  reactions.  Synergism  or  svnergetic  reaction  logi- 
cally  appears  to  be  a  form  of  stimulation,  the  term  applying,  how- 
ever, only  to  cooperative  phenomena  that  might  not  be  produced 


STIMULATION  BY  ASSOCIATIVE  INTERACTION  291 

by  either  of  the  associated  organisms  acting  alone.  Molliard 
(1903)  first  recorded  the  influence  of  one  microorganism  in  stimu- 
lating sporulation  by  another.  He  secured  apothecia  of  Ascobolus 
on  carrot  only  when  a  bacterial  contaminant  was  present.  The 
same  sort  of  influence  between  species  of  fungi  associated  in  the 
same  culture  was  first  described  by  Heald  and  Pool  ( 1908).  They 
secured  an  abundance  of  perithecia  of  Melanospora  pampecma 
grown  in  a  mixture  with  Fasarhim  moniliforme,  Melanospora 
ciilmorum,  or  Basispor'mm  gallannn.  Similar  reactions  occurred 
if  M.  pampeana  was  planted  on  the  media  after  these  fungi  had 
grown  on  them  and  they  had  been  sterilized. 

McCormick  (1925)  secured  perithecia  from  monoconidial  cul- 
tures of  Thielavia  basicola,  grown  mixed  with  Cladosporhim  ful- 
vum,  Aspergillus  umbrosus,  A.  glaucus,  Eurotium  amstelodami,  or 
Fusicladmm  pirinum.  If  aqueous  extracts  of  these  fungi  were 
passed  through  a  Berkefeld  filter,  the  filtrate  retained  its  effective- 
ness in  stimulating  perithecial  production.  Asthana  and  Hawker 
(1936)  got  active  stimulation  of  fruiting  in  Melanospora  destruens 
and  other  Ascomycetes  by  the  addition  to  the  culture  medium  of 
the  ether-insoluble  fraction  of  nutrient  solutions  "staled"  by 
Fusarium,  Botrytis,  or  Melanospora  itself.  Arrillaga  (1935)  noted 
that  the  presence  of  Diaporthe  citri  stimulated  the  formation  of 
reproductive  structures  by  Phytophthora  citrophthora. 

Evidence  of  synergetic  effects  is  not  confined  to  responses  in 
cultures.  It  appears  also  to  be  manifest  when  a  mixture  of  or- 
ganisms is  grown  in  tissues.  Fawcett  (1931)  employed  combina- 
tions of  several  pathogens  of  citrus  to  inoculate  into  the  bark  of 
citrus  trees,  with  the  result  that  lesions  developed  more  rapidly 
than  when  one  organism  alone  comprised  the  inoculum.  Fawcett 
used  in  these  experiments  Diplodia  natalensis,  Colletotrichum 
gloeosporioides,  Diaporthe  citri,  Sphaceloma  jawcetti,  and  Phy- 
tophthora citrophthora.  Savastano  and  Fawcett  (1929)  found 
that  Oospora  citri-aurantii  accelerated  the  rate  of  decay  of  citrus 
fruits  when,  as  inoculum,  it  was  mixed  with  other  organisms  of 
decay. 

More  attention  should  be  given  to  the  synergetic  reactions  in- 
volved in  the  production  of  lesions  on  plant  parts.  Once  a  lesion 
has  been  initiated  by  the  primary  organism,  it  soon  becomes  in- 
vaded by  secondary  organisms.  These  secondary  species  may 
be  found  in  some  instances  to  play  an  important  role  in  the  pro- 


292  ASSOCIATIVE  EFFECTS  AMONG  FUNGI 

duction  of  mature  lesions.  Evidence  strengthening  this  supposi- 
tion is  found  in  the  frequent  occupancy  of  lesions  by  secondary- 
invaders. 

Wolf  (1916)  found  fungi  belonging  to  Gloeosporium,  Fu- 
sarium,  and  Phoma  associated  with  citrus  canker,  whose  primary 
cause  is  Phytomonas  citri.  Of  these  fungi  a  species  of  Phoma 
was  noted  to  be  capable  of  secreting  cellulase,  invertase,  diastase, 
and  maltase,  and  from  this  fact  it  was  concluded  that  this  Phoma 
is  actively  associated  with  processes  involved  in  the  destruction  of 
citrus  tissues. 

GENERAL  CONSIDERATIONS 

The  numerous  observations  cited  in  the  foregoing  account  may 
be  assumed  to  prove  the  obvious  fact  that  fungi  interact,  but  the 
assumption  is  not  warranted  that  certain  combinations  are  always 
antagonistic  or  stimulatory,  as  the  case  may  be,  under  all  condi- 
tions. Combinations  that  are  antagonistic  in  culture  may  not  be 
so  under  natural  conditions,  as  Broadfoot's  (1933)  experiences 
with  Ophiobolns  gramims  and  certain  other  soil-borne  organisms 
indicate.  Whether  an  associative  interaction  is  beneficial  or  in- 
jurious may  prove  to  be  a  matter  of  adjustment  of  climatic, 
edaphic,  and  biotic  factors  whose  balance  is  delicately  poised. 

The  possibility  that  fungi  occur  within  plants  that  appear  to 
be  entirely  normal  is  worthy  of  consideration,  and  it  is  indicated 
that  systematic  attempts  should  be  made  to  isolate  fungi  from 
"normal  tissues."  If  this  were  done,  it  should  not  come  as  a 
surprise  to  discover  that  certain  fungi  may  prove  capable  under 
some  environmental  conditions  of  producing  serious  diseases, 
under  others  of  being  benign,  and  under  still  others  of  inducing 
no  evidence  of  abnormality.  No  doubt  many  of  the  fungus  asso- 
ciations in  the  soil  are  intricately  complex.  Whether  stability  is 
ever  attained  among  soil  fungi  or  whether  a  condition  approxi- 
mating such  a  vegetational  climax  as  a  prairie  or  a  hardwood  forest 
ever  obtains  among  fungi  is  extremely  doubtful. 

Attention  has  been  centered  in  this  account  on  the  effect  of 
one  fungus  on  another,  to  the  almost  complete  exclusion  of  the 
interaction  of  bacteria,  protozoa,  and  green  plants  with  fungi. 
Much  has  been  learned  from  studies  of  these  problems,  but  these 
topics  are  regarded  as  outside  the  scope  of  the  present  summary. 
Interactions  between  parasites  and  saprophytes  on  living  host 


GENERAL  CONSIDERATIONS  293 

plants  appear  to  be  less  complex  than  interactions  between  micro- 
organisms in  the  soil,  primarily  because  a  smaller  number  of  spe- 
cies is  involved.  Undoubtedly  the  spores  of  many  species  germi- 
nate at  the  surface  of  the  plant,  but  only  those  of  the  pathogenic 
species  succeed  in  producing  infections.  Once  the  lesions  are 
formed,  however,  saprophytes  may  enter.  In  some  instances 
tissue  plantings  from  young  lesions  are  found  to  yield  pure  cul- 
tures of  the  pathogen,  but  at  a  later  date  the  tissues  always  yield 
a  mixture  of  the  pathogen  and  one  or  more  secondary  invaders. 
Still  later  it  may  be  impossible  to  isolate  the  primary  fungus,  the 
secondary  ones  may  also  have  been  eliminated,  and  the  tissues  may 
be  completely  occupied  by  tertiary  species.  It  is  highly  probable 
that  successions  of  this  sort  do  not  result  simply  from  exhaustion 
of  specific  food  materials  by  the  several  organisms  concerned.  A 
solution  of  the  problem  of  these  interactions  must  be  based  upon 
an  understanding  of  the  physiology  of  each  organism  concerned, 
especially  of  their  enzyme-producing  abilities  and  the  metabolic 
products  they  form.  Only  a  beginning  has  as  yet  been  made  in 
this  field  of  research. 

The  existence  of  several  species  of  fungi  in  the  same  lesion  may 
also  be  interpreted  to  indicate  that  the  conception  of  mono- 
etiology  of  disease  in  plants,  as  in  animals,  is  altogether  too  narrow 
and  may  actually  lead  to  misinterpretations. 

LITERATURE  CITED 

Abraham,  E.  P.,  E.  Chain,  C.  M.  Fletcher,  A.  D.  Gardner,  N.  G.  Heatley, 

and  M.  A.  Jennings,  "Further  observations  on  penicillin,"  Lancet,  2:  7, 

177-188,  1941. 
Allen,  M.  C,  and  C.  M.  Haenseler,  "Antagonistic  action  of  Trichoderma 

on   Rhizoctonia    and    other   soil    fungi,"    Phytopathology,   25: 244-252, 

1935. 
Arrillaga,  J.  G.,  "The  nature  of  inhibition  between  certain  fungi  parasitic 

on  citrus,"  Phytopathology,  25:161-115,   1935. 
Asthana,  R.  P.,  and  L.  E.  Hawker,  "Influence  of  certain  fungi  on  the 

sporulation  of  Melanospora  destruens  Shear  and  of  some  other  Ascomy- 

cetes,"  Ann.  Botany,  50:  325-343,  1936. 
Bamberg,  R.   H.,  "Bacteria  antibiotic  to    Ustilago  zeae"  Phytopathology, 

27:881-890,  1931. 
Bary,  A.  de,  Beitrage  zur  Morphologie  und  Physiologie  der  Pilze,  4:  85,  1881. 
Boyle,  C,  "Studies  on  the  physiology  of  parasitism.     X.  The  growth  re- 
actions of  certain  fungi  to  their  staling  products,"  Ann.  Botany,  38:  113- 

135,  1924. 


294  ASSOCIATIVE  EFFECTS  AMONG  FUNGI 

Broadfoot,  W.  C,  "Studies  on  foot  and  root  rot  of  wheat.  II.  Cultural 
relationships  on  solid  media  of  certain  microorganisms  in  association 
with  Ophiobolus  graniinis  Sacc,"  Can..].  Research,  8:  545-552,  1933. 

Buller,  A.  H.  R.,  Researches  on  fungi,  Vol.  3.  Longmans,  Green  and  Co., 
London.     1924.     (Cf.  432-473.) 

Calev,  D.  A  I.,  "The  phenomenon  of  mutual  aversion  between  monospore 
mvcelia  of  the  same  fungus  (Diaporthe  pemiciosa  Alarchal)  with  a  dis- 
cussion of  sex  heterothallism  in  fungi,"  /.  Genetics,  13:  353-370,  1923. 
"The  inheritance  of  the  capacity  for  showing  mutual  aversion  between 
monospore  mvcelia  of  Diaporthe  pemiciosa  Alarchal,"  /.  Genetics, 
24:  1-63,  1931.' 

Clutterbuck,  P.  W.,  R.  Lowell,  and  H.  Raistrick,  "Studies  in  the  bio- 
chemistry of  microorganisms.  XXVI.  The  formation  from  glucose  by 
members  of  the  Penicillhmi  chrysogenum  series  of  a  pigment,  an 
alkali-soluble  protein,  and  penicillin— the  antibiotic  substance  of  Flem- 
ming,"  Biochem.  J.,  26:  1901-1918,  1932. 

D'Aeth,  H.  R.  X.,  "A  survey  of  interaction  between  fungi,"  Biol.  Rev. 
Cambridge  Philos.  Soc,  24:103-131,  1939. 

Dodge,  B.  O.,  "Heterothallism  and  hypothetical  hormones  in  Neurospora," 
Bull.  Torrey  Botan.  Club,  5^:517-522,  1931. 

Dutcher,  J.  D.,  "The  chemical  nature  of  gliotoxin:  a  microbial  compound 
produced  by  the  fungus  Gliocladium  fimbriatum,"  J.  Bact.,  42:815-816, 
1941. 

Eastcott,  E.  V.,  "\Yildiers'  bios.  The  isolation  and  identification  of  bios. 
I,"  /.  Physiol.  Chem.,  32:  1093-1111,  1928. 

Endo,  S.,  "Studies  on  antagonism  of  microorganisms.  I.  Growth  of  Hy- 
pochnus  centrifugus  (Lev.)  Tul.  as  influenced  by  the  antagonistic  action 
of  other  microorganisms,"  Miyazaki  Coll.  Agr.  Forestry  Bull.,  3:95-118, 
1931. 

II.  "Growth  of  Hypochnus  sasakii  Shirai  as  influenced  by  the  antagonistic 
action  of  other  microorganisms,"  Miyazaki  Coll.  Agr.  Forestry  Bull., 
4:  133-158,  1932. 

III.  "Pathogenicity  of  Hypochnus  centrifugus  (Lev.)  Tul.  and  Hypochnus 
sasakii  Shirai  in  the  presence  of  other  microorganisms,"  Miyazaki  Coll. 
Agr.  Forestry  Bidl.,  4:  159-184,  1932a. 

Fawcett,  H.  Sm  "The  importance  of  investigations  on  the  effects  of  known 
mixtures  of  microorganisms,"  Phytopathology,  27:545-550,  1931. 

Garrett,  S.  D.,  "Soil  conditions  and  the  take-all  disease  of  wheat,"  Ann. 
Appl.  Biol.,  23:  667-699,  1936. 

Greaney,  F.  J.,  and  J.  E.  AIachacek,  "Studies  on  the  control  of  root-rot 
disease  of  cereals  caused  bv  Fusarhnn  culmorum  (W.  G.  Smith)  Sacc. 
and  Helminth osporiwn  sativum  P.  K.  and  B.  II.  Pathogenicity  of 
Helminth os porium  sativum  as  influenced  by  Cephalothecium  roseinn 
Corda  in  greenhouse  pot  tests,"  Sci.  Agr.,  75:377-386,  1935. 

Heald,  F.  D.,  and  V.  W.  Pool,  "The  influence  of  chemical  stimulation  upon 
the  production  of  perithecia  of  Melanospora  pampeana  Spcg,"  Nebr. 
Agr.  Expt.  Sta.  Ann.  Rept.,  22:  130-134,  1908. 


LITERATURE  CITED  295 

Hoppe,  P.  E.,  "Intraspecific  and  interspecific  aversion  in  Diplodia,"  /.  Agr. 

Research,  53:671-680,  1936. 
Johnson,  Delia,  "The  antibiosis  of  certain  bacteria  to  smuts  and  some  other 

fungi,"  Phytopathology,  21:  843-863,  1931. 
Kogl,  F.,  and  N.  Fries,  "tiber  den  Einfluss  von  biotin,  aneurin  und  mcso- 

inosit  auf  das  Wachstum  verschiedener  Pilzarten,"  Hoppe-Sey lev's  Z. 

physiol.  Chem.,  249:  93-110,  1937. 
Leonian,  L.  H.,  and  V.  G.  Lilly,  "Studies  on  the  nutrition  of  fungi.     IV. 

Factors  influencing  the  growth  of  some  thiamin-requiring  fungi,"  Am. 

J.  Botany,  21:  18-26,  1940. 
Lutz,  O.,  "tjber  den  Einfluss  gebrauchter  Nahrslosung  auf  Keimung  und 

Entwicklung  einiger  Schimmelpilze,"  Ann.  Mycol.,  7:91-133,  1909. 
Machacek,  J.  E.,  "Studies  on  the  association  of  certain  phytopathogens," 

McDonald  College  Tech.  Bull,  7:  1928. 
McCormick,  F.  A.,  "Perithecia  of  Thielavia  basicola  Zopf  in  culture  and 

the   stimulation   of   their   production    by   extracts   from    other   fungi," 

Cornell  Agr.  Expt.  Sta.  Bull.,  269:  539-554,  1925. 
Millard,  W.  A.,  and  C.  B.  Taylor,  "Antagonism  of  microorganisms  as  the 

controlling  factor  in  the  inhibition  of  scab  by  green  manuring,"  Ann. 

Appl.  Biol.,  14:202-216,  1927. 
A'Iolliard,  M.,  "Role  des  bacteries  dans  la  production  des  peritheces  des 

Ascobolus,"  Compt.  rend.,  735:899-901,  1903. 
Moreau,  F.,  and  M.  C.  Moruzi,  "Recherches  experimentales  sur  la  formation 

des   peritheces   chez   les    'Neurospora,' "    Comp.   rend.,   192:  1476-1478, 

1931. 
Nickerson,  W.  J.,  and  K.  V.  Thimann,  "The  chemical  control  of  conjuga- 
tion in  Zygosaccharomyces.    II,"  Am.  J.  Botany,  30:94-100,  1943. 
Nikitinsky,  J.,  "tiber  die  Beeinflussung  der  Entwicklung  einiger  Schimmel- 
pilze durch  ihre  Stoffwechselprodukte,"  Jahrb.  wiss.  Botan.,  40:  1-93, 

1904. 
Porter,  C.  L.,  "Concerning  the  characters  of  certain  fungi  as  exhibited  by 

their  growth  in  the  presence  of  other  fungi,"  Am.  J.  Botany,  11:  168-188, 

1924. 
Porter,  C.  L.,  and  J.  C.  Carter,  "Competition  among  fungi,"  Botan.  Rev., 

4:  165-182,  1938. 
Pratt,  Clara  A.,  "The  staling  of  fungal  cultures.    I.  General  and  chemical 

investigation  of  staling  by  Fusarium,"  Ann.  Botany,  38:  563-595,  1924. 
II.  "The  alkaline  metabolic  products  and  their  effect  on  the  growth  of 

fungal  spores,"  Ann.  Botany,  38:  S99-6X5,  1924a. 
Raistrick,   H.,   "Biochemistry  of  the  lower  fungi,"   Ergeb.  Enzymforsch., 

1:  345-363,  1932. 
"Certain    aspects    of   the    biochemistry    of    the    lower    fungi    (moulds)," 

Ergeb.  Enzy?nforsch.,  7:316-349,  1938. 
Raper,  J.  R.,   "Role  of  hormones  in  the   sexual  reaction   of   heterothallic 

Achylas,"  Science,  n.s.,  89:  321-322,  1939. 
"Sexual  hormones  in  Achvla.     I.  Indicative  evidence  for  a  hormonal  co- 

ordinating  mechanism,"  Am.  J.  Botany,  26:  639-650,  1939a. 


296  ASSOCIATIVE  EFFECTS  AMONG  FUNGI 

Raper,  J.  R.,  "Sexual  hormones  in  Achyla.  II.  Distance  reactions,  conclusive 
evidence  for  a  hormonal  coordinating  mechanism,"  Am.  J.  Botany,  21: 
162-173,  1940. 

Sanford,  G.  B.,  "Some  factors  affecting  the  pathogenicity  of  Actinomyces 
scabies,"  Phytopathology,  16:  525-547,  1926. 

Sanford,  G.  B.,  and  W.  C.  Broadfoot,  "Studies  on  the  effects  of  other  soil- 
inhabiting  microorganisms  on  the  virulence  of  Ophiobolus  graminis 
Sacc,"  Sci.  Agr.,  U:  512-528,  1931. 
"On  the  prevalence  of  pathogenic  forms  of  Helminth osporium  sativum 
and  Fusarium  culmoruin  in  the  soil  of  wheat  fields  and  its  relation  to  the 
root-rot  problem,"  Can.  J.  Research,  10:  264-274,  1934. 

Satoh,  S.,  "Studies  on  the  effects  of  nutrient  solutions  used  by  Ophiobolus 
miyabeanus  on  the  germination  and  development  of  another  fungus," 
Forsch.  Gebeite  Pflanzenk.,  2:71-83,  1931. 

Savastano,  G.,  and  H.  S.  Fawcett,  "A  study  of  decay  in  Citrus  fruits  pro- 
duced by  inoculations  with  known  mixtures  of  fungi  at  different  con- 
stant temperatures,"  /.  Agr.  Research,  39:  163-198,  1929. 

Schopmeyer,  H.,  and  E.  J.  Fulmer,  "The  production  of  yeast-growth  stimu- 
lants by  the  molds.  I.  Aspergillus  niger,  Trichodernia  lignorum,  and 
Aspergillus  clavatus,"  J.  Bact.,  22:23-28,  1931. 

Vigneaud,  V.  du,  D.  B.  Melville,  Paul  Gyory,  and  C.  S.  Rose,  "On  the 
identitv  of  vitamin  H  with  biotin,"  Science,  92:62-6},  1940. 

Waksman,  S.  A.,  "Associative  and  antagonistic  effects  of  microorganisms. 
I.  Historical  review  of  antagonistic  relationships,"  So/7  Sci.,  43:  5 1-68, 

1937. 
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Weindling,  R.,  '"Trichoderma  lignorum  as  a  parasite  of  other  soil  fungi," 

Phytopathology,  22:837-845,  1932. 
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Trichoderma  lignorum  on  Rhizoctonia  solani  and  of  other  soil  fungi," 

Phytopathology,  24: 1153-1179,  1934. 
"Isolation  of  toxic  substances  from  the  culture  filtrates  of  Trichoderma 

and  Gliocladium,"  Phytopathology y  21:  1175-1177,  1937. 
"Association  effects  of  fungi,"  Botan.  Rev.,  4:  475-496,  1938. 
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from  the  culture  filtrate  of  Trichoderma,"  Phytopathology,  26:  1068- 

1070,  1936. 
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molds  and  other  fungi,"  Plant  Physiol.,  7:629-641,  1932. 
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Chapter  13 

MYCORRHIZAE  AND  MYCOTROPHY 

Our  knowledge  of  the  existence  of  a  dual  relationship  of  fungi 
with  the  roots  of  green  plants  begins  with  the  classic  work  of 
Frank  (1885).  He  regarded  mycorrhizae*  (literally,  fungus 
roots)  as  compound  structures  constituted  of  two  components,  a 
fungus  and  a  root.  These  components  are  associated  in  a  nutri- 
tional or  mycotrophic  relationship,  and  the  structure  produced  by 
their  association  is  morphologically  distinct,  in  the  same  sense  that 
a  lichen  is  distinct  from  the  alga  and  the  fungus  composing  it. 
These  findings  by  Frank  immediately  stimulated  others  to  under- 
take studies  on  mycorrhizae,  and  interest  in  the  problems  that 
have  arisen  has  not  flagged  to  the  present  day.  Nevertheless  no 
problem  involving  fungi  is  so  little  appreciated  and  understood  bv 
mycologists  today,  and  there  does  not  appear  to  be  any  of  greater 
significance.  Much  of  the  work  on  mycorrhizae  has  been  done 
by  persons  with  such  divergent  interests  as  foresters,  silvicultur- 
ists,  physiologists,  morphologists,  pathologists,  and  cytologists,  and 
in  consequence  an  overwhelmingly  voluminous  literature  on  my- 
corrhizae has  accumulated.  An  invaluable  bibliograohv  on  the 
subject,  covering  more  than  900  typed  pages,  was  prepared  by 
Kelly  (1932).  As  a  consequence  of  the  numerous  publications 
it  might  be  supposed  that  mycorrhizae  are  thoroughly  understood, 
but  many  phases  of  this  subject  still  remain  controversial.  The 
conflict  of  observations,  opinions,  and  conclusions  may  be  at- 
tributed in  part  to  the  dangerous  habit,  even  among  scientists,  of 
making  generalizations.  Interested  students  and  investigators  will 
find  the  monographs  by  Rayner  (1927),  Hatch  (1937),  and  Bjork- 

*  Frank  (1885,  p.  129):  "Die  ganze  Korper  ist  also  weder  Baumwurzel 
noch  Pilze  allein,  sondern  ahnlich  wie  die  Thallus  von  Flechten,  eine 
Vereinigung  zweier  verschiedener  Wesen  zu  einem  einheitlichen  morpho- 
logischen  Organ,  welches  vieleicht  passend  also  Pilzwurzel,  Mycorhiza, 
bezeichnet  werden  kann." 

291 


298  MYCORRHIZAE  AND  MYCOTROPHY 

man  (1942)  indispensable  in  providing  a  knowledge  of  the  present 
status  of  studies  on  mycorrhizae. 

Occurrence  of  mycorrhizae.  Formerly  it  was  generally  be- 
lieved  that  relatively  few  species  of  plants  possess  mycorrhizae. 
Alycorrhizal  species  were  then  regarded  as  objects  of  scientific 
interest  or  even  of  curiosity.  It  is  becoming  more  and  more  ap- 
parent from  cumulative  records,  however,  that  they  involve  a 
wide  variety  of  plants  and  that  they  occur  widely  throughout  the 
world.  Mycorrhizae  occur  on  trees,  shrubs,  and  herbs  on  essen- 
tially all  kinds  of  soils  ranging  from  the  Arctic  regions  to  the 
tropics.  In  1934  Asai  [Burges  (1936)]  examined  members  of  134 
families  of  plants  in  Japan  and  found  mycorrhizae  associated  with 
82%  of  them.  McDougall  and  Glasgow  (1929)  found  mycor- 
rhizae in  28  species  of  composites.  Samuel  [Burges  (1936)]  re- 
corded the  occurrence  of  mycorrhizae  in  Australia  on  Euphor- 
biaceae,  Geraniaceae,  Graminiaceae,  Leguminosae,  Liliaceae, 
Mvrtaceae,  Plantaginaceae,  Ranunculaceae,  Rosaceae,  and  Vio- 
laceae.  They  have  also  been  noted  on  members  of  the  Burma- 
niaceae,  Cunoniaceae,  Ericaceae,  Epicridaceae,  Lauraceae,  Or- 
chidaceae,  Pyrolaceae,  Rutaceae,  and  Sapindaceae  [Burges 
(1936)].  Nearly  all  species  of  coniferous  and  hardwood  trees 
examined  have  proved  to  be  mycotrophic.  Moreover,  an  ever- 
increasing  number  of  crop  plants  are  being  found  to  possess 
mycorrhizae. 

The  mycorrhizal  habit  is  not  restricted  to  the  seed  plants. 
Fungal  threads  were  noticed  in  the  thalli  of  the  liverwort,  Preissia, 
nearly  100  years  ago.  Since  then,  principally  from  the  observa- 
tions of  Nemec  in  1899,  Galenkin  in  1902,  and  Cavers  in  1903 
[Ravner  (1927)],  intracellular  hyphae  are  of  rather  common  oc- 
currence within  the  rhizoids  and  ventral  parts  of  the  thalli  in  both 
Jungermanniaceae  and  Marchantiaceae.  Convincing  proof  of  the 
functional  nature  of  this  association,  however,  is  lacking.  Several 
investigators  have  attempted  to  isolate  each  constituent  in  pure 
culture  in  order  to  learn  of  the  possible  interdependence  among 
them.  Such  experiments  have  been  uniformly  unsuccessful,  be- 
cause it  has  been  impossible  to  isolate  the  fungus  on  artificial 
media.  In  consequence  the  opinion  has  been  expressed  that  in  the 
Hepaticae  mycorrhizae  may  be  lacking  and  the  associated  fungi 
mav  indeed  be  highly  specialized  parasites. 


KINDS  OF  MYCORRHIZAE  299 

Among  Bryophyta  internal  mycelium  has  been  found  of  com- 
mon occurrence  in  certain  genera,  such  as  Buxbaumia  and  Tetra- 
plodon,  but  whether  this  is  a  mutualistic  relation  is  a  point  still 
lacking  experimental  proof. 

In  regard  to  mycotrophv  among  Pteridophyta  there  is  also  a 
conflict  of  opinion.  A  Pythium-like  fungus  has  been  found  in 
the  prothalli  of  several  species  of  Lycopodium.  Alycorrhizae 
have  been  described  as  occurring  in  the  root  cortex  of  Ophio- 
glossum  and  Botrychium.  The  endophytic  mycelium  from  cer- 
tain marattiaceous  ferns  is  claimed  to  sporulate  when  isolated  in 
pure  culture,  an  indication  that  the  fungus  may  not  be  the  true 
symbiont.  Rayner  (1927)  records  the  presence  in  Pferidium 
aquilinium,  a  true  fern,  of  typical  endophytic  mycorrhizae,  with 
arbuscules  and  sporangioles  occurring  within  the  root  cortex. 
The  evidence  that  ferns  are  absolutely  dependent  upon  the  fungal 
associate,  in  any  case,  may  fairly  be  said  to  be  not  too  convincing. 

Kinds  of  mycorrhizae.  Various  characteristics  have  been  em- 
ployed as  bases  of  distinction  in  efforts  to  classify  mycorrhizae. 
Most  commonly  mycorrhizae  are  spoken  of  as  either  ectotrophic 
or  endotrophic.  The  ectotrophic  group  comprises  those  in  which 
the  fungus  remains  in  large  part  as  a  mantle  over  the  exterior  of 
the  roots,  whereas  the  endotrophic  group  comprises  those  in 
which  the  hyphae  are  within  the  host  cells.  In  Frank's  original 
descriptions  (1885)  he  directed  attention  to  intercellular  hyphae 
beneath  the  mantle.  These  intercellular  hyphae  invest  the  cor- 
tical cells  and  have  been  called  the  "Harti^-net."  As  mi^ht  be 
expected,  forms  intermediate  between  the  true  ectotrophic  and 
the  true  endotrophic  exist.  Such  forms  have  been  termed  ectend- 
otrophic.  Hatch  and  Doak  (1933),  however,  include  the  ec- 
tendotrophic  forms  among  the  ectotrophic  as  transitional  stages 
between  endotrophic  and  ectotrophic. 

Melin  (1925)  described  three  types  of  mycorrhizae  on  Scots 
pine,  the  external  form  constituting  the  basis  of  separation.  He 
designated  them  as  follows:  (a)  "Gabelmykorrhiza"  (forked), 
(b)  "Knollenmykorrhiza"  (knotted),  and  (c)  "einfach  Alykor- 
rhiza"  (simple).  The  first  type  is  most  common  in  nature,  espe- 
cially in  woodland  soils  having  an  abundant  layer  of  raw  humus. 
It  is  characterized  by  the  possession  of  short,  dichotomously 
branched  roots  invested  with  mantles  of  various  colors,  the  color 
being  determined  by  the  species  of  fungus  involved  in  its  pro- 


300 


MYCORRH1ZAE  AND  MYCOTROPHY 


duction.  The  second  type  he  noted  to  occur  under  the  same  con- 
ditions as  the  first,  but  the  fusion  of  mantles  merged  clusters  of 
forked  roots  and  thereby  produced  knots  or  tuber-like  growths. 
The  third  type  is  constituted  of  long,  thin,  unbranched  structures, 
which  occur  upon  the  roots  of  heath-inhabiting  species  and  are 
believed  to  be  conditioned  by  decreased  "virulence"  of  the  fun- 


Fig.  47.  Diagram  of  root  in  cross-sections,  one-half  being  normal,  the  other 
mycorrhizal.  The  cells  of  the  cortex  are  hypertrophic,  and  all  are  en- 
veloped   by   fungus   filaments,   forming   a   mvcorrhiza    of   the    ectotrophic 

type.     (After  Hatch  and  Doak.) 

gus.  Decreased  virulence,  in  turn,  is  the  result  of  growth  in  the 
more  acid  soils  whose  mineral  content  is  relatively  unavailable. 
Melin's  observations,  involving  mycorrhizae  on  pine,  spruce,  and 
larch,  led  him  to  conclude  that  mycorrhizal  types  represent  phases 
or  stages  in  development.  The  endotrophic  condition  is  transi- 
tional to  the  ectendotrophic,  which  finally  becomes  transformed 
into  a  typical  ectotrophic  type.  During  this  transition  the  invad- 
ing hyphae  are  gradually  digested  and  eliminated  by  the  host 
cells. 

No  doubt  a  great  deal  of  the  confusion  in  understanding  the 
structure  and  function  of  mycorrhizal  associations  arises  from 


KINDS  OF  MYCORRH1ZAE  301 

failure  to  distinguish  between  "long  roots"  and  "short  roots,"  as 
pointed  out  by  Hatch  and  Doak  (1933).  Frank  (1885)  and  most 
European  investigators,  including  Alelin  (1925),  are  in  accord 
that  "short  roots"  are  invariably  mycorrhizal  roots.  Observations 
by  Noelle  (1910)  on  the  anatomical  differences  between  long 
roots  (Bereicherungswurzel)  and  short  roots  (Ernahrungswurzel) 
of  pine,  confirmed  by  Hatch  and  Doak  (1933),  are  summarized 
as  follows: 

Long  Roots  Short  Roots 

Root  cap  present.  Root  cap  absent. 

Diarch  or  polyarch.  Monarch. 

Have  secondary  growth.  Lack  secondary  growth. 

Root    hairs    arise    from    second  or       Root  hairs  arise  from  epidermal  cells. 

third  layer  of  cortical  cells.  Branch  dichotomously. 

Branch  racemosely.  Ratio  of  stele  diameter  to  total  di- 

Ratio  of  stele  diameter  to  total  di-          ameter  low. 

ameter  high. 

These  anatomical  differences  support  the  theory  that  mycor- 
rhizae  are  distinct  morphological  structures,  as  Frank  (1885)  first 
maintained.  They  also  indicate  that  long  roots  are  permanent 
structures,  whereas  short  ones  are  ephemeral,  lasting  at  most 
throughout  one  season. 

Hatch  and  Doak  (1933),  like  earlier  workers,  distinguish  three 
kinds  of  short  roots:  (1)  uninfected  short  roots,  (2)  pseudo- 
mycorrhizal  roots,  and  ( 3 )  mycorrhizal  roots. 

The  first  kind  is  exceedingly  rare  and  is  characterized  by  the 
following  features:  (a)  formation  of  root  hairs  from  epidermal 
cells,  (b)  continuous  slow  elongation,  (c)  no  hypertrophy  of 
cortical  cells,  (d)  complete  lack  of  fungal  hyphae,  and  (e)  dichot- 
omous  branching. 

The  second  type,  called  pseudomycorrhizae  by  Alelin,  may  be 
differentiated  by  these  characteristics:  (a)  absence  of  root  hairs, 
(b)  early  cessation  of  elongation,  (c)  complete  absence  of  hyper- 
trophy of  root  cortex,  (d)  lack  of  intercellular  fungal  net,  (<?) 
occasional  dichotomous  branching,  and  (f)  intracellular  invasion 
by  soil-inhabiting  fungi. 

Endotrophic  mycorrhizae,  such  as  occur  among  Ericaceae  and 
Orchidaceae,  are  not  to  be  confounded  with  the  intracellular 
hyphae  in  pseudomycorrhizal  roots.  These  hyphae  do  not  occur 
in  masses  but  may  penetrate  the  cells  in  small  numbers,  involving 


302  MYCORRHIZAE  AND  MYCOTROPHY 

even  the  parenchyma  cells  of  the  central  cylinder.  One  or  more 
distinct  species  may  be  involved  in  one  and  the  same  pseudo- 
mycorrhiza. 

In  the  third  kind  the  following  features  are  noteworthy:  (a) 
presence  of  intercellular  weft  or  Hartig  net,  (b)  presence  of  a 
fungal  mantle,  (c)  hypertrophy  of  cortical  cells,  (d)  occasional 
intracellular  hyphae  in  cortical  cells,  (e)  profuse  dichotomous 
branching,  and  (f)  continued  elongation  during  one  growing 
season. 

Fungi  involved  in  mycorrhizal  formation.  Numerous  spe- 
cies of  funm  have  been  found  to  be  associated  with  mycorrhizae, 
and  it  is  not  the  present  purpose  to  list  all  of  them  but  merely  to 
indicate  their  number  and  taxonomic  diversity.  In  short,  mem- 
bers of  each  of  the  three  large  classes,  Phycomycetes,  Ascomv- 
cetes,  and  Basidiomycetes,  enter  into  mycorrhizal  formation.  The 
most  extensive  lists  assembled  appear  to  be  those  of  the  Italian 
mycologist  Peyronel  [Rayner  (1927)],  who  designates  the  fol- 
lowing species: 

1.  On  Fagus  sylvatica,  Cortinarius  proteus,  C.  bivelus,  Boletus 
cyanescens,  B.  chrysenteron,  Hypochmis  cyanescens,  Scleroderma 
vulgare,  Amanita  rubescens,  Lactavius  subdulcis,  L.  blennius, 
Russula  emetica,  and  R.  nigricans. 

2.  On  Cory  his  avellana,  Lactarins  coryli,  L.  subdulcis,  Boletus 
cbrysenteron,  Strobilomyces  strobilaceus,  Hypochmis  cyanescens, 
Amanita  rube sc ens,  Rhodopaxillus  nudus,  Cortinarius  proteus,  C. 
multiformis,  C.  violaceus,  and  Hydmnn  repandum. 

3.  On  Betula  alba,  Amanita  muse  aria,  Amanitopsis  vaginata, 
Lactavius  necator,  L.  torminosus,  Boletus  scaber,  Scleroderma 
vulgare,  Russula  rhodoxantha,  and  Trichoderma  flavobrunneum. 

4.  On  Larix  decidua,  Amanita  muscaria,  Russula  laricina,  Hy- 
grophorus  bresadolae,  H.  lucorum,  Scleroderma  vulgare,  Lacta- 
rins rufus,  Gomphidius  gracilis,  and  Paxillus  lateralis. 

5.  On  Popolus  tremella,  Cortinarius  collinitus. 

6.  On  Quercus  robur,  Amanita  citrina,  Lactarius  subdulcis,  and 
Russula  cyanoxantha. 

7.  On  Cast an ea  vesca,  Amanita  rube  sc  ens,  Russula  lepida,  R. 
rubra,  and  Scleroderma  vulgare. 

.Mycologists  have  long  known  that  certain  Hymenomycetes  are 
restricted  to  the  area  beneath  particular  species  of  trees  and  are 
never  collected  under  other  kinds  of  trees.     In  Sweden  Boletus 


MYCORRHIZAL  FORMATION  303 

luteus,  for  example,  occurs  constantly  on  the  litter  under  Finns 
montana.  Elsewhere  in  Europe  it  has  been  found  under  P.  mon- 
tana,  P.  austriaca,  and  P.  sylvestris  and  is  presumed  to  be  respon- 
sible for  mycorrhizae.  Similarly  Boletus  elegans  occurs  under 
Larix  and  is  supposed  to  be  restricted  to  larches.  Noack  (1889) 
observed  that  Geaster  fimbriatus,  G.  fornicatus,  and  Cortinarius 
calisteus  form  mycorrhizae  on  pine,  and  Tricholoma  terreus  on 
spruce.  Masui  (1926)  observed  Cantharellus  floccosits  as  the 
mycorrhizal  associate  on  Abies  firma  in  Japan.  Aielin  (1925) 
regarded  Boletus  luteus,  B.  gramriatus,  B.  variegatus,  and  B.  badius 
as  responsible  for  the  production  of  "Knollenmykorrhiza"  on 
Finns  sylvestris  in  Sweden.  His  "Gabelmykorrhiza"  on  pine, 
fungal  components  of  which  he  identified  as  Mycelium  radicis 
sylvestris  f$,  and  M.  radicis  sylvestris  y,  have  features  resembling 
the  mycelia  of  species  of  Tricholoma  and  Cortinarius,  respec- 
tively. 

Certain  hypogean  Ascomycetes,  including  Elaphomyces  gran- 
ulatus,  Terfezia  leonis,  and  Tuber  sp.,  form  mycorrhizae  on  hard- 
woods. The  evidence  that  species  of  Penicillium  can  produce 
mycorrhizae  appears  to  be  unconvincing. 

The  mycorrhizal  associates  in  liverworts  and  in  many  herba- 
ceous seed  plants  are  Pythium-like  or  Phytophthora-like  in  aspect. 

A  Rhizoctonia  type  of  fungus  is  the  common  endophyte  of 
orchids.  Organisms  of  similar  appearance  have  been  isolated  from 
the  roots  of  wheat,  corn,  barley,  potatoes,  tobacco,  carrots,  and 
other  flowering  plants. 

Peyronel  has  attributed  the  cause  of  confusion  in  the  identity 
of  the  fungal  constituent  of  mycorrhiza  to  the  coincidental  inva- 
sion of  the  roots  by  two  distinct  fungi,  one  a  Phycomycete,  the 
other  a  Rhizoctonia-like  species.  The  Phycomycete  produces 
vesicles  and  arbuscles  that  may  eventually  be  digested  by  the 
host  cells,  and  it  is  overgrown  by  the  second  species.  In  1924 
Peyronel  published  a  list  of  species,  distributed  among  37  families, 
that  possessed  this  dual  type  of  invasion  [Rayner  (1927)].  It 
may  be  inferred  from  his  observations  that  the  presence  of  two 
mycorrhizal  associates  in  one  and  the  same  host  root  occurs  widely 
among  seed  plants. 

Several  endophvtes  of  orchids  have  been  specifically  identified 
by  Bernard.     From  Cattleya  and  Cypripedium  he  isolated  Rhi- 


304  MYCORRH1ZAE  AND  MYCOTROPHY 

zoctonia  repens;  from  Phalaenopsis  and  Yanda,  R.  mucoroides; 
from  Odontoglossum,  R.  lanuginosa. 

Fundamental  knowledge  regarding  endotrophic  mvcorrhizae 
in  Ericaceae  comes  from  the  studies  of  Ternetz  published  in  1907 
[Ravner  (1927)].  Ternetz  became  interested  in  the  possibility 
of  nitrogen  fixation  by  the  endophytes  that  she  invariably  found 
in  Ericaceae  growing  in  peaty  soils.  From  5  ericaceous  species 
she  isolated  pycnidium-forming  fungi,  to  which  she  gave  the 
names  Phovia  radicis  oxy cocci,  P.  radicis  andromedae,  P.  radicis 
vaccinii,  P.  radicis  tetralicis,  and  P.  radicis  ericae.  She  was  able 
to  show  that  each,  when  grown  in  a  liquid  nitrogen-free  medium, 
was  capable  of  fixing  appreciable  quantities  of  nitrogen.  From 
these  results,  obligatory  symbiosis  among  Ericaceae  has  been  in- 
ferred to  exist,  as  Ravner  has  claimed,  in  a  series  of  studies  involv- 
ing Calluna  vulgaris.  In  this  species  the  endophyte  occurs  within 
the  seed  and  permeates  the  entire  plant.  Ravner  also  found  (1929) 
that  the  endophytic  mycelium  ramifies  throughout  the  stem  tis- 
sues of  Vaccinium  oxy  coccus  and  V.  macro  car  pon  and  that  ova- 
rian infection  occurs  in  V .  vitisidaea,  V.  myrtilhis,  V.  pennsyha- 
nicttm,  V.  ovatnm,  V.  vacillans,  and  V.  corymbosam.  Ravner's 
claims,  however,  have  been  disputed.  There  exists  a  body  of  evi- 
dence that  ericaceous  species,  notably  cranberries,  have  been 
grown  successfully  for  a  term  of  years,  apart  from  the  endophyte. 
Significance  must  be  attached,  however,  to  the  fact  that  in  nature 
certain  species  always  possess  endotrophic  mvcorrhizae  and  that 
vigorous  growth  is  promoted  by  the  presence  of  the  fungus.  Re- 
cent studies  by  Barrows  (1941)  show  that  an  endophyte  occurs 
within  the  roots,  stems,  flowers,  ovules,  and  fruits  of  trailing  ar- 
butus, Epigaea  repens. 

A  most  unusual  kind  of  mvcorrhizal  relationship  exists  between 
the  tuberous,  non-chlorophyllous  orchid,  Gastroidea  elata,  and 
Arviillaria  viellea  [Kusano  (1911)1.  The  rhizomorphs  of  this 
fungus,  which  is  widely  known  because  of  its  ability  to  destroy 
forest  trees,  attack  the  tubers  in  such  a  way  that  the  outer  layers 
contain  a  dense  mass  of  thick-walled  hyphae;  beneath  it  occurs  a 
region  containing  thin-walled  hyphae,  and  the  innermost  layer 
contains  a  few  slender  hyphae.  Tubers  associated  with  rhizo- 
morphs produce  offsets  which  remain  dormant  during  the  winter 
and  develop  flowers  in  the  following  summer.  If  mvcorrhizae 
are  not  formed,  flowers  are  not  developed. 


FUNCTION  OF  MYCORRH1ZAE  305 

Another  endotrophic  mycorrhizal  relationship,  which  is  of  un- 
usual interest  and  has  been  studied  rather  extensively,  involves 
the  grasses,  Lolhtm  perenne  and  L.  temulentum.  The  fungus  in- 
vades the  growing  point,  penetrates  the  carpels,  and  has  been 
demonstrated  to  occupy  the  ovules  and  embryo.  Sampson  (1935) 
called  attention  to  the  fact  that  fungus-free  seed  can  be  made  to 
produce  fungus-free  plants  that  set  seed.  On  the  other  hand,  seed 
containing  the  endophyte  may  produce  plants  that  again  are 
mycorrhizal.  This  fungus  is  not  identified,  but  there  are  reasons 
for  believing  it  may  be  a  smut. 

Function  of  mycorrhizae.  Although  knowledge  of  the  exist- 
ence of  mycorrhizae  dates  back  at  least  to  the  fourth  century  b.c. 
[Kelly  (1932)],  definite  information  concerning  their  true  struc- 
tural nature  may  be  said  to  begin  with  Frank's  observations  in 
1885.  In  the  years  that  followed,  conjecture  as  to  their  function 
was  rife,  and  from  the  publication  of  Frank's  classical  studies  to 
the  present,  numerous  theories  on  this  subject  have  been  advanced. 
Of  these  only  two  have  been  accorded  general  acceptance.  In 
one  theory  mycorrhizae  are  regarded  as  pathological  structures 
induced  by  the  parasitic  action  of  the  fungus  upon  the  root  tis- 
sues. The  other  theory  is  that  mycorrhizae  are  symbiotic  struc- 
tures that  facilitate  the  absorption  and  utilization  of  organic  ma- 
terials, especially  of  organic  nitrogen,  contained  in  humus.  It 
appears  that  evidence  in  support  of  these  theories  may  be  best  pre- 
sented by  a  brief  review  of  a  few  of  the  numerous  publications 
on  mycorrhizae. 

Over  100  years  ago  the  mode  of  nutrition  of  Monotropa  hypo- 
pitys,  a  flowering  plant  lacking  chlorophyll,  attracted  the  atten- 
tion of  botanists.  This  curious  plant,  classed  as  a  saprophyte  in 
modern  botanical  textbooks,  grows  with  its  roots  intermingled 
with  those  of  beeches,  spruces,  and  other  species  of  trees.  In 
consequence  some  workers  regarded  the  Monotropa  as  a  root 
parasite,  and  thev  noted  that  its  roots  were  covered  with  "a  whit- 
ish, silky,  somewhat  fibrous  material,  connected  with  the  decaying 
leaves."  The  fungal  nature  of  this  material  was  first  recognized 
in  1832  by  Elias  Fries.  Several  early  workers  demonstrated  that 
Monotropa  is  not  a  root  parasite  by  the  simple  expedient  of  trans- 
planting and  maintaining  it  apart  from  tree  roots.  In  spite  of  this 
fact,  final  settlement  of  the  mode  of  its  nutrition  was  deferred 
until   1881,  when  Kamiensky    (1881,    1882)    again   showed   that 


306 


MYCORRHIZAE  AND  MYCOTROPHY 


Alonotropa  will  grow  independently  of  tree  roots  and  that  the 
roots  of  both  the  tree  and  the  Alonotropa  are  invested  with  a 
similar  fungus  mantle.  Furthermore  this  mantle  is  organically 
connected  with  hvphae  that  course  between  the  cells  of  the  root 
cortex.  In  criticism  of  Kamiensky's  work,  however,  it  may  be 
indicated  that  he  did  not  present  experimental  evidence  that  either 
the  trees  or  the  Alonotropa  are  dependent  upon  the  fungus. 


mill 


^pvjni 


Fig.  48.  Diagram  of  young  root,  the  upper  side  mvcorrhizal,  the  lower 
normal.  The  root-hair  zone,  K  (in  black),  occurs  near  the  root  tip,  M. 
The  increased  absorbing  surface  in  A,  B,  C,  and  D  (in  black)  is  to  be 
compared  with  that  in  E,  F,  G,  and  H.  The  surface  area  active  in  ab- 
sorption in  mvcorrhizal  roots  must  also  take  account  of  the  surface  area 
of  the  fungus  filaments.     (After  Hatch.) 

From  about  1840  the  association  of  truffles,  especially  with  oak, 
beech,  and  hornbeam,  attracted  botanical  attention.  Certain  early 
students  of  this  problem  definitely  established  that  the  mycelia 
of  truffles  are  connected  with  the  roots  of  these  trees,  but  the 
relationship  was  supposed  to  be  parasitic.  At  first  Frank's  interest 
in  the  matter  was  centered  upon  the  possibility  of  cultivating 
truffles  and  other  hvpogeous  fungi,  especially  Elaphomyces  {rranu- 
latus,  in  the  forest.  As  an  outgrowth  of  this  interest  he  established 
the  fact  that  the  roots  of  certain  trees,  especially  members  of  the 
Cupulifereae,  are  invariably  invaded  by  fungi.  Aloreover,  he  was 
led  to  formulate  the  theory  that  the  relationship  is  not  one  of  para- 
sitism but  of  definite  beneficial  symbiosis,  in  which  the  fungal 


FUNCTION  OF  MYCORRHIZAE  301 

component,  in  lieu  of  root  hairs,  functions  to  absorb  water  and 
mineral  salts  from  the  soil.  Some  of  Frank's  experiments  involved 
growing  seedlings  in  culture  solutions  free  from  mycorrhizae.  He 
found  that  such  trees  made  entirely  satisfactory  growth,  a  result 
that  has  been  repeatedly  verified  by  others.  Frank's  interpreta- 
tions immediately  created  a  great  deal  of  interest  throughout 
Europe,  and  from  the  investigations  that  were  undertaken  in  the 
next  few  years  a  barrage  of  criticism  arose.  The  net  result  of 
these  studies  was  the  general  admission  that  mycorrhizae  are  of 
widespread  occurrence  in  nature,  but  many  workers  questioned 
the  mycotrophic  relationship. 

Stahl's  comprehensive  study  (1900)  of  mycorrhizae  is  a  land- 
mark among  contributions  to  the  literature  of  this  subject.  In  it 
he  elaborated  the  thesis  that  the  incidence  of  mycorrhizal  devel- 
opment is  correlated  inversely  with  soil  fertility.  Supporting 
evidence  for  this  thesis  rests  in  part  upon  the  assumption,  since 
confirmed  by  a  host  of  investigators,  that  in  the  keen  competition 
between  vascular  plants  and  soil  fungi  for  essential  minerals,  the 
fungus  mycelium  possesses  superior  mechanism.  Presumably  the 
basis  for  this  superiority  is  that  the  ratio  of  surface  area  to  volume 
is  vastly  greater  in  fungus  hyphae  than  in  roots.  For  this  reason 
non-mycorrhizal  plants,  such  as  Sambiicus  nigra,  Cvperaceae,  and 
various  ferns,  are  at  a  disadvantage  when  growing  on  infertile  soils, 
in  competition  with  mycorrhiza-formers. 

Stahl's  observations  also  bore  out  his  assumption  that  different 
species  of  plants  differ  in  the  extensiveness  of  their  root  systems 
and  their  rates  of  transpiration.  Species  with  extensive  root  sys- 
tems and  with  the  capability  of  losing  water  rapidly  might  be 
expected  to  be  best  fitted  for  competition.  Actually  Stahl  found 
that  the  reverse  is  true,  for  the  reason  that  species  possessing  ex- 
tensive root  systems  and  being  capable  of  transpiring  rapidly  tend 
to  be  autotrophic,  whereas  those  with  restricted  root  systems  and 
slow  transpiration  rates  are  mycotrophic. 

Rayner  (1934)  concluded  from  researches  involving  pines  that 
there  is  a  "direct  causal  relation  between  mvcorrhiza  development 
and  the  thrifty  growth  in  seedlings  of  various  species  of  Pinus." 
Further  evidence  in  support  of  Stahl's  mineral-nutrition  theory  is 
advanced  by  Hatch  (1937)  in  an  extensive  series  of  experiments. 
He  emphasizes  that  the  absorbing  surface  area  of  short  roots  is 
increased  through  the  presence  of  mycorrhizae  by  the  following: 


308  MYCORRH1ZAE  AND  MYCOTROPHY 

(a)  continued  elongation,  (b)  increased  diameter,  (c)  dichoto- 
mous  branching,  (d)  delay  in  suberization  of  cortex,  and  (e)  ac- 
quisition of  additional  surface  area,  the  composite  of  that  of  the 
hvphae.  His  three  interpretations  made  in  conclusion  are:  (1) 
that  mvcotrophic  relationship  is  a  symbiotic  mechanism  to  in- 
crease the  absorption  of  soil  nutrients;  (2)  that  the  extent  of  the 
surface  area  of  short  roots  is  determined  bv  the  availability  of 
minerals,  mvcorrhizal  roots  being  rarely  formed  in  fertile  soils 
but  produced  in  abundance  in  infertile  soils;  and  (3)  that  trees  are 
dependent  upon  symbiotic  association  with  mycorrhizal  fungi  for 
all  their  mineral  nutrients  and  therefore  for  their  ability  to  exist  in 
all  except  the  most  fertile  soils.  Experiments  by  Mitchell,  Finn, 
and  Rosendahl  (1937)  on  mycorrhizae  as  related  to  mineral  ab- 
sorption by  coniferous  seedlings  led  them  to  arrive  at  conclusions 
similar  in  all  essentials  to  those  of  Hatch.  Bjorkman  (1942)  found 
that  light,  nitrogen,  and  phosphorus  are  each  decisive  factors  gov- 
erning the  formation  of  mycorrhizae. 

Buries  (1936)  postulated  that  the  higher  plants  benefit  from 
association  with  fungi  by  absorbing  the  nutrients  made  soluble  as 
a  result  of  decomposition  by  the  soil  fungi.  He  does  not  believe 
that  there  is  any  mutualistic  relationship  between  tree  roots  and 
fungi  but  that  mycorrhizae  represent  a  controlled  parasitic  at- 
tack. Some  support  of  this  idea  appears  from  Rayner's  (1934, 
1936)  experiments,  in  which,  after  inoculation  with  mycorrhizal 
fungi,  she  noted  markedly  improved  growth  of  pine  seedlings  at 
a  period  in  advance  of  the  actual  formation  of  mycorrhizae.  She 
attributed  this  stimulation  to  the  elaboration  of  growth-promoting 
substances  by  the  fungus  and  to  the  nutrients  liberated  to  the 
seedlings  by  the  activity  of  the  fundus.  In  view  of  the  body  of 
evidence  that  is  being  accumulated  on  the  elaboration  of  auxins 
by  fungi,  these  substances  may  well  be  important  factors  in  in- 
creasing the  growth  of  plants  possessing  mycorrhizae. 

Much  has  been  written  to  indicate  that  mycorrhizal  fungi  are 
parasitic  and  that  the  balance  may  be  easily  tipped  toward  one  or 
the  other  partner  in  the  relationship.  The  observations  of  Masui 
(1926,  1927)  in  Japan  and  of  McDougall  (1914)  in  this  country 
inclined  them  to  regard  the  association  as  one  of  parasitism  by 
the  fungus. 

Bernard's  experiments  (1909),  summarized  in  her  "L'evolution 
dans  la  svmbiose  des  Orchidees,"  are  fundamental  to  an  apprecia- 


FUNCTION  OF  MYCORRHIZAE 


309 


tion  of  the  nature  of  endotrophic  mycorrhizae.  In  an  earlv  re- 
port *  she  concluded  that  the  fungal  component  is  a  benign  para- 
site causing  chronic  pathogenesis.  She  became  interested  in  this 
problem  because  of  the  difficulty  that  orchid  growers  were  experi- 
encing in  germinating  seed  and  raising  seedlings.     In  the  green- 


Fig.  49.  A.  Short,  lateral  roots  dichotomously  branched,  typical  of  mycor- 
rhizae on  pine.  B.  Somewhat  enlarged  mycorrhizae  on  pine.  (After 
Hatch.)  C.  Sketch  of  ectotrophic  mycorrhiza  on  pine,  showing  mantle 
and  "Hartig  net."  (After  Doak.)  D.  Locus  of  endotrophic  mycorrhiza 
(stippled  area)  in  germinating  orchid  seed,  Odontoglossum.  E.  Cell  from 
stippled  area  showing  hvphae  of  Rhizoctoma  lanuginosa.  (After  Bernard.) 
F.  Ectendotrophic  mycorrhiza  in  cell  of  strawberry  root.     (After  O'Brien 

and  McNaughton.) 

houses  of  successful  growers  she  noted  that  certain  fungi  were 
present  in  the  soil  around  the  roots  and  that  endotrophic  mycelium 
occurred  within  the  tissues.  If  seed  were  sown  near  parent  plants, 
germination  resulted.  If  the  seed  were  grown  aseptically,  ger- 
mination failed.  These  observations  led  her  to  believe  that  the 
presence  of  the  endophvte  was  essential  for  germination  and 

*  She  considered  orchids,  ''comme  les  plantes  atteintes  d'une  maladie 
parasitaire  chronique  qui  commence  a  la  germination  et  persiste  en  general 
jusqu'a  l'etat  adulte;  maladie  benigne  en  un  certain  sens.  .  .  ." 


310  MYCORRH1ZAE  AND  MYCOTROPHY 

growth.  She  isolated  the  endophvte  from  several  genera,  getting 
organisms  that  were  morphologically  similar  but  were  dissimilar 
in  action  when  used  reciprocally  to  inoculate  seedlings.  If,  for 
example,  she  inoculated  seed  of  Phalaenopsis  with  the  fungus  iso- 
lated from  the  same  host,  normal  germination  followed,  and  the 
mycelium  was  kept  in  bounds  by  the  digestive  activity  of  the  cells 
of  the  embryo.  If  instead  she  used  the  fungus  isolated  from 
Odontoglossum,  germination  stopped  short  at  an  early  stage,  and 
intracellular  digestion  of  the  fungus  was  excessive.  In  certain 
other  orchids,  such  as  Bletilla  hyacinthia,  the  seed  germinated  even 
when  the  fungus  was  absent,  but  the  seedlings  did  not  survive 
beyond  the  first  leaf  stage. 

Bernard  was  able  to  grow  seedlings  to  a  size  suitable  for  trans- 
planting in  the  absence  of  the  endophvte,  if  she  supplied  sugar 
solutions  and  salep  of  varying  concentrations.  She  interpreted 
this  ability  to  germinate  in  the  absence  of  the  endophvte  to  be 
caused  by  a  physico-chemical  stimulus  of  the  sugar  and  not  to  be 
produced  by  the  sugar  as  a  food. 

More  recently  Knudson  (1929)  summarized  a  series  of  studies 
(1922,  1925)  on  the  food  relationship  in  these  non-symbiotic  ger- 
minations. He  found  that  the  embryos  of  Cymbidium,  Vanda, 
Ophrvs,  and  Epipactis  lack  chlorophyll  for  the  first  5  or  6  weeks. 
They  must,  therefore,  obtain  soluble  food  from  the  substratum  in 
which  they  are  grown.  When  Knudson  supplied  Cattleya  em- 
bryos with  sugar  for  the  period  of  a  month  and  then  removed 
them  to  a  medium  lacking  sugar,  the  seedlings  continued  to  make 
good  growth  for  5  or  more  years.  Sugar  concentrations  in  pure 
cultures  as  low  as  0.02%  yielded  good  (Terminations.  Knudson 
was  also  able,  in  PfefTer's  solution  fortified  with  a  mixture  of  peat 
and  sphagnum  and  adjusted  to  pH  4.6,  to  germinate  embryos  just 
as  rapidly  as  occurs  in  the  presence  of  the  endophvte.  .Moreover, 
he  was  able  successfully  to  substitute  a  species  of  Phytophthora 
isolated  from  lilies  for  the  true  endophytic  Rhizoctonia.  He  con- 
cluded from  these  extensive  studies  that  the  unusual  requirements 
of  orchid  seed  for  germination  must  be  explained  by  their  inability 
to  synthesize  food.  The  embryos  must  therefore  be  regarded  as 
saprotrophic  in  early  development  and  the  associated  fungus  as 
mildly  pathogenic,  pathogenicity  being  controlled  by  the  physio- 
logical condition  of  the  orchid.  In  criticism  it  may  be  noted  that 
the  universal  occurrence  of  the  endophvte  in  orchid  roots  in 


IMPORTANCE  OF  MYCORRH1ZAE  TO  FORESTRY  311 

nature  is  not  satisfactorily  explained  by  these  experiments  of 
Knudson. 

Importance  of  mycorrhizae  to  forestry.  Evidence  from  ob- 
servations extending  over  a  period  of  years  has  been  accumulating 
which  tends  to  show  that  mycorrhizae  plav  an  important  role  in 
reforestation  and  afforestation.  As  long  ago  as  1917  [Hatch 
(1937)]  Aielin  noticed  that  seedlings  of  pine  and  spruce,  started 
from  wind-distributed  seed  in  recently  drained  peat  bogs,  ex- 
hibited nitrogen  starvation  and  eventually  died  unless  they  be- 

O  J  J 

came  invaded  with  mycorrhizal  funoi.  Seedlings  in  entire  nur- 
series  in  Australia,  southern  Rhodesia,  the  Netherlands  East  Indies, 
and  the  Philippines  remained  unthrifty  when  the  nurseries  were 
located  outside  the  natural  range  of  the  species  being  grown 
[Hatch  (1936)].  When  soil  from  established  nurseries  or  from 
sites  where  the  species  was  endemic  was  incorporated  as  inoculum 
in  these  seed  beds,  however,  the  seedlings  recovered  and  grew 
normally.  Similarly,  non-mycorrhizal  seedlings  made  poor 
growth  in  plantations  until  they  were  inoculated  with  small  quan- 
tities of  soil  containing  mycorrhizal  fungi. 

More  convincing  evidence  of  the  beneficial  nature  of  mycor- 
rhizae has  been  supplied  by  Rayner  (1934,  1936,  1939),  Hatch 
(1936,  1937),  and  Young  (1940).  Rayner  reported  experiments 
in  which  she  applied  pure  cultures  of  mycorrhizal  fungi  to  soils 
in  which  seedlings  were  making  poor  growth  and  in  which  my- 
corrhizae were  infrequent.  As  a  result  of  such  inoculations,  seed- 
ling growth  was  markedly  stimulated,  and  correlated  mycorrhizal 
formation  was  abundant. 

Since  transplants  in  the  Prairie  States  grew  poorly,  Hatch 
planted  Finns  strobus  seed  in  pots  of  prairie  soil  in  an  effort  to 
determine  the  cause.  The  seedlings  grew  poorly,  and  mycor- 
rhizae were  lacking.  He  then  inoculated  a  portion  of  the  pots 
with  pure  cultures  of  mycorrhizal  fungi.  The  inoculated  seed- 
liners  responded  by  increased  growth  over  the  uninoculated  ones 
to  the  extent  that,  after  two  months,  analyses  showed  the  inocu- 
lated seedlings  had  75%  more  potassium,  86%  more  nitrogen,  and 
234%  more  phosphorus  than  the  uninoculated.  Young  grew  1600 
Pinus  caribaea  in  soil  that  had  never  grown  pines.  He  mixed 
manure  and  pine  needles  with  the  soil  to  supply  organic  materials. 
As  inoculum  he  used  7  mycorrhizal  fungi.  In  all  cases  the  un- 
inoculated controls  made  the  poorest  growth,  with  best  growth 


312  MYCORRHIZAE  AND  MYCOTROPHY 

in  those  inoculated  with  Boletus  viscidus.  The  differences  would 
no  doubt  have  been  greater  if  he  had  not  used  manure.  Australian 
mvcorrhizal  fungi  might  also  be  expected  to  have  been  better 
suited  as  inoculum. 

These  observations  and  experiments,  although  not  numerous, 
indicate  several  very  obvious  conclusions.  In  the  first  place,  at- 
tempts to  exclude  diseases  and  pests  from  prairie  or  other  treeless 
regions  by  starting  nurseries  from  seed  are  doomed  to  failure 
unless  suitable  mvcorrhizae  producers  are  introduced.  Second, 
mvcorrhizal  fungi  perish  in  areas  that  have  been  long  denuded, 
and  thev  must  be  reintroduced  if  the  areas  are  to  be  reforested. 
Third,  planting  failure  can  result  if  the  environment  of  the  plant- 
ing site  is  unfavorable  for  the  growth  of  the  fungal  component. 
This  conclusion  is  supported  by  the  experiments  of  Romell 
[Hatch  (1937)],  who  found  that  mycorrhizal  fungi  may  be  more 
exacting  in  their  site  requirements  than  are  the  trees  with  which 
they  became  established  in  this  mycorrhizal  relationship. 

In  the  light  of  these  studies  on  mycorrhizae,  the  fleshy  fungi 
growing  on  the  forest  floor  have  uses  aside  from  supplying  the 
mycologist  with  objects  with  which  he  may  occupy  his  time,  or 
the  layman  with  victims  against  which  he  may  employ  his  toe  to 
vent  his  pent-up  emotions. 

For  use  in  silviculture  further  knowledge  should  be  sought  by 
attempting  to  synthesize  mycorrhizae  from  fleshy  fungi  and  for- 
est trees.  Studies  of  this  sort  are  still  too  limited  in  number  and 
scope.  The  value  of  such  work  is  indicated  by  Alodess  (1941). 
He  employed  pure  cultures  of  Hymenomycetes  and  Gastromy- 
cetes  with  pines  and  spruce,  finding  that  Scots  pine  developed 
mycorrhizae  with  Amanita  mappa,  A.  musctiria,  A.  pantherina, 
Boletus  flavidus,  Entoloma  rhodopoliuvh  Lactarius  helvus,  Paxil- 
lus  primulas,  Rhizopogon  luteolus,  R.  roseolus,  Scleroderma  au- 
rantium,  Tricholoma  albobrumieum,  T.  imbricatum,  T.  pessunda- 
tinih  and  T.  vacciniwm,  and  that  Picea  abies  synthesized  mycor- 
rhizae with  each  of  the  species  of  Amanita,  Boletus,  Lactarius, 
Tricholoma,  and  Scleroderma  that  has  been  mentioned. 

Tuberizatiox.  From  time  to  time  evidence  has  been  presented 
which  indicates  that  tuberization  in  certain  plants  may  be  induced 
by  mvcorrhizal  fungi.  In  this  connection  the  work  of  Bernard 
on  the  group  of  tuberous  orchids  is  of  especial  significance.  She 
found  that  the  seeds  of  Bletilla,  sown  aseptically,  develop  into 


TUBER1ZATION  SIS 

seedlings  with  slender  stems  and  with  leaves  borne  at  distinct  in- 
ternodes,  whereas  in  the  presence  of  the  endophyte  the  axes  of  the 
seedlings  are  thick,  the  internodes  short,  and  the  leaves  crowded. 
These  observations  led  her  to  conclude  that  a  causal  relationship 
between  invasion  by  the  endophyte  and  tuberization  exists  and 
also  induced  her  to  explore  the  possibility  that  fungi  are  the  cause 
of  tuberization  in  Ranunculus  ficariae  and  Solamim  tuberosum 
[  Bernard  (1911),  Bernard  and  Magrou  (1911)1.  After  Bernard's 
untimely  death  the  experiments  were  continued  by  Magrou 
(1921,  1924).  He  observed  mycorrhizae  in  Solanum  magia,  pre- 
sumably an  ancestor  of  the  cultivated  potato,  and  5.  dulcamara 
and  named  the  associated  fungus  Mucor  solani.  He  reported  that 
this  fungus  was  capable  of  infecting  Solanum  tuberosum  raised 
from  sterilized  seed.  His  observations  and  conclusions  have  not 
remained  unchallenged,  however,  and  in  fairness  may  be  said  to 
require  confirmation  by  the  performance  of  a  series  of  synthetic 
experiments.  Only  on  the  basis  of  such  experiments  can  his  find- 
ings be  accepted  or  discarded.  There  still  remains  the  interesting 
possibility  that  the  endophyte  may  provide  the  stimulus  that  ini- 
tiates tuberization,  and  that  it  may  be  entirely  digested  by  the  host 
cells  by  the  time  the  tuber  is  mature. 

Constantin  (1922)  summarized  his  studies  of  tuberization  as 
follows:  "The  association  of  perennial  species  of  plants  with  soil 
fungi  has  brought  about  a  permanent  symbiosis— a  condition 
which  does  not  occur  with  annual  species.  Since  the  perennial 
character  in  plants  is  due  to  the  low  temperatures  of  high  altitudes 
and  latitudes,  cold  climates  may  be  considered  as  favorable  to  the 
establishment  of  symbiosis.  Cultivated  potatoes  have  lost  the 
mycorrhizal  relations  of  the  primitive  forms  to  which  tuberization 
was  due,  and  in  order  to  produce  tubers  without  this  relationship 
they  must  be  grown  in  cold  climates." 

The  recent  report  of  Lutmari  (1945)  directs  attention  to  Ac- 
tinomycetes  within  tubers  of  potato  and  the  roots  of  artichoke, 
parsnip,  carrot,  and  beet.  The  filaments,  demonstrable  by  special 
stains,  pass  between  the  cells  and  are  intimately  applied  to  them. 
Their  role  remains  unknown,  but  Lutman  concludes,  "The  effects 
of  actinomyces  filaments  surrounding  every  cell  cannot,  at  this 
time,  be  even  estimated,  but  the  materials  which  they  withdraw 
from  the  cells  and  the  products  which  they  excrete  and  which 


314  MYCORRHIZAE  AND  MYCOTROPHY 

must  be  absorbed  bv  the  cells  cannot  fail  to  change  the  charac- 
teristics of  the  cells." 

Implications.  The  classical  interpretations  of  the  mechanisms 
involved  in  absorption  of  water  and  mineral  nutrients  by  seed 
plants  must  be  modified  somewhat  or  must,  in  some  measure,  be 
supplanted  by  a  more  complicated  system  in  the  light  of  the  fore- 
going consideration  of  mvcorrhizae.  Certain  seed  plants,  espe- 
ciallv  trees,  and  certain  fungi  have  been  demonstrated  to  be  nu- 
tritionallv  interdependent.  This  interdependence  is  a  partnership, 
and,  as  in  anv  partnership,  both  members  may  profit  mutually  or 
one  member  may  exploit  the  other.  Apparently  the  advantages 
that  accrue  to  each  member  of  the  partnership  outweigh  the  dis- 
advantages when  environmental  factors  are  normal,  but  this  bal- 
ance  may  become  upset  in  times  of  stress.  The  mycologist  may 
speculate  to  the  satisfaction  of  his  scientific  soul  on  how  and  why 
such  a  relationship  between  totally  unrelated  organisms  ever  be- 
came established,  only  to  arrive  eventually  at  the  unsatisfactory 
conclusion  that  living  things  are  interdependent. 

LITERATURE  CITED 

Barrows,  Florence  L.,  "Propagation  of  Epigaea  repens.    II.  The  endophytic 

fungus,"  Contrib.  Boyce  Thompson  Inst.,  77:431^40,  1941. 
Bernard,  X.,  "L'evolution  dans  la  symbiose  des  Orchidees  et  leur  champig- 
nons commensaux,"  Ann.  sci.  not.  Botan.,  9:  1-96,  1909. 
"Les  mycorhizes  des  Solanum,"  Ann.  sci.  not.  Botan.,  14:  235-252,  1911. 
Bernard,  N.,  and  J.   Magrou,   "Sur  les  mycorhizes   des   Pomme   de  terre 

sauvage,"  Ann.  sci.  not.  Botan.,  9  me.  ser.,  14:  252-258,  1911. 
Bjorkman,    Erik,    "Uber    die    Bedingungcn    dcr    Mykorrhizabildung    bei 

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Botan.  Z.,  5^:458-461,  1881. 


LITERATURE  CITED  315 

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Mem.  soc.  nationale  sci.  not.  math.  Cherbourg,  24:  5-40,  1882. 
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U.  S.  Dept.  Agr.,  Washington,  D.  C.     1932. 
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13:  1-25,  1922. 
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Botan.  Gaz.,  19:  345-379,  1925.' 
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Congr.  Plant  Sci.  Ithaca,  2:  1183-1189,  1929. 
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mellea"  J.  Coll.  Agr.,  Imp.  Univ.  Tokyo,  4:  1-66,  1911. 
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plants,"  Vt.  Agr.  Expi.  Sta.  Bull.,  522.    72  pp.     1945. 
McDougall,  W.-B.,  "On  the  mycorrhizas  of  forest  trees,"  Am.  J.  Botany, 

7:51-74,  1914. 
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Am.  J.  Botany,  16:  224-228,  1929. 
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3:  181-273,  1921. 
"Remarques   sur   les    cultures    experimentales   de    pomme    de    terre    avec 

endophyte,"  Ann.  sci.  not.  Botan.,  10  me.  ser.,  6:  285-288,  1924. 
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reference    to    its    mycorrhizal    fungus,    Cantharellus    floccosus    Schw.," 

Mem.  Coll.  Sci.,  Kyoto  Imp.  Univ.,  Ser.  B.,  2:  16-84,  1926. 
"A  study  of  the  ectotrophic  mycorrhizas  of  woody  plants,"  Mem.  Coll. 

Sci.,  Kyoto  Imp.  Univ.,  Ser.  B,  3:  149-279,  1927. 
Melin,  Elias,   Untersuchnngen  iiber  die  Bedeutung  der  Baummy  corrhiza, 

eine  okologisch-physiologische  Studie.    152  pp.    G.  Fischer,  Jena.     1925. 
Mitchell,  H.  F.,  R.  F.  Finn,  and  R.  O.  Rosendahl,  "The  relation  between 

mycorrhizae  and  the  growth  and  nutrient  absorption  of  conifer  seed- 
lings in  nursery  beds,"  Black  Rock  Forest  Paper,  1:  58-73,  1937. 
Modess,  O.,  "Zur  Kenntnis  der  Mykorrhizabildner  von  Kiefer  und  Fichte," 

Symbolae  Botan.  Upsalienses,  5:  3-147,  1941. 
Noack,  R.,  "Liber  Mycorrhizenbildene  Pilze,"  Botan.  Z.,  47:389-397,  1889. 
Noelle,  W.,  "Studien  zur  vergleichenden  Anatomie  und  Morphologie  der 

Koniferenwurzeln  mit  Riicksicht  auf  die  Systematik,"  Botan.  Z.,  68:  169- 

266,  1910. 
Rayner,  M.   C,  Mycorrhiza,  an  account  of  non-pathogenic  infection   by 

fungi  in  vascular  plants  and  Bryophytes.    246  pp.    Weldon  &  Wesley, 

Ltd.,  London.    1927. 
"The  biology  of  fungus  infection  in  the  genus  Vaccinium,"  Ann.  Botany, 

43:  55-70,  1929. 
"Mycorrhiza  in  relation  to  forestry.     I.  Researches  on  the  genus  Pinus, 

with  an  account  of  experimental  work  in  a  selected  area,"  Forestry, 

8:96-125,  1934. 
"The  mycorrhizal  habit  in  relation  to  forestry.    II.  Organic  composts  and 

the  growth  of  trees,"  Forestry,  10:  1-22,  1936. 


316  MYCORRHIZAE  AND  MYCOTROPHY 

Rayner,  M.  C,  "The  mvcorrhizal  habit  in  relation  to  forestry.  III.  Organic 
composts  and  the  growth  of  young  trees,"  Forestry,  13:  19-35,  1939. 

Sampson,  K.,  "The  presence  and  absence  of  an  endophytic  fungus  in  Lolhim 
temulentum  and  L.  perenne"  Trans.  Brit.  Alycol.  Soc,  19:  337-343,  1935. 

Stahl,  E.,  "Der  Sinn  der  Mycorrhizenbildung,"  Jahrb.  whs.  Botan.,  34:  534- 
688,  1900. 

Young,  H.  E.,  "Mycorrhizae  and  growth  of  Pinus  and  Araucaria.  The  in- 
fluence of  different  species  of  mycorrhiza-forming  fungi  on  seedling 
growth,"  /.  Australian  Inst.  Agr.  Sci.,  6:  21-25,  1940. 


Chapter  14 

GENETICS  OF  FUNGI 

The  principles  upon  which  the  science  of  genetics  rests  were 
established  by  Mendel  in  1865  but  remained  unrecognized  until 
the  beginning  of  the  present  century.  He  determined  from  hy- 
bridization experiments  with  peas  that  heritable  characters  behave 
as  units.  These  characters  may  be  allelomorphic,  that  is,  they 
may  operate  as  pairs,  one  member  of  which  is  dominant,  the  other 
recessive.  The  characters  must  therefore  be  controlled  by  factors 
or  determiners  which  maintain  their  individuality  throughout  the 
developmental  cycle  and  are  transmitted  from  generation  to  gen- 
eration. Moreover,  in  the  second  hybrid  generation  or  later  these 
characters  segregate  or  become  assorted  in  definite  numerical 

ratios. 

With  the  rediscovery  of  Mendelism  at  the  beginning  of  the 
twentieth  century  attention  turned  largely  to  studies  of  genetics 
of  seed  plants  and  higher  animals.  The  application  of  Mendelism 
to  fungi  has  constituted  a  neglected  field  of  inquiry  until  the  past 
few  years.  Some  of  the  reasons  will  become  apparent  in  the  ac- 
count that  follows.  Not  the  least  of  them  is  the  small  size  of  nuclei 
and  chromosomes  and  their  constituents.  These  facts  militate 
seriously  against  the  procurement  of  microscopic  evidence  to  sub- 
stantiate macroscopic  evidence  of  inheritance. 

SEXUAL  AND  ASEXUAL  STAGES  OF  FUNGI 

In  order  to  appreciate  and  properly  evaluate  genetic  studies  of 
funo-i  it  is  necessary  to  recall  certain  knowledge  that  is  funda- 
mentally axiomatic.  In  the  normal  life  cycle  of  fungi  generally 
there  occur  fusions  between  pairs  of  gametes.  This  phase  is 
called  the  sexual  stage  in  contrast  to  the  asexual  stage,  in  which 
vegetative  units  are  capable  independently  of  propagating  the 
fungus.     The  fusion  of  gametes,  called  fertilization,  produces  a 

317 


318  GENETICS  OF  FUNGI 

one-celled  structure  called  the  zygote.  The  most  important  part 
of  each  gamete  is  the  nucleus.  Gametes  of  fungi  are  not  known  to 
possess  any  appreciable  or  functional  cytoplasm,  such  as  is  known 
to  occur  among  seed  plants.  Undoubtedly  gametes  of  fungi 
possess  functional  cytoplasm,  but  as  yet  proof  of  cytoplasmic  in- 
heritance either  is  not  forthcoming  or  is  meager. 

Each  gametic  nucleus  is  constituted  of  chromatic  materials,  the 
chromosomes.  Each  zygote  contains  In  chromosomes  and  is 
therefore  diploid.  As  a  rule,  however,  among  the  Basidiomycetes 
and  Ascomycetes,  when  the  two  gametic  nuclei  are  brought  into 
juxtaposition,  they  do  not  fuse  immediately  but  remain  as  a  pair. 
Then  the  two  divide  at  one  and  the  same  time,  the  process  being 
called  conjugate  nuclear  division  and  giving  rise  to  two  daughter 
pairs.  Hundreds  or  even  thousands  of  successive  conjugate  nu- 
clear divisions  may  follow,  extending  in  time  over  a  period  of 
weeks  or  months.  Finally  two  such  paired  nuclei  come  to  lie  in 
special  cells  (basidia  in  the  Basidiomycetes,  teliospores  in  the 
Uredinales,  chlamydospores  in  the  Ustilaginales,  young  asci,  asco- 
gonia,  or  ascogenous  hyphae  in  the  Ascomycetes),  where  they 
actually  fuse. 

The  fusion  nucleus  resulting  contains  2/7  chromosomes  and  is 
thus  diploid.  Shortly  after  fertilization  the  fusion  nucleus  divides 
twice.  The  processes  involved  in  these  two  divisions  constitute 
meiosis.  In  one  of  the  divisions  the  number  of  chromosomes  is 
reduced  to  77,  and  the  other  division  is  homotypic  (equational). 
Sex  factors  are  segregated  during  meiosis.  Each  of  the  four  nuclei 
resulting  from  meiosis  contains  n  chromosomes,  the  haploid  num- 
ber. In  the  Basidiomycetes  each  of  the  four  nuclei  migrates  into 
a  developing  basidiospore,  which  is  a  haploid  cell.  When  these 
basidiospores  germinate,  they  produce  haploid  mycelia;  if  two 
such  mycelia  or  their  equivalents  of  opposite  sex  fuse,  cells  again 
containing  a  conjugate  pair  of  nuclei  arise.  In  the  Ascomycetes 
each  of  the  four  haploid  nuclei  again  undergoes  a  mitotic  division, 
whereupon  each  of  the  eight  haploid  nuclei  becomes  invested  with 
a  wall  and  is  an  ascospore.  The  germination  of  ascospores  gives 
rise  to  haploid  mycelia,  and  the  nuclei  may  again  become  paired 
in  preparation  for  fusion  within  the  ascogonium,  young  asci,  or 
ascogenous  hyphae,  as  the  case  may  be. 


HOMOTHALL1SM  AND  HETEROTHALLISM  319 

HOMOTHALLISM  AND  HETEROTHALLISM 

From  the  above  generalizations  we  may  pass  on  to  their  sig- 
nificance. For  a  long  time  it  was  held  that  the  spore  or  the  indi- 
vidual derived  from  any  spore  is  totipotent.  This  concept,  it  may 
be  interjected,  as  employed  in  studies  of  monosporous  cultures,  has 
been  both  a  great  deterent  to  progress  and  a  potent  factor  in  pro- 
moting progress  in  the  acquisition  of  knowledge  of  fungi.  It  has 
hindered  progress  because  many  workers  have  regarded  a  mono- 
sporous culture  of  a  fungus  as  a  whole  organism,  whereas  it  may 
be,  as  we  now  know,  only  a  "hemi-organism."  On  the  other  hand, 
the  concept  has  promoted  knowledge  because  by  use  of  mated 
monosporous  cultures  it  has  been  possible  to  learn  that  each 
individual  may  not  be  totipotent  but  may  require  another  comple- 
mentary culture.  In  1904  Blakeslee  (1904)  first  proved,  for  a 
number  of  species  of  Zygomycetes,  that  zygospores  can  be  ob- 
tained only  when  mycelia  of  opposite  sex  are  mated.  If  he  grew 
mycelium  from  a  single  conidium,  sporangia  and  conidia  were 
formed  in  abundance,  but  gametangia  and  zygospores  were  not 
produced.  To  those  organisms  requiring  two  thalli  of  opposite 
sex  potentialities  for  fertilization,  he  applied  the  term  heterothallic. 
One  strain  or  race  he  called  plus  (  +  ),  and  the  other  minus  (  — ). 
Sex  in  these  species  is  segregated  in  bipolar  fashion  at  meiosis.  On 
the  other  hand,  in  Sporodinia  grandis  mycelia  from  single  conidia 
produce  zygospores  and  are  therefore  hermaphroditic,  and  sex 
segregation  is  entirely  lacking.  Subsequently  both  heterothallism 
and  homothallism  have  been  found  to  occur  side  by  side  in  genera 
in  all  the  larger  groups  of  fungi. 

In  Phycomycetes.  BurgefT  (1928)  isolated  from  Phy  corny ces 
blakesleeamis  a  number  of  variant  or  mutant  races  to  which  he 
gave  such  form  names  as  arbusculus,  mucoroides,  gracilis,  and 
pallens.  When  various  crosses  between  the  original  P.  blake- 
sleeamis and  any  one  of  the  forms  were  made,  the  progeny  ap- 
peared like  that  of  the  original  except  in  the  crosses  with  mucor- 
oides.  The  type  of  progeny,  therefore,  is  determined  by  a  single 
factor  that  is  recessive  in  the  form  and  dominant  in  the  original; 
this  was  true  in  all  crosses  with  mutants  except  in  the  form 
mucoroides.  Burgeff  also  noted  certain  linkages  with  the  factor 
for  sex.    For  example,  in  his  crosses  of  arbuscula  with  the  normal, 


320 


GENETICS  OF  FUNGI 


the  heterozygous  zygospores  were  (Arb  arb  +  — ).  When  these 
were  germinated,  half  of  them  gave  four  different  haploid  deriva- 
tives with  the  respective  constitutions  (Arb  +),  (Arb  — ), 
{or})  _)_)?  and  (arb  — ).    The  other  half  yielded  only  two  different 


Fig.  50.  Plew-age  cmser'ma.  A.  Normal  perithecium,  external  appearance. 
B.  Normal  ascus,  bearing  four  ascospores.  C.  Occasionally  asci  are  found 
bearing  five  ascospores,  two  of  which  are  smaller  than  normal.  Mycelium 
from  small  ones  bear  ascogonia,  D,  and  spermatia.  E.  The  mycelium  from 
normal  spores  can  produce  perithecia;  the  spermatia  and  ascogonia  borne 
on  mvcelia  from  small  spores  are  self-incompatible  and  hence  self-sterile, 
but  compatible  and  fertile  if  reciprocally  crossed.  F.  Spermatia  borne  by 
phialide-like    lateral    branches.      G.    Trichogync    with    empty    spermatium 

attached.     (Adapted  from  Ames.) 


HOMOTHALLISM  AND  HETEROTHALLISM 


321 


types,  either  (Arb  -f- )  and  (arb  — )  or  (Arb  — )  and  (arb  -f). 

To  explain  this  condition  BurgefT  assumed  properly  that  one  or 

both  factor  pairs  must  segregate  at  the  second  division.    If  both 

pairs  of  factors  had  segregated  at  the  first  division,  there  would 

have  been  only  two   haploid 

types,    either    (Arb    +)    and 

(arb    — )    or    (Arb    — )    and 

(arb  +). 

In  Ascomycetes.    The  most 

illuminating   grenetical   studies 

among  Ascomycetes  have  con- 

cerned     Neurospora      [Shear 

and    Dodge     (1927),    Dodge 

(1927,  1928,  1930,  1931,  1940), 

Wilcox     (1928),     Lindegren 

(1929,     1933,     1936,     1939)]. 

The    best-known    species    of 

this    genus    is    N.    sitophila, 

known    as    the    pink    bakery 

mold,  which  is  cosmopolitan 

in  distribution.    It  has  a  Mo- 

nilia  conidial  stage.  Some  of 

the  species,  represented  by  N. 

sitophila   and    N.    crassa,    are  ,         .         MM„«.n«jrt„  nf 

r  .  Fig.  51.     Schematic  representation  or 

eight-spored     and     obligately    potentialities  of  ascospores  of  Plenr- 
heterothallic.      Each    spore    is     age  anserina.    Circles  represent  nuclei 
uninucleate      and      unisexual,     of  one  sex,  and  black  dots  nuclei  of 
four  spores  being  of  (  +  )  sex    the  °PPosite  sex;    Although  the  asci 
reaction  and  four  of  (— )  sex 
reaction.     Other  species,  such 
as   N.    tetrasperma,   are   nor- 
mally four-spored,  each  spore  being  binucleate  and  bisexual.    Oc- 
casionally in  this  species  one  or  more  of  the  spores  are  giants  or 
dwarfs,  as  occurs  also  in  Pleurage  anserina,  a  widely  distributed 
dung-fungus    [Wolf    (1912),    Dowding    (1931),    Ames    (1934). 
Usually  the  giant  spore  replaces  two  normal  spores.    The  dwarf 
spores  occur  in  pairs,  each  containing  a  single  nucleus.     In  N. 
tetrasperma  [Dodge   (1927)]   all  eight  of  the  nuclei  may  occa- 
sionally occur  within  one  giant  spore. 

In  order  to  learn  something  of  sex  segregation  Shear  and  Dodge 


always    have    eight   nuclei,   the    asco- 
spores may  be  uninucleate,  binucleate, 
trinucleate,  or  quadrinucleate. 


322 


GEXET1CS  OF  FUNGI 


(1927)  and  Dodge  (1927,  1928)  isolated  each  of  the  eight  asco- 
spores  of  N.  crassa  and  found  that  four  are  (-)-)  and  the  other 
four  (  — ).  This  discovery  left  unanswered  the  question  of  when 
segregation  of  sex  factors  occurs.    Manifestly  it  might  be  possible 


Sterile 


Perithecia 


Sterile 


Perithecia 


_-- r-  Sterile 


Perithecia 


^.*?  Sterile 


Perithecia 


Fig.  52.  Schematic  representation  of  a  fivc-spored  ascus  of  Pleurage  anserina. 
The  small  spores  are  of  opposite  sex,  the  large  spores  of  both  sexes.  If 
planted  on  agar  plates,  the  mycelium  of  each  bears  both  ascogonia  and 
spermatia.     The  conditions  of  fertility  and  sterility  are   indicated  by  the 

matings  in  each  culture.     (After  Ames.) 

to  determine  this  question  if  each  of  the  ascospores  was  isolated 
and  it  were  known  what  position  within  the  ascus  each  occupies. 
Colonies  from  each  could  then  be  mated  reciprocally  with  each 
of  the  others.  Accordingly  Wilcox  (1928)  employed  N.  sito- 
phila  in  such  experiments,  finding  that  (-f-)  and  (  — )  ascospores 
alternate  in  pairs  in  the  series  of  eight.  This  discovery  indicates 
that  the  sex  factors  are  segregated  at  the  second  division  of  the 
fused  nucleus  of  the  primary  ascus. 


HOMOTHALL1SM  AND  HETEROTHALLISM  323 

Another  type  of  evidence  has  been  provided  by  Dodge  (1927) 
from  cytological  study  of  N.  tetrasperma.  In  this  species  the 
spindle  of  the  first  nuclear  division  is  longitudinal  with  respect 
to  the  ascus,  and  the  two  daughter  nuclei  come  to  lie  one  above 
the  other  in  the  ascus.  At  the  second  division  two  types  of  posi- 
tion and  orientation  of  the  spindle  may  occur.  The  spindles  may 
lie  approximately  parallel,  perhaps  just  slightly  oblique  to  the 
long  axis,  or  else  are  aqain  longitudinal.  The  spindles  of  the 
third  division  are  nearly  transversely  oriented,  bringing  non-sister 
nuclei  into  symmetrical  arrangement.  On  delimitation  of  the 
spores  two  non-sister  nuclei  are  included  in  each  ascospore, 
whether  segregation  takes  place  in  the  first,  second,  or  third 
division. 

A  somewhat  different  explanation  may  account  for  the  situation 
in  PI  enrage  cms  er  in  a  [Dowding  (1931)].  She  found  that  the 
paired  dwarf  spores  are  always  of  opposite  sex.  This  discovery, 
together  with  the  fact  that  normal  spores  are  always  bisexual, 
indicates  that  the  (  +  )  and  (-)  nuclei  are  arranged  alternately 
at  time  of  spore  formation.  This  alternate  arrangement  might  be 
taken  as  prima  facie  evidence  that  sex  segregation  occurs  at  the 
third  division.  Dowding  indicates,  however,  that  the  ascus 
is  so  wide  that  there  is  opportunity  for  the  nuclei  or  even  the 
young  spores  to  slip  by  each  other,  so  that  the  final  arrangement 
0f  (_j_)  and  (  — )  nuclei  could  permit  segregation  of  sex  factors 
at  any  of  the  divisions. 

Lindegren  ( 1929)  found  that  the  ratio  of  first-division  to  second- 
division  segregation  0f  sex  in  Nenrospora  crassa  is  8:15.    Later 

CO  L 

(1936,  1939)  he  determined  that  the  gene  for  sex  is  linked  with 
other  factors  and,  by  determining  crossing-over  percentages,  was 
able,  for  the  first  time  with  fungi,  to  construct  chromosome  maps. 
These  data  provide  an  explanation  of  the  mechanism  involved 
and  appear  to  prove  that  the  chromosomes  disjoin  at  the  first  divi- 
sion and  that  the  factors  are  segregated  at  the  second  division. 
Lindegren  also  emphasizes  that  pure  lines  of  fungi  must  be  ob- 
tained by  inbreeding  as  stock  for  genetical  studies.  Such  stocks 
also  serve  best  for  experimentation  on  interspecific  hybrids,  one 
of  which  was  secured  by  Dodge  (1928)  by  crossing  the  eight- 
spored  N.  sitophila  with  the  four-spored  N.  tetrasperma. 

Dimock  (1939)  hybridized  strains  of  Hypomyces  ipomoeae 
obtained  by  isolating  single  ascospores.     From  these  isolations 


324 


GENETICS  OF  FUNGI 


o 


o 


o 
o 


G 


Fig.  53.  Diagrams  to  illustrate  sex  of  ascospores  of  Neurospora  tetraspervia, 
conditioned  bv  whether  sex  is  segregated  at  the  first  division  of  the  primary 
ascus  nucleus  or  at  the  second  nuclear  division.  Above.  Segregation  at  the 
first  division,  C,  resulting  in  four  free  nuclei  of  one  sex  after  the  third 
division,  and  four  nuclei  of  the  other  sex,  E.  Two  of  the  four  spores 
formed  are  therefore  of  one  sex,  F,  and  two  of  the  other.  The  two  upper 
ascospores  may  both  be  +  (G)  with  the  lower  pair,  or  the  pairs  may  occupy 
the  reverse  positions.  Below.  Sex  not  separated  in  C  at  the  first  division 
of  the  fusion  nucleus,  but  separated  in  the  second  division.  When  asco- 
spores are  delimited,  each  contains  part  +  and  — ,  F,  or  else  sex  may  not 
segregate  at  all,  and  each  nucleus  is  as  shown  in  G.     (Adapted  from  Dodge.) 


HOMOTHALLISM  AND  HETEROTHALL1SM  325 

he  obtained  four  strain  groups,  which  he  designated  purple,  alba, 
revohtta,  and  revecta.  When  he  attempted  to  inbreed  bv  mating 
within  each  of  these  strains,  perithecia  were  not  produced  except 
in  one  purple  X  purple  mating.  When  back-crossed  to  normal, 
all  had  low  fertility  except  the  alba  strains.  The  evidence,  he  be- 
lieves, indicates  that  these  variants  in  H.  ipomoeae  arise  by  gene 
mutation. 

Edgerton  and  his  associates  (1945)  employed,  in  crosses,  strains 
of  Glomerella,  isolated  from  Ipomoea,  that  differed  only  in  that 
some  were  (-f-)  and  the  others  (  — ).  In  certain  of  these  crosses 
each  ascus  contained  four  ascospores  of  the  (  +  )  type  and  four 
of  the  ( — )  type.  In  others  all  ascospores  were  of  the  ( — )  type. 
Some  (  +  )  strains  originating  from  single  ascospores  segregated 
into  two  strains,  but  no  explanation  of  this  phenomenon  based  on 
nuclear  constitution  has  been  forthcoming. 

The  synthesis  of  vitamins  and  amino  acids  may  be  gene  con- 
trolled, and  loss  of  such  synthetic  ability  has  been  induced  by 
treatment  of  Neurospora  crassa  with  X-rays  and  ultraviolet  light. 
Tatum  (1944)  secured  approximately  400  mutant  strains  from 
60,000  single-spore  cultures.  Among  these  mutants  were  strains 
which  required  each  of  the  B  vitamins  except  folic  acid  and  ribo- 
flavin. Others  required  most  of  the  amino  acids.  These  muta- 
tions involved  only  a  single  gene.  One  strain  was  unable  to  com- 
plete the  synthesis  when  supplied  with  /^-alanine  and  pantoyl-lac- 
tone. It  required  that  pantothenic  acid  be  supplied  as  such  from 
an  exogenous  source  [Tatum  (1944)].  From  the  results  of  such 
differences  among  strains  of  N.  crassa  the  question  arises  of  why 
some  are  able  to  synthesize  their  required  vitamins  and  what  the 
mechanism  is  for  loss  of  such  ability  by  other  strains. 

Lindegren  (1945)  in  an  extended  study  of  cultivated  yeast 
demonstrated  ( -f- )  and  ( — )  races  that  must  be  mated  to  secure 
ascospores. 

In  Basidiomycetes.  Two  investigators,  Bensaude  (1918)  and 
Kniep  (1919),  working  independently,  called  attention  to  the 
fact  that  heterothallism  occurs  among  Hymenomycetes  and  that 
it  is  correlated  with  the  presence  of  long-known  mycelial  struc- 
tures called  clamp  connections.  Since  then  a  large  number  of 
other  workers  have  contributed  to  our  knowledge  of  sexuality 
and  genetics  of  Basidiomycetes,  those  dealing  mostly  with  Hy- 
menomycetes having  come  from  Buller  and  his  students  and  those 


326 


GENETICS  OF  FUNGI 


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Fig.  54.  Above.  Schematic  representation  of  sex  segregation  at  the  first 
nuclear  division  in  Neurospora  sitophila.  There  result  two  possible  arrange- 
ments of  the  ascospores  with  regard  to  sex,  as  shown  in  H.  Either  the  four 
spores  at  the  upper  end  of  the  ascus  are  +  and  the  four  at  the  lower  end  — , 
or  else  the  fours  are  in  reverse  position.  (After  Dodge.)  Below.  Schematic 
representation  of  sex  segregation  at  the  second  nuclear  division  in  Neuro- 
spora sitophila.    There  result  four  possible  arrangements  of  ascospores  with 

regard  to  sex,  as  shown  in  H. 


HOMOTHALL1SM  AND  HETEROTHALLISM 


321 


dealing  with  rusts  and  smuts  from  Stakman  and  his  students.  It 
should  be  kept  clearly  in  mind  that  the  Hymenomycetes  do  not 
possess  sexual  organs,  although  they  occur  in  the  Uredinales,  nor 


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toot 


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oott 

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otto 
toot 


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oott 
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otto 
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ttoo 

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toot 


Fig.  55.  Schematic  representation  of  sex  segregation  at  the  third  nuclear 
division  in  Neitrospora  sitophila.  Each  of  the  pair  at  C,  the  first  division, 
and  each  of  the  pair  at  F,  the  second  division,  is  H ,  but  at  the  third  divi- 
sion +  and  -  segregate.  There  result  16  possible  arrangements  of  the 
ascospores  with  regard  to  sex  potentialities,  as  shown  by  the  series  of  rings 


below. 


(After  Dodge.) 


do  they  produce  definitive  sex  cells.  Instead  sexual  functions  are 
carried  out  by  paired  nuclei.  Nevertheless  most  of  the  species 
are  heterothallic  and  exhibit  a  definite  sexual  process.  The  basi- 
diospores,  whether  of  a  homothallic  or  a  heterothallic  species,  are 
haploid;  that  is,  their  nuclei  contain  n  chromosomes.  When  two 
haploid  mycelia  of  opposite  sex  of  a  heterothallic  species  grow 


328  GENETICS  OF  FUNGI 

in  contact,  hvphal  fusions  occur,  and  the  mycelia  become,  in  con- 
sequence, dicarvotic  (two-nucleate).  The  nuclei  become  associ- 
ated in  conjugate  pairs  of  (//)  +  (7;)  chromosomes.  Then,  as  the 
dicarvotic  mycelium  continues  to  grow,  conjugate  nuclear  divi- 
sions occur,  but  with  each  conjugate  division  a  clamp  connection 
separates  the  two  pairs  of  daughter  nuclei.  Finally  a  conjugate 
pair  is  delimited  in  each  basidium.  Here  they  fuse,  whereupon 
meiosis  occurs,  and  each  resulting  haploid  nucleus  migrates  into  a 
developing  basidiospore. 

Up  to  this  point  observations  are  quite  in  accord.  Kniep  (1919, 
1922)  found  in  Schizophyllum  commune  and  Aleurodiscus  poly- 
gonius  that  sometimes  two  of  the  tetrad  of  basidiospores  were  of 
one  sex  and  two  of  the  other  sex,  although  each  species  is  normally 
quadrisexual,  that  is,  quadripolar  or  quadripotential.  In  explana- 
tion he  proposed  that,  when  the  abnormal  situation  obtained,  dis- 
junction of  sex  occurred  in  the  first  division.  The  quadrisexual 
situation  he  explained  by  assuming  that  sex  is  determined  by  two 
pairs  of  allelomorphic  factors,  which  segregate  independently  of 
each  other  during  the  second  division. 

In  Coprimis  rostmpiamis  Newton  (1926)  found  only  two  kinds 
of  spores  in  each  basidium,  two  (A)  spores  and  two  (a)  spores,  in 
which  case  sex  is  determined  by  one  set  of  factors.  In  C.  lagopus 
she  (1926)  found,  however,  as  had  Kniep,  that  sex  is  determined 
by  two  pairs  of  linked  factors,  so  that  the  nucleus  of  the  primary 
basidium  has  the  constitution  AaBb.  The  basidiospores  then  can 
be  (1 )  AB,  Ab,  aB,  and  ab\  or  (2)  two  AB  and  two  ab\  or  (3)  two 
Ab  and  two  aB.  Similar  results  have  been  obtained  by  others  with 
Hypholoma  fascicular -e  and  Colly  bia  velutipes.  Newton  analyzed 
42  tetrads,  25  of  which  were  of  the  first  of  the  3  types,  9  of  the 
second,  and  8  of  the  third. 

Brunswik  (1924)  analyzed  93  tetrads  of  Coprimis  fimetarius 
(lagopus)  with  these  findings:  37  gave  all  four  types  of  spores  AB, 
Ab,  aB  and  ab\  29  gave  the  two  types  AB  and  ab;  27  gave  the  two 
types  Ab  and  aB. 

These  data,  together  with  those  of  other  observers  [Buller 
(1931)],  show  that  sexuality  is  both  bipolar  and  tetrapolar  among 
Basidiomvcetes.  The  mechanism  of  these  patterns  of  behavior, 
as  Dodge  ( 1940)  indicates,  is  readily  explainable  if  we  assume  that 
the  genotypes  of  the  parental  nuclei  in  the  matings  made  by  New- 
ton and  by  Brunswik  were  either  AB  X  ab  or  Ab  X  aB.    This 


HOMOTHALL1SM  AND  HETEROTHALLISM  32<s 

assumption  would  account  for  the  presence  of  two  types  of  bi- 
polar basidia  in  equal  proportions,  if  reduction  (segregation) 
occurred  in  the  first  division  and  there  was  random  segregation 
without  genetic  linkage.  With  such  genotypes  a  simple  crossing- 
over  during  meiosis  would  account  for  the  tetrapolar  basidia. 

Further  light  on  this  problem  was  shed  by  the  studies  of  Sass 
(1929).  He  found  four-spored  and  two-spored  forms  of  each  of 
the  three  species  Coprinus  ephemeras,  Nancoria  semiorbiciilatus, 
and  Galera  tenera.  The  two-spored  form  of  each  is  normally 
homothallic.  The  four-spored  forms  are  heterothallic  and  bi- 
sexual, and  sex  is  determined  by  one  pair  of  Mendelian  factors. 

Pamis  stiptictis  from  Europe  is  non-luminous,  but  the  same  spe- 
cies from  North  America  is  luminous.  Studies  by  Macrae  (1942) 
of  both  European  and  North  American  strains  of  this  fungus  show 
that  each  strain  is  heterothallic  and  tetrapolar.  When  she  crossed 
a  luminous  with  a  non-luminous  one,  the  haploid  mycelium  of  the 
Fi  generation  was  luminescent.  Luminosity  is  therefore  dominant 
and  is  governed  by  a  single  pair  of  factors. 

hi  Ustilaginales.  Some  of  the  more  important  contributions  to 
the  genetics  of  smut  fungi  are  those  of  Stakman  and  Christiansen 
(1927),  Christiansen  (1929),  Hanna  (1929),  Dickinson  (1931), 
Flor  (1932),  Allison  (1937),  Kernkamp  (1939),  and  Schmitt 
(1940).  The  smuts  constitute  a  group  of  destructive  plant  para- 
sites which,  in  regard  to  their  sexual  process,  resemble  the  other 
Basidiomycetes  generally  in  that  thev  lack  sexual  organs  and 
definitive  gametes.  Their  most  distinctive  feature,  the  mature 
chlamydospore  or  smut  spore,  is  uninculeate.  Its  nucleus  is  a  2n 
structure.  At  germination  meiosis  occurs,  and  each  haploid  nu- 
cleus finds  its  way  into  a  basidiospore  or  sporidium.  According 
to  Hanna  (1929),  infection  of  maize  by  Ustilago  zeae  is  accom- 
plished by  haploid  mycelia,  and  the  chance  meeting  of  two  hap- 
loid mycelia  of  opposite  sex  within  the  host  tissues  is  followed  by 
hyphal  fusions,  whereupon  the  mycelial  cells  are  dicaryotic.  Pre- 
viously Stakman  and  Christiansen  (1927)  had  failed  to  obtain 
fusions  in  artificial  cultures  between  strains  of  opposite  sex  but 
had  found  hyphal  fusions  and  clamp  connections  in  hyphae  within 
the  maize  tissues.  Moreover,  infections  from  monosporidial  cul- 
tures failed  to  result  in  the  production  of  smut  galls  and  of 
chlamydospores.    When  dicaryotic  mycelium  eventually  becomes 


330 


GENETICS  OF  FUNGI 


transformed  into  young  chlamydospores,  the  conjugate  nuclear 
condition  still  obtains,  and  actual  fusion  takes  place  only  within 
the  maturing  chlamydospore. 

Stakman  and  Christiansen  (1927),  by  isolating  the  individual 
sporidia,  were  able  to  show  that  U.  zeae  is  heterothallic,  and  by 


Ustilago  hordei 


<b  §  ^ 


XD     CIX 


Ustilago  medians 


W  (3)  W 


F,  {    Ss    -     I    +    . 


^XE)    ®C± 


+ 


(§>  WZ&. 


F*0000  0000 Fz 


Fig.  56.  Schematic  representation  of  hybridization  of  two  species  of  smuts, 
one  smooth-walled  and  one  rough-walled.  P  represents  parents.  The  sex 
factor,  +  or  — ,  segregates  independently  of  the  chlamydospore-wall  char- 
acter. 5  in  sporidia  represents  spiny  walls;  s  in  sporidia  represents  smooth 
walls  with  S  dominant.  In  the  Fi  generation  all  spore  walls  are  spiny.  In 
the  F-2  generation  the  ratio  of  spinv-walled  spores  to  smooth-walled  spores 
is  4:0,  3:1,  and  2:2,  if  all  possible  combinations  are  made. 

the  same  techniques  Flor  (1932)  showed  that  this  situation  exists 
also  in  Tilletia  tritici  and  T.  levis. 

Working  with  oat  smut,  Ustilago  levis,  Dickinson  (1931),  con- 
sidered that  the  two  pairs  of  factors  Aa  and  Bb,  representing  sex 
and  color,  were  additive  in  their  effect,  AB  causing  brown  color, 
ab  causing  cream  color,  and  either  Ab  or  aB  causing  velknv  color. 
He  isolated  the  four  sporidia  of  known  position.  It  was  apparent 
that  the  haploid  parental  mating  was  AB  X  ab,  that  is  brown  X 
cream.     Out  of  this  mating  came  tetrads  of  sporidia  of  three 


HOMOTHALLISM  AND  HETEROTHALL1SM  331 

groups  in  the  proportion  of:  (1)  two  AB  and  two  ab,  (2)  two 
Ab  and  aB,  (3)  one  each  of  AB,  aby  aB,  and  Ab.  Segregation 
would  appear  therefore  to  occur  in  the  fashion  described  bv 
Newton  (1926)  and  Brunswik  (1924)  in  Coprimts  lagopus,  with 
the  linkage  and  crossing-over  mechanisms  as  interpreted  by  Dodge 
(1940).  These  observations  bv  Dickinson  (1931)  are  further 
substantiated  bv  the  findings  of  Schmitt  (1940)  on  Ustilago  zeae. 
The  segregations  of  factors  for  colonv  color,  sex,  and  tvpe  of 
growth  (sporidial  or  mvcelial)  occurred  in  both  the  first  and  the 
second  divisions.  For  each  of  these  characters  numerical  ratios 
of  1:1,  3:1,  and  1:3,  were  found,  with  a  4:0  segregation  for  sex 
in  one  case  amoncr  several  thousand. 

Smuts  constitute  especially  favorable  material  for  genetical 
studies  for  the  reason  that  all  the  sporidia  from  a  promvcelium 
can  be  isolated  and  can  then  be  propagated  in  culture.  Each  spo- 
ridium  by  budding  can  be  made  to  form  numerous  haploid  in- 
dividuals that  can  be  mated  under  controlled  conditions.  Gene- 
tic studies  of  smuts  have  been  concerned  with  colony  characters 
and  tendency  to  sector.  Other  studies  have  included  such  factors 
as  color  of  the  peridium  of  sori,  pathogenicity,  sex  compatibility, 
color  of  the  chlamydospores  and  the  nature  of  their  walls,  and 
tendency  to  be  myceloid  or  to  form  buds  [Christiansen  and 
Rodenheiser  (1940)']. 

Kernkamp  (1942)  isolated  monosporidial  lines  of  U.  zeae  to 
study  the  effects  of  genetic  and  environmental  factors  on  types 
of  colonial  growth.  Some  isolates  were  entirely  sporidial,  some 
entirely  mycelial,  and  some  intermediate.  Strictly  sporidial  lines 
could  not  be  mated  and  could  not  infect  maize.  The  growth 
types  of  sporidial  or  of  mycelial  lines  could  not  be  modified  by 
changes  in  concentration  of  food  or  by  addition  of  certain  vita- 
mins, poisons,  amino  acids,  or  other  substances.  The  growth 
type  of  intermediate  lines,  however,  could  be  modified  for  in- 
creased sporidial  production  by  the  presence  of  dextrose  or  for 
mycelial  production  by  unfavorable  growth  conditions. 

Stakman  and  his  associates  (1943)  found  that  mutation  is  un- 
believably common  in  U.  zeae.  In  this  smut  mutability  and  con- 
stancy are  governed  by  genetic  factors,  as  has  been  determined 
from  the  results  of  numerous  crosses  between  monosporidial  lines 
of  opposite  sex.  Stakman  and  his  associates  conclude,  "Ustilago 
zeae  definitely  comprises  an  indefinite  number  of  biotypes  that 


552 


GEXET1CS  OF  FUNGI 


Fig.  57.     Hybrids  between  monosporidial  lines  of  Ustllago  zeae.     Progeny 

of  the  four  primary  sporidia  from  each  of  three  chlamydospores.     Note 

recombination   of  characters.      (Courtesy  of  E.   C.  Stakman.) 


HOMOTHALL1SM  AND  HETEROTHALLISM  333 

• 

differ  either  widely  or  slightly  in  every  observable  character  or 
combination  of  characters.  New  ones  are  continually  being  pro- 
duced as  a  result  of  mutation  and  of  recombinations  resulting 
from  interbiotypic  hybridization." 

In  Uredinales.  The  Uredinales,  or  rust  fungi,  are  a  group  of 
obligate  parasites  of  enormous  economic  importance,  because 
many  of  them  attack  crop  plants.  Although  many  studies,  from 
which  have  come  a  number  of  fundamentals  concepts,  have  been 
concerned  with  their  sexuality,  an  understanding  of  this  subject 
was  first  established  by  the  investigations  of  Craigie  (1927,  1927a, 
1928).  He  showed  that  the  pycnia  are  functional  structures  and 
that  the  pycniospores  are  essential  in  diploidization. 

Undoubtedly  many  rusts  are  heterothallic,  for  Craigie's  studies 
have  shown  that  such  is  the  situation  in  Pucclma  graminis,  P. 
helianthi,  P.  coronata,  P.  pringsheimiana,  and  Gymno  sporangium 
sp.  At  germination  of  the  teliospore,  whose  mature  cells  are  uni- 
nucleate, the  nucleus  divides  meiotically  within  the  promycelium, 
the  homolomje  of  the  basidium,  and  the  four  resultant  nuclei  are 
haploid.  Each  migrates  through  a  sterigma  into  the  basidiospore 
that  arises  at  the  apex  of  a  sterigma.  Craigie  found  that  these 
basidiospores  are  of  either  (-+-)  or  (  — )  potentialities.  If  mono- 
sporidial  inoculations  are  made,  pycnia  containing  pycniospores 
are  developed.  However,  aecia  never  develop  in  association  with 
such  pycnia  unless  pycniospores  from  a  pycnium  of  opposite  sex 
are  applied.  In  nature  this  interchange  of  pycniospores  is  accom- 
plished either  by  insects  attracted  to  the  sugary  exudate  in  which 
pycniospores  are  embedded  or  by  water.  Buller  (1940)  has 
shown  that  flexuous  hyphae  extend  from  the  orifices  of  the  pycnia 
and  that  pycniospores  fuse  with  these  flexuous  hyphae.  The 
pycniospores  are  thus  spermatia,  and  the  flexuous  hyphae  are  re- 
ceptive surfaces  comparable  to  trichogynes.  Buller  (1940)  has 
observed  flexuous  hyphae  in  21  species  belonging  in  Coleospo- 
rium,  Cronartium,  Gymnoconia,  Gymnosporangium,  Melampsora, 
Alelampsorella,  Alilesia,  Phragmidium,  Pucciniastrum,  Puccinia, 
and  Uromyces. 

If  spermatization  is  accomplished,  aecia  bearing  dicaryotic 
aeciospores  with  conjugate,  (n)  -f  (72),  nuclei  are  developed. 

In  full-cycled  rusts,  not  only  the  aeciospores  but  also  the  myce- 
lia  arising  when  they  germinate,  the  urediniospores  and  the  my- 
celia  arising  from  their  germination,  and  the  young  teliospores 


334  GENETICS  OF  FUNGI 

are  dicarvotic.  The  thousands  of  nuclear  divisions  that  occur 
meanwhile  are  conjugate,  and  the  complete  cycle  from  the  mono- 
caryotic  to  the  dicarvotic  condition  and  back  again  to  the  mono- 
caryotic  may  require  a  period  of,  at  one  extreme,  only  a  few  days 
to,  at  the  other,  5  to  7  years,  as  in  Cronartium  ribicola. 

Inability  to  grow  rusts  on  artificial  media  has  no  doubt  inter- 
fered  to  some  extent  with  genetical  studies  of  them.  Nevertheless 
such  studies  have  been  energetically  pursued,  especially  by  Stak- 
man  and  his  associates  at  the  Minnesota  Experiment  Station  and 
by  a  ^roup  at  tne  Dominion  Cereal  Rust  Laboratory  in  Canada. 
The  presence  of  barberry  bushes  in  areas  devoted  to  cereal  crops 
permits  the  development  in  nature  of  new  races  or  strains  of  rusts 
by  hybridization.  There  is  abundant  evidence  that  such  new- 
hybrid  rusts  are  continuously  beino-  developed  and  that  their 
presence  accounts  for  the  breaking  down  of  resistance  in  cereal 
varieties  that  possess  a  high  degree  of  resistance  to  old  strains  of 
rusts.  The  production  of  new  strains  of  rusts  tends  to  nullify  the 
laborious  efforts  of  plant  breeders  to  develop  resistant  varieties  of 
cereals  and  to  control  cereal  rusts  bv  use  of  these  resistant  varieties. 

Newton  and  Johnson  (1940)  crossed  Puccini a  graminis  tritici 
and  P.  graminis  avenae,  finding  them  completely  interfertile. 
These  workers  were  concerned  primarily  with  pathogenic  po- 
tentialities. Crosses  within  the  avenae  variety  showed  that  the 
less  virulent  pustule  type  is  dominant  over  the  more  virulent  type, 
whereas  within  the  tritici  variety  the  less  virulent  type  is  dominant 
in  some  crosses  but  recessive  in  others.  In  reciprocal  crosses  be- 
tween these  two  varieties  the  maternal  cytoplasm  appears  to  exer- 
cise the  controlling  influence.  A  cross  between  a  variant  whose 
urediniospores  were  orange  and  a  variant  whose  urediniospores 
were  grayish-brown  gave  all  normal  red  color  in  the  Fi  genera- 
tion. When  selfed,  four  different  colors-red,  orange,  grayish- 
brown,  and  white— appeared  in  the  F2  generation,  with  a  distribu- 
tion ratio  suggesting  9:3:3:1,  respectively. 

In  experiments  with  physiologic  races  of  P.  graminis  tritici, 
Johnson  and  Newton  (1940)  found  that  absence  of  pustules, 
which  they  called  O  type,  was  dominant  over  large  pustules  (4 
type)  on  Kanred  wheat.  When  this  hybrid  was  selfed,  the  O  type 
was  approximately  3  times  as  abundant  in  the  F2  generation  as 
the  4  type.    In  this  instance  pathogenic  behavior  is  governed  by 


DOMINANCE  AND  LETHAL  FACTORS  335 

a  single  factor  pair.  On  Mindum  wheat  the  4  type  was  dominant 
over  very  small  pustules  ( 1  type)  with  a  3 : 1  ratio  in  the  F2 
generation.  On  the  other  hand,  when  the  emmer  variety,  Vernal, 
served  as  the  host,  the  1  tvpe  was  15  times  as  abundant  as  the  4 
tvpe  in  the  F2  generation.  Pathogenic  behavior  on  Vernal  emmer 
appears  therefore  to  be  governed  by  duplicate  factors.  Johnson 
and  Newton  conclude  that  the  genes  in  the  binucleate  uredinio- 
spores  function  as  if  they  occurred  in  a  single  diploid  nucleus. 

DOMINANCE  AND  LETHAL  FACTORS 

The  existence  of  dominance  and  recessiveness  among  fungi 
would  appear  to  have  been  amply  demonstrated  in  the  studies  de- 
scribed, which  are  representative  of  experiments  among  the  larger 
groupings  of  fungi.  This  Mendelian  principle  can  be  demon- 
strated for  interested  students,  however,  by  hybridizing  an  eight- 
spored  Neurospora  with  a  four-spored  Neurospora.  All  the  Fx 
progeny  will  be  found  to  be  eight-spored.  Similarly,  when  a 
rough-spored  race  of  smut  is  crossed  with  a  smooth-spored  one, 
all  the  Fi  are  rough. 

Lethal  factors  exist  among  fungi,  just  as  they  are  known  to 
occur  among  seed  plants.  Dodge  (1934)  reported  the  results  of 
studies  on  N.  tetrasperma,  known  to  possess  bisexual  ascospores.  ■ 
After  treatment  with  X-rays  a  strain  appeared  that  was  practi- 
cally self -sterile,  as  manifest  by  ascus  abortion.  When  this  strain 
was  mated  with  a  normal  one,  the  Fx  generation  gave  asci  that 
formed  spores  normally.  Further  results  showred  that  at  meiosis 
the  lethal  factor  was  segregated,  so  that  each  bisexual  ascospore 
contained  a  normal  nucleus  and  one  with  the  lethal  factor.  This 
situation  insured  the  transmission  from  generation  to  generation 
of  the  lethal  factor. 

More  recently  Fischer  (1940)  noted  a  haplo-lethal  factor  in  five 
collections  of  Ustilago  bullata  on  species  of  Agropyron,  Bromus, 
Elymus,  and  Festuca.  When  he  germinated  the  chlamydospores 
and  isolated  the  basidiospores  in  monosporidial  cultures,  he  found 
that  approximately  half  yielded  typical  colonies,  and  in  the  re- 
mainder the  basidiospores  budded  a  few  times  and  then  underwent 
complete  lysis.  Fischer  was  able  to  show  that  the  lethal  factor 
was  sex-linked  in  four  of  the  five  collections. 


336  GENETICS  OF  FUNGI 


RESUME 

Mendelian  principles  apply  in  genetical  studies  of  fungi,  just 
as  in  similar  studies  involving  other  living  organisms.  By  means 
of  hybridization  evidence  has  been  obtained  of  dominance  and  re- 
cessiveness,  of  segregation  in  predictable  numerical  ratios,  of  sex 
linkage,  of  lethal  factors,  of  mutations,  of  crossing-over  at  reduc- 
tion division,  and  of  other  genetic  features.  As  Dodge  (1940)  has 
aptly  said,  "The  fungi  in  their  reproduction  and  inheritance  fol- 
low exactly  the  same  laws  that  govern  these  activities  in  higher 
plants  and  animals."  The  practical  consideration  to  be  kept  in 
mind,  a  conclusion  that  follows  from  these  facts,  is  that  new  races 
of  fungi  are  continually  arising  by  hybridization.  This  fact  must 
be  taken  into  account  in  breeding  plants  for  disease  resistance. 

LITERATURE  CITED 

Allison,  C.  C,  "Studies  on  the  genetics  of  smuts  of  barley  and  oats  in  rela- 
tion to  pathogenicity,"  Minn.  Agr.  Expt.  Sta.  Tech.  Bull.,  119:  1-34,  1937. 

Ames,  L.  A  I.,  "Hermaphroditism  involving  self-sterility  and  cross-fertility 
in  the  ascomvcete  Plenrage  anserina,"  My  col.,  26:  392-414,  1934. 

Bensaude,  AL,  "Recherches  sur  le  cycle  evolutif  et  la  sexualite  chez  la  Basi- 
diomvcetes,"  These   (Paris),  Nemours.     153  pp.     1918. 

Blakeslee,  A.  F.,  "Sexual  reproduction  in  the  Alucorineae,"  Proc.  Am.  Acad. 
Sci.,  40:205-319,  1904. 

Brunswik,  H.,  "Untersuchungen  iiber  die  Geschlechts-  und  Kern-verhalt- 
nisse  bei  der  Hvmenomvzetengattung  Coprinus,"  Bot.  Abhandlung. 
herausg.  K.  von  Goebel,  5:  1-152,  1924. 

Buller,  A.  H.  R.,  Researches  on  Fungi,  Vol.  IV.    329  pp.    Longmans,  Green 
&  Co.,  London.     1931. 
"The  flexuous  hvphae  of  Puccinia  graminis  and  of  other  rust  fungi,"  Proc. 
3rd  Intern.  Congr.  Microbiol.,  p.  534,  1930. 

Burgeff,  H.,  "Variabilitat,  Vererbung  und  mutation  bei  Phycomyces  blake- 
slee amis  BgrT.,"  Z.  Indukt.  Abstain.  Vererb.,  49:  26-94,  1928. 

Christiansen,  J.  J.,  "Alutation  and  hvbridization  in  Ustilago  zeae.  Part  II. 
Hybridization,"  Minn.  A^r.  Expt.  Sta.  Tech.  Bull.,  6):  85-108,  1929. 

Christiansen,  J.  J.,  and  H.  A.  Rodenheiser,  "Phvsiologic  specialization  and 
genetics  of  the  smut  fungi,"  Bot  an.  Rev.,  6:  389-425,  1940. 

Crak;ie,  J.  H.,  "Experiments  on  sex  in  rust  fungi,"  Nature,  120:  116-117,  1927. 
"Discovery  of  the  function  of  pycnia  and  aecia  in  certain  rust  fungi," 

Nature,  120:765-767,  1927a. 
"On  the  occurrence  of  pvcnia  and  aecia  in  certain  rust  fungi,"  Phyto- 
pathology, 18:  1005-1015,  1928. 


LITERATURE  CITED  337 

Dickinson,  S.,  "Experiments  on  the  physiology  and  genetics  of  the  smut 

fungi.    Cultural  characters.    II.  The  effect  of  certain  external  conditions 

o 

on  their  segregation,"  Proc.  Roy.  Soc.  B,  108:  395-423,  1931. 
Dimock,  A.  W.,  "Studies  on  ascospore  variants  of  Hypomyces  ipomoeae" 

My  col.,  31:  709-727,  1939. 
Dodge,  B.  O.,  "Nuclear  phenomena  associated  with  heterothallism  and  honio- 
thallism  in  the  ascomycete  Neurospora,"  /.  Agr.  Research,  35:  289-305, 
1927. 
"Production  of  fertile  hybrids  in  the  ascomycete  Neurospora,"  /.  Agr. 

Research,  36:  1-14,  1928. 
"Breeding  albinistic  strains  of  the  Monilia  bread  mold,"  My  col.,  22:  9-38, 

1930. 
"Inheritance  of  the  albinistic  non-conidial  characters  in  inter-specific  hy- 
brids in  Neurospora,"  My  col.,  23:  1-50,  1931. 
"A  lethal  for  ascus  abortion  in  Neurospora,"  My  col.,  26:  360-376,  1934. 
"Second-division  segregation  and  crossing-over  in  the  fungi,"  Bull.  Torrey 
Botan.  Club,  67:467-476,  1940. 
Dowding,  E.  S.,  "The  sexuality  of  the  normal,  giant,  and  dwarf  spores  of 

Fleurage  anserina  (Ces.)  Kuntze,"  Ann.  Botany,  45:  1-15,  1931. 
Edgerton,  C.  W.,  S.  J.  P.  Chilton,  and  G.  B.  Lucas,  "Genetics  of  Glome  - 
rella.     II.   Fertilization   between   strains,"   Am.  J.   Botany,  52:115-118, 
1945. 
Fischer,  G.  W.,  "Two  cases  of  haplo-lethal  deficiency  in  Ustilago  bullata 

operative  against  saprophytism,"  My  col.,  32:  275-289,  1940. 
Flor,  H.  H.,  "Heterothallism  and  hvbridization  in  Tilletia  tritici  and  T. 

levis,"  J.  Agr.  Research,  44:49-5$,  1932. 
Hanna,  W.  F.,  "The  problem  of  sex  in  Coprinus  lagopus,"  Ann.  Botany, 
39:431-457,  1925. 
"Studies  in  the  phvsiologv  and  cytology  of  Ustilago  zeae  and  Sorosporhnn 
reilianum"  Phytopathology,  72:415-442,  1929. 
Johnson,  T.,  and  M.  Newton,  "Mendelian  inheritance  of  certain  pathogenic 
characters  of  Puccinia  graminis  tritici"  Can.  J.  Research,  18:  599-611, 
1940. 
Kernkamp,  AI.  F.,  "Genetic  and  environmental  factors  affecting  growth  tvpes 
of  Ustilago  zeae,"  Phytopathology,  29:473-484,  1939. 
"The   relative   effect  of   environmental   and   genetic   factors   on   growth 
types  of  Ustilago  zeae,"  Phytopathology,  32:  554-567,  1942. 
Kniep,  H.,  "Uber  morphologische  und  phvsiologische  Geschlechtsdifferen- 
zierung,"  Verhandl.  physik.-med.  Ges.  Wurzburg,  46: 1-18,  1919. 
"Uber  Schlechtsbestimmung  und  Reduktionsteilung,"    Verhandl.  physik.- 
med.  Ges.  Wurzburg,  47:  1-29,  1922. 
"Verehrbungserscheinungen  bei  Pilzen,"  Bibliogr.  Genet.,  5:  371-478,  1929. 
Lindegren,  C.  C,  "The  genetics  of  Neurospora.    II.  The  segregation  of  sex 
factors  in  asci  of  N.  crassa,  N.  sitophila,  and  N.  tetrasperma,"  Bull. 
Torrey  Botan.  Club,  59:  119-138,  1929;  III,  60:  133-154,  1933. 
"A   six-point   map    of   the    sex    chromosome    of   Neurospora   crassa,"   J. 
Genetics,  32:  234-256,  1936. 


338  GENETICS  OF  FUNGI 

Lindegren,  C.  C,  "Non-random  crossing-over  in  the  second  chromosome 

of  Neurospora  crassa,"  Genetics,  24:  1-7,  1939. 
"Yeast  o-enetics:  life  cycles,  hybridization,  vitamin  synthesis,  and  adaptive 

enzymes,"  Bact.  Rev.,  9:  111-170,  1945. 
Macrae,    Ruth,    "Interfertility    studies    and    inheritance    of    luminosity    in 

Panus  stipticm,"  Can.  J.  Research,  20:411-434,  1942. 
Newton,  D.  E.,  "Bisexual ity  of  individual  strains  of  Coprimts  rostrupianus" 

Ann.  Botany,  40:  105-128,  1926. 
"The  distribution  of  spores  of  diverse  sex  on  the  hymenium  of  Coprimts 

lagopus,"  Ann.  Botany,  40:891-917,  1926a. 
Newton,  D.  E.,  and  T.  Johnson,  "Variation  and  hybridization  in  Puccinia 

grawinis,"  Proc.  3rd  Intern.  Congr.  Microbiol.,  p.  544,  1940. 
Sass,  J.  E.,  "The  cytological  basis  for  homothallism  and  heterothallism  in  the 

Agaricaceae,"  Am.  J.  Botany,  76:663-701,  1929. 
Schmitt,  C.   G.,  "Cultural  and  genetic  studies  on    Ustilago  zeae,"  Phyto- 
pathology, 30:381-398,  1940." 
Shear,  C.  L.,  and  B.  O.  Dodge,  "Red  bread-mold  fungi  of  the  Monilia  sito- 

phila    group,    life    histories    and    heterothallism,"    /.    Agr.    Research, 

34: 1019-1042,  1927. 
Stakman,  E.  C,  and  J.  J.  Christiansen,  "Heterothallism  in  Ustilago  zeae," 

Phytopathology,  77:827-834,  1927. 
Stakman,  E.  C,  M.  F.  Kernkamp,  T.  H.  King,  and  W.  J.  Martin,  "Genetic 

factors  for  mutability  and  mutant  characters  in  Ustilago  zeae,"  Am.  J. 

Botany,  30:  37-48,  1943. 
Tatum,  E.  L.,  "Nutrition,  genetics,  and  'Neurospora,'  "  Stanford  Med.  Bull., 

2:  1-4,  1944. 
"Biochemistry  of  fungi,"  Ann.  Review  Biochem.,  73:667-704,  1944a. 
Wilcox,  M.  S.,  "The  sexuality  and  arrangement  of  the  spores  in  the  ascus 

of  Neurospora  sitophila,"  Mycol.,  20:  3-16,  1928. 
Wolf,  F.  A.,  "Spore  formation  in  Podospora  anserina    (Rabh.)    Winter," 

^7272.  Mycol.,  70:60-64,  1912. 


Chapter  15 

POISONOUS  AND  EDIBLE  FUNGI 

When  mention  is  made  of  poisonous  fungi,  most  persons  im- 
mediately think  of  toadstools,  regarding  them  as  comprising  all 
the  poisonous  forms.  These  persons  separate  toadstools  (Todes 
Stuhl)  from  mushrooms,  placing  all  poisonous  species  in  the  toad- 
stool group  and  all  edible  ones  in  the  mushroom  group.  Such  a 
distinction  is  unwarranted  and  mycologically  meaningless.  In 
the  present  account,  which  is  by  no  means  comprehensive,  con- 
sideration will  be  given  to  certain  fleshy  fungi  and  also  to  other 
well-known  species  that  are  poisonous,  especially  to  humans. 

POISONOUS  FLESHY  FUNGI 

Fleshy  fungi  have  long  been  employed  for  food,  and  it  has  as 
long  been  known  that  some  species  are  extremely  poisonous. . 
Thousands  of  species  are  edible,  however,  whereas  relatively  few 
are  toxic  to  man.  Sickness  and  fatalities  from  eating  mushrooms 
can  be  attributed  only  to  lack  of  knowledge.  Anyone  can  learn 
to  recognize  the  poisonous  species,  and  it  cannot  be  too  strongly 
emphasized  that  such  knowledge  constitutes  the  only  safe  guide 
to  determining  which  species  are  to  be  avoided.  A  beginner  can 
soon  learn  to  recognize  a  few  of  the  choicest  and  most  common 
edible  species  and  can  confine  his  collections  for  the  table  to  these 
species,  which  include  the  common  mushroom,  Fsalliota  campes- 
tris,  the  shaggy  mane,  Coprinas  comatiis,  the  common  ink  cap, 
C.  atr  anient  arms,  the  glistening  ink  cap,  C.  micaceus,  the  oyster 
mushroom,  Pleurotus  ostreatus,  the  parasol  mushroom,  Lepiota 
procera,  the  honey  agaric,  Armillaria  mellea,  the  velvet-stemmed 
mushroom,  Colly  bia  vehitipes,  the  morel,  Morchella  esculent  a,  all 
coral  fungi,  and  all  puffballs  that  are  pure  white  in  section.  While 
gathering  these,  the  student  will  gradually  become  acquainted 

with  the  poisonous  ones. 

339 


340 


POISONOUS  AND  EDIBLE  FUNGI 


Fig.  58.    Sonic  common  poisonous  fungi.    A.  Amanita  phalloides.    B.  Clito- 
cybe  Mud  ens.    C.  Pavaeoiits  retirugis.    D.  Amanita  caesarea.    E.  Morchella 

escitlenta. 


POISONOUS  FLESHY  FUNGI  341 

A  compendium  bv  Dujarrac  de  la  Riviere  and  Heim  (1938) 
constitutes  an  invaluable  source  of  information  about  poisonous 
fun^i.  The  earlier  series  of  researches  on  poisonous  mushrooms 
and  their  toxic  properties  by  Ford  and  his  associates  (1906,  1906a, 
1907,  1907a,  1911,  1913,  1914,  and  1926)  should  also  be  read  by 
all  mycologists  and  laymen  who  collect  fungi  for  food. 

It  appears  that  in  ancient  times  the  Babylonians,  Romans,  and 
Greeks,  both  those  of  hig-h  estate  and  of  the  lower  classes,  em- 
ployed  mushrooms  in  season  as  delicacies  and  as  daily  food.  The 
fact  that  deaths  from  poisoning  occurred  among  their  notables 
may  be  regarded  as  evidence  that  the  ancients  were  not  able  to 
distinguish  between  noxious  and  harmless  species.  History  re- 
cords that  such  outstanding  civic  and  political  leaders  as  Pope 
Clement  VII,  Emperor  Jovian,  Emperor  Charles  VI,  Emperor 
Claudius  (his  wife  Agrippina  is  said  to  have  added  poison  to  his 
dish  of  boleti),  the  widow  of  Czar  Alexis,  and  the  wife,  two  sons, 
and  a  daughter  of  the  Greek  poet  Euripides  were  among  the 
victims  of  poisonous  mushrooms.  Galen  cautioned  his  patients 
against  using  mushrooms,  stating,  "Few  of  them  are  good  to  be 
eaten,  and  most  of  them  do  suffocate  and  strangle  the  eater," 
although  his  "Amanitae"  almost  certainly  were  Psalliota  campes- 
tris.  The  renowned  Greek  physician  Dioscorides  states,  "Fungi 
have  a  two-fold  difference,  for  they  are  either  good  for  food,  or 
are  poisonous;  their  poisonous  nature  depends  on  various  causes, 
for  such  fungi  grow  amongst  rusty  nails,  or  rotten  rags,  or  near 
serpents'  holes,  or  on  trees  producing  noxious  fruits." 

Some  appreciation  of  the  number  of  fatalities  from  mushroom 
poisoning  can  be  gained  from  Ford  and  Clark's  (1914)  report 
assembled  from  various  sources.  In  the  Les  Vosges  area  of  south- 
western France  the  annual  death  toll  is  about  100,  and  in  Japan 
480  deaths  occurred  in  8  years.  Sartory  [Ford  and  Clark  (1914), 
p.  169]  lists  153  fatal  cases  in  a  2-week  period  in  1912  in  France. 
In  1911  there  were  22  deaths  in\he  vicinity  of  New  York  City 
within  a  10-dav  period.  Throughout  the  world  a  large  number 
of  fatalities  undoubtedly  are  due  to  poisonous  mushrooms  every 
year.  A  vast  majority  is  caused  by  the  "death  angel,"  Amanita 
phalloides.  Rolfe  (1928,  p.  232)  has  expressed  the  opinion,  "This 
inglorious  trio  [Amanita  phalloides,  A.  virosa,  and  A.  verna]  is 
responsible  for  fully  ninety  per  cent  of  the  deaths  from  fungus 
poisoning- 


•>■> 


542 


POISONOUS  AND  EDIBLE  FUNGI 


Classification  of  fleshy  fungi  according  to  toxic  effect. 
Toxicologists  have  classified  poisonous  fleshy  fungi  according  to 
the  effects  that  thev  produce  upon  the  human  system  [Ford 
(1926)].    On  this  basis  they  may  be  divided  into  the  following 

groups: 

1.  Fungi  whose  toxicity  is  first  manifest  6  to  15  hours  after  in- 
gestion and  that  cause  degeneration  of  the  nervous  tissues  and 
glandular  parenchymatous  tissues,  especially  the  liver.    The  clini- 


Conic 


Infundibuliform 


Umbonate  Campanulate 


Fig.  59.  Types  of  pilei  of  agarics  in  diagram,  indicating  variation  in  form 

used  in  ireneric  determinations. 

cal  symptoms  consist  of  sudden  seizure  by  severe  abdominal 
pains,  accompanied  by  vomiting  and  diarrhoea.  Abundant  blood 
and  mucus  appears  in  the  vomitus  and  stools.  The  victim  loses 
weight  rapidly,  passes  into  a  coma  after  2  to  5  days,  and  succumbs. 
Recovery  is  very  rare.  Poisoning  of  this  type  is  caused  by  inges- 
tion of  Amanita  phalloides,  A.  virosa,  and  A.  verna,  more  rarely 
by  Pholiota  autumnalis  and  Hygrophoms  conic  us. 

2.  Funoi  whose  poisonous  effects  appear  soon  after  ingestion 
and  that  act  chiefly  by  stimulating  and  then  paralyzing  the  cen- 
tral nervous  system.  Poisoning  is  manifest  by  profuse  perspira- 
tion and  salivation,  retching,  and  diarrhoea,  accompanied  by  de- 
lirium, hallucinations,  and  convulsions.  The  patient  may  die  from 
paralysis  of  respiration.  This  complex  is  caused  mainly  by  Ama- 
nita muse  aria.  Similar  clinical  symptoms  may  be  induced  by  A. 
pant  her  in  a,  Inocybe  infelix,  I.  infida,  and  Clitocybe  illudens.  In 
Siberia  decoctions  of  dried  A.  muse  aria  are  sometimes  used  to 


POISONOUS  FLESHY  FUNGI  343 

induce   orgies  of  intoxication  somewhat  similar  to  those  from 
hashish. 

3.  Fungi  whose  irritant  principles  act  on  the  mucous  mem- 
branes of  the  gastrointestinal  tract  soon  after  the  fungi  are  eaten. 
The  clinical  symptoms,  consisting  of  griping  pains  in  the  stomach, 
dizziness,  nausea,  vomiting,  and  diarrhoea,  subside  rather  abruptly, 
and  recovery  proceeds  rapidly.  This  type  of  poisoning  is  induced 
by  Riissula  emetica,  Lactariits  torminosus,  Lepiota  morgani,  Ento- 
lovia  lividum,  Boletus  sat  anus,  B.  mineato-olivaceus,  and  some  of 
the  species  of  Amanita. 

4.  Fungi  that  contain  hemolytic  principles.  The  symptoms  are 
abdominal  distress,  dizziness,  and  vomiting.  The  vomitus  contains 
blood.  The  victim  may  have  convulsions  and  may  pass  into  pro- 
found sleep.  During  convalescence  mild  jaundice  develops.  The 
ingestion  of  Helvetia  esculenta  commonly  causes  this  type  of 
poisoning,  which  may  also  be  induced  by  other  species  of  Helvella 
and  by  Amanita  rubescens. 

5.  Fungi  that  stimulate  the  central  nervous  system  in  a  manner 
somewhat  like  alcoholic  intoxicants.  The  victim  feels  greatly  ex- 
hilarated and  laughs  immoderately.  His  gait  is  staggering,  and  he 
has  the  feeling  that  he  is  walking  on  air.  This  type  of  intoxica- 
tion lasts  for  24  to  48  hours  after  the  ingestion  of  Fanaeolus  papi- 
lionaceus  or  P.  campanulatus. 

Identification  of  poisonous  mushrooms.  As  has  previously 
been  stated,  a  person  can  learn  to  recognize  the  poisonous  fleshy 
mushrooms  if  he  applies  himself  to  the  task.  In  order  to  do  so, 
he  must  become  familiar  with  the  salient  structural  features  that 
are  employed  by  the  mycologist  in  identifying  mushrooms.  Rela- 
tively few  species  will  be  found  to  be  poisonous.  Each  of  the 
more  common  poisonous  species  will  be  briefly  characterized  in 
the  following  account. 

Amanita  phalloides.  The  fructifications  of  this  species  vary  in 
color,  being  white,  green,  olive,  amber,  and  rarely  yellowish. 
They  grow  singly  and  are  5  to  7  in.  tall.  The  pileus  or  cap  is 
white,  viscid,  and  convex,  with  or  without  scales  at  the  surface. 
The  stipe  or  stem  is  smooth  and  of  the  same  color  as  the  pileus. 
The  gills  are  white  and  free  from  the  stipe.  The  annulus  or  veil 
breaks  at  the  margin  of  the  cap  and  clings  skirt-like  near  the  top 
of  the  stipe.    The  volva  or  cup  is  variable  because  of  the  manner 


344 


POISONOUS  AND  EDIBLE  FUNGI 


in  which  it  ruptures.  It  may  be  cup-like  or  appear  as  a  bulbous 
expansion  at  the  base  of  the  stipe.  Since  the  volva  may  be  deeply 
buried  in  the  leaf  mold,  care  must  be  exercised  while  collecting 
to  remove  the  entire  fructification.  This  is  of  special  importance, 
because  A.  phalloides  mav  be  mistaken  for  Lepiota  naucina,  a 
common  edible  species. 


Free 


Adnate 


Adnexed 

Fig.  60.     Diagrams  illustrating  types  of  attachment  of  gills  to  the  stipe,  a 
character  used  in  determination  of  genera  among  agarics. 

Amanita  mm c aria.  This  fungus,  called  the  fly  agaric  because 
it  has  been  used  as  a  fly  poison,  grows  in  fields  or  open  woods. 
The  striking  yellow  to  orange  and  even  red  color  of  the  fructifi- 
cations characterizes  this  species,  which  is  4  to  6  in.  tall.  The 
pileus  is  3  to  5  in.  broad.  Prominent  warty  scales  cover  the 
pileus.  The  gills  are  white.  The  veil  remains  around  the  stem  as 
a  large,  membranous,  pendent  collar.     The  base  of  the  stipe  is 

bulbous. 

Other  white  species  of  Amanita.  Several  other  typically  white 
species  of  Amanita,  including  A.  verna,  A.  virosa,  and  A.  spreta, 
are  as  deadly  poisonous  as  is  A  phalloides.  All  possess  a  volva, 
an  annulus,  and  white  gills  and  have  scales  on  the  expanded  pileus. 
The  possession  of  these  characters  positively  identifies  the  fungus 
as  a  species  of  Amanita.     Since  nearly  all  species  of  Amanita, 


POISONOUS  FLESHY  FUNGI 


345 


whether  white  or  some  color,  are  known  to  be  poisonous,  it  is  pru- 
dent sedulously  to  avoid  all  of  them. 

Lepiota  morgani.  The  genus  Lepiota  lacks  the  volva  but  in 
other  features  looks  like  Amanita.  Lepiota  morgani  grows  in 
fields  and  open  woods,  especially  in  the  Ohio  Valley,  and  is  not 
uncommon  in  the  vicinity  of  Durham,  North  Carolina.    The  fruc- 


Fig.  61.  Shapes  of  spores  in  outline.  A.  Amanita  phalloides.  B.  Amanita 
verna.  C.  Lepiota  morgani.  D.  Amanita  muscaria.  E.  Lepiota  procera. 
F.  Clitocybe  illudens.  G.  Rnssida  emetica.  H.  Psalliota  campestris.  I. 
Panaeolus  retimgis.    J.  Amanitopsis  strangulata.    K.  Entoloma  sp.    L.  Bole- 

tinus  sp.    M.  Hebeloma  crnstidtf  orme . 

tifications  are  4  to  8  in.  tall,  and  the  convex-to-flat  cap  may  be 
equally  broad.  The  stipe  has  a  club-shaped  base.  The  color 
varies  from  grayish  white  to  buff  or  pale  amber.  Irregular  scales 
or  patches  occur  on  the  cap.  The  annulus  is  large,  thick,  and 
movable.  The  gills  are  free,  rather  broad,  ventricose,  and  white 
at  first,  changing  to  bright  green  and  then  to  dull  green.  The 
color  is  so  striking  as  to  prevent  this  species  from  being  mistaken 
for  any  edible  one. 

Clitocybe  illudens.  The  fructifications  of  this  fungus  occur  in 
dense  clusters,  each  being  3  to  7  in.  tall  and  2  to  5  in.  broad.  They 
are  luminescent,  hence  the  common  name  jack-o'-lantern.     The 


346  POISONOUS  AND  EDIBLE  FUNGI 

color  ranges  from  saffron  yellow  to  orange.  The  caps  are  plane 
to  centrally  depressed.  The  gills  are  decurrent,  of  the  same  color 
as  the  cap,  and  narrowed  at  each  end.  The  stipes  are  firm,  smooth, 
and  solid,  tend  to  be  excentric,  and  are  darker  near  the  base. 

Clitocybe  dealbata  yar.  sudorifica.  Clusters  of  fructifications  of 
this  fungus,  also  called  C.  sudorifica,  occur  on  lawns  or  on  other 
grassy  sites.  They  are  %  to  1  Ys  in.  tall,  and  the  caps  are  %  to  1  % 
in.  broad.  The  color  throughout  is  grayish  white.  The  caps  are 
plane,  depressed,  or  umbilicate,  and  the  margin  splits  irregularly. 
The  stipes  have  a  spongy  center.  The  gills  are  thin,  narrow,  and 
adnate  or  slightly  decurrent.  A  few  cases  of  poisoning  have  also 
been  attributed  to  C.  vwrbrfera  and  C.  nebulosus. 

Lactarius  torrmnosus.  When  the  fructifications  of  Lactarius 
are  broken,  a  milky  or  colored  juice  exudes.  This  characteristic 
serves  to  distinguish  Lactarius  from  all  other  ^ill-bearingr  fungi. 
The  flesh  is  always  very  brittle.  Lactarius  torminosus  occurs  on 
the  ground  in  woods  in  late  summer.  The  fructifications  occur 
singly.  They  are  2  to  4  in.  tall  with  a  pileus  of  approximately  the 
same  breadth.  They  are  convex  and  depressed  in  the  center.  The 
gills  are  crowded,  thin,  and  whitish.  The  stipe  is  cylindrical,  even, 
and  hollow.  The  milk  is  white,  unchangeable,  and  acrid.  The 
pilei  have  an  uneven  mixture  of  pink  and  ochre  colors  and  are 
very  hairy  at  the  margins. 

Russula  emetica.  Species  of  Russula  are  at  once  separated  from 
Lactarius  by  the  absence  of  milky  juice,  although  they  resemble 
Lactarius  in  all  other  respects.  Russula  emetica  fruits  during  sum- 
mer and  autumn.  It  is  a  very  beautiful  and  very  fragile  species. 
The  fructifications  are  2  to  4  in.  tall,  and  the  cap  is  equally  broad. 
They  are  pink  when  young  and  darker  red  when  older.  The 
stipes  are  stout  and  spongy  within.  The  caps  are  plane  to  de- 
pressed and  are  furrowed  near  the  margin.  The  gills  are  free, 
broad,  not  crowded,  and  white. 

Pholiota  autuiunalis.  Species  of  Pholiota  are  ochre-spored. 
They  possess  an  annulus,  and  the  gills  are  adnate.  Pholiota  auturn- 
nalis fruits  on  decaying  wood.  The  fructifications  are  clustered 
and  are  1  to  2  in.  tall.  The  caps  are  convex,  cinnamon-rufous  to 
dingy  yellow,  and  striate  on  the  margin.  The  stipes  are  slender, 
fibrillose,  hollow,  and  somewhat  paler  than  the  cap. 

hwcybe  bifida.  Ochre-spored  species  with  a  fibrillose  uni- 
versal veil  are  included  in  Inocybe.     hwcybe  infida  occurs  on 


POISONOUS  FLESHY  FUNGI 


341 


mossy  ground  during  autumn.  The  fructifications  are  1  to  2  in. 
tall.  The  caps  are  %  to  1  in.  broad,  campanulate,  and  whitish 
with  a  brownish  umbo.  The  gills  are  annexed,  close,  narrow,  and 
cinnamon-colored.  The  stipes  are  slender,  hollow,  and  white. 
Inocybe  injelix.  This  species  occurs  throughout  summer  among 
mosses  or  on  bare  soil.  Its  size  agrees  with  that  of  /.  bifida.  The 
campanulate  pilei  are  floccosely  squamulose  and  grayish  brown  or 


Fig.  62.  Relationship  of  structural  features  in  Amanita.  A.  Undifferentiated 
"egg"  B.  Button  stage,  in  which  the  gills  are  differentiating  in  the  upper 
portion.  C.  Opening  of  the  pileus,  showing  at  one  side  the  ruptured  uni- 
versal veil  and  annulus.  D.  Expanded  pileus,  in  section,  with  scales  on  the 
pileus  and  volva  surrounding  the  base  of  the  stipe.  Both  structures  are  re- 
mains of  the  universal  veil. 

amber.  The  gills  are  adnexed,  close,  broad,  ventricose,  and  rusty. 
The  stipes  are  equal,  solid,  silky  fibrillose,  whitish  above  and 
brownish  below. 

Hebeloma  criistidijorme.  In  Hebeloma  are  placed  ochre-spored 
species  with  adnate  gills  and  with  a  delicate  fibrillose  veil  that  is 
present  only  on  the  young  caps.  All  species  are  unwholesome. 
Hebloma  cmstulij orme  appears  on  lawns  in  autumn.  It  is  2  to  3 
in.  tall,  and  the  caps  are  equally  broad.  The  caps  are  convex  to 
umbonate,  tan-colored,  darker  over  the  center,  and  viscid.  The 
gills  are  adnate  but  rounded  near  the  stem,  and  their  edge  is 
white  and  irregular.  The  stipe  is  stuffed,  enlarged  below,  and 
wThitish.  It  is  reported  that  H.  fastibile  causes  the  same  type  of 
symptoms  as  does  Amanita  miiscaria. 


348  POISONOUS  AND  EDIBLE  FUNGI 

Entoloma  lividum  and  E.  sinuatum.  Entoloma  is  characterized 
by  being  pink-spored  with  gills  that  are  adnate  to  sinuate.  All  the 
species  should  be  avoided.  Entoloma  lividum  and  E.  sinuatum 
have  been  proved  to  be  poisonous.  Thev  differ  mainly  in  that 
the  stipe  of  E.  lividum  is  solid  and  of  E.  sinuatum  hollow.  They 
grow  gregariously  in  the  woods.  The  fructifications  are  3  to  5  in. 
tall.  The  caps  are  2  to  3  in.  broad,  convex,  becoming  centrally 
depressed,  moist,  even,  and  vellowish  white,  with  a  wavy  margin 
and  sulcate  surface. 

Panaeolus  papilionaceus  and  P.  retirugis.  In  Panaeolus  are  in- 
cluded black-spored  agarics  that  grow  on  dung  or  on  grassy, 
manured  ground.  The  pilei  are  thin,  with  even  margins  that  ex- 
tend beyond  the  gills.  The  gills  are  spotted  with  brown  and  black; 
the  stipes  are  long  and  slender.  The  pilei  of  both  P.  papilionaceus 
and  P.  retirugis  are  conic  and  grayish  to  smoky,  with  fragments  of 
veil  attached  around  the  margin.  The  centers  of  the  pilei  are  com- 
monly darker  than  the  margins.  The  gills  are  adnate  and,  as  the 
caps  expand,  tend  to  separate  more  and  more  from  the  stipe. 

Boletus  sat  anus,  B.  luridus,  and  B.  mineato-ol'rcaceus.  In  Boletus 
are  placed  fleshv,  central-stalked  polypores.  The  caps  are  con- 
vex, and  the  pore  layer  is  quite  readily  separable  from  the  sub- 
stance of  the  cap.  Many  discolor  immediately  on  being  bruised. 
Some  persons  maintain  that  none  of  the  species  should  be  eaten. 
Many  are  bitter  and  possess  disagreeable  odors.  Boletus  mineato- 
olivaceus  possesses  caps  2  to  6  in.  broad.  They  are  red,  becoming 
ochre-red  with  a«e.  The  flesh  is  yellow  but  instantly  becomes 
blackish  blue  when  bruised. 

The  caps  of  B.  luridus,  about  8  in.  across,  are  dirty  olivaceous 
yellow;  the  flesh  is  vellowish,  becoming  blue.  The  tubes  are  yel- 
lowish,  becoming  green.  The  stipes  are  approximately  6  in.  long 
and  yellowish  above  and  blackish  at  the  base. 

Hygrophorus  conicus.  Hvgrophorus  contains  the  white-spored 
species  in  which  the  tissue  of  the  cap  is  continuous  with  that  of  the 
stem.  The  <nlls  are  distant,  the  edge  being  acute  at  the  margin, 
are  gradually  thickened  toward  the  stipe,  and  are  characteristically 
waxy,  appearing  to  be  sodden.  Hygrophorus  conicus  grows  in 
woods  in  mossy  or  grassv  situations.  It  has  conic  pilei,  about  2  in. 
broad,  fragile,  slightly  viscid,  and  red,  orange,  or  yellow,  blacken- 
ing when  bruised.  Gills  are  close,  ventricose,  almost  free,  and 
yellowish.     Stipes  are  yellow,  fibrous,  equal,  and  striate. 


POISONOUS  FLESHY  FUNGI 


349 


Morchella  esculenta.  The  morels  are  disk  fungi  that  appear  in 
late  spring  in  damp  situations.  Morel  fruits  possess  a  distinct  cap 
and  stalk.  The  cap  varies  in  shape  with  the  species,  being  spheri- 
cal, ovate,  cylindrical,  or  conic.  A  network  of  ridges  and  pits 
covers  the  outer  surface.  The  stipe  is  stout  and  irregularly 
wrinkled.  All  species  are  buff  to  light  ochre.  The  fructifications 
of  M.  esculenta  may  be  as  high  as  6  in.  tall.  The  cap  is  oval  in 
outline,  and  the  pits  are  irregularly  arranged.      , 


Fig.  63.  Structural  diagrams  of  Boletus.  A.  Young  unopened  pileus  in  which 
the  entire  fructification  is  still  enclosed  within  the  universal  veil.  B.  Ex- 
panded pileus,  showing  the  annulus  and  remnants  attached  to  the  rim 
of  the  pileus.     C.  Opened,  mature  pileus  with  stipe,  cap,  and  pore  surface. 

Persons  who  gather  mushrooms  should  learn  to  recognize  the 
foregoing  poisonous  species  and  should  sedulously  avoid  eating 
them.  Although  the  judicious  use  of  such  knowledge  constitutes 
the  best  and  only  safeguard,  many  other  so-called  tests  to  deter- 
mine whether  a  given  form  is  poisonous  may  be  mentioned.  Silver 
spoons  or  coins  are  said  to  turn  black  when  dipped  into  a  dish  of 
cooked  poisonous  mushrooms.  Poisonous  species  are  said  to  peel 
with  readiness.  Species  that  are  bright  colored,  that  have  unde- 
sirable odors,  or  that  have  a  bitter  taste  when  freshly  gathered  are 
claimed  to  be  toxic.  The  reliability  of  these  and  similar  tests  is 
vouched  for  bv  the  world-famous  authority,  "They  say.'1  All 
such  tests  are  without  foundation  and  must  be  regarded  as  sheer 
nonsense. 


350  POISONOUS  AND  EDIBLE  FUNGI 

Toxicology.  The  vast  amount  of  experimentation  that  has  been 
conducted  to  determine  the  nature  of  the  toxic  principles  in 
poisonous  fleshy  fungi  can  be  appreciated  from  Ford  and  Clark's 
report  (1914).  They  indicate  that  in  1826  Letellier  extracted 
from  Amanita  phalloides  a  heat-stable  substance  that  he  called 
amanitin.  Later  he  found,  in  addition  to  this  thermostable  sub- 
stance that  he  thought  to  be  a  glucosidal  alkaloid,  a  substance 
capable  of  attacking  mucous  membranes.  In  1877  Ore  [Ford  and 
Clark  (1914),  p.  f  71  ]  ascribed  poisoning  by  A.  phalloides  to  a  hy- 
pothetical alkaloid  that  he  named  phalloidin.  In  1891  Robert 
[Ford  and  Clark  (1914),  p.  177]  extracted  from  A.  phalloides  a 
hemolytic  substance,  readily  destroyed  by  heat,  which  he  named 
phallin.  At  first  he  believed  it  to  be  the  essential  poison,  but  he 
later  extracted  an  alcohol-soluble  alkaloid  that  was  extremely 
poisonous  to  his  experimental  animals. 

The  analyses  by  Ford  (1906)  showed  that  A.  phalloides  con- 
tains, besides  phallin,  the  hemolytic  principle  of  Robert,  another 
substance  of  toxic  nature.  Ford  verified  the  thermolabile  nature 
of  phallin  and  found  that  the  other  substance  was  heat-stable  and 
resistant  to  digestion  by  pepsin  and  pancreatin.  He  also  prepared 
antiserum  that  was  effective  against  the  stable  substance  but  had  no 
neutralizing  effect  on  phallin.  To  this  stable  extractive  Ford 
gave  the  name  amanita-toxin. 

Schlesinger  and  Ford  (1907)  purified  amanita-toxin  to  the  ex- 
tent that  it  did  not  give  the  reactions  of  proteins,  glucosides,  or 
alkaloids,  and  concluded  that  it  ".  .  .  appears  to  be  an  aromatic 
phenol  so  combined  with  an  amine  group  that  it  readily  forms  an 
indol  or  pyrrol  ring." 

Since  Amanita  virosa,  A.  verna,  Pholiota  autumnalis,  and  Hygro- 
phorns  conicns  induce  similar  clinical  symptoms,  they  may  be  as- 
sumed to  contain  the  same  amanita-toxin  as  does  A.  phalloides. 
Other  species  which  contain  amanita-toxin  are  A.  porphyria,  A. 
strobilijorvris,  A.  radicata,  A.  chlorinosoma,  A.  viappa,  A.  vior- 
risii,  A.  citrina,  A.  cremilata,  and  Avianitopsis  volvata. 

The  toxic  principle  in  Amanita  vniscaria  was  isolated  by 
Schmiedeberg  and  Roppe  [Ford  and  Clark  (1914),  p.  1771  in 
1869  and  given  the  name  muscarine.  There  was  also  isolated  from 
this  same  species  the  alkaloid  choline,  which,  on  uniting  with 
oxygen,  as  it  does  when  the  flv  agaric  decays,  becomes  muscarine. 
Robert    [Ford  and  Clark   (1914),  p.   177 J    maintained  that  this 


FOOD  VALUE  OF  FLESHY  FUNGI  S51 

fungus  contains  a  third  alkaloid,  which  he  called  "pilz-atropin." 
Muscarine  depresses  the  same  nerves  that  are  stimulated  by  "pilz- 
atropin"  and  atropin,  both  of  which  therefore  are  physiological 
antitodes  for  muscarine.  Persons  who  have  been  poisoned  by 
A.  miiscaria  and  whose  heart  has  nearly  ceased  pulsating  may  be 
given  atropin,  with  the  result  that  heart  action  will  again  become 

strong. 

Studies  on  muscarine  indicate  that  it  is  not  a  chemical  entity 
but  a  group  of  at  least  five  substances,  having  the  empirical  form- 
ula C5H15NO2.  Muscarine  occurs  in  Amanita  pantherina,  Bole- 
tus satanus,  B.  luridus,  and  Russula  emetica.  Clitocybe  illudens, 
Lactarius  torminosns,  lnocybe  bifida,  and  /.  decipiens  contain  a 
muscarine-like  principle  that  may  be  similar  to  that  in  Amanita 

miiscaria. 

There  occurs  in  Helvetia  esculenta  a  water-soluble,  heat-labile, 
hemolytic  principle  that  has  been  identified  as  helvellic  acid, 
C12H20O7.  It  is  generally  agreed  that  fresh  specimens  are  free 
from  this  poison  but  that  it  occurs  in  old  or  decaying  morels. 

FOOD  VALUE  OF  FLESHY  FUNGI 

The  food  value  of  mushrooms  is  indicated  by  analyses  made 
years  ago  by  Mendel  (1898).  Certain  of  his  data  are  presented 
in  Table  27.  Mendel  pointed  out  that  these  percentages  do  not 
represented  the  digestible  fraction.  For  example,  he  found  that 
only  about  one-seventh  of  the  total  nitrogen  in  Coprinus  comatus 
is  actually  digestible.  No  determinations  were  made  of  the  nu- 
tritive value  of  the  ether  extract,  that  is,  the  fatty  substances,  but 
Mendel  assumed  that  the  digestible  portion  of  this  fraction  must 
be  similar  to  that  of  the  total-nitrogen  fraction. 

TABLE  27 
Composition  of  Certain  Edible  Fungi 

Constituents 


Dry 


{percentage  on  dry-weight  basis) 


Matter  Total  Protein  Ether 

Species              (percentage)          N             N  extract  Ash 

Coprinus  comatus             7.81  5.79         1.92  3.3  12.5 

Morchella  esculenta         10.46  4.66         3.49  29.3  10.4 

Pleurotus  ostreatus         26 .  30  2 .  40         1.13  31.5  6.1 

Psalliota  campestris          8 .  20  4.75         3.57         11.6 


352  POISONOUS  AND  EDIBLE  FUNGI 

Mendel  concluded  that  mushrooms  have  a  low  caloric  value. 
Nevertheless  he  properly  regarded  them  as  being  among  the  most 
appetizing  of  culinary  delicacies  and  as  adding  greatly  to  the 
palatabilitv  of  many  foods  when  cooked  as  savories  with  them. 

Later  workers  are  inclined  to  regard  mushrooms  as  having 
amounts  of  nitrogenous  substances,  carbohydrates,  and  fats  that 
would  rank  them,  in  regard  to  nutritive  value,  along  with  fresh 
vegetables.  Data  of  Sabalitschka  [IvanofT  and  Zwetkoff  (1932)] 
showed  that  Psalliota  campestris  and  Boletus  edulis  have  a  high 
protein  content.  This  finding  was  confirmed  by  Saburow  and 
YVasiliew  [IvanofT  and  Zwetkoff  ( 1932)],  who  recorded  the  pro- 
tein content  of  these  two  species  as  32.06%  and  31.25%,  respec- 
tively, these  figures  being  based  on  the  weight  of  dry  substance. 
On  the  other  hand,  other  edible  species  may  be  low  in  proteins, 
since  Saburow  and  Wasiliew  found  in  Colly bia  velutipes  8.87% 
and  in  Tricholoma  portentosum  10.50%.  They  also  reported 
lar^e  variation  in  fat  content  between  species,  Boletus  edulis  hav- 
ing 1.6%  and  B.  scaber  9.69%.  Since  the  proportions  of  proteins, 
carbohydrates,  and  fats  that  are  digestible  by  man  remain  un- 
known, the  true  nutritive  value  of  mushrooms  likewise  remains 
a  mystery. 

Fleshy  species  most  used  as  food.  The  fleshy  fruit-bodies  of 
fungi  that  are  used  as  food  in  most  parts  of  the  world  are  not 
cultivated  but  occur  in  forests,  mainly  on  the  forest  floor.  The 
choicest  species  include  Psalliota  (Agaricus)  campestris,  P.  arven- 
sis,  Boletus  edulis,  Lepiota  procera,  Lactarius  deliciosus,  Coprinus 
comatus,  Cantharellus  cibarius,  Pleurotus  ostreatus,  and  Fistulina 
hepatica.  Among  other  highly  prized  species  are  the  morels,  in- 
cluding Morchella  esculenta,  M.  conic  a,  Gyroviitra  gigas,  and  G. 
esculenta,  the  truffles,  especially  Tuber  aestivum  and  T.  vielano- 
spervnmu  and  certain  puffballs.  In  parts  of  Australia  and  Tas- 
mania use  is  made  of  the  large  sclerotia  of  Polyporus  viylittae, 
which  are  called  "native  bread"  and  "black-fellow's  bread."  The 
natives  in  Tierra  del  Fuego  eat  large  quantities  of  Cyttaria,  espe- 
cially C.  gunnii,  C.  hookeri,  C.  darwinii,  and  C.  harioti,  which 
grow  parasiticallv  on  the  branches  of  Nothofagus. 

Artificial  cultivation  of  fleshy  fungi.  In  light  of  the  fact 
that  the  excellence  of  certain  species  has  long  been  appreciated, 
it  is  not  surprising  to  find  that  attempts  were  made  by  the  ancients 
to  cultivate  them.     At  present,  however,  few  species  are  culti- 


FOOD  VALUE  OF  FLESHY  FUNGI  353 

vated  in  any  country.  Psalliota  campestris,  the  common  mush- 
room, is  apparently  the  species  most  widely  grown  under  arti- 
ficial conditions.  Precise  directions  for  the  commercial  growing 
of  this  mushroom  are  available  but  are  not  relevant  to  this  account. 
A  few  of  the  general  features  involved  in  its  culture,  however, 
seem  pertinent.  Caves,  cellars,  abandoned  mines,  and  special  types 
of  glasshouses  are  suitable  for  growing  mushrooms,  provided  that 
temperature,  moisture,  and  ventilation  are  properly  controlled. 
Of  these  factors,  temperature  is  perhaps  the  most  vital;  it  should 
be  kept  within  the  range  53°  to  63°  F.  High  relative  humidity 
is  required,  but  the  site  should  not  be  wet. 

Mushroom  growers  attach  great  emphasis  to  proper  prepara- 
tion of  the  manure.  Stable  manure,  including  the  litter  used  for 
bedding,  is  piled  deeply,  mixed  with  loam,  and  turned  and  re- 
piled  until  a  suitable  compost  is  formed.  The  compost  is  then 
placed  in  beds  and  is  implanted  with  spawn,  that  is,  with  blocks 
of  humus  permeated  with  the  mycelium  of  the  mushroom.  After 
several  weeks  the  beds  are  cased.  This  process  consists  in  cover- 
ing the  beds  to  a  depth  of  1  or  2  in.  with  a  layer  of  loam.  The 
beds  then  require  occasional  sprinkling  to  keep  them  moist.  The 
mushrooms  should  soon  begin  to  appear.  In  France  morels  are 
grown  in  much  the  same  way,  except  that  bits  of  fruit  bodies  are 
used  as  spawn. 

In  parts  of  China  Hirneola  polytricha,  under  the  Chinese  name 
Mil  Erh,  is  grown  under  semiartificial  conditions.  Sapling  oaks 
{Quercus  variabilis)  are  cut  into  poles,  allowed  to  lie  on  the 
ground  for  several  months,  and  then  stacked  in  small  piles  in  moist 
places.  The  gelatinous  fruit  bodies  are  developed  the  following 
year.  The  Chinese  similarly  grow  the  large  sclerotia  of  Poria 
cocos  on  partly  buried  pine  poles. 

The  fruit  bodies  of  Armillaria  shii-take  are  produced  artificially 
on  a  large  scale  in  Japan  and  are  marketed  under  the  name  shii- 
take. The  name  shii  applies  to  an  evergreen  oak,  Quercus  cuspi- 
data.  Recently  cut  logs  of  this  oak  are  soaked  in  water,  and  the 
bark  is  loosened  by  pounding;  holes  are  then  made  in  the  logs, 
and  pieces  of  wood  decayed  by  the  fungus  are  placed  therein. 
After  about  2  years  the  mushrooms  appear.  By  proper  manage- 
ment of  cutting,  the  coppice  growth  from  the  stumps  attain 
cutting  size  in  about  20  years.  Tracts  are  thus  reforested  to  con- 
tinue the  production  of  crops  of  shii-take. 


354  POISONOUS  AND  EDIBLE  FUNGI 

ERGOT  AND  ERGOTISM 

The  name  ergot,  which  is  properly  applied  to  the  sclerotial  stage 
of  Claviceps  purpurea,  is  derived  from  the  old  French  argot  and 
refers  to  the  resemblance  of  the  sclerotium  to  a  cock's  spur. 
Er^ot,  when  ingested  bv  man  and  various  animals,  has  long  been 
known  to  be  poisonous,  causing  a  disease  known  as  ergotism. 
Both  the  disease  and  its  cause  have  come  to  be  well  known  and 
have  attracted  the  attention  of  a  large  number  of  investigators. 
Two  monographic  treatises  on  this  subject,  one  by  AtanasofT 
(1920)  and  the  other  by  Barger  (1931),  are  especially  note- 
worthy. That  bv  AtanasofT  is  concerned  primarily  with  matters 
of  plant-pathological  and  mycological  interest,  whereas  that  by 
Barger  deals  primarily  with  ergotism.  Barger's  interests  were 
centered  on  this  problem  for  more  than  20  years,  and  his  compre- 
hensive report,  although  intended  primarily  for  the  student  and 
the  practitioner  of  medicine,  is  also  of  wide  general  usefulness. 

Historical  account.  It  becomes  apparent  from  the  account 
by  Barker  (1931)  that  the  antiquity  of  ergotism  cannot  be  estab- 
lished with  certainty.  There  is  little  likelihood  that  the  ancient 
Greeks  and  Romans  knew  this  disease,  as  is  maintained  by  Robert 
[Barger  (1931),  pp.  40-42].  Certain  diseases  mentioned  by  Hip- 
pocrates and  Galen  and  interpreted  by  Robert  and  others  to  be 
ergotism  seem  to  have  been  some  other  disorder.  It  seems  highly 
probable  that  an  outbreak  of  ergotism  was  first  chronicled  by 
some  unknown  writer  in  the  Annates  Xanthensis  in  a.d.  857. 
Translated,  his  statement  is:  "A  great  plague  of  swollen  blisters 
consumed  the  people  by  a  loathesome  rot,  so  that  their  limbs  were 
loosened  and  fell  off  before  death."  Confusion  also  exists  regard- 
ing the  cause  of  the  epidemics  called  "holy  fire"  {ignis  sacer)  that 
occurred  throughout  the  succeeding  period  of  about  800  years. 
The  gangrenous  condition  of  limbs,  resulting  in  death  or  the  loss 
of  hands  and  feet,  undoubtedly  was  ergotism,  although  anthrax, 
erysipelas,  scurvy,  and  plague  may  have  accounted  for  a  portion 
of  the  mortality. 

The  modern  history  of  ergotism  begins  with  an  account  by 
Dodart  [Barger  (1931),  pp.  59-60]  of  an  epidemic  in  the  Sologne 
district  of  France  in  1676.  In  1777,  in  this  same  district,  about 
8000  persons  are  said  to  have  succumbed  from  ergotism.    In  1770 


ERGOT  AND  ERGOTISM 


355 


Fig.  64.  Poisonous  Ascomycetes  on  grasses.  A.  Gibber -ell a  saubinettii  (G. 
zeae)  in  small  clusters  on  barley  glumes.  B.  Cluster  of  perithecia  of  G. 
saubinettii.  D.  Ascospores.  E.  Conidia  of  the  Fusarium  stage.  F.  Branch 
of  panicle  of  Paspalum  laeve,  certain  of  the  ovaries  having  been  replaced 
by  sclerotia  of  Claviceps  paspali.  G.  Sclerotium  of  C.  paspali  that  has  hiber- 
nated, after  which  three  perithecial  stromata  developed.  H.  The  conidia  of 
C.  paspali  belong  to  the  form  Genus  Sphacelia  and  occur  on  the  surface  of 
the  stromata  that  later  become  sclerotia. 


356  POISONOUS  AND  EDIBLE  FUNGI 

an  outbreak  involved  the  inhabitants  of  several  European  coun- 
tries, and  subsequentlv  there  have  been  manv  epidemics  through- 
out the  whole  of  Europe,  some  of  them  widespread  and  all  of  them 
producing  horrible  suffering  and  disfigurement. 

The  date  of  the  first  use  of  ergot  as  a  drug  cannot  be  fixed,  but 
the  first  published  mention  of  its  use  to  induce  uterine  contrac- 
tions occurs  in  Adam  Lonicer's  Kreuter bitch  in  1582.  The  ergot 
grains  are  therein  described  as  "long,  black,  hard,  narrow  corn 
pegs,  internallv  white,  protruding  like  long  nails  from  between 
the  grains  in  the  ear,"  and  three  sclerotia  are  designated  as  consti- 
tuting a  dose.  Subsequentlv  for  a  period  extending  throughout 
the  eighteenth  century  midwives  in  various  European  countries 
used  ergot  to  expedite  lingering  parturition.  Its  use  did  not  enter 
into  pharmaceutical  practice,  however,  nor  was  it  employed  by 
the  medical  practitioner.  In  the  United  States  ergot  was  medically 
introduced  under  the  name  of  puhis  parturiens  early  in  the  nine- 
teenth century. 

Early  writers  were  not  in  accord  on  the  true  nature  of  ergot. 
Caspar  Bauhin  refers  to  it  as  Secale  luxurious  in  his  Fhytopinax, 
published  in  1596  [Barger  (1931),  p.  10].  Until  the  middle  of  the 
nineteenth  century  many  writers  regarded  eroot  grains  as  degen- 
erated  kernels.  Among  the  causes  assigned  for  this  degeneration 
were  improper  nutrition,  failure  of  the  flowers  to  become  fertil- 
ized, injury  from  insects,  and  excessive  rainfall.  Fries  (1822) 
considered  the  ergot  grain  as  a  fungus  structure;  he  gave  it  the 
name  Spervwedia  davits  but  later  (1849)  changed  this  name  to 
Claviceps  purpurea.  Leveille  (1827)  observed  that  the  sugary 
secretions  on  young  sclerotia  contained  conidia.  Thinking  that 
the  conidia  were  reproductive  structures  belonging  to  a  fungus 
parasitizing  the  sclerotia,  he  named  this  supposed  parasite  Sphacelia 
segetum.  He'  (1842)  maintained  that  the  ergot  itself  was  a  de- 
generated kernel.  Mcvcn's  observations  (1841)  on  ergot  led  him 
to  conclude  that  the  sclerotium  is  an  early  stage  of  the  Sphacelia 
segetum  that  Leveille  had  described  nearly  15  years  before.  The 
chapter  on  the  nature  of  ergot  was  finally  concluded  by  Tulasne 
(1853),  who  established  that  the  conidia,  sclerotia,  and  perithecial 
stromata  constitute  developmental  stages  of  one  and  the  same 
fungus,  which  he  called  Claviceps  purpurea  (Fr.). 

The  structure  and  development  of  Claviceps  purpurea  have  been 
recounted  in  some  detail  [Falck  (1911),  Stager  (1903),  Zimmer- 
man (1906),  Kirchhoff  (1929),  Killian  (1919)].    This  fungus  at- 


ERGOT  AND  ERGOTISM 


351 


tacks  various  cereal  and  forage  grasses.  It  is  most  commonly 
known  in  the  sclerotial  or  ergot  stage  as  it  occurs  on  rye.  The 
rye  grain  is  replaced  by  the  ergot  "grain"  or  sclerotium.  The 
fungus  may  first  be  noted  at  the  time  of  the  flowering  of  the  rye, 


Fig.  65.  Stages  in  the  development  of  ergot,  Claviceps  purpurea,  on  rye.  A. 
Ergot  grains  (sclerotia)  appearing  as  dark  spurs  and  replacing  the  rye  grains. 
B.  Young  infected  rve  ovarv,  at  whose  surface  conidia  are  formed.  C.  De- 
tail of  surface  of  young  infected  ovarv.  D.  Mature  ascus  of  C.  purpurea, 
bearing  eight  thread-like  ascospores.  E.  Diagram  of  apex  of  perithecial 
stroma,  showing  perithecia  arranged  near  the  periphery.  F.  Sclerotium 
in  spring,  bearing  several  club-shaped  perithecial  stromata. 

when  the  young  rye  ovaries  are  covered  with  masses  of  conidia 
that  collect  in  droplets.  These  droplets  ("honey  dew")  are  dis- 
persed by  insects.  By  the  time  the  normal  grain  is  ripe,  the  ergot 
grains  are  also  mature.  When  the  grain  is  threshed,  the  ergot 
grains  are  admixed  with  the  rye. 

Ergotism  in  livestock.  There  is  reason  to  believe  that  sclerotia 
from  all  species  of  Claviceps  are  poisonous.  From  various  parts  of 
the  world  have  come  reports  of  the  poisonous  effect  of  ergotized 


358  POISONOUS  AND  EDIBLE  FUNGI 

pasture  grasses  and  of  ergotized  hav  when  consumed  by  domestic 
animals.  The  fungi  involved  are  mainly  Claviceps  purpurea  and 
C.  paspali.  Poisoning  from  C.  purpurea  occurs  when  animals  are 
fed  rye  as  grain  or  are  pastured  on  ergot-infected  Loliwn  perenne, 
Poa  pratensis,  or  Agrostis  alba.  Several  serious  outbreaks  of 
ergotism  among  cattle  and  horses,  caused  by  C.  purpurea  on 
Ely  mils  canadensis,  fed  as  hay,  have  been  reported  from  the  prairie 
regions  of  the  central  United  States.  Claviceps  paspali,  occurring 
on  several  species  of  Paspalum  used  as  forage  grasses,  is  known 
to  cause  poisoning  of  cattle  in  the  Argentine,  Natal,  and  the  south- 
ern United  States. 

Poisoning  bv  C.  purpurea  causes  lameness  and  swelling  of  one 
or  more  limbs;  in  severe  cases,  as  the  result  of  impairment  of  cir- 
culation, the  extremities  may  become  oangrrenous.  Ears,  horns, 
hoofs,  toes,  feet,  and  tails  may  become  necrotic  and  may  slough 
off.  The  loss  to  stockmen  from  abortion  by  cows  and  mares  is 
heavy  when  ergot  is  abundant.  Gastric  disturbances  and  varying 
degrees  of  paralysis  are  other  symptoms  of  ergot  poisoning  in 
horses  and  cattle. 

An  epidemic  of  poisoning  by  C.  paspali  in  Mississippi  was 
studied  by  Brown  and  Ranck  (1915)  and  Brown  (1916).  Their 
feeding  trials  involved  guinea  pigs,  young  calves,  and  more  mature 
young  cattle.  Thev  noted  that  affected  animals  are  highly  nerv- 
ous  and  are  unable  to  coordinate  their  movements.  Paralysis  may 
ensue,  and  in  consequence  affected  cattle  are  unable  to  reach  water 
to  drink.  If  ergotized  grass  was  kept  from  the  sick  animal,  and 
water  and  feed  were  given  after  the  administration  of  a  purgative, 
recovery  followed. 

Toxicology.  Many  painstaking  chemical  analyses  have  been 
made  to  isolate  and  identify  the  active  principle  in  ergot,  as  is 
apparent  from  Barger's  (1931)  monograph.  In  1875  Tanret 
[Barger  (1931)]  isolated  what  he  regarded  as  a  pure  alkaloidal 
substance  and  as  the  active  principle,  and  called  it  ergotinine.  In 
1884Kobert  [Barger  (1931)]  identified  three  substances,  ergotinic 
acid,  sphacelic  acid,  and  cornutine.  Ergotinic  acid  is  a  nitrogen- 
ous elucoside  that  causes  inflammation  of  mucous  membranes  and 
hemolysis.  Robert  first  thought  sphacelic  acid  caused  uterine 
contractions  but  later  attributed  this  action  to  cornutine.  At 
first  cornutine  was  thought  to  cause  convulsions  and  paralysis. 
In   1897  Jacoby  isolated  a  phenol-like  substance  that  he  called 


TOXICITY  OF  GIBBERELLA  SAUBINETTII  359 

sphacelotoxin.  When  acted  upon  by  an  alkaloidal  base,  sphacelo- 
toxin  became  secalintoxin,  and  when  purified,  it  became  the 
ergotinine  of  Tanret.  Analysis  by  Kraft  in  1901  yielded  two  alka- 
loids, Tanret's  crystalline  ergotinine  and  an  amorphous  hydro- 
ergotinine.  In  1906  Barger  and  Dale  [Barger  (1931)]  maintained 
that  Kraft's  hydroergotinine  is  ergotoxin,  CssH^OeNg,  an  alkaloid 
capable  of  increasing  blood  pressure,  of  causing  gangrene  on  the 
combs  of  hens,  and  of  inducing  uterine  contractions.  Tanret,  who 
first  gave  the  formula  of  his  ergotinine  as  C35H40O6N4,  later 
changed  it  to  C35H40O5N.-,.  After  years  of  study  Barker  con- 
eluded  that  the  correct  formula  of  ergotinine  is  C33H35O5N5. 

Reports  of  studies  on  the  nature  of  the  toxic  principle  in  ergot 
appeared  almost  simultaneously  from  several  laboratories.  Stoll 
and  Burkhart  (1935)  called  their  purified  alkaloid  ergobasine; 
Thompson    (1935)    called   his   ergostetrine.     Dudley   and   Moir 

(1935)  named  their  substance  ergometrine.  Kharasch  and  Le- 
gault  (1935)  called  their  product  ergotocin.  They  got  0.1  to  0.3 
mg  of  ergotocin  from  3  to  4  grams  of  ergot  grains,  an  amount 
held  to  constitute  a  dose.    Kharasch,  King,  Stoll,  and  Thompson 

(1936)  compared  the  melting  points  of  the  four  alkaloids,  ergoba- 
sine, ergostetrine,  ergometrine,  and  ergotocin,  and  those  of  certain 
of  their  salts,  and  also  the  optical  properties  of  each  in  different 
solvents,  and  came  to  the  conclusion  that  the  four  names  are 
synomymous. 

The  alkaloidal  content  of  ergot  varies  with  the  year  and  with  the 
locality.  Spanish  and  Portuguese  ergot  assays  0.05  to  0.30%, 
whereas  ergot  from  Russia  and  Poland  varies  from  0.02  to  0.10%. 
The  superiority  of  the  Spanish  and  Portuguese  ergots  may  be 
causally  related  to  moisture.  When  stored  at  high  humidities, 
ergot  deteriorates,  deterioration  being  correlated  with  increased 
histamine  content.  When  stored  dry,  it  keeps  for  long  periods,  al- 
though pharmaceutical  supply  manufacturers  avoid  buying  ergot 
that  is  more  than  a  year  old. 

TOXICITY  OF  GIBBERELLA  SAUBINETTII   (G.  ZEAE) 

AND  FUSARIUM  SPP. 

The  heads  or  inflorescences  of  various  grasses  may  be  para- 
sitized by  a  polymorphic  ascomycetous  fungus,  Gibberella  scaibi- 
nettii,  that  is  especially  destructive  to  barley,  oats,  rye,  wheat,  and 


360  POISONOUS  AND  EDIBLE  FUNGI 

corn.  On  small  qrains  the  disease  is  known  by  the  common  name 
scab.  The  causal  fungus  is  most  frequently  encountered  in  its 
conidial  stage,  which  is  of  the  Fusarium  type.  As  the  cereal  crop 
approaches  maturity,  conidia  of  the  Fusarium  stage  are  present  in 
profusion  at  the  surface  of  the  grains  and  glumes.  This  fungus, 
especially  as  it  occurs  on  barley,  has  long  been  known  to  be 
poisonous.  The  status  of  present-day  knowledge  of  its  toxicity 
in  connection  with  scabby  barley  is  summarized  in  a  report  by 
Christiansen  and  Kernkamp  (1936). 

Long  ago  peasants  in  Russia  found  that  scabby  barley,  when 
used  in  bread-making  or  when  fed  to  livestock,  is  toxic.  In 
northern  Russia  this  toxicity  came  to  be  attributed  to  Fusarium 
avenaceum  (Fr.)  Sacc,  and  in  southern  Russia,  to  Fusarium 
gramineum  Schwabe.  In  the  United  States  about  a  dozen  species 
of  Fusarium  are  known  to  be  associated  with  barley  scab. 

Barley  scab  was  unusually  abundant  in  1928  in  the  Upper  Mis- 
sissippi Valley.  Much  of  this  diseased  barley  was  used  to  feed 
swine,  and  in  consequence  of  complaints  of  sickness  in  the  herds, 
special  efforts  were  made  to  learn  more  about  the  poisonous  prop- 
erties of  Fusarium-affected  barley.  Some  of  the  diseased  crop  was 
exported  to  Europe,  where  similar  complaints  arose  from  its  use 
as  feed  for  swine.  The  results  of  experimentation  that  was  initi- 
ated in  the  United  States  and  in  Europe  leave  no  doubt  that  the 
feeding  of  scabby  barley  is  responsible  for  sickness  among  do- 
mestic animals.  In  their  entirety  these  experiments  showed  that 
such  barley  is  poisonous  to  horses,  cattle,  sheep,  pigs,  chickens, 
and  dogs,  ruminants  being  able  to  tolerate  greater  proportions  of 
affected  grains. 

Christiansen  and  Kernkamp  (1936)  observed  that  pigs  refuse  to 
eat  scabby  barley  unless  they  can  get  nothing  else.  If  the  propor- 
tion of  affected  kernels  is  as  much  as  16° o,  it  is  extremely  toxic, 
and  if  as  much  as  32%,  the  pigs  refuse  to  eat  it.  Poisoning  is 
manifested  by  loss  of  appetite,  listlessness,  and  weakness  and 
nausea;  death  may  ensue.  These  investigators  found  that  the 
poisonous  principle  is  v\ater-soluble  and  heat-stable.  An  aqueous 
extract  from  15  grams  of  scabby  barley,  when  administered  orally 
through  a  stomach  tube  to  a  pig  weighing  100  lb,  caused  vomiting. 
An  overdose  of  extract  from  Fusarium-infected  corn  caused 
death. 


IMPLICATIONS  361 

Christiansen  and  Kernkamp  isolated  several  species  of  Fusarium 
from  affected  barley  kernels,  F.  gramineimi  being  most  common. 
Extracts  from  pure  cultures  of  these  species  did  not  prove  toxic 
to  pigs,  although  they  refused  to  eat  barley  that  had  been  used 
as  a  culture  medium  unless  it  was  masked  by  mixture  with  a  suffi- 
cient quantity  of  other  feed.  When  Christiansen  and  Kernkamp 
inoculated  wheat,  barley,  and  corn  with  F.  gram'meum  at  a  time 
when  the  grain  was  developing,  the  ripened  kernels  were  found 
to  contain  the  toxic  principle.  Moreover,  affected  grain  retained 
its  toxicity  for  long  periods,  at  least  3  years.  Affected  kernels 
tend  to  float  at  the  surface  of  water;  this  fact  can  be  utilized  in 
separating  normal  and  scabby  grains. 

Concerning  the  chemical  nature  of  the  toxic  principle  little  has 
been  established  to  date,  except  that  it  is  water-soluble  and  ther- 
mostable. Schroeter  and  Strassberger  (1931)  found  large  quanti- 
ties of  choline  and  fatty  acid  esters  of  choline  in  Fusarium- 
affected  grain  and  expressed  the  opinion  that  these  substances 
constitute  the  toxic  principle. 

It  may  be  recalled  that  the  proximate  cause  of  wilting  in  vascu- 
lar diseases  of  crop  plants  associated  with  species  of  Fusarium  is 
commonly  regarded  as  a  toxin.  The  experiments  with  Fusarium- 
affected  grain  indicate,  as  a  line  of  departure,  the  employment  of 
animals  in  studies  involving  the  nature  of  such  toxins  in  Fusaria 
causing  vascular-wilt  diseases. 

IMPLICATIONS 

In  the  past,  studies  of  poisonous  fungi  have  been  concerned 
mainly  with  the  identity  of  the  poisonous  fungus,  with  the  na- 
ture of  its  toxic  principle,  and  with  the  effects  of  this  principle 
upon  animals  and  man.  Too  little  is  yet  known  about  fungi 
poisonous  to  seed  plants.  It  is  indicated  that  future  studies  should 
stress  plant  toxemias  to  a  greater  extent  than  have  those  of  the 
past,  in  order  to  account  for  the  disease  syndrome.  By  the  use 
of  plant  toxins  as  antigens,  it  should  be  possible  to  produce  specific 
antitoxins.  Furthermore  the  ultracentrifuge  and  electron  micro- 
scope should  enable  the  worker  to  purify  fungus  toxins  and  anti- 
toxins and  thus  to  learn  something  more  of  their  physical  prop- 
erties and  eventually  of  their  chemical  constitution. 


362  POISONOUS  AND  EDIBLE  FUNGI 


LITERATURE  CITED 

Atanasoff,  D.,  "Ergot  of  grains  and  grasses"  (stenciled  copy,  107  pp.).  U.  S. 
Dept.  Agr.,  Bur.  Plant  Industry.     1920. 

Barger,  G.,  "Ergot  and  ergotism,"  a  monograph  based  on  the  Dohme  lectures 
delivered  in  Johns  Hopkins  University.  279  pp.  Gurney  and  Jackson, 
London.     1931. 

Brown,  H.  B.,  "Life  history  and  poisonous  properties  of  Claviceps  paspali," 
J.  Agr.  Research,  7:401-406,  1916. 

Brown,  H.  B.,  and  E.  AI.  Ranck,  "Forage  poisoning  due  to  Claviceps  paspali 
on  Paspalum,"  Miss.  Agr.  Expt.  Sta.  Tech.  Bull.,  6:3-35,  1915. 

Christiansen,  J.  J.,  and  H.  C.  H.  Kernkamp,  "Studies  on  the  toxicity  of 
blighted  barley  to  swine,"  Minn.  Agr.  Expt.  Sta.  Tech.  Bull.,  113.  38 
p.    1936. 

Dudley,  H.  W.,  and  J.  C.  .Moir,  "The  new  active  principle  of  ergot," 
Science,  81:559-560,  1935. 

Dujarrac  de  la  Riviere,  D.,  and  Roger  Helm,  Les  champignons  toxiques. 
Paris.     1938. 

Falck,  R.,  "Uber  die  Luftinfektion  des  Mutterkorns  {Claviceps  purpurea 
Tul.)  und  die  Verbreitung  prlanzlicher  Infektionskrankheiten  durch 
Temperaturstromungen,"  Z.  Forst-  und  Jagdwese?i,  43:202-221,  1911. 

Ford,  W.  W.,  "The  toxicological  constitution  of  Amanita  phalloides"  /. 
Expt.  Med.,  5*:  437-450,  1906. 
"The  toxins  and  antitoxins  of  poisonous  mushrooms,"  /.  Injections  Dis- 
eases, 3:  191-224,  1906a. 
"On  the  presence  of  hemolytic  substances  in  edible  fungi,"  /.  Injections 

Diseases,  4:  434-439,  1907.  ' 
"A  clinical  study  of  mushroom  intoxication,"  Johns  Hopkins  Hosp.  Bull., 

18:1-21,  1907a. 
"The  distribution  of  haemolysins,  agglutinins,  and  poisons  in  fungi,  espe- 
cially the  Amanitas,  the  Entolomas,  the  Lactarius,  and  the  Inocybes," 
/.  Pharmacol.,  2:285-318,  1911. 
"A  new  classification  of  mycetismus  (mushroom  poisoning),"  /.  Pharma- 
col., 29:  305-309,  1926. 

Ford,  W.  W.,  and  E.  D.  Clark,  "A  consideration  of  the  properties  of 
poisonous  fungi,"  Mycol.,  6:  167-191,  1914. 

Ford,  W.  W.,  and  J.  L.  Sherrick,  "On  the  properties  of  several  species  of 
the  Polvporaceae  and  of  a  new  variety  of  Clitocvbe,  Clitocybe  dealbata 
sudorifica  Peck,"  /.  Pharmacol,  2:  549-558,  1911. 
"Further  observations  of  fungi,  particularly-  Clitocybe  sudorifica  Peck, 
Pholiota  autumnalis  Peck,  and  Inocybe  decipiens  Bresadola,"  /.  Pharma- 
col., 4:  321-332,  1913. 

Fries,  Elias  M.,  Systema  Mycologicum,  2:  p.  268.    1822. 
Swmna  vegetab'ilium  Scandinaviae,  p.  381.     1849. 

Iwanoff,  X.  X.,  and  E.  S.  Zwetkoff,  "The  biochemistry  of  fungi,"  Ann. 
Rev.  Biochem.,  2:521-540,  1932. 


LITERATURE  CITED  363 

Kharasch,  M.  S.,  H.  King,  A.  Stoll,  and  M.  R.  Thompson,  "The  new  ergot 

alkaloid,"  Science,  83:  206-207,  1936. 
Kharasch,  M.  S.,  and  R.  R.  Legault,  "Ergotocin,"  Science,  ^7;  388,   1935. 
Killian,  Charles,  "Sur  la  sexualite  de  l'ergot  de  Seigle,  le  Claviceps  purpurea 

Tulasne,"  Bull.  soc.  my  col.  Fra?ice,  25:  182-197,  1919. 
Kirchhoff,   H.,   "Beitrage   zur  Biologie   und   Physiologie   des   Mutterkorn- 

pilzes,"  Zentr.  Bakt.,  Parasitenk.,  11  Abt.,  77:310-369,  1929. 
Leveille,  J.  H.,  "Memoire  sur  le  genre  Sclerotium,"  Comp.  rend.,  14:446- 

448,  1842. 
"Memoire  sur  l'ergot,  an  nouvelles  recherches  sur  la  cause  et  les  effets  de 

l'ergot,  considere  sous  le  triple  rapport  botanique,  agricole  et  medical," 

Mem.  Soc.  Limn.  Paris,  5:  565-569,  1927. 
Mendel,  L.  B.,  "The  chemical  composition  and  nutritive  value  of  some  edible 

American  fungi,"  Am.  J.  Physiol.,  1:  225-238,  1898. 
Meyen,  F.  J.  B.,  Pflaiizenpathologie.    p.  192.     1841. 
Rolfe,  R.  T.,  and  F.  W.  Rolfe,  The  romance  of  the  fungus  world.    309  pp. 

J.  B.  Lippincott  Co.,  Philadelphia.     1928. 
Schlesinger,  H.,  and  W.  W.  Ford,  "On  the  chemical  properties  of  Amanita 

toxin,"  /.  Biol.  Chem.,  5:279-383,  1907. 
Schroeter,    G.,   and   L.    Strassberger,    "Cholin   als    Schadstoff   in   kranker 

Gerste,"  Biochem.  Z.,  232:452^58,  1931. 
Stager,   R.,    "Infektionsversuche   mit    Gramineen   bewohnenden   Claviceps- 

Arten,"  Botan.  Z.,  61:  111-158,  1903. 
Stoll,  A.,  and  E.  Burkhardt,  "L'ergobasine,  nouvel  alcaloide  de  l'ergot  de 

seigle,  soluble  dans  l'eau,"  Compt.  rend.,  200:  1680-1682,  1935. 
Thompson,  M.  R.,  "The  new  active  principle  of  ergot,"  Science,  81:636- 

638,  1935. 
Tulasne,  L.  R.,  "Memoire  sur  l'ergot  des  Glumacees,"  Ann.  soc.  nat.  botan., 

3  ser.,  20:5-56,  1853. 
Zimmerman,  A.,  "Erganzende  Versuche  zur  Feststellung  der  Keimfahigkeit 

altere  Sklerotien  von  Claviceps  purpurea,"  Z.  Pflanzenkr.,  16:129-131, 

1906. 


Chapter  16 

MEDICAL  MYCOLOGY 

The  fungi  which  are  pathogenic  to  man  occupy  a  position 
which  mav  well  be  designated  as  a  "no  man's  land"  for  both  the 
mycologist  and  the  medical  practitioner.    Even  well-trained  my- 
cologists have  no  first-hand  knowledge  of  humanly  pathogenic 
fungi,  and  these  organisms  remain  quite  unknown  to  the  physician, 
since  they  are  given  little,  if  any,  attention  in  the  curricula  of  our 
best  medical  schools.    Lack  of  proper  appreciation  of  these  fungi 
may  also  be  attributed  in  part  to  the  fact  that  the  mycologist  is 
quite  unacquainted  with  the  clinical  aspects  or  clinical  variations 
and  pathological  anatomy  of  the  diseases  which  they  produce  and 
that  the  physician  is  lost  in  the  maze  of  controversial  taxonomic 
and  cultural  difficulties  which  both  he  and  the  mycologist  have 
fostered.    Some  of  these  problems  have  arisen  because  the  patho- 
genic fungi  exhibit  so  much  variation  in  appearance  when  in 
lesions  and  when  grown  on  various  culture  media.    In  addition, 
some  confusion  may  be  attributed  to  difficulties  in  interpreting 
many  of  the  studies  and  descriptions  of  the  pathogens.    Experi- 
enced, well-trained  mycologists  with  the  organisms  available  for 
critical  study  find  these  taxonomic  problems  very  puzzling  and 
time-consuming.     As  a  consequence  a  confusion  has  developed 
which  will  depend  for  clarification  upon  collaborative  studies 
among  clinicians,  pathologists,  taxonomists,  serologists,  biochem- 
ists, and  epidemiologists.     No  single  investigator,  working  inde- 
pendently,  can   hope   to   establish   order  in   a   field   so   chaotic. 
Thousands  of  papers  on  medical  mycology,  many  of  them  case 
reports,  have  been  published  since  1900.    An  appreciation  of  the 
status  and  scope  of  this  subject  can  be  gained  from  Dodge's  (1935) 
Medical  Mycology  and  from  the  excellent  recent  summaries  by 
Tate  (1929),  Ramsbottom  (1931),  Gregory  (1935)  and  Emmons 
(1940).    The  medical  practitioner  will  find  the  volume  by  Lewis 

364 


MEDICAL  MYCOLOGY  365 

and  Hopper  (1939)  especially  helpful  in  diagnosis  and  in  identi- 
fication. 

Similarly  the  physician  will  find  the  Manual  of  Clinical  Mycol- 
ogy by  Conant,  Martin,  Smith,  Baker,  and  Callaway  (1944)  indis- 
pensable in  dealing  with  mycotic  diseases.  It  discusses  systemati- 
cally and  briefly  symptoms,  differential  diagnosis,  prognosis,  im- 
munology, etiology,  identification,  isolation  and  cultivation  of  the 
fungus,  and  range  of  the  disease. 

It  would  seem  that  medical  mycology  is  not  surpassed  bv  any 
other  field  of  mycological  study  in  potential  importance  and  in 
appeal  to  the  scientific  imagination  of  the  young  investigator 
seeking  new  and  difficult  problems  whose  solution  means  much 
to  the  welfare  of  the  human  race. 

On  the  basis  of  present-day  knowledge  certain  general  state- 
ments regarding  fungi  pathogenic  to  man  appear  to  be  war- 
ranted. These  statements  are  therefore  categorically  presented 
in  the  following  introductory  paragraphs.  In  the  first  place  the 
number  of  species  known  to  be  pathogenic  to  man  is  limited. 
These  are  mostly  imperfect  fungi;  a  few  are  Ascomycetes,  closely 
related  to  the  yeasts,  and  a  few  are  Actinomycetes,  whose  syste- 
matic position  is  still  a  matter  of  dispute. 

Little  is  definitely  known  about  their  source  in  nature  except 
that  circumstantial  evidence  indicates  that  some  of  them  originate 
on  plants.  Some  species,  especially  among  the  Trichophytoneae, 
occur  also  on  wild  and  domestic  animals  and  are  transmitted  to 
man  only  by  being  implanted. 

Entrance  to  the  body  is  gained  (a)  through  hair  follicles,  but 
never  through  sweat  glands,  (b)  through  the  nasal  passages  and 
thence  into  the  lungs,  and  (c)  through  abrasions  or  injuries,  as 
through  scratches  or  wounds  made  by  thorns  or  splinters.  In  a 
few  species  entrance  appears  to  be  gained  through  the  enteron. 

The  types  of  tissue  reactions  induced  in  man  by  fungi  are  ex- 
tremely variable.  Some  species  remain  quite  superficial  in  their 
effect,  whereas  others  produce  deep  lesions  or  involve  such  internal 
organs  as  the  lungs,  spleen,  and  liver.  Some  are  local,  and  some 
systemic.  Among  the  common  tissue  changes  are  congestion, 
edema,  exudation,  hyperplasia,  necrosis,  scar-tissue  formation,  and 
suppuration  with  accompanying  migration  of  polymorphonuclear 
cells. 


366  MEDICAL  MYCOLOGY 

In  artificial  culture  many  of  these  pathogens  have  a  very  differ- 
ent appearance  from  the  way  they  look  in  tissues.  Some  of  them 
are  filamentous  when  grown  at  room  temperature  but  under 
otherwise  similar  conditions  are  yeast-like  in  appearance  when 
cultivated  at  incubator  temperature,  37.5°  C. 

HISTORICAL  MATERIAL 

Medical  mycology  may  be  said  to  begin  with  Schoenlein,  who 
in  1839  associated  a  fungus  with  favus,  a  form  of  ringworm  char- 
acterized by  lesions  and  having  bright  yellow  crusts  composed  of 
small  cup-like  scales.  The  causal  organism  was  given  the  name 
Achorion  schoenleini  by  Remak  6  years  later.  In  the  same  year 
Malmsten  employed  the  generic  name  Trichophyton  for  the  ring- 
worm pathogen.  The  deeply  seated,  suppurative  form  of  ring- 
worm known  as  kerion  was  shown  in  1856  to  be  induced  by  a 
Trichophyton  originating  from  animals.  Further  proof  of  trans- 
mission from  animal  to  animal  followed,  as  well  as  demonstration 
by  various  workers  that  ringworm  can  be  transmitted  to  man 
from  horse,  cow ,  dog,  or  cat.  All  in  all,  however,  little  important 
work  in  this  field  was  accomplished  until  Sabouraud  began  his 
studies  in  the  early  1890's.  The  publication  of  his  monumental 
Les  Teignes  (1910)  constitutes  the  beginning  of  the  modern  era 
of  investigation  and  is  the  foundation  upon  which  all  present-day 
studies  in  medical  mycology  are  based. 

The  medical  worker  has  found  it  convenient  to  designate  by 
the  term  "mycoses"  (literally  "filled  with,  or  full  of,  fungi")  the 
diseases  of  man  and  animals  caused  by  fungi.  This  terminology 
has  a  definite  significance  for  the  mycologist,  since  the  generic 
name  of  the  pathogen  and  the  suffix  "osis"  are  combined,  as  in 
Actinomycosis,  Torulosis,  Histoplasmosis,  and  Blastomycosis,  and 
it  will  be  employed  in  the  discussion  that  follows.  Confusion 
arises,  however,  when  "osis"  and  "mycosis"  are  applied  to  clin- 
ically distinct  mycoses,  such  as  may  be  produced  by  one  and  the 
same  fungus  involving  different  organs  and  tissues,  for  example, 
"onchomycosis"  when  the  nails  are  involved,  "sychosis"  when 
the  beard  is  involved,  and  "dermatomycosis"  when  the  glabrous 
skin  is  involved.  Similarly,  the  wisdom  of  retaining  the  name  "der- 
matophytes" or  "dermatomycetes"  for  those  fungi  that  invade 
the  keratinized  layers  of  the  epidermis  and  such  appendages  or 


COCCIDIOIDES  IMMITIS 


361 


modifications  as  the  hair,  nails,  hooves,  feathers,  and  horns  may 
be  questioned.  One  might  with  equal  reason  indicate  by  the  term 
"caulophytes"  those  fungi  involving  plant  stems,  "fructophytes," 
those  involving  fruits,  and  "phyllophytes,"  those  attacking  foliage! 

The  account  that  follows  is 
intended  as  an  introduction  to 
the  mycologic  features  of  some 
of  the  better-known  human 
pathogens.  The  scope  of  the 
field  can  be  appreciated  only 
by  consultation  of  certain  vo- 
luminous monographic  studies, 
such  as  those  of  Sabouraud 
(1910),  Brumpt  (1935),  and 
Dodge  (1935).  It  is  also  quite 
apparent  that  all  too  little  is  as 
yet  known  of  the  mycotic  flora 
of  the  surface  of  the  normal 
body  and  of  the  protective 
mechanisms  which  the  skin  af- 
fords to  invasion  by  fungus 
pathogens. 

COCCIDIOIDES  IMMITIS 


Fig.  66.  Coccidioides  immitis.  A. 
Hypha  from  nutrient  agar,  tending 
to  be  racket-shaped.  B.  Arthro- 
spores  from  culture.  C.  Spores,  one 
of  them  germinating  from  globular 
sporangium-like  cell,  which  con- 
tains numerous  spores.  (After 
Moore.) 


This  organism,  wThich  causes 
a  highly  fatal  disease,  was  first 
reported  in  Argentina  but  is 
best  known  in  California,  Ari- 
zona, and  Texas.  The  disease 
is  commonly  known  in  its  acute 
form  as  valley  fever;  the  medi- 
cal profession  calls  it  coccidioidal  granuloma.  It  has  been  re- 
ported to  occur  among  cattle,  sheep,  and  dogs,  but  as  yet  there  is 
little  evidence  of  transmission  from  animals  to  man  or  man  to  ani- 
mals. Emmons  (1942)  reported  that  the  pathogen  occurs  in  ro- 
dents, including  deer  mice,  pocket  mice,  kangaroo  rats,  and  ground 
squirrels,  in  Arizona  and  also  that  he  was  able  to  isolate  it  from  soil. 

The  early  history  of  coccidioidomycosis  is  summarized  in  an 
account  by  Rixford,  Dickson,  and  Beck   (1931).     The  disease 


568  MEDICAL  MYCOLOGY 

may  be  manifest  as  a  mild,  pleurisv-like,  respiratory  infection, 
with  chills,  night  sweats,  and  headache.  After  2  or  3  weeks  papil- 
lomatous eruptions  appear  on  the  arms,  thighs,  and  scalp,  and 
occasionally  the  knee  and  ankle  joints  are  arthritic.  Examination 
by  X-ray  may  reveal  pulmonary  nodules  resembling  primary 
tuberculosis.  The  sputum  is  mucopurulent  and  may  contain 
blood. 

Ulcerative  lesions  on  the  face  and  neck  may  characterize  an- 
other form  of  the  disease.  Such  lesions  slowly  become  subcu- 
taneous and  may  spread  to  the  meninges  and  spinal  cord.  If  the 
miliary  type  of  involvement  develops,  the  fever  is  high,  prostra- 
tion is  marked,  and  death  occurs  after  a  few  weeks. 

When  present  in  the  tissues,  Coccidioides  'nmriith,  described  by 
Stiles  in  a  report  by  Rixford  and  Gilchrist  (1896),  consists  of 
large,  thick-walled,  spherical  cells  that  may  reach  a  diameter  of 
50  to  70  /*.  At  maturity  these  cells  function  as  sporangia,  although 
they  have  been  misinterpreted  by  some  to  be  asci.  By  cleavage 
their  content  gives  rise  to  a  large  number  of  spores,  which  escape 
by  rupture  of  the  sporangial  wall.  From  a  comparative  study  of 
15  strains  by  Baker,  Alrak,  and  Smith  (1943)  it  has  been  con- 
cluded that  the  organism  is  a  Phycomycete. 

This  fungus  in  cultures  on  semisolid  media  forms  creamy  white, 
cottony  mycelium.  By  fragmentation  chlamydospore-like  oidia 
are  produced.  Sporangia  and  sporangiospores  are  developed,  how- 
ever, if  cultured  under  reduced  oxygen  tension  in  the  presence  of 
tcrcf  albumen  or  serum. 

The  acute  type  of  the  disease  probably  enters  through  the  pul- 
monary route.  The  pathogen  has  been  isolated  from  the  soil,  but 
soil  may  not  constitute  its  natural  habitat.  In  patients  who  re- 
cover spontaneously,  and  among  residents  of  the  San  Joaquin 
Valley  generally,  intradermal  injection  of  killed  cultures  of  the 
fungus  results  in  rather  severe  skin  reactions. 

CRYPTOCOCCUS  HISTOLYT1CUS 

Approximately  30  species  of  Cryptococcus  are  reported  to  be 
pathogenic  to  man,  Cryptococcus  histolyticus,  a  cause  of  blasto- 
mycosis, being  perhaps  the  best  known.  Reports  of  blastomy- 
cosis include  a  disease  which  in  the  United  States  manifests  itself 
by  a  disturbance  of  the  central  nervous  system,  clinically  like 


HISTOPLASA1A  CAPSULATUM  369 

chronic  meningitis,  whereas  in  Europe  ulcerative  lesions  of  the 
skin  and  underlying  tissues  are  a  more  common  manifestation. 
The  evidence  by  Benham  (1934)  indicates  that  European  blasto- 
mycosis and  American  torulosis  are  identical.  Freeman's  (1931) 
account  of  clinical  appearance  and  pathology  shows  that  there 
may  be  chronic  respiratory  involvement  which  leads  to  a  diagnosis 
of  tuberculous  meningitis.  The  pathogen  is  presumed  to  enter 
through  the  respiratory  tract. 

The  etiology  of  this  disease  remains  confused.  Freeman  (1931) 
indicates  that  several  organisms  may  produce  the  same  disease 
complex. 

The  pathogen  is  usually  known  as  Torida  histolytica  or  Crypto- 
coccus  hominis.  It  is  one  of  the  Saccharomycetaceae,  having  ovoid 
to  elliptical  cells  occurring  singly  or  in  groups  and  invested  by  a 
thick  gelatinous  capsule.  It  forms  white  to  yellowish  white, 
pasty,  opaque  colonies  on  agar.  Its  only  known  method  of  repro- 
duction is  by  buds,  unless  the  researches  of  Todd  and  Hermann 
(1936)  are  confirmed.  Their  study  of  the  developmental  cycle 
shows  endospore  formation  of  the  type  found  in  Debaryomyces, 
in  consequence  of  which  they  referred  the  pathogen  to  D.  homi- 
nis. It  has  been  suggested,  on  the  basis  of  priority,  that  the  proper 
binomial  is  D.  neoformans. 

A  generalized  blastomycosis,  manifest  as  cutaneous  abscesses,  is 
caused  by  the  closely  related  Blastomy  ces  dermatitidis,  also  known 
as  Gilchristia  dermatitidis  or  Xymonema  dermatitidis. 

HISTOPLASMA  CAPSULATUM 

Approximately  30  years  ago  Darling  reported  the  occurrence 
among  the  natives  of  Panama  of  a  disease  characterized  clinically 
by  fever,  emaciation,  anemia,  splenomegaly,  leucopenia,  and  ulcer- 
ation of  the  nose,  throat,  and  intestines.  He  was  not  able  to  iso- 
late the  etiologic  agent  but  believed  it  was  a  protozoan,  to  which 
he  gave  the  name  Histoplasma  capsidatwn.  Subsequently  other 
cases  of  histoplasmosis  were  recorded  in  widely  separately  places, 
and  in  1932  de  Monbreun  (1934)  isolated  and  described  the  causal 
fungus.  In  the  mononuclear  blood  cells  and  lymph  vessels  it  exists 
as  yeast-like  cells  with  thick  capsules.  When  the  organism  is  kept 
at  body  temperature  on  blood  or  serum  media,  this  form  of  the 
pathogen  persists.    When  grown  on  other  agar  media,  however,  it 


310 


MEDICAL  MYCOLOGY 


is  filamentous  and  produces  peculiar  spherical  conidia  or  chlamy- 
dospores,  covered  with  finger-like  outgrowths,  10  to  25  /x  in 
diameter. 

Its  relationship  to  other  fungi  is  not  clearly  established.  It  has 
been  interpreted  to  be  related  to  Coccidioides  and  placed  in  the 
Genus  Posadasia  anions  the  Endomvcetaceae.  Studies  by  Howell 
( 1939),  however,  in  which  Histoplasma  was  compared  with  Sepe- 


Fig.  67.  Histoplasma  capsulatimi.  A.  Mycelium  from  culture.  B.  Aleuro- 
spores  that  form  on  aerial  mycelium,  showing  characteristic  protrusions. 
C.  Aleurospore  in  optical  section.     D.  Aleurospores  that  form  submerged. 

Their  walls  are  smooth. 

donium  and  other  fungi  related  to  Sepedonium  show  that  these 
two  genera  are  closely  related  Fungi  Imperfecti.  Sepedonium  is 
never  yeast-like,  however,  and  it  may  produce  phialospores,  which 
are  not  known  to  be  developed  among  species  of  Histoplasma. 
Conant  (1941)  reported  that  in  its  parasitic  form  within  tissues 
Histoplasma  is  always  yeast-like  with  thick  capsules.  On  blood 
agar  incubated  at  37°  C  it  buds,  yeast-like,  but  at  room  tempera- 
ture it  is  myceloid  and  forms  tuberculate  chlamydospores. 
Conant  too  regards  it  as  closely  related  to  Sepedonium. 


PHIALOPHORA  VERRUCOSA 

This  is  amono;  the  organisms  involved  in  a  chronic  infection  of 
the  skin  and  subcutaneous  tissues,  characterized  by  the  presence 


PHIALOPHORA  VERRUCOSA 


311 


of  warty  or  cauliflower-like  excrescences.  Usually  the  hands  are 
involved;  the  feet  are  especially  susceptible  to  infection.  Other 
parts  also  are  known  to  bear  the  nodular  ulcers.  The  disease  has 
a  wide  geographical  distribution  [Emmons  (1940)]  in  the  tropics 
of  both  hemispheres,  especially  among  laborers  who  work  bare- 
footed. There  is  no  evidence  of  spread  from  person  to  person. 
The  pathogen  appears  to  enter  through  injuries,  such  as  those 
from  thorns  or  splinters. 


Fig.  68.    A.  Phialophora  verrucosa,  the  spores  borne  in  a  phial  and  adhering 

in  a  mass  at  the  opening  of  the  phial.    B.  Hormodendroii  pedrosoi,  conidio- 

phores  and  chains  of  conidia  that  arise  as  buds. 

Two  names,  chromoblastomy  cosis  and  dermatitis  verrucosa, 
both  of  which  have  been  criticized,  have  been  applied  to  the  dis- 
ease. The  name  chromoblastomycosis  is  criticized  on  the  grounds 
that  the  fungus  cells  within  the  tissues,  although  pigmented,  do  not 
bud  in  yeast-like  fashion  but  divide  by  septation.  The  roughening 
of  the  skin  indicated  by  the  name  dermatitis  verrucosa  does  not 
give  an  adequate  clinical  picture,  since  other  tissues  and  related 
conditions  are  included  in  the  disease  complex. 

The  causal  agency  was  first  described  by  Medlar  (1915)  as 
Phialophora  verrucosa,  one  of  the  Dematiaceae,  although  the  dis- 
ease was  first  observed  by  Pedroso  in  Brazil  4  years  earlier.  Phialo- 
phora, when  seen  in  scrapings  or  in  biopsied  dermal  papillae,  con- 


312  MEDICAL  MYCOLOGY 

sists  of  thick-walled,  brown,  spherical  cells  or  two  or  three  closely 
associated  cells.  In  its  saprophytic  phase  on  agar  it  is  mvceloid 
and  grayish  black.  Sporulation  occurs  from  lateral  conidiophores, 
which  are  phial-like  or  cup-like  with  funnel-shaped  mouths.  The 
small  spores  are  formed  in  the  base  of  the  cup  and  are  extruded 
but  adhere  in  a  spherical  mass  at  the  mouth  of  the  cup. 

The  natural  habitat  of  P.  verrucosa  is  revealed  bv  the  work  of 
Conant  (1937).  He  found  that  Cadophora  americana,  one  of  sev- 
eral species  that  cause  a  blueing  of  wood  pulp,  is  morphologically 
and  culturally  identical  with  P.  verrucosa.  Further  evidence  of 
their  identity  comes  from  their  antigenic  similarity,  established  by 
Martin  (1938). 

iVnother  closely  related  species,  Hormodendrwn  pedrosoi,  de- 
scribed by  Brumpt  in  1922  [Brumpt  (1935)],  causes  an  involve- 
ment whose  clinical  aspects  cannot  be  distinguished  from  those 
induced  by  P.  verrucosa.  This  fact  has  been  established  by  several 
investigators,  among  whom  are  Emmons  (1936)  and  Martin, 
Baker,  and  Conant  (1936).  Further  evidence  adduced  by  Em- 
mons and  Carrion  (1937)  showed  that  some  strains  of  H.  pedrosoi 
may  form  phialospores  in  culture.  Not  only  have  morphologic 
relationships  been  established  between  these  two  fungi  that  pro- 
duce chromoblastomycosis,  but  also  serologic  evidence  of  Martin, 
Baker  and  Conant  (1936)  and  Conant  and  Martin  (1937)  shows  a 
very  close  relationship.  These  workers  found  that  H.  pedrosoi 
causes  specific  complement-fixing  antibodies  to  form  in  the  pa- 
tients' serum  and  that  there  is  a  cross-antigenic  relationship  be- 
tween strains  of  Hormodendrum  and  Phialophora.  The  taxono- 
mic  difficulties  that  have  arisen  in  this  complex  are  indicated  by 
combinations  which  have  placed  the  pathogen  in  such  genera  as 
Gomphinaria,  Fonsecaea,  Carrionia,  Acrotheca,  and  Trichospor- 
ium.  Presumably  one  variable  species  only  is  involved  in  the  pro- 
duction of  chromoblastomycosis,  as  is  indicated  in  the  brief  but 
comprehensive  account  by  Carrion  (1942). 

MALASSEZ1A  OVALIS 

Approximately  75  years  ago  Malassez  reported  the  occurrence 
of  an  organism,  Pityrosporimi  ovale,  in  the  squamae,  follicles,  and 
sebaceous  glands  of  the  scalp.  Since  then  many  papers  have  been 
published,  interest  in  this  organism  being  centered  on  its  possible 


ACTINOMYCES  BOVIS  313 

relationship  to  baldness.  Some  workers  have  maintained  that  this 
organism  is  the  cause  of  dandruff  and  seborrheic  dermatitis; 
others,  that  it  is  a  harmless  saprophyte.  Unna,  one  of  the  foremost 
students  of  this  problem,  is  among  those  who  believe  that  P.  ovale, 
which  he  called  the  "bottle  bacillus"  because  of  the  shape  of  the 
cells,  is  the  etiologic  agent  in  this  scaly  condition  of  the  scalp; 
he  designated  the  disease  "pityriasis  capitis." 

Among  the  recent  workers  who  regard  this  organism  as  patho- 
genic is  xMoore  (1935),  Ota  and  Huang  (1933),  on  the  other  hand, 
concluded  that  their  yeast-like  isolates  from  seborrheic  dermatitis, 
belonging  to  Pityrosporum,  were  saprophytes.  The  most  critical 
study  of  this  whole  problem  is  that  of  MacKee  and  his  associates 
(1938).  They  made  direct  examination  of  the  scrapings  of 
normal  and  diseased  scalps  and  in  one  series  found  P.  ovale  in  86 
of  the  100  cases  examined,  prevalence  being  little  different  on  the 
normal  and  on  the  diseased  scalps.  From  these  scrapings  they  also 
cultured  species  of  molds  belonging  to  Aspergillus,  Rhizopus,  Al- 
ternaria,  Chaetomium,  Torula,  Dematium,  and  Mycoderma,  and 
in  addition  several  species  of  Staphylococcus.  MacKee  and  his 
associates  conclude:  'The  occurrence  at  times  of  the  organism 
[P.  ovale]  on  all  types  of  scalps  and  the  fact  that  it  may  occa- 
sionally be  found  in  as  large  numbers  on  the  normal  scalp  as  on  one 
with  severe  dandruff  leads  one  to  consider  the  possibility  that  this 
yeast  is  a  saprophyte,  and  grows  well  in  the  presence  of  scaling 
or  in  sebaceous  material  but  is  not  responsible  for  the  presence 
of  these  findings." 

D 

ACTINOMYCES  BOVIS 

Bacteriologists  and  mycologists  are  not  in  accord  on  the  sys- 
tematic  position  of  Actinomyces,  bacteriologists  regarding  it  as 
among  the  Schizomvcetes,  and  mycologists  including  it  among 
the  Hvphomycetes.  Actinomyces  is  a  large  genus  and  includes 
not  only  many  species  that  are  pathogenic  to  man  and  other  ani- 
mals, but  also  a  few  plant  pathogens  and  many  species  that  are 
normal  inhabitants  of  the  soil. 

The  mycelium  of  Actinomyces  consists  of  very  slender, 
branched  hyphae,  commonly  about  1  [x  in  diameter.  More  or  less 
specialized  branches  become  sporogenous  and  by  segmentation 


314 


MEDICAL  MYCOLOGY 


form  chains  of  spores.  These  sporogenous  hyphae  are  coiled,  the 
rotation  of  the  helix  and  the  type  of  coiling  being  characteristic 
of  the  species. 

The  best  known  of  the  species  pathogenic  to  man  is  Actino- 
myces bovis,  described  by  Harz  (1879)  in  1879.  It  causes  a 
chronic  disease  known  to  the  medical  profession  as  actinomycosis 
and    characterized    by    the    formation    of    suppurative    tumors. 


Fig.  69.  Actinomyces  bovis.  A.  Filamentous  appearance  of  colony  in  cul- 
ture. B.  The  hyphae  from  culture  when  smeared  on  microscopic  slide 
fragment  to  become  bacteria-like.  C.  "Sulphur  granule"  taken  from  abscess 
and  stained  to  show  peripheral  clubs.    D.  View  of  clubs  with  magnification 

slightly  increased  over  that  in  C. 

Farmers  and  cattlemen  are  more  commonly  afflicted  than  are 
persons  in  other  occupations.  The  disease  involves  not  only  man 
but  also  such  other  animals  as  horses,  cows,  sheep,  and  pigs,  as 
well  as  many  species  of  wild  animals.  In  cattle  the  disease  is  called 
"lumpy  jaw,"  "wooden  tongue,"  or  "sarcoma  of  the  jaw."  In 
man  A.  bovis  may  involve  any  part  of  the  body  but  is  most  com- 
mon on  the  head  and  neck.  About  60°  0  of  all  cases  are  cervico- 
facial, 14  are  thoracic,  and  8  to  18°o  involve  the  abdominal 
organs. 

Many  cervico-facial  cases  arise  from  dental  defects  or  after 
the  extraction  of  teeth.  Studies  by  Emmons  (1935)  show  that  in 
a  high  percentage  of  instances  the  causal  fungus  can  be  isolated 
from  the  normal  mouth,  carious  teeth,  tonsillar  crvpts,  or  drain- 


SPOROTRICHUM  SCHENCKII  315 

ing  sinuses.  He  found  it  in  47%  of  extirpated  tonsils  in  Puerto 
Rico. 

Meningitis  and  endocarditis  are  amon<?  the  occasional  manifes- 
tations  of  actinomycosis.  In  generalized  actinomycosis  evidence 
indicates  that  the  pathogen  is  spread  through  the  blood  stream. 

Emmons  (1935)  has  shown  that  some  of  the  confusion  regard- 
ing the  causal  fungus  has  arisen  because  it  is  a  microaerophilic 
species  and  must  not  be  confused  with  aerobic  contaminants.  It 
appears  to  be  widespread  on  vegetation,  so  that  it  is  inadvisable 
to  chew  straws,  sticks,  weeds,  or  plant  stems.  Slight  wounds  ap- 
pear to  serve  as  portals  of  entry  for  the  fungus  into  the  tissues. 
Further  confusion  in  etiology  arises  because  the  aerobic  species, 
Actinomyces  hominis,  is  primary  in  approximately  10%  of  Actino- 
myces cases. 

Such  generic  names  as  Nocardia,  Streptothrix,  Oospora,  and 
Discomyces  have  been  applied  to  this  fungus.  Some  workers  pre- 
fer to  use  for  it  the  name  Actinomyces  Israeli.  An  extensive  bibli- 
ography on  actinomycosis  exists.  In  a  publication  by  Musgrave 
and  his  associates  (1908)  that  appeared  in  1908  more  than  1500 
titles  of  papers  on  this  disease  are  assembled. 

In  the  diagnosis  of  actinomycosis  the  presence  of  granulation 
tissue  and  of  pus-containing  "sulphur  granules"  should  be  sought. 
These  granules  are  composed  of  radially  arranged  hyphae,  which 
are  terminated  peripherally  by  eosin-staining  clubs,  the  clubs  be- 
ing sheathed  hyphal  tips.  Emmons  (1935)  states  that  these  clubs 
are  not  formed  within  tonsillar  tissues.  Observations  by  Lentze 
(1938),  involving  55  cases  of  true  actinomycosis,  showed  that 
granules  can  be  demonstrated  in  80%  of  the  cases.  He  placed 
the  pus  in  a  drop  of  methylene  blue  and  noted  that  the  leucocytes 
which  take  the  methylene  blue  invest  a  cauliflower-shaped  mesh- 
work  of  threads  whose  periphery  consists  of  bluish-green  clubs. 

SPOROTRICHUM  SCHENCKII 

A  comprehensive  account  of  the  Genus  Sporotrichum  and  the 
clinical  aspects  of  diseases  it  induces  are  contained  in  the  mono- 
graphic treatise  by  Beurmann  and  Gougerot  (1912).  One  species, 
.S.  schenckii,  first  described  by  Schenck  in  the  United  States  in 
1898  [Emmons  (1940)]  is  definitely  pathogenic  to  man.  Certain 
other  species,  including  5.  beiirmanni  and  5.  equi,  are  believed  to 


316 


MEDICAL  MYCOLOGY 


be  specifically  identical  with  5.  schenckii.  This  organism  com- 
monly enters  through  some  minor  injury,  such  as  a  barberry,  rose, 
or  bramble  puncture.  Evidence  also  points  to  inoculation  from 
splinters  or  into  abrasions  incurred  in  the  work  of  clearing  land. 
An  ulcerative  lesion  that  fails  to  heal  develops.  Gradually  subcu- 
taneous abscesses  form  that  spread  along  the  lymphatics,  dissemi- 
nation apparently  being  hematogenous.    Once  the  disease  becomes 


Fig.  70.  Sporotrichum  schenckii.  (Adapted  from  Moore.)  A.  Germinat- 
ing spores.  B.  Yeast-like  spores.  C.  Aleurospores  laterally  formed  in  cul- 
ture. D.  Terminally  formed  spores  that  may  become  chlamydospore-like. 
E.   Both   intercalary   and   terminal   chlamydospores   may   form   in   culture. 

F.  Conidia  formed  abundantly. 

systemic,  various  organs,  muscles,  bones,  lungs,  joints,  and  other 
tissues,  including  the  brain  and  viscera,  become  involved. 

Sporotrichosis  may  occur  spontaneously  in  horses,  dogs,  cats 
and  rabbits.  Attention  was  called  by  du  Toit  (1942)  to  the  occur- 
rence of  5.  beitrmanni  on  wood,  mud,  and  other  materials  in  a 
mine  in  the  Transvaal,  where  an  outbreak  of  sporotrichosis  in- 
volved 650  among  2500  native  miners.  The  organism  was  intro- 
duced by  a  worker.  Sterilized  wood  and  mud  constituted  good 
substrata  for  the  cultivation  of  S.  beurmanni. 

On  agar  the  fungus  forms  white  colonies  that  may  become 
brownish  with  age.  Temperatures  within  the  range  30°  to  38°  C 
are  optimum.  The  hyphae  are  much  branched,  and  chlamydo- 
spores appear  on  media  poor  in  nutrients.    Conidiophores  are  not 


MON1LIA   (CANDIDA)  SPP.  311 

differentiated,  but  profuse  clusters  of  ovoid  hyaline  conidia  arise 
laterally  or  terminally  on  short  branches. 

Beurmann  and  Gougerot  isolated  from  various  plants  species 
of  Sporotrichum  that  they  believed  were  pathogenic.  Further 
evidence  in  support  of  its  occurrence  on  vegetation  is  supplied 
by  Benham  and  Kesten  (1932).  They  inoculated  carnation  buds 
with  S.  schenckii,  and  a  bud  rot  resembling  the  well-known  bud- 
rot  disease  caused  by  S.  poae  developed.  When  reisolated,  it  was 
still  virulent  for  man.  These  experiments  are  especially  note- 
worthy, because  they  constitute  the  first  successful  transmission 
of  a  human  disease  to  a  plant. 

This  fungus  is  among  the  few  that  produce  specific  agglutinins 
when  spores  are  used  as  antigens.  Spores  may  be  agglutinated  in 
high  dilutions,  indicating  strong  antigenic  properties. 

MONILIA  (CANDIDA)  SPP. 

Within  the  Genus  Monilia,  as  used  in  a  medical  sense,  are  in- 
cluded those  fungi  having  sparse  mycelial  development  and  repro- 
ducing by  budding  to  form  white,  smooth  colonies  on  as^ar.  The 
numerous  species  in  this  genus  rather  readily  dissociate  into  rou^h 
and  smooth  colonies  on  artificial  media;  they  vary  in  virulence. 
Some  of  them  are  filamentous  at  room  temperature  but  veast- 
like  at  body  temperature,  and  others  are  filamentous  on  ordinary 
agars  and  yeast-like  on  blood  agar.  They  are  entirely  distinct 
from  Monilia  as  used  by  the  plant  pathologist  to  designate  conidial 
stages  of  Sclerotinia.  Dodge  (1935)  places  them  in  the  Eremas- 
caceae  Imperfectae. 

.Manifestly  a  number  of  generic  types  are  represented  anions; 
the  medical  Monilias,  and  accord  has  not  been  reached  on  their 
proper  binomials.  These  taxonomic  problems  are  set  forth  clearly 
in  a  recent  report  by  Conant  (1940);  it  is  apparent  that  for  final 
agreement  action  by  the  International  Botanical  Congress  will  be 
necessary.  Amon^  those  who  have  studied  the  classification  of 
this  group  are  Benham  (1931),  Langeron  and  Talice  (1932), 
Shrewsbury  (1934),  Lamb  and  Lamb  (1935),  Dodge  (1935), 
Martin  and  his  associates  (1937),  and  Langeron  and  Guerra 
(1938).  The  generic  name  Candida  seems  to  be  the  preferred 
one  for  medical  species  of  Monilia. 


318 


MEDICAL  MYCOLOGY 


Morphologic  bases  for  separating  species  seem  to  be  inadequate, 
since  clinically  similar  cases  in  the  hands  of  a  single  investigator 
have  vielded  organisms  that  have  been  placed  in  as  many  as  a 
half-dozen  different  species.  This  fact  induced  Benham  (1931) 
to  supplement  morphologic  differences  with  variations  in  fermen- 
tative ability  and  serologic  characteristics.  Lamb  and  Lamb 
(1935)  used  fermentation  and  precipitation  reactions  in  specific 


Fig.  71.     A.  Hvphal  elements  and  budding  spores  of  Candida  albicans.    B. 

Malassezia  oralis,  showing  thin-walled   and   thick-walled  spores.     Growth 

usually  results  in  buds,  but  short  hyphae  may  be  formed. 

separation.  Martin  and  his  associates  (1937)  employed  differ- 
ences in  growth  habits  on  blood  agar,  corn-meal  agar,  and  Sabou- 
raud's  agar,  together  with  fermentation  reactions,  in  their  identifi- 
cation of  species.  All  students  of  the  group  clearly  recognize 
the  inherent  variability  and  dissociative  potentialities  of  Monilia. 

Two  species  of  Monilia  are  singled  out  from  this  aggregate  as 
being  of  most  interest.  These  include  M.  albicans  (Candida  tropi- 
calis)  and  M.  psilosis  (Syringospora  albicans  and  S.  psilosis,  re- 
spectively, according  to  Dodge). 

Monilia  albicans  is  best  known  in  connection  with  thrush,  a  dis- 
ease of  the  throat  and  mouth  of  children;  rarely  it  occurs  also  in 
old  or  debilitated  persons.  In  addition  it  is  of  importance  as  an 
etiolouic  accent  in  pulmonary  moniliasis  and  may  also  attack  the 
nails,  producing  chronic  paronychia,  may  involve  the  mucous 
membranes  of  the  genitalia,  or  may  cause  skin  lesions  on  the  palmar 


THE  TRICHOPHYTON EAE  319 

and  interdigital  surfaces.  It  may  establish  secondary  infection  in 
pulmonary  tuberculosis  and  has  been  recorded  to  be  present  in 
the  mouths  of  normal,  healthy  persons  in  the  proportion  of  3  to 
24%. 

Monilia  psilosis  is  associated  with  sprue,  a  disease  primarily  of 
the  tropics,  which  involves  the  intestinal  tract.  Prolonged  diar- 
rhoea and  anemia  are  the  most  outstanding  symptoms.  Change  of 
climate  and  vitamin  deficiency  have  also  been  assigned  etiologic 
roles  in  sprue,  and  M.  psilosis  is  now  generally  believed  to  be  a 
secondary  cause  of  the  disease. 

ASPERGILLUS  FUM1GATUS 

Species  of  Aspergillus  are  predominantly  saprophytes,  but 
Dodge  (1935)  has  assembled  published  reports  showing  that  ap- 
proximately 30  species  may  at  times  be  pathogenic.  Aspergillus 
jumigatiis  is  among  those  that  are  regularly  pathogenic.  It  attacks 
man,  particularly  in  humid  regions,  most  commonly  producing 
symptoms  that  clinically  resemble  those  of  pulmonary  tubercu- 
losis. If  the  sputum  is  examined,  conidia  will  be  found,  but  no 
trace  of  Mycobacterium  tuberculosis.  Neither  are  tubercles 
formed  in  the  lungs,  and  upon  treatment  with  potassium  iodide  the 
lung  involvement  usually  clears  promptly. 

Aspergillosis  may  be  regarded  as  an  occupational  disease  for  the 
reason  that  it  is  most  prevalent  among  those  who  work  with  abra- 
sives, force-feed  fowls,  or  prepare  furs  or  feathers  for  use  as  wear- 
ing apparel.  The  same  species  involves  the  lungs  of  birds,  espe- 
cially quails  and  grouse,  and  may  cause  severe  epizootics  among 
them. 

Some  of  the  other  pathogenic  species  quite  regularly  involve  the 
auditory  passages  or  the  nails  or  are  associated  with  abscesses 
or  asthma. 

THE  TRICHOPHYTONEAE  OR  RINGWORM  FUNGI 

The  Trichophytoneae  constitute  a  group  of  100  to  200  species 
of  Fungi  Imperfecti  that  parasitize  man  and  various  animals  by 
invading  the  keratinized  layers  of  the  skin  and  its  modifications, 
such  as  hair,  nails,  feathers,  hooves,  and  horns.  The  resulting 
dermatomycoses  are  commonly  known  as  ringworm,  tinea,  dhobie 


380  MEDICAL  MYCOLOGY 

itch,  barber's  itch,  athlete's  foot,  herpes,  favus,  or  kerion.  Nearly- 
all  these  fungi  grow  readily  on  any  common  culture  medium,  but 
most  laboratories  employ  the  standard  media  of  Sabouraud  to  cul- 
tivate them.  On  his  "proof  medium,"  containing-  sugars,  growth 
is  especially  luxuriant,  and  the  various  species  exhibit  their  char- 
acteristic cultural  aspects.  On  his  "preserving  medium,"  high  in 
peptone  and  lacking  sugars,  growth  is  less  rapid  in  most  species, 
and  pleomorphic  changes  are  inhibited. 

There  is  nothing  about  their  mycelium  to  enable  the  worker  to 
differentiate  the  Trichophytoneae  from  many  fungi  commonly 
encountered  in  the  laboratory.  Various  hvphal  structures  and 
various  types  of  spores  which  develop  in  culture  are  employed, 
however,  to  identify  and  classify  the  numerous  species.  They 
may  be  briefly  described,  without  reference  to  any  particular 
genus  or  species,  as  follows: 

a.  Racket-shaped  hyphae.  Sabouraud  applied  the  term 
"raquette  cells"  to  hyphae  each  of  whose  cells  is  of  considerablv 
greater  diameter  at  one  end  than  at  the  other.  When  these  hyphae 
occur  in  series,  they  have  somewhat  the  appearance  of  tennis 
rackets  placed  end  to  end. 

b.  Terminal  clubs.     When  the  apices  of  hyphae  were  vari- ' 
ously  enlarged,  they  were  called  "terminal  clubs"  by  Sabouraud. 

c.  Pectinate  hyphae.  Hyphae  bearing  short,  denticulate  pro- 
jections along  one  side  are  called  "pectinate  hyphae."  Usually  this 
portion  of  the  hypha  is  curved,  and  the  projections  form  on  the 
convex  surface.  If  the  projections  appear  as  short  hyphae,  they 
are  termed  "nodular  organs." 

d.  Spiral  hyphae.  In  certain  species  the  terminal  hyphae  are 
coiled  into  a  rather  tight  spiral,  making  up  the  so-called  "spiral 
hyphae."  These  structures  are  regarded  by  some  workers  as  com- 
parable with  the  hvphal  ornamentations  on  the  peridia  of  certain 
(A  mnoascaceae  and  as  an  indication  of  relationship  with  this 
family. 

e.  Arthrospores.  In  the  parasitic  stage  the  terminal  hyphae 
become  closely  segmented,  and  the  segments  round  up  and  be- 
come separate  cells.  These  are  the  arthrospores,  which  constitute 
the  sole  means  of  reproduction  in  nature,  if  the  possible  existence 
of  an  ascal  stage  is  disregarded. 

f.  Chlamydospores.  If  chlamydospores  are  classified  on  the 
basis  of  their  point  of  origin,  there  are  three  types,  terminal, 


THE  TRICHOPHYTONEAE 


381 


Fig.  72.  Types  of  reproductive  cells  produced  by  Dermatophytes.  A-F 
apply  to  Microsporum;  G,  to  Epidermophyton;  H-O,  to  Trichophyton; 
PS,  to  Achorion.  A.  Racket  cells  of  Microsporum.  B.  Aleurospores.  C. 
Pectinate  hypha.  D.  Macroconidia^or  fuseaux.  E.  Nodular  organ.  F. 
Spiral  hypha.  G.  Epidermophyton  macroconidia.  H.  Aleurospores  budding 
from  hvphae  of  Trichophyton  in  culture.  /.  Intercalary  chlamydospores. 
/.  Arthrospores.  K.  Pectinate  hypha.  L.  Spiral  hypha.  M.  Pedicellate 
chlamydospores.  N.  Racket  cells  in  series.  O.  Fuseaux  or  macrospores. 
P.  Aleurospores   of  Achorion.     Q.  Chlamydospores.     R  and  S.  Pectinate 

hypha. 


382 


MEDICAL  MYCOLOGY 


lateral,  and  intercalary.  When  the  chlamydospores  are  large  and 
spindle-shaped,  thev  are  known  as  fuseaux,  according  to  the  ter- 
minology of  Sabouraud.     Fuseaux  may  be  borne  terminally  or 

laterally;  they  occur  singly. 
Thev  may  be  smooth,  or  the 
entire  surface  or  a  portion  of  it 
may  be  covered  with  projec- 
tions. They  may  consist  of  one 
cell  or  be  septate.  In  some  in- 
stances lateral  chlamydospores 
are  borne  on  a  pedicel  and 
hence  are  called  "pedicellate 
chlamydospores."  This  type  of 
chlamydospore  may  be  sepa- 
rate from  the  parent  hypha  or 
may  lack  a  septation. 

g.  Aleuries  or  aleuro- 
spores.  Spores  that  develop  by 
migration  of  protoplasts  from 
the  hyphal  cell  into  the  devel- 
oping spores,  leaving  the  hy- 
phal cell  empty,  are  known  as 
aleuries  or  aleurospores.  They 
may  not  be  abstricted  and  may 
remain  attached,  or  a  septum 
may  be  laid  down.  The  hy- 
phae  that  bear  aleuries  may  be 
simple  or  copiously  branched. 
The  aleuries  of  copiously 
branched  hyphae  may  adhere 
in  grape-like  bunches. 

Classification.  The  clas- 
sification of  the  members  of 
this  group  is  a  difficult  task,  and  considerable  disagreement  exists 
concerning  what  characteristics  constitute  an  adequate  basis  for 
distinguishing  genera  and  species.  Clinical  aspects  of  the  disease 
complex  have  been  given  precedence  by  some  workers,  purely 
mycological  features  by  others,  cultural  characters  by  others, 
and  host  relations  by  others.  This  situation  may  be  illustrated 
bv  the  delimitation  of  the  Genus  Achorion  to  include  fungi  which 


W ) 


/°#t°o 


>. 


•K 


Fig.  73.  Diagrams  illustrating  the  re- 
lationship of  the  fungi  to  hairs  in: 
A.  Microsporum.  B.  Endothrix  Tri- 
chophyton. C.  Ectothrix  Tricho- 
phyton. Spores  arise  at  or  near  the 
opening  of  the  hair  follicle.  (After 
Henrici.) 


THE  TR1CHOPHYTONEAE  383 

cause  favus,  whereas  it  is  known  that  this  disease  may  be  caused 
by  some  species  of  Trichophytum  (Trichophyton)  and  Micro- 
sporum  (Microsporon)  as  well.  Again  Microsporum  is  under- 
stood to  include  those  species  which  produce  a  sheath  of  closely 
aggregated  tiny  spores,  never  in  chains,  around  the  basal  part  of 
the  hair.  In  Trichophyton,  on  the  other  hand,  the  infecting 
hyphae  are  intrapilar  and  become  closely  segmented,  appearing 
as  chains  of  spores.  The  spores,  however,  arise  in  chains  from  a 
circumpilar  sheath.  In  some  species  the  circumpilar  portion  dis- 
appears; these  were  regarded  by  Sabouraud  as  "endothrix."  In 
others  the  circumpilar  sheath  is  the  most  prominent  feature; 
hence  these  species  are  termed  "ectothrix."  The  transition  group 
between  these  two  constitute  Sabouraud's  "neoendothrix"  species. 

Species  of  Epidermophyton  and  Endodermophyton  are  under- 
stood to  be  limited  to  the  glabrous  skin.  The  only  kind  of  spores 
formed  in  culture  by  Epidermophyton  are  separate  fuseaux;  by 
Endodermophyton,  arthrospores. 

Several  systems  of  classification  have  been  proposed,  including 
those  by  Sabouraud  (1910)  and  its  modifications  (1929),  by  Ota 
and  Langeron  (1923),  by  Langeron  (1926),  by  Grigoraki  (1925, 
1929),  by  Langeron  and  Milochevitch  (1930),  and  by  Dodge 
(1935).  The  system  of  Sabouraud  is  fundamental  and  is  in  general 
usage  among  students  of  this  group,  since  it  has  the  merit  of  being 
workable.  A  comparison  of  his  larger  groupings  with  those  em- 
ployed by  Dodge  is  shown  in  Table  28. 

Emmons  (1934)  found  by  a  study  of  representative  members  of 
this  group  that  botanical  characteristics  exist  as  means  for  classify- 
ing them  and  that  such  characteristics  should  replace  clinical  ones. 
He  employed  shape,  size,  and  method  of  formation  of  conidia  to 
separate  Trichophyton,  Microsporum,  and  Epidermophyton. 
Trichophyton  possesses  clavate  conidia  that  are  thin-walled  and 
have  few  septations;  Epidermophyton,  conidia  that  are  clavate  to 
ovate  and  are  thick- walled  with  few  septations;  and  Microsporum, 
conidia  that  are  spindle-shaped,  thick-walled,  and  frequently  sep- 
tate. Emmons  regarded  spirals,  chlamydospores,  and  nodular 
organs  as  of  little  value  in  classification. 

In  separating  species  Dodge  (1935)  based  his  key  largely  on  cul- 
tural characteristics  of  giant  colonies.  This  means  of  identifica- 
tion becomes  increasingly  useful  as  the  student  gains  experience 


384 


MEDICAL  MYCOLOGY 


TABLE  28 

Classification 

of  Trichophyton eae, 

as  Used  by  Sabouraud 

and  by  Dodge 

Sabouraud's 

Dodge's 

Type 

Classification 

Classification 

Synonyms 

Species 

Trichophyton 

Trichophyton 

T.  tonsurans 

Endothrix 

Endothrix 

Malstenia 

T.  tonsurans 

Sabouraudia 

T.  sabouraudia 

Neoendothrix 

Neoendothrix 

Neotrichophyton  Cast. 

Ectothrix 

Ectotrichophton  Cast. 

Megaspores 

Megatrichophyton 

Enutotrichophyton 

M .  roseum 

Faviformes 

Favotrichophyton 

Eufavotrichophyton 

Grubyella  (pro  parte) 

F.  ochraceum 

Bodinia 

Bodinia  Ota  et  Lang. 

F.  violaceum 

Microides 

Ectotrichophyton 

E.  mentagrophxtes 

gypseums 

Spiralia  Grig. 

E.  mentagrophytes 

niveums 

Microtrichphyton  N. 

E.  felinum 

Microsporum 

Microsporum 

Sabouraudites  Ota  et  Lang. 

Neomicrosporum 

Neomicrosporum 

Eumicrosporum 

Eumicrosporum 

Achorion 

Achorion 

Grubyella  Ota  et  Lang. 

Neoachorion 

Lophophyton 

Euachorion 

Euachorion 

Epidermophyton 

Epidermophyton 

E.  floccosum 

Endodermophyton 

E.  concentricum 

with  cultures  and  becomes  more  and  more  familiar  with  them  in 
the  laboratory  routine. 

Studies  of  the  type  conducted  by  Conant  (1936,  1936a,  and 
1937),  in  which  the  investigator  has  at  his  disposal  a  large  number 
of  species  and  strains,  offers  the  best  means  of  solving  the  confus- 
ing taxonomic  problems  of  the  Trichophytoneae.  Conant  made 
biometric  studies  but  may  not  have  had  a  sufficient  number  of 
strains  of  each  species  to  become  familiar  with  the  extremes  of 
variation  within  a  given  species.  In  criticizing  these  studies,  Em- 
mons (1940)  pointed  out  that,  if  Conant  had  examined  more 
strains  of  Micros porinn  fulvum  and  M.  gypseum,  he  probably 
would  have  regarded  them  as  specifically  identical.  At  any  rate 
it  must  be  emphasized  that  the  inherent  tendency  of  all  species  to 
vary  must  never  be  lost  sight  of  by  students  of  this  group  nor  of 
any  other  group  of  fungi. 

The  difficulties  attendant  on  making  specific  identification  by 
clinical  aspects  are  illustrated  by  the  experiments  of  Dowding  and 
Orr  (1937).  They  isolated  Trichophyton  gypsevm  from  three 
clinically  distinct  diseases,  namely  kerion,  tinea  circinata,  and  vesi- 
cular lesions  on  feet. 


THE  TRICHOPHYTONEAE  385 

Another  technique  for  identification  arises  from  the  work  of 
Davidson,  Dowding,  and  Buller  (1932).  They  observed  that  hy- 
phal  fusions  or  anastomoses  occur  between  hvphae  of  the  same 
mycelium  or  between  mvcelia  of  different  origin  but  of  the  same 
species,  and  that  no  hyphal  fusions  form  between  mvcelia  of  dif- 
ferent species.  If,  then,  the  investigator  has  stock  cultures  whose 
identity  is  known,  it  becomes  possible  by  suitable  pairings  to  estab- 
lish the  identity  of  unknown  isolates.  In  their  studies  Davidson, 
Dowding,  and  Buller  employed  Micros porinn  audoiiini,  M.  lano- 
sinn,  and  Trichophytum  gypsenm. 

Relationship  of  ringworm  fungi  with  other  fungi.  Evi- 
dence has  been  presented  to  show  that  the  ringworm  fungi  are 
conidial  forms  of  Gymnoascaceae  and  that  they  have  lost  their 
ability  to  produce  asci.  Some  of  this  evidence  includes  the  fact 
that  Ctenomyces  servants,  growing  naturally  on  feathers,  possesses 
as  peridial  ornaments  spiral  hyphae  that  are  like  those  of  certain 
species  of  small-spored  Trichophyton,  and  that  it  forms  aleuro- 
spores  and  spindles  in  culture.  Nannizzi  (1926)  is  among  those 
who  would  classify  the  ringworm  fungi  with  the  Gymnoascaceae. 
He  maintained  that  they  should  be  grown  on  hair,  feathers,  horn, 
or  skin  and  that  the  morphologic  structures  developed  on  syn- 
thetic media  are  all  abnormalities.  When  he  cultivated  Achorion 
gypsenm  on  these  animal  decidua,  he  reported  the  development 
of  asci  and  ascospores  like  those  of  Gymnoascus.  Tate  (1929) 
was  unable,  however,  to  confirm  Nannizzi's  findings;  moreover 
they  remain  without  confirmation  for  other  species,  and  hence  it 
must  be  concluded  that  all  these  problems  of  relationships  require 
further  study. 

Pleomorphism.  The  phenomena  of  production  of  physiologi- 
cal species  by  fungi  and  of  sectoring,  saltation,  and  mutation  were 
discussed  in  Chapter  7.  The  term  pleomorphism  is  not  to  be  asso- 
ciated with  these  phenomena;  it  applies  to  a  peculiar  and  confus- 
ing change  that  is  especially  prevalent  among  ringworm  fungi. 
When  these  fungi  are  grown  on  sugar-containing  media  and  have 
reached  their  maximum  development,  which  is  usually  attained 
after  4  to  6  weeks,  white,  downy  tufts  suddenly  appear  on  the 
surface  of  the  mature  colonies,  suggesting  the  presence  of  a  sur- 
face contaminant.  These  tufts  grow  rapidly,  enveloping  the 
whole  surface  and  spreading  beyond  the  margin  of  the  primary 
colony,  until  a  mantle  of  pure  white,  downy  mycelium  envelops 


386  MEDICAL  MYCOLOGY 

the  entire  surface.  If  a  fragment  of  this  pleomorphic  mycelium 
is  planted  on  a  fresh  medium,  the  cultures  obtained  are  like  the 
pleomorphic  mycelium,  and  these  characteristics  are  retained  on 
subsequent  repeated  transfer.  Pleomorphic  forms  do  not  revert 
to  the  normal  once  they  have  been  isolated. 

The  most  striking  feature  of  these  pleomorphic  colonies  is  that 
the  majority  of  them  remain  completely  sterile,  whereas  other 
species  may  form  chlamydospores  or  may  bear  small,  little  differ- 
entiated, lateral  spores.  For  this  reason  pleomorphic  forms  of  the 
different  species  are  very  similar  to  each  other,  and  identification 
has  been  difficult  and  very  confusing.  Many  are  so  similar,  in 
fact,  that  some  workers  question  the  plurality  of  species  among 
ringworm  fungi. 

Variation  in  this  tendency  to  produce  pleomorphic  forms  exists 
among  these  fungi.  Pleomorphism  is  common  among  small- 
spored,  animal-infecting  species  of  Trichophyton  and  among  spe- 
cies of  Microsporon  from  animals  but  is  rare  or  non-existent 
among  species  of  Trichophyton  attacking  man.  Tate  (1929) 
states  that  it  is  not  known  to  occur  in  Microsporon  aiidoidni  or  in 
Trichophyton  radians  and  T.  denticulatum. 

According  to  Sabouraud,  nutritional  and  temperature  factors 
most  favorable  for  growth  are  also  most  favorable  for  the  develop- 
ment of  pleomorphic  forms.  The  presence  of  about  4%  of  carbo- 
hydrates in  the  medium  and  constant  temperatures  of  30°  to  37°  C 
induced  pleomorphic  changes,  whereas  media  with  3%  of  peptone 
and  no  carbohydrates  tended  to  prevent  pleomorphic  develop- 
ment. 

When  Langeron  and  Milochevitch  (1930)  grew  Sab  our  audit  es 
asteroides  ( the  generic  termination  ites  should  be  limited  to  genera 
of  fossils),  S.  granulosus,  S.  lacticolor,  and  S.  gypseus,  all  of  which 
are  pleomorphic  on  sugars,  on  cereals,  straw,  dung,  or  synthetic 
media  enriched  with  dextrin  or  soluble  starch,  pleomorphic  forms 
did  not  appear.  They  concluded  that  monosaccharides  and  disac- 
charides  are  toxic  and  that  these  sugars  induce  pleomorphic 
change,  whereas  polysaccharides  and  the  colloidal  complexes  of 
the  natural  substrata  are  not  toxic  and  may  be  used  without  first 
being  cleaved. 

Emmons  (1932)  cultured  Achorion  gypseuni  on  horn,  starting 
with  a  single  aleurospore.  Six  distinct  pleomorphic  variants  arose 
from  the  progeny,  and  all  were  so  different  that,  if  they  had  been 


THE  TR1CHOPHYTONEAE  381 

isolated  from  lesions  on  patients,  they  might  have  been  regarded 
as  distinct  species.  When  subcultures  were  isolated,  using  aleuro- 
spores  or  fuseaux  from  these  variants,  each  produced  a  culture 
like  those  from  the  particular  variant  from  which  it  originated. 
Furthermore  none  of  the  variants  reverted  to  the  parent  form. 
Three  different  kinds  of  pleomorphic  forms  are  also  known  for 
Micro sporum  lanosum,  and  all  are  reversible  to  each  other  but 
not  to  the  primary  form.  The  three  include  a  coarse,  shaggy, 
downy  form  (the  most  common  one),  a  white,  downy  form,  and 
an  immersed,  glabrous,  brown  form. 

The  most  remarkable  feature  of  pleomorphism  is  exhibited  by 
the  results  of  animal  inoculations.  When  used  as  inoculum,  the 
pleomorphic  forms  produce  lesions  that  are  indistinguishable  from 
those  arising  from  inoculum  with  the  primary  or  normal  form. 
When  the  fungus  is  reisolated  from  the  infected  hairs  or  scales,  it 
invariably  grows  like  the  pleomorphic  form.  Langeron  and  Talice 
(1930)  used  the  pleomorphic  form  of  Sabonraudites  felinus  as 
inoculum,  obtained  a  typical  lesion  on  guinea  pig,  and  were  able 
to  reisolate  only  pleomorphic  mycelium.  In  its  normal  parasitic 
phase  this  fungus  consists  of  an  ectothrix  sheath  of  spores  sur- 
rounding the  infected  hair  and  of  hyphae  internal  to  the  hair.  In 
the  pleomorphic  form  the  ectothrix  sheath  was  without  spores. 
If  the  pleomorphic  culture  used  as  inoculum  is  completely  pleo- 
morphic and  quite  sterile,  the  cultures  reisolated  from  scales  and 
hairs  are  likewise  quite  sterile. 

Mycides.  In  1912  Jadassohn  made  the  interesting  observation 
that  primary  localized  infections  (mycoses)  by  species  of  Tricho- 
phytoneae  may  be  accompanied  by  secondary  lesions  (mycides) 
on  distant  parts  of  the  body  in  which  no  fungus  can  be  found. 
These  mycides  have  come  to  be  designated  as  trichophytides,  epi- 
dermophytides,  microsporides,  etc.,  depending  upon  the  genus 
responsible  for  the  primary  lesions.  Jadassohn  [Gregory  (1935)] 
explained  this  phenomenon  as  an  allergic  reaction,  since  he  found 
that  secondary  lesions  could  be  produced  by  rubbing  the  spores 
into  the  skin  of  other  children.  This  external  origin  of  mycides, 
however,  has  not  been  substantiated  in  subsequent  investigations. 
Instead  they  have  been  determined  to  arise  from  spores  or  toxic 
products  of  the  pathogen  liberated  in  the  primary  lesions  and  dis- 
seminated by  the  blood  stream.  The  reaction  appears,  therefore, 
to  result  from  hypersensitivity  to  the  fungus  protein.     Evidence 


388  MEDICAL  MYCOLOGY 

in  support  of  internal  origin  comes  from  the  symmetrical  distribu- 
tion of  rashes  or  eruptions  (the  uid"  lesions)  on  the  body  surface 
and  from  the  isolation  of  spores  from  the  circulating  blood.  Greg- 
ory (1935)  summarized  the  findings  of  various  workers  regarding 
the  isolation  of  fungi  from  the  blood.  He  noted  that  among  the 
fungi  isolated  are  Trichophyton  inter  digit  ale,  T.  granulosum,  T. 
gypseinn,  T.  cerebrifonne,  A  chorion  schoerleini,  A.  qiiinckeanuni, 
and  Microsporia!!  audouini. 

Wise  and  Wolf  (1936)  pointed  out  that  the  vesicular  eruptions 
on  the  hands  of  patients  with  primary  mycotic  infections  on  the 
feet  may  not  necessarily  be  ids.  In  their  opinion,  however,  such 
eruptions,  except  in  persons  with  occupational  eczema  or  eczema 
of  unknown  cause  nearly  always  occur  coincidentally  with  in- 
fection of  the  feet. 

Species  other  than  Trichophytoneae  may  evoke  the  formation 
of  ids,  as  Monilia  |  Hopkins  ( 1932)  ]  and  Sporotrichum  are  known 
to  do.  Evidence  presented  by  Hopkins  shows  that  Monilia  in  the 
alimentary  tract  may  produce  substances  which  induce  skin  lesions 
in  the  sensitized  person. 

Some  persons  possess  a  related  allergy  to  such  common  fungi 
as  Cladosporium,  Penicillium,  and  Aspergillus,  present  in  house- 
hold dust  or  in  clothing.  Consideration  of  this  subject  is  outside 
the  province  of  this  book;  the  student  may  introduce  himself  to 
this  problem  by  consulting  the  report  by  Rackemann,  Randolph, 
and  Guba  (1937-38).  They  found  that  the  tomato-mold  fundus, 
Cladosporhnn  fulvum,  may  irritate  the  nasal  mucosa  and  eyes, 
producing  asthma. 

Ids  may  also  appear  on  sensitized  animals.  De  Lamater  and  Ben- 
ham  (1938)  inoculated  Trichophyton  gypseinn  through  the  skin 
and  into  the  blood  stream  of  guinea  pigs,  whereupon  widely  dis- 
seminated fungus-free  lesions  developed. 

Fluorescence.  Margarot  and  Devese  (1924-25)  made  the  in- 
teresting observation  that  the  affected  hairs  of  patients  with  Alicro- 
sporum  ringworm  or  with  favus  and  also  cultures  of  the  causal 
fungi  exhibit  a  greenish  fluorescence  if  examined  with  ultraviolet 
light  filtered  through  Wood's  nickel  oxide  glass.  This  discovery 
has  proved  a  useful  tool  in  diagnosis.  Others  have  confirmed  and 
extended  these  observations  and  have  sought  an  explanation  of  the 
source  of  these  fluorescent  properties.  Kinnear  ( 1931 )  concluded 
that  fluorescence  is  resident  in  the  fungus  itself  in  the  case  of 


THE  TRICHOPHYTON EAE  389 

Microsporwn  audowni,  Trichophyton  crateri forme,  T.  acumina- 
tum, T.  sulfureum,  and  T.  polygonum  and  that  it  is  retained  in  the 
hairs  when  treated  with  potassium  hydroxide  for  indefinite 
periods.  In  endothrix  trichophyta  and  in  favus,  however,  fluo- 
rescence was  attributed  to  keratin  of  the  hairs. 

Davidson  and  Gregory  (1932)  noted  that  the  ectothrix  tricho- 
phyta, Trichophyton  gypseum  and  T.  album,  do  not  exhibit 
greenish  fluorescence,  but  with  certain  species  with  endothrix 
hvphae,  such  as  Achorion  schoenleinii  fluorescence  resides  in  the 
hair,  as  Kinnear  (1931)  maintained.  They  extended  their  obser- 
vations by  defatting,  in  warm  water  or  in  ether,  hairs  infected  by 
Microsporwn  audpuini,  M.  felinum,  or  Achorion  schoenleini  and 
then  extracting  with  potash  and  secured  a  fluorescent  extract.  The 
hairs  so  treated  were  no  longer  fluorescent.  Normal  hairs  and 
Trichophyton-infected  hairs,  moreover,  did  not  yield  a  fluores- 
cent substance  by  this  same  procedure.  These  results  may  be  re- 
garded as  proof  that  the  invading  fungus  produces  some  hydro- 
lytic  change  in  the  hair  substance  and  that  this  product  has  fluo- 
rescent properties.  The  exact  nature  of  the  substance  still  remains 
unknown. 

Physiologic  activities.  Both  Tate  (1929)  and  Dodge  (1935) 
have  briefly  reviewed  the  publications  dealing  with  the  physiology 
of  the  Trichophytoneae  that  are  peculiarly  adapted  to  living  on 
keratinized  tissues.  Since  the  early  studies- of  Verujsky  (1887)  on 
the  activities  of  Trichophyton  tonsurans  and  Achorion  schoen- 
leini many  investigators  have  been  concerned  with  the  physiology 
of  this  group  of  fungi.  Verujsky  found  that  both  species  grow 
best  in  neutral  or  slightly  acid  media,  with  3  3  °  C  the  optimum  tem- 
perature. Both  produce  proteolytic  enzymes,  as  is  evidenced  by 
the  liquefaction  of  gelatin.  Trichophyton  tonsurans  can  utilize 
glucose  and  maltose,  but  A.  schoenleini  does  not  possess  the  ability 
to  ferment  these  sugars. 

A  considerable  number  of  these  fungi  have  been  grown  in  pure 
culture  for  periods  varying  from  a  few  months  to  two  years  with- 
out loss  of  virulence,  such  substrates  as  feathers,  horn,  leather,  silk, 
straw,  and  wood  [Dodge  (1935)]  being  employed.  The  organ- 
isms tested  include  Trichophyton  flavum,  T.  floccosum,  T.  granu- 
losum,  T.  inter  digit  ale,  T.  mentagrophytes,  Achorion  gypseum, 
and  A.  muris. 


390  MEDICAL  MYCOLOGY 

Roberts  (1894)  tried  unsuccessfully  to  demonstrate  a  "kero- 
lvtic"  enzyme  bv  growing  certain  species  on  hairs  as  a  substrate. 
Later  Tate  (1929a)  failed  to  demonstrate  a  keratin-cleaving 
enzvme  in  Trichophyton  radiolatum,  T.  tonsurans,  Microsporuiu 
lanosum,  M.  audouini,  or  Achorion  schoenleini.  All  species  were 
capable  of  utilizing  maltose,  starch,  casein,  and  tributyin  and, 
except  for  T.  tonsurans,  urea.  None,  however,  produced  peptase, 
invertase,  lactase,  zymase,  and  inulase. 

Goddard  (1934),  employing  Trichophyton  interdigitale  and 
Microsporia!!  lauosuiu,  found  that  both  showed  increased  growth 
in  media  containing  glucose,  mannose,  fructose,  and  arabinose. 
There  was  a  slight  increase  with  sucrose,  but  not  with  lactose. 
Casein  and  peptone  were  hydrolyzed  to  amino  acid  and  ammonia, 
with  a  sparing  action  in  the  presence  of  glucose. 

The  production  of  pigments  among  Trichophytoneae  and  the 
properties  of  these  pigments  have  been  given  consideration  by 
Tate  (1929a)  and  others.  Such  species  as  Trichophyton  acumi- 
natum, T.  magnini,  T.  vinosnm,  Sabouraudites  ruber,  and  5.  radio- 
latus  form  red  to  reddish  brown  pigments,  which  are  soluble  in 
dilute  acids  and  acid  alcohol.  In  these  solvents  the  color  is  yellow, 
changing  to  a  reddish  hue  if  alkali  is  added.  Reversal  of 'color 
change  may  be  accomplished  repeatedly.  Evidence  indicates  that 
these  are  anthracene  pigments  like  those  in  Physcia  and  certain 
other  lichens. 

IMPLICATIONS 

Medical  mycology  is  still  in  its  infancy.  This  conclusion  is 
evident  to  staff  members  of  hospitals  where  there  are  practitioners 
trained  to  recognize  and  diagnose  mycoses.  In  hospitals  not  so 
staffed  the  etiologic  role  of  fungi  is  not  even  suspected  in  many 
instances.  This  condition  will  continue  to  exist  until  this  subject 
receives  proper  consideration  in  the  curricula  of  medical  schools. 

A  "run-of-the-mine"  mycologist  could  not  expect  to  contribute 
materially  to  medical  mycology.  To  become  a  medical  mycolo- 
gist, he  should  supplement  his  training  by  the  usual  courses  re- 
quired for  a  degree  in  medicine,  with  additional  special  training  in 
bacteriology,  biochemistry,  pathology,  and  immunology.  Finally, 
his  laboratory  should  be  so  located  as  to  insure  ready  contact 
with  the  clinical  aspects  of  fungus  diseases. 


LITERATURE  CITED  391 


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Benham,  Rhoda  W.,  "Certain  Monilias  parasitic  on  man,  their  identification 
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Benham,  Rhoda  W.,  and  Beatrice  Kesten,  "Sporotrichosis,  its  transmission 
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Beurmann,  L.,  and  H.  Gougerot,  Les  Sporotrichosis.  825  pp.  Felix  Alcan, 
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Brumpt,  E.,  Precis  de  parasitologic    Masson  et  Cie,  Paris.     1935. 

Carrion,  A.  L.,  "Chromoblastomycosis,"  My  col.,  34:424-441,  1942. 

Conant,  N.  F.,  "Studies  in  the  genus  Microsporum.  I.  Cultural  studies," 
Arch.  Dennatol.  Syphilol.,  33:  665-683,  1936. 

II.  "Biometric  studies,"  Arch.  Dermatol.  Syphilol.,  34:  79-89,  1936a. 

III.  "Taxonomic  studies,"  Arch.  Dermatol.  Syphilol,  35:781-808,  1937. 
"The  occurrence  of  a  human  pathogenic  fungus  as  a  saprophyte  in  na- 
ture," My  col,  29:  597-598,  1937a. 

"The    taxonomy    of    anascosporous    yeast-like    fungi,"    My copathologia, 

2:255-266,  1940. 
"A  cultural  study  of  the  life  cycle  of  Histoplasma  capsidatum  Darling 
1906,"  /.  Bact.,  41:  563-578,  1941. 

Conant,  N.  F.,  and  D.  S.  Martin,  "The  morphologic  and  serologic  rela- 
tionships of  the  various  fungi  causing  dermatitis  verrucosa  (chromo- 
blastomycosis)," Am.  J.  Trop.  Med.,  11:  553-577,  1937. 

Conant,  N.  F.,  D.  S.  Martin,  D.  T.  Smith,  R.  D.  Baker,  and  J.  L.  Calloway, 
Manual  of  clinical  mycology.  348  pp.  W.  B.  Saunders  Co.,  Philadel- 
phia.    1944. 

Davidson,  A.  M.,  Eleanor  S.  Dowding,  and  A.  H.  R.  Buller,  "Hyphal  fu- 
sions in  dermatophytes,"  Can.  J.  Research,  6:  1-20,  1932. 

Davidson,  A.  M.,  and  P.  H.  Gregory,  "Note  on  an  investigation  into  the 
fluorescence  of  hairs  infected  by  certain  fungi,"  Can.  J.  Research,  7:  378- 
385,  1932. 

Dodge,  C.  W.,  Medical  mycology.  Fungous  diseases  of  man  and  other 
animals.     900  pp.     C.  V.  Mosby'Co.,  St.  Louis.     1935. 

Dowding,  Eleanor  S.,  and  H.  Orr,  "Three  clinical  types  of  ringworm  due 
to  Trichophyton  gypseum"  Brit.  J.  Dermatol.  Syphilis,  49: 298-307, 
1937. 

Emmons,  C.  W.,  "Pleomorphism  and  variation  in  the  dermatophytes,"  Arch. 
Dermatol.  Syphilol,  25:987-1001,  1932. 
"Dermatophytes :  a  natural  grouping  based  on  the  form  of  the  spores  and 

accessory  organs,"  Arch.  Dermatol.  Syphilol,  30:337-362,  1934. 
"Actinomyces   and   actinomycosis,"   Puerto   Rico   J.  Pub.   Health    Trop. 
Med.,  11:63-76,  1935. 


392  MEDICAL  MYCOLOGY 

Emmons,  C.  W.,  uHormodendron  pedrosoi,  an  etiologic  agent  in  chromo- 
blastomvcosis,"  Puerto  Rico  J.  Pub.  Health   Trop.  Med.,  11: 639-650, 
1936. 
'Medical  mycology,"  Botan.  Rev.,  5:474-514,  1940. 

"Isolation  of  Coccidioides  from  the  soil  and  rodents,"  U.  S.  Pub.  Health 
Rept.,51:  109-111,  1942. 

Emmons,  C.  \V.,  and  A.  L.  Carrion,  "Sporulation  of  the  Phialophora  type  in 
Hormodendrum,"  Mycol.,  29:327-333,  1937. 

Freeman,  Walter,  "Torula  infection  of  the  central  nervous  system," 
/.  Psych.  Neur.,  43:  236-345,  1931. 

Goddard,  D.  R.,  "Phases  of  the  metabolism  of  Trichophyton  interdigitale 
Pricstlev,"  /.  Infectious  Diseases,  54:  149-163,  1934. 

Gregory,  P'.  H.,  "The  dermatophytes,"  Biol.  Rev.,  70:208-233,  1935. 

Grigoraki,  L.,  "Recherches  cytologiques  et  taxonomiques  sur  les  dermato- 
phytes et  autres  champignons  parasites,"  Ann.  sci.  not.  Botan.,  Ser.  10, 
7:  165^44,  1925. 
"Dermatophytes  et  dermatomycoses,"  Ann.  Derm.  Syphiligr.,  VI,  10:  18- 
53,  1929. 

Harz,  C.  O.,  "Actinomyces  bovis,  ein  neuer  Schimmel  in  den  Gewebcn 
des  Rindes,"  Dent.  Z.  Tiervied.,  Suppl.  to  Bd.  5  (Jahresber,  Central- 
Tierarznei  Schule  in  Mi'tnchen,  1877-78),  pp.  125-140,  1879. 

Hopkins,  J.  G.,  ".Moniliasis  and  moniliids,"  Arch.  Derm.  SyphiloL,  25:599- 
614,  1932. 

Howeel,  Arden,  "Studies  on  Histoplasma  capsulatum  and  similar  form  spe- 
cies.   I.  .Morphology  and  development,"  Mycologia,  31:  191-216,  1939. 

Kinnear,  J.,  "Wood's  glass  in  the  diagnosis  of  ringworm,"  Brit.  Med.  /., 
7:791-793,  1931. 

I.vmater,  E.  D.  de,  and  R.  W.  Benha.m,  "Experimental  studies  with  derma- 
tophytes," /.  Investigative  Dermatol.,  i:  451—488,  1938. 

Lamb,  J.  H.,  and  .Margaret  L.,  "A  grouping  of  the  Monilias  by  fermentation 
and  precipitation  reactions,"  /.  Infectious  Diseases,  56:8-20,  1935. 

Langeron,  .M.,  "Travaux  recents  sur  la  classification  des  dermatophytes." 
Ann.  parasitol.  humaine  comparee,  4:  193-198,  1926. 

Langeron,  .M.,  and  P.  Guerra,  "Xouvelles  recherches  de  zymologie  medi- 
cale,"  Ann.  parasitol.,  76:36-84,  162-179,  429-478,  481-525,  193S. 

Langeron,  M.,  and  S.  Milochevitch,  ".Morphologie  des  dermatophytes  sur 
milieux  naturels  et  milieux  a  base  de  polysaccharides.  F.ssai  de  classifi- 
cation,"' Ann.  parasitol  humaine  comparee,  8:  465-508,  1930. 

Langeron,  M..  \\d  R.  Y.  Taeice,  "Noveau  type  de  lesion  pilaire  experimen- 
tale  produite  par  la  culture  purement  pleomorphique  du  Sabouraudites 
felinus."  Ann.  parasitol.  humaine  comparee,  8: 419-421,  1930. 
"Xouvelles  methodes  d'etude  et  essai  de  classification  des  champignons 
levuriformes."  Ann.  parasitol.  humaine  comparee,  10:  1-89,  1932. 

Lentze,  T.  A.,  '"Zur  Bakteriologie  und  Vakzintherapie  der  aktinomykose," 
Zentr.  Bakt.  Parasitenk.,  Orig.,  141: 21-36,  1938. 

Lewis,  Geori.e  M.,  and  Mary  E.  Hopper,  An  introduction  to  medical  my- 
cology.   342  pp.    The  Year  Book  Publishers,  Inc.,  Chicago.     1943. 


LITERATURE  CITED  393 

MacKee,  G.  M.,  and  G.  M.  Lewis,  "Dandruff  and  seborrhea.     I.  Flora  of 

normal  and  diseased  scalps,"  /.  Investigative  Dermatol.,  1:  131-139,  1938. 
Margarot,  J.,  and  P.  Devese,  "Aspect  de  quelques  dermatoses  en  lumiere 

ultrapara-violette,"    Bull.    soc.   sci.   vied.    biol.    Montpellier,    6: 375-378, 

1924-25. 
Martin,  D.  S.,  "The  antigenic  similarity  of  a  fungus,  Cadophora  americana, 

isolated  from  wood  pulp  to  Phialophora  verrucosa  isolated  from  patients 

with  dermatitis  verrucosa  (chromoblastomycosis),"  Am.  J.  Trop.  Med., 

7£:  42 1-426,  1938. 
Martin,  D.  S.,  R.  D.  Baker,  and  N.  F.  Conant,  "A  case  of  verrucous  dema- 

titis    caused    by    Hormodendrum   pedrosoi    (chromoblastomycosis)    in 

North  Carolina,"  Am.  J.  Trop.  Med.,  16:  593-618,  1936. 
Martin,  D.  S.,  C.  P.  Jones,  K.  F.  Yao,  and  L.  E.  Lee,  "A  practical  classifi- 
cation of  the  Monilias,"  /.  Bad.,  34:99-130,  1937. 
Medlar,  E.  M.,  "A  new  fungus,  Phialophora  verrucosa,  pathogenic  for  man," 

Mycol.,  7:  200-203,  1915. 
Monbreun,   W.    A.    de,    "The    cultivation    and    cultural    characteristics    of 

Darling's  Histoplasma  capsulatum"  Am.  J.  Trop.  Med.,  14:93-125,  1934. 
Moore,  M.,   "Cultivation  and  study  of  Pityrosporum  ovale,  the   so-called 

bottle  bacillus  of  Unna,"  Arch.  Dermatol.  SyphiloL,  31:  661-671,  1935. 
Musgrave,  W.  E.,  M.  T.  Clegg,  and  M.  Polk,  "Streptothricosis  with  special 

reference  to  the   etiology  and   classification   of  mycetoma,"   Philip.  J. 

Sci.,  Ser.  B,  3:  447-544,  1908. 
Nannizzi,  A.,   "Richerche  sui  rapporti  morfologici  e  biologici  tra  Gym- 

noascee  e  Dermatomiceti,"  Ann.  mycol.,  24:  85-129,  1926. 
Ota,  M.,  and  P.  T.  Huang,  "Sur  les  champignons  du  genre  Pityrosporium 

Sabouraud,"  Ann.  parasitol.  humaine  comparee,  77:49-69,  1933. 
Ota,  M.,  and  M.  Langeron,  "Nouvelle  classification  des  dermatophytes," 

Ann.  parasitol.  humaine  comparee,  1:  305-336,-  1923. 
Rackemann,  F.  M.,  T.  G.  Randolph,  and  E.  F.  Guba,  "The  specificity  of 

fungous  allergy,"  /.  Allergy,  9: 447-453,  1937-38. 
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in  relation  to  medicine,  Chap.  I,  pp.  11-70.     H.  M.  Stationery  Office, 

London.    1931. 
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loma," Calif.  Dept.  Pub.  Health,  Spec.  Bull,  51.    1931. 
Rixford,  E.,  and  T.  C.  Gilchrist,  "Two  cases  of  Protozoan  (Coccidioidal) 

infection  of  the  skin  and  other  organs,"  Jolms  Hopkins  Hosp.  Rept., 

7:209-268,  1896. 
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309,  1894. 
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"Generalities  concernant  les  dermatophytes.    II.  La  classification  naturelle 

des  dermatophvtes,"  Ann.  Derm.  Syphiligr.,  VI,  10:  569-580,  1929. 
Shrewsbury,  J.  F.  D.,  "The  genus  Monilia,"  /.  Path.  Bact.,  38:  313-354,  1934. 
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27:31-54,  1929a. 


S94  MEDICAL  MYCOLOGY 

Todd,  R.  A.,  and  W.  W.  Hermann,  "The  life  cycle  of  the  organism  causing 
yeast  meningitis,"  /.  Bact.,  32:  89-104,  1936. 

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Verujsky,  D.,  "Recherches  sur  la  morphologie  et  la  biologie  du  Tricho- 
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Dermatol.  Syphilol.,  34:  1-14,  1936. 


Chapter  17 
GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI 

Plant  geography  is  admittedly  a  tremendously  valuable  branch 
of  botanical  knowledge,  and  its  fundamentals,  in  relation  to  mosses, 
ferns,  and  especially  seed  plants,  are  now  relatively  well  under- 
stood. Apparently,  however,  for  reasons  that  will  become  mani- 
fest in  the  discussion  which  follows,  any  consideration  of  the  geo- 
graphical distribution  of  fungi  at  this  stage  of  mycological  devel- 
opment has  a  limited  usefulness,  partly  because  to  date  this  phase 
of  inquiry  has  received  little  attention.  Nevertheless  it  should 
eventually  come  to  be  recognized  as  having  a  very  practical  and 
very  general  interest. 

Bisby  (1933)  has  said,  "Mycologists  have  been  able  to  map  with 
accuracy  the  geographic  distribution  of  comparatively  few  fungi." 
The  worker  who  turns  his  attention  to  this  subject  is  early  im- 
pressed with  the  fact  that  vast  portions  of  the  earth's  surface  re- 
main completely  unexplored  for  fungi  and  hence  are  literally  terrae 
incognitae  fungornm.  Such  distributional  data  as  are  contained 
in  monographs  on  special  groups  of  fungi  or  in  accounts  of  species 
of  economic  importance  afford  a  basis  for  certain  generalizations. 
Much  additional  pertinent  information  has  been  catalogued  in 
herbaria  but  remains  unpublished  and  hence  quite  unavailable. 

In  a  report  Bisby  and  Ainsworth  (1943)  state  that  the  exact  dis- 
tribution of  but  few  of  the  3600  genera  including  37,000  "good" 
species  of  known  fungi  has  been  determined.  Distribution  of 
genera  by  continents,  as  given  by  Bisby  (1943),  is  as  follows: 
Europe  1800,  North  America  1700,  South  America  1100,  Asia 
1100,  Africa  800,  and  Australia-New  Zealand  600. 

On  first  thought  it  might  appear  that  the  nutritional  factor 
should  be  all  important  in  determining  the  distributional  range  of 
fungi  for  the  reason  that  they  are  either  saprotrophic  or  para- 
trophic  in  food  habits.  Food  is  not,  however,  the  sole  factor,  for, 
just  as  with  holophytic  plants,  natural  distribution  has  been  found 

395 


396  GEOGRAPHICAL  DISTRIBUTION  OF  FUXGI 

to  be  governed  bv  the  interaction  of  interrelated  and  interde- 
pendent  factors,  climatic,  edaphic,  and  biotic. 

The  validity  of  this  conclusion  becomes  apparent  if,  for  ex- 
ample, an  attempt  is  made  to  deduce  the  probable  distributional 
range  of  certain  parasitic  fungi  from  knowledge  of  the  range  of 
their  hosts.  The  student  may  think  that  each  parasite  should  be 
coextensive  in  range  with  its  host  (suscept),  only  to  discover  that, 
although  such  is  the  situation  among  certain  species,  it  is  not 
among  others.  Such  observations  lead  to  the  conclusion  that 
endemism  exists,  that  is,  certain  fungi  are  indigenous  on  native 
species  within  particular  areas  where  they  have  become  dispersed 
by  natural  agencies.  These  certain  species  may  eventually  be 
spread  to  areas  outside  their  natural  range,  but  only  as  a  result  of 
"artificial"  introduction,  chiefly  by  man.  In  a  very  real  sense 
man  has  interfered  in  no  small  measure  with  the  natural  factors 
that  influence  the  distribution  of  fungi.  To  retard  or  prevent 
artificial  dissemination  of  pathogenic  species,  quarantines  have 
been  instituted,  eradication  campaigns  have  been  organized  and 
conducted,  inspection  procedures  have  become  compulsory  in 
connection  with  shipment  of  plants  or  plant  parts  from  one  local- 
ity to  another,  and  researches  have  been  and  are  being  made  to 
produce  hosts  that  are  resistant  to  disease.  Problems  which  have 
arisen  as  a  result  of  disturbance  of  biological  balance  by  man  and 
of  his  attempts  to  rectify  them,  therefore,  constitute  an  interesting 
and  important  phase  of  the  geography  of  fungi. 

For  a  discussion  of  the  structural  features  possessed  by  certain 
species  that  aid  in  their  geographical  distribution  the  reader  is 
referred  to  Chapter  8,  Spore  Dissemination.  In  this  chapter  in- 
formation will  also  be  found  on  such  natural  agencies  as  air  cur- 
rents,  rains,  streams,  floodwaters,  and  insects  and  various  other 
animals  as  factors  in  distribution.  In  a  very  real  sense  fungi  tend 
continually  to  extend  their  range,  some  behaving  as  settlers  and 
others  as  tourists. 

In  the  account  that  follows,  greatest  emphasis  will  be  placed 
on  the  geographic  distribution  of  fungi  as  modified  by  man 
through  the  introduction  and  cultivation  of  exotic  plants  of  eco- 
nomic importance.  The  presentation  will  not  follow  the  logical 
arrangement  based  on  the  distribution  of  fungi  as  governed  by 
climatic,  edaphic,  and  biotic  factors,  but  will  be  artificial  and  will 
be  based  on  fungus  groupings. 


DISTRIBUTION  OF  MYXOMYCETES  391 

DISTRIBUTION  OF  MYXOMYCETES 

Collectors  of  Mvxomycetes  are  quite  universally  inclined  to 
the  opinion  that  this  group  is  among  the  most  ubiquitous  and  cos- 
mopolitan of  organisms.  Intensive  collecting,  even  in  restricted 
areas  at  widelv  distant  points,  has  yielded  for  each  locality  only 
from  one-third  to  one-half  of  all  the  species  known  throughout 
the  world.  Nevertheless  the  geographical  distribution  of  slime 
molds  is  not  fortuitous  but  depends  upon  such  dominant  factors 
in  each  locality  and  for  each  species  as  temperature,  moisture, 
kind  of  substrate  and  its  acidity  or  alkalinity,  and  other  factors. 

More  species  of  slime  molds  have  been  recorded  for  temperate 
regions  than  for  the  tropics,  but  this  phenomenon  appears  to  be 
causally  related  to  the  greater  interest  in  collecting  in  the  tem- 
perate zones.  Some  species,  however,  are  limited  to  temperate  re- 
gions; others,  such  as  Trichamphora  pezizoides  and  Alwisia  bom- 
bar  da,  to  tropical  or  subtropical  regions  [Martin  (1940)].  This 
observation  need  not  necessarily  be  interpreted  as  proof  that  tem- 
perature is  the  primary  and  controlling  factor  in  determining  the 
range  of  slime  molds  in  general.  Otherwise  it  becomes  difficult 
to  explain  numerous  observations  like  those  of  Smith  (1931),  who 
noted  that  in  Colorado  species  of  Badhamia  prefer  decaying  aspen 
or  cottonwood  logs,  whereas  species  of  Cribraria  are  restricted 
to  coniferous  wood.  As  a  result  of  several  years'  experience  in 
collecting  slime  molds,  Smith  (1931)  concluded  that  moisture, 
especially  adequate  rainfall  for  considerable  periods,  is  the  primary 
desideratum  for  their  growth,  the  proper  kind  of  decaying  vege- 
table matter  being;  secondary.  He  correlated  the  Greater  rainfall 
at  elevations  of  8000  to  9000  feet  in  Colorado  with  the  greater 
abundance  of  species.  Even  though  he  collected  Stemonitis  fusca, 
Comatrichia  nigra,  and  several  species  of  Cribraria  and  Arcvria  on 
dry  exposed  slopes,  they  invariably  were  found  only  on  the  lower 
side  of  logs  kept  moist  by  melting  snow.  The  fact  that  the  lower 
side  of  logs  is  preferred  by  slime  molds  is  not  regarded  as  a  re- 
sponse to  gravity,  an  opinion  on  which  there  is  general  accord. 
Smith  (1931)  and  MacBride  (1914)  do  not  contend  that  any  of 
the  species  they  collected  in  the  high  mountains  near  the  timber 
line  are  alpine. 


398  GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI 

The  constant  occurrence  of  lime  granules  as  a  constituent  part 
of  the  fructifications  among  species  of  Badhamia,  Craterium, 
Diderma,  Diachea,  Didvmium,  Fuligo,  Leocarpus,  Alucilago,  and 
Phvsarum  and  their  absence  in  others,  for  example,  among  jComa- 
trichia  and  Stemonitis,  are  not  without  significance.  Carr  (1939) 
reported  that  90%  of  the  species  on  sandstone  soils  in  a  region  in 
Virginia  are  "non-lime  species"  and  88%  of  those  on  limestone 
soils  in  this  same  region  are  "lime  species."  From  comparison  of 
collections  made  in  Sweden  with  those  made  along  the  border 
between  Bolivia  and  Argentina,  Fries  (1903)  concluded  that  lime- 
containing  species  predominate  over  non-lime-containing  species 
in  the  tropics,  but  that  the  reverse  is  true  in  temperate  regions. 
That  regional  distribution  is  not  determined  entirelv  by  the  cal- 
careousness  of  soils  is  borne  out  by  the  findings  of  other  collectors, 
as  Martin  (1940)  has  indicated. 

Thorn  and  Raper  (1930)  found  that  numerous  species  may  be 
isolated  from  arable  soils,  where  they  occur  in  the  plant  debris 
and  litter.  Abundant  evidence  is  at  hand  to  show  that  they  sub- 
sist upon  various  fungi  and  bacteria  that  decompose  plant  re- 
mains. The  influence  of  food  in  distribution  is  further  evidenced 
by  the  rather  constant  occurrence  of  certain  species  among  mosses, 
of  others  on  decaying  coniferous  leaves,  and  of  others  on  decaying 
leaves  of  hardwoods. 

Some  slime  molds  may  develop  well  above  the  ground.  Smith 
(1931)  collected  Lycogala  fusco-flavum  and  Mucilago  spongiosa 
var.  solida  8  to  10  feet  up  on  exposed,  heart-rotted  trunks  of  Cot- 
tonwood. The  plasmodium  of  some  species,  such  as  Phy sarin n 
cinereum,  may  climb  upon  blades  of  grass  or  other  vegetation 
immediately  before  becoming  transformed  into  sporangia. 

Plasmodiophora  brassicae  is  now  essentially  world-wide  in  dis- 
tribution. Its  wide  host  range  among  cruciferous  species  and  its 
preference  for  acid  soils  constitute  the  important  factors  that  have 
contributed  to  this  broad  range.  Evidence  indicates  that  for  over 
200  years  market  gardeners  have  contended  with  club-root  disease, 
which  it  causes  on  cabbage,  radishes,  and  turnips.  In  Europe  it  is 
most  destructive  in  the  northern  portions  of  the  continent.  It  has 
been  reported  from  nearly  all  parts  of  the  United  States  and  from 
Alaska  and  Canada.  A  monograph  on  Plasmodiophorales  by 
Karling  (1942)  contains  an  extensive  bibliography  on  the  range 
of  this  organism  and  on  other  features. 


DISTRIBUTION  OF  PHYCOMYCETES  399 

Spongospora  subterranea,  causing  powdery  scab  of  potato,  ap- 
pears to  be  endemic  to  Equador  and  Peru.  It  has  become  estab- 
lished throughout  the  British  Isles,  continental  Europe,  .Madagas- 
car, the  area  bordering  the  Mediterranean  Sea  on  the  east  and 
south,  South  Africa,  New  Zealand,  and  Tasmania.  The  shipment 
of  infected  tubers  from  one  region  to  another  undoubtedly  is  the 
primary  means  of  dispersal  of  this  organism. 


DISTRIBUTION  OF  PHYCOMYCETES 

The  lists  of  Bisby  and  his  associates  (1929)  and  of  Bisby 
(1933)  indicate  that  85%  of  all  Phycomycetes  present  in  Mani- 
toba and  40%  of  those  in  India  occur  also  in  Europe.  Of  35 
species,  mostly  Mucorales,  present  in  soil  in  North  America  26  are 
also  European.  The  significance  of  nutrition  as  a  factor  in  distri- 
bution among  Phycomycetes  is  apparent  when  the  Peronosporales 
are  considered  in  contrast  to  other  phycomycetous  orders.  The 
distribution  of  Peronosporales,  all  obligate  parasites,  is  definitely 
limited  by  that  of  the  hosts. 

Less  is  known  regarding  the  distributional  range  of  saprophytic 
species  of  Phycomycetes  in  general  than  that  of  pathogenic  spe- 
cies, but  Rhizopus  nigricans  and  Mucor  mucedo,  both  cosmopoli- 
tan species,  are  notable  exceptions.  Seemingly  both  can  thrive 
wherever  man  lives,  and  both  utilize  the  remains  of  numerous 
kinds  of  plants  as  food. 

Students  of  soil  fungi  have  shown  that  species  of  Mucor  are 
universally  present  in  arable  soils  and  also  in  many  virgin  soils. 
Another  soil-borne  genus  is  Allomyces,  which  is  peculiarly  suited 
to  wet  sites,  its  members  being  commonly  regarded  as  "water 
molds."  Allomyces  arbusciila,  representative  of  this  genus,  has 
been  collected  in  wet  soil  on  all  continents.  Since  water  molds 
do  not  thrive  in  the  oceans  and  since  A.  arbuscula  is  unable  to 
tolerate  salinity,  no  explanation  of  its  wide  geographical  range  is 
forthcoming. 

The  distribution  of  coprophilous  Phycomycetes,  such  as  species 
of  Pilobolus,  is  conditioned,  not  by  climate  and  soil,  but  only  by 
the  migration  of  the  herbivor.  Browsing  animals  eat  the  sporangia 
that  are  lodged  on  vegetation  near  dung  piles.  The  spores  germi- 
nate when  voided  with  the  feces,  and  within  a  few  days  Pilobolus 
will  mature  a  crop  of  sporangia  and  discharge  them. 


400  GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI 

Endemic  species,  artificially  dispersed.  The  existence  of 
endemism  among  pathogenic  Phvcomycetes  can  be  shown  by 
numerous  examples.  Among  them  is  Physodcnua  zeae-maydis} 
which  is  known  to  have  existed  for  about  40  years  in  the  south- 
eastern United  States,  throughout  the  area  south  of  the  Ohio  River 
and  east  of  the  Mississippi  River.  It  is,  however,  found  sparingly 
in  the  Corn  Belt  north  and  west  of  this  range,  but  here  it  occurs 
sporadically.  It  produces  serious  losses  within  its  normal  range, 
especially  in  low,  poorly  drained  lands  during  seasons  of  abun- 
dant and  frequent  rains.  This  fungus  has  been  dispersed  widely 
outside  the  United  States,  as  is  shown  by  records  of  collections  in 
India,  China,  Japan,  Rhodesia,  Sierra  Leone,  Guatemala,  and  Mex- 
ico. It  would  be  expected  to  occur  wherever  corn  has  been  in- 
troduced, provided  that  moisture  and  temperature  are  favorable. 

Another  example  of  this  kind  is  the  organism  that  causes  potato 
wart,  Synchytrium  endobioticum,  first  described  from  Hungary 
in  1896.  Soon  thereafter  it  was  encountered  in  other  portions  of 
central  Europe,  where  it  is  presumably  indigenous,  for  example,  in 
Czechoslovakia,  Poland,  Silesia,  Austria,  and  Germany.  In  1902 
it  was  reported  in  the  British  Isles,  in  1912  in  Canada,  in  1918  in 
the  United  States,  in  1922  in  South  Africa,  and  in  1929  in  Peru 
and  Russia.  Meantime  stringent  quarantines  were  established  in 
many  countries  to  prevent  the  introduction  and  spread  of  this 
organism. 

Among  the  classic  examples  of  a  pathogenic  species  that  has 
been  artificially  dispersed  is  Fhytophthora  infestans.  This  fungus, 
native  of  the  northern  Andes,  home  of  the  potato,  was  introduced 
into  Europe  and  North  America  between  1830  and  1840.  In  1845 
and  1846  an  cpiphvtotic  so  severe  as  to  cause  failure  of  the  potato 
crop  occurred  throughout  northern  Europe,  especially  in  Ireland, 
where  famine  resulted.  This  pathogen  was  introduced  into  India 
between  1870  and  1880  and  into  Australia  and  South  Africa  be- 
tween 1900  and  1910. 

North  America  has  contributed  an  organism,  Plasmopara  viti- 
colii,  which  becomes  notoriously  destructive  when  introduced 
into  new  areas.  This  downy  mildew  was  first  described  in  1834 
and  was  transplanted  into  France  with  grape  nursery  stock  early 
in  the  I870's.  There  it  produced  an  epiphvtotic  in  1879  and 
rapidly  spread  throughout  the  vineyards  of  France  and  Italy.  Ef- 
forts to  check  this  grape  disease  led  to  the  discovery  and  use  of 


DISTRIBUTION  OF  PHYCOMYCETES  401 

Bordeaux  mixture  as  a  fungicide.  By  1907  the  malady  had  reached 
South  Africa,  and  in  1917  it  caused  the  first  severe  outbreak  in  the 
vineyards  of  Australia. 

The  tobacco  downy  mildew,  Peronospora  tabacina,  endemic  to 
Australia,  seemingly  has  been  introduced  both  into  North  America 
and  South  America,  and  there  seems  no  reason  for  supposing  it 
will  not  spread  eventuallv  to  other  continents  or  countries.  Evi- 
dence indicates  that  it  has  been  known  in  Australia  for  more  than 
50  years.  It  first  appeared  in  Florida  in  1921  and  in  Rio  Grande 
do  Sul,  Brazil,  in  1938.  Apparently  it  was  eradicated  from  Florida 
in  the  first  season  of  its  introduction,  but  it  reappeared  in  1931. 
Since  then  it  has  gradually  spread  northward  in  the  United  States, 
reaching  Connecticut  and  Massachusetts  in  1937  and  southern 
Ontario,  Canada,  in  1938.  Clayton  and  Stevenson  (1943)  are  of 
the  opinion,  however,  that  this  fungus  is  native  to  all  temperate 
regions  having  an  indigenous  Nicotiana  flora. 

Influence  of  latitude.  Meager  data  are  available  on  latitude 
as  a  factor  in  limiting  the  range  of  Phycomycetes,  but  it  is  ap- 
parent that  climatic  zonation  occurs.  Phytophthora  parasitica  var. 
nicotianae,  for  example,  is  regarded  as  tropical  and  subtropical 
and  was  first  recorded  on  tobacco  from  the  East  Indies  in  1896. 
Since  then  it  has  been  found  to  occur  on  this  crop  in  India,  Japan, 
Indo-China,  the  Philippine  Islands,  Nyasaland,  Cameroons, 
Uganda,  Rhodesia,  Puerto  Rico,  Jamaica,  and  Guatemala.  More 
recently  the  disease  appeared  in  Florida,  North  Carolina,  Virginia, 
and  Kentucky  and  in  Greece,  Rumania,  and  Bulgaria,  all  of  which 
are  in  the  North  Temperate  Zone.  In  tropical  regions  tobacco 
plants  of  all  ages  are  subject  to  attack,  whereas  in  more  northerly 
areas  infection  does  not  occur  until  the  warmest  weather,  at  which 
season  the  plants  are  essentially  mature. 

Choanephora  cucurbitamm  grows  most  abundantly  in  tropical 
and  subtropical  regions  but  extends  into  adjacent  temperate  zones. 
Collections  of  it  have  been  reported  throughout  the  East  Indies, 
Malaya,  Burma,  India,  the  Gold  Coast,  Sierra  Leone,  the  West 
Indies,  and  the  southern  United  States,  commonly  on  fading  flow- 
ers of  cotton,  okra,  althea,  squash,  watermelon,  cowpea,  chili, 
cassava,  papaw,  peanut,  hibiscus,  and  dahlia.  The  closely  related 
Blakeslea  trispora  is  quite  restricted  to  tropical  and  subtropical 
areas  having  abundant  and  frequent  rains.     During  1942,  which 


402  GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI 

was  a  very  wet  season,  however,  this  fungus  was  noted  on  tobacco 
flowers  in  the  vicinity  of  Durham,  North  Carolina. 

DISTRIBUTION  OF  ASCOMYCETES 

This  discussion  of  the  distribution  of  Ascomycetes  must  of 
necessity  be  fragmentary  and  is  in  no  sense  proportional  to  the 
vast  bodv  of  data  on  this  group  that  has  been  accumulated. 
Nevertheless  the  material  is  believed  to  be  representative  for  the 
group  as  a  whole.  Many  species  of  great  economic  importance 
have  been  spread  by  man  to  the  extent  that  they  now  occur  in  all 
countries  where  the  hosts  are  cultivated.  The  severity  of  the  dis- 
eases which  thev  cause  is  modified,  to  be  sure,  by  latitude,  by 
seasonal  differences  in  climate,  or  by  application  of  palliative  or 
control  measures.  Fungi  of  this  kind  include  Taphrina  deformans 
and  Sclerotinia  jracticola  on  peach  and  Venturia  inaeqitalis  on 
apple.  Venturia  inaequalis  occurs  througout  the  United  States, 
Mexico,  and  Canada,  but  it  rarely  is  found  in  the  Coastal  Plains 
of  the  southeastern  United  States.  In  Europe  it  has  been  noted  in 
the  British  Isles,  Belgium,  Netherlands,  Portugal,  France,  Switzer- 
land, Norway,  Sweden,  Denmark,  Germany,  Austria,  Czecho- 
slovakia, Russia,  Greece,  and  Bulgaria.  Moreover  it  is  reported 
from  India,  New  Zealand,  Tasmania,  Rhodesia,  Morocco,  Argen- 
tina, and  Peru  and  mav  therefore  be  presumed  to  be  global  in 
distribution. 

The  observations  of  Fawcett  and  Lee  (1926)  show  that  Dia- 
porthe  citri  on  citrus  is  another  in  the  same  group  of  organisms. 
This  fundus  was  first  studied  in  Florida  in  1892  and  was  subse- 
quently  found  in  Brazil,  Argentina,  Mexico,  the  West  Indies, 
China,  Japan,  Palestine,  Algeria,  South  Africa,  and  South  Aus- 
tralia. Its  symptom-complex  includes  dying  bark  of  twigs,  stem- 
end  rot  of  ripe  fruits,  and  melanose  markings  on  leaves,  twigs,  and 
fruits.  The  melanose  form  of  the  disease  does  not  occur  in  Cali- 
fornia or  at  least  is  very  rare,  whereas  it  is  always  very  abundant 
in  central  Florida. 

The  fact  that  pathogenic  species,  especially,  are  capable  of 
maintaining  themselves  for  indefinite  periods  saprogenically,  as  is 
Thielavia  basicola  (Tknelaviopsis  basicola),  constitutes  a  compli- 
cating factor  in  distribution.  Thielavia  basicola  attacks  many  spe- 
cies  of  legumes,  especially  beans,  clovers,  lupins,  peas,  soybeans, 


DISTRIBUTION  OF  ASCOMYCETES  403 

and  vetches,  but  may  also  seriously  involve  tobacco,  flax,  cotton, 
and  watermelon.  Collection  records  indicate  its  presence  in  Cen- 
tral Asia,  the  Philippine  Islands,  Queensland  and  New  South  Wales 
in  Australia,  the  British  Isles,  Russia,  Turkey,  Rumania,  Hungary, 
Czechoslovakia,  Germany,  France,  Switzerland,  Italy,  Puerto  Rico, 
the  United  States,  and  Canada. 

Distribution  of  powdery  mildews.  Of  the  60  species  and 
varieties  of  Erysiphaceae  listed  by  Salmon  (1900),  22  are  confined 
to  the  Old  World  and  19  to  the  New  World,  leaving  19  that  are 
common  to  both  hemispheres.  This  situation  is  accounted  for  in 
part  by  the  limitation  of  certain  mildews  to  particular  hosts  and 
to  the  seemingly  almost  complete  lack  of  specialization  in  other 
species.  Erysiphe  tortilis,  confined  to  Cormis  sanguinea,  Uncinula 
geniculata,  to  Morns  rubra,  and  Podosphaera  biuncinata,  to  Hania- 
nielis  virginiana,  are  examples  of  highly  restricted  species.  Unci- 
nula aceris  is  limited  to  species  of  Acer,  U.  flexitosa  to  Aesculus, 
and  Spaerotheca  lanestris  to  Quercus.  Less  restriction  is  exhibited 
by  Erysiphe  graminis,  which  occurs  only  on  various  Gramineae, 
by  Uncinula  salicis  on  Salicaceae,  and  by  Sphaerotheca  pannosa  on 
Rosaceae.  On  the  other  hand,  Erysiphe  cichoracearum,  E.  poly- 
gon!,  and  Phyllactinia  cor y lea  are  world-wide  and  attack  a  wide 
range  of  hosts.  Phyllactinia  corylea,  for  example,  is  recorded  on 
48  host-genera  in  27  families  of  plants.  Continental  distribution 
of  powdery  mildews  has  been  summarized  by  Salmon  (1900)  as 
shown  in  Table  29. 


TABLE  29 

JTION    OF    Po 

WDERY 

Mildews 

BY    CONTINI 

Total 

Number  of 

Country 

Number 

Endemics 

Europe 

32 

12 

Africa 

8 

.  . 

Asia 

28 

5 

Australia  an 

d 

New  Zealand 

5 

1 

America 

28 

19 

DlSTRBUTION    OF    PyrENOMYCETES    AND    DlSCO.MYCETES.       Bisby 

(1933)  indicates  that  about  half  of  the  species  of  Pyrenomycetes 
listed  from  Manitoba  [Bisby  et  al.  (1929)]  are  known  to  occur 
in  Europe.    Moreover,  only  about  12%  of  those  in  the  list  from 


404  GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI 

India  [Butler  and  Bisbv  (1931)]  occur  in  Europe.  Seemingly 
this  group  contains  members  that  are  restricted  in  range,  and  many 
of  them  are  confined  to  the  tropics  or  subtropics. 

Of  the  operculate  discomycetes  listed  in  Seayer's  monograph 
(1928)  35  °0  are  limited  to  North  America  and  61  %  are  common 
to  both  North  America  and  Europe.  This  group,  which  is  almost 
wholly  saprophytic,  is  thus  quite  cosmopolitan. 

Distribution  of  exotics.  Endothia  parasitica,  the  chestnut- 
blight  fungus,  is  the  best  known  and  also  the  most  destructive 
ascomycete  introduced  into  the  United  States.  It  was  first  noted 
by  Merkel  in  the  New  York  Zoological  Park  in  1904  and  thence 
spread  with  alarming  rapidity  throughout  the  entire  Appalachian 
region  where  Castanea  dent  at  a  is  native.  In  1913  Meyer  found 
that  this  organism  is  endemic  on  Castanea  mollissima  in  northern 
China. 

Ceratostomella  ulmi,  causing  the  so-called  Dutch  elm  disease 
[Clinton  and  McCormick  (1936)],  appeared  in  Holland  in  1919, 
spread  throughout  continental  Europe  and  the  British  Isles,  and 
was  first  found  in  the  United  States  in  1930.  It  is  presumed  to 
have  been  introduced  into  the  United  States  on  burl  elm  logs. 
Now  it  is  gradually  spreading  on  American  elms  in  northern  New 
Jersey  and  other  localities  in  the  vicinity  of  New  York  City. 

Dasyscypha  ellisiana,  widely  prevalent  in  the  eastern  United 
States  on  the  bark  of  pines,  is  a  much  less  spectacular  exotic.  It 
was  first  collected  by  de  Schweinitz  in  1931  and  does  not  injure 
pines  in  any  way.  Only  recently,  how  ever,  it  was  found  capable 
of  attacking  Fsendotsnga  taxifolia  [Hahn  and  Avers  (1934)],  a 
species  that  does  not  grow  in  the  natural  range  of  D.  ellisiana. 

Species  with  erratic  distribution.  Plausible  explanations  are 
lacking  to  account  for  the  peculiar  distributional  range  of  many 
Ascomvcetes.  For  example,  Urnula  geaster,  first  collected  near 
Austin,  Texas,  in  1893,  was  known  only  from  that  location  until 
1938,  when  it  was  found  in  Japan.  So  large  and  so  striking  a  disk 
fungus  could  scarcely  have  escaped  observation  elsewhere  had 
it  been  present.  A  similar  opinion  is  held  regarding  Sarcoscypha 
minuscula,  occurring  on  dead  cedar  foliage,  which  is  known  only 
from  Portugal,  Bermuda,  and  the  Yosemitc  National  Park  [Seaver 
(1942)].  Furthermore,  Poronia  leporina,  which  is  abundant  on 
rabbit  dung  in  Bermuda  [Seaver  (1942)|,  has  been  collected  in 
North  America  only  three  times  during  a  period  of  over  50  years. 


DISTRIBUTION  OF  BASIDIOMYCETES  405 

Also,  Ophionectria  cylindrothecia  is  abundant  on  sterns  of  pal- 
metto palm  in  Bermuda  [Seaver  (1942)]  and  has  been  found  on 
cornstalks  in  Ohio. 

Many  fungi  are  limited  to  particular  substrata,  but  the  under- 
lying reasons  for  this  limitation  are  unknown.  None  of  the  spe- 
cies of  Melanconis,  Pseudovalsa,  Prosthecium,  and  Titania  occurs 
on  coniferous  wood  [Wehmeyer  (1941)],  whereas  each  species 
of  Keithia  is  limited  to  a  certain  conifer.  Keithia  tetraspora  occurs 
on  Juniperus  communis,  K.  jnniperi  on  Jwiiperus  virginiana,  K. 
tsugae  on  Tsuga  canadensis,  K.  thujina  on  Tlnija  occidentalism  and 
K.  chaviaecyparissi  on  Chamaecyparis  thyoides. 

Until  more  is  known  about  the  reasons  for  differences  between 
host  species  and  varieties  in  susceptibility  to  a  given  fungus  and 
about  the  influence  of  environment  on  the  aggressiveness  or  viru- 
lence of  pathogenic  fungi,  no  one  can  prophesy  the  probable  out- 
come of  their  introduction  into  new  areas.  Lophoderminm 
pinastri,  for  instance,  has  long  been  known  in  Europe  as  a  serious 
menace  in  pine-seedling  nurseries,  but,  although  this  fungus  is 
not  uncommon  in  the  United  States,  it  is  as  yet  nowhere  a  major 
problem. 

DISTRIBUTION  OF  BASIDIOMYCETES 

Obligate  parasitism,  as  correlated  with  host  range,  is  a  primary 
factor  in  accounting  for  the  distribution  of  the  smuts  and  rusts. 
This  is  not  so,  however,  among  Hymenomycetes  and  Gastro- 
mycetes  generally,  even  among  those  that  are  not  saprophytic. 

Distribution  of  smuts.  The  monograph  by  Clinton  (1906) 
contains  206  species  of  smuts,  of  which  114  are  strictly  North 
American.  Several  of  the  smuts,  including  Ustilago  zeae  on  maize 
and  the  stinking  smuts  of  wheat,  Tilletia  foetans  and  T.  tritici 
[Holton  and  Heald  (1941)],  are  now  and  have  been  for  a  con- 
siderable period  essentially  coextensive  in  range  with  that  of  their 
host.  Certain  others  are  less  widely  dispersed.  These  include 
Tilletia  horrida  on  rice,  which  is  endemic  in  China  and  is  known 
also  from  Indo-China,  Burma,  the  Philippine  Islands,  and  adjacent 
tropical  and  subtropical  areas.  It  was  first  introduced  during  the 
late  1890's  into  South  Carolina  with  seed  rice  sent  from  China 
[Anderson  (1899)].  Subsequently  it  has  spread  to  Louisiana  and 
Arkansas.  Another  smut,  alien  to  the  United  States,  is  Urocystis 
tritici,  causing  flag  smut  of  wheat.    In  all  likelihood  this  smut  is 


406  GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI 

endemic  to  the  Mediterranean  area.  It  was  first  noted  in  the 
United  States  in  1919  and  was  early  studied  by  Tisdale,  Dugan,  and 
Leighty  (1923)  and  Griffiths  (1924).  It  has  been  recorded  from 
China,  Japan,  India,  Australia,  Tasmania,  South  Africa,  Egypt, 
Tunis,  Italy,  Cyprus,  and  Spain.  Dissemination  in  Australia  is 
attributed  to  horses  that  are  permitted  to  forage  on  wheat  straw; 
the  smut  spores  pass  intact  through  the  alimentary  tract  and  then 
grow  in  the  droppings. 

Distribution  of  rusts.  More  is  known  about  the  distribution 
of  rusts  than  that  of  any  other  basidiomycetous  group.  Arthur 
(1929)  considers  Europe  and  North  America  as  the  best-explored 
regions  of  the  earth  for  rusts,  and  he  states  that,  as  far  as  their 
rust  flora  is  concerned,  yast  areas  of  other  continents  remain 
almost  wholly  unknown.  The  Genus  Melampsora,  according  to 
Cunningham  (1931),  constitutes  the  only  member  of  the  Melamp- 
soraceae  that  is  world-wide,  most  other  rusts  of  this  family  being 
confined  to  Europe,  Asia,  and  America.  Alilesia  also  is  regarded  as 
world-wide  by  Faull  (1932).  Another  distributional  peculiarity 
noted  by  Cunningham  (1931)  is  that  species  of  Milesia  and  Puc- 
ciniastrum,  but  none  of  Cronartium,  are  found  in  New  Zealand, 
whereas  species  of  Cronartium,  but  none  of  Milesia  nor  of  Puc- 
ciniastrum,  thrive  in  Australia.  In  connection  with  Uredinopsis, 
attacking  ferns  and  firs,  Faull  (1938)  states  that  13  species  occur 
in  the  Western  Hemisphere  north  of  Mexico,  3  in  Europe,  12  in 
Asia,  and  1  in  Africa.  Uredinopsis  m&crosperma  is  the  most  widely 
dispersed  one,  but  strangely  it  is  entirely  absent  in  many  regions 
where  its  fern  host,  Pteridium  latiusculum,  thrives.  Some  species 
have  very  limited  ranges,  such  as  U.  adianti  in  northeastern  Asia 
and  U.  investita  in  the  mountains  of  Guatemala,  both  on  Adian- 
tum.  However,  although  U.  mayoriana  is  known  from  Colombia, 
far  from  the  range  of  fir,  it  is  capable  of  producing  aecia  when 
artificially  inoculated  on  fir. 

Of  the  33  species  and  2  varieties  of  Milesia,  also  fir-fern  rusts, 
recognized  by  Faull  (1932),  only  one,  Milesia  vogesiaca,  is  com- 
mon to  both  the  Old  World  and  the  New  World.  Nine  species 
have  been  taken  in  the  United  States  and  Canada,  7  in  Central 
America,  northern  South  America,  and  the  West  Indies,  13  in 
Asia,  1 1  in  Europe,  2  in  Africa,  and  1  in  Australia.  Many  species 
of  .Milesia  have  the  ability  to  perpetuate  themselves  for  years  in 
the  entire  absence  of  species  of  Abies,  which  are  the  aerial  hosts. 


DISTRIBUTION  OF  BASIDIOMYCETES  401 

Furthermore  many  of  them  produce  new  crops  of  uredinospores 
in  the  spring  before  the  old  fern  leaves  die. 

Among  the  Pucciniaceae,  the  distribution  of  Puccinia,  Uro- 
myces,  and  Phragmidium  is  global  [Cunningham  ( 193 1 )  ] .  Trans- 
chel'ia  pruni-spinosae  occurs  throughout  the  world  wherever 
peaches  and  plums  are  grown,  and  Phrag7mdhtm  disciflorum  is 
found  wherever  cultivated  roses  can  flourish.  Other  limitations 
imposed  by  host  are  exhibited  by  Uromycladium,  confined  to 
acacias  in  Australia  and  the  East  Indies,  and  by  Phragmidium,  con- 
fined to  Rosaceae.  Except  for  a  few,  all  species  of  Gymnosporan- 
gium  have  Rosaceae  as  aecial  hosts.  Ravenelia  typically  occurs 
on  leguminous  hosts,  but  a  few  of  its  approximately  100  species 
attack  Euphorbiaceae  and  Tiliaceae. 

Influence  of  climate  on  rust  distribution.  From  the  many  sur- 
veys that  have  been  made  of  whether  the  short-cycled  rusts  and 
long-cycled  ones  are  proportionally  alike  in  all  regions  of  the 
world,  it  appears  that  short-cycled  species  are  relatively  more 
abundant  in  mountainous  regions  and  in  northern  areas  than  they 
are  in  lowlands  and  in  the  tropics.  This  fact  indicates  that,  just  as 
temperature  is  a  limiting  factor  in  latitudinal  and  altitudinal  dis- 
tribution of  seed  plants,  so  it  is  similarly  operative  among  rusts. 
In  his  summary  of  this  subject  as  it  pertains  to  North  America, 
Arthur  ( 1929)  divided  the  continent  into  the  boreal  zone,  in  which 
23%  of  the  total  rust  population  is  short-cycled,  the  temperate 
zone,  in  which  19%  is  short-cycled,  and  the  tropic  zone,  in  which 
15%  is  short-cycled. 

Latitudinal  zonation  of  rusts  is  strikingly  indicated  by  Arthur 
(1929)  as  shown  in  Table  30.  Some  of  these  genera  are  plainly 
more  northern  than  others,  and  Ravenelia  and  Uropyxis  are  to  be 
considered  tropical  and  subtropical.  In  fact,  only  3  species  of 
Ravenelia,  namely,  R.  opaca,  R.  cassiaecola,  and  R.  epiphylla, 
range  north  of  40°  north  latitude. 

Endemism  among  rusts.  Since  so  many  rusts  attack  plants  of 
economic  importance,  it  would  be  anticipated  that  each  area  into 
which  alien  plants  or  plant  parts  have  been  introduced  would  con- 
tain non-native  species  of  rusts.  That  such  is  the  case  is  shown 
by  the  work  of  Arthur  (1929).  Of  approximately  1000  species  of 
North  American  rusts,  only  about  600  are  held  to  be  endemic. 
McAlpine  (1906)  regards  31  of  the  161  rusts  in  Australia  as 
aliens. 


408  GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI 

TABLE  30 

Latitudinal  Zonation  of  North  American  Rust  Genera 

Boreal         Temperate       Tropical 


Genus 

Area 

Area 

Area 

Coleosporium 

1 

21 

16 

Melampsora 

8 

12 

3 

Pucciniastrum 

7 

10 

2 

Cronartium 

4 

6 

2 

Uredinopsis 

3 

6 

1 

Hyalospora 

1 

4 

0 

Milesia 

2 

2 

3 

Puccinia 

130 

358 

261 

Uromyces 

28 

108 

70 

Ravenelia 

0 

22 

44 

Gymnosporangium 

5 

33 

2 

Phragmidium 

13 

16 

2 

Uropyxis 

0 

6 

5 

Total  202  604  411 

The  list  of  rusts  introduced  into  North  America,  in  the  account 
by  Arthur  (1929),  contains  such  important  species  as  Cronartium 
ribicola,  Uromyces  appendiciilatus  phase  oil,  U.  appendiculatus 
vignae,  U.  betae,  U.  caryophyllinus,  U.  trifolii,  Puccinia  arachidis, 
P.  asparagi,  P.  chrysanthemi,  P.  glumarwn,  P.  malvacearum,  P. 
rubigo-vera  secalis,  and  P.  rubigo-vera  tritici. 

Cronartium  ribicola  was  first  known  from  collections  made  in 
Russia  before  1856.  In  1861  it  was  noted  in  Finland;  in  1871,  in 
East  Prussia;  in  1880,  in  Sweden;  in  1885,  in  Norway;  in  1889,  in 
France;  in  1892,  in  the  British  Isles;  and  in  1906,  in  the  United 
States. 

Puccinia  malvacearum  is  endemic  in  Chile,  where  it  was  first 
noted  in  1852.  It  did  not  reach  North  America  until  34  years 
later.  Meantime  it  spread  to  Australia  in  1857,  to  Spain  in  1869, 
to  France  in  1872,  to  Germany  and  the  British  Isles  in  1873,  to 
Italy  in  1874,  to  Switzerland  in  1875,  to  Greece  in  1877,  to  Sweden 
in  f887,  and  to  Finland  in  1890. 

Distribution  of  Septobasidium.  The  symbiotic  relationship 
between  Septobasidium  and  scale  insects,  clarified  by  the  work  of 
Couch  (1938),  serves  as  the  most  potent  factor  in  accounting  for 
the  distribution  of  members  of  this  genus.  If,  for  example,  the 
symbiotic  scale  insect  is  limited  to  the  tropics,  then  the  particular 


DISTRIBUTION  OF  BASIDIOMYCETES  409 

species  of  Septobasidium  is  likewise  restricted  to  the  tropics. 
Couch  (1938)  found  that  species  occurring  in  the  southeastern 
United  States  are  entirely  different  from  those  in  the  West  Indies. 
Moreover,  some  West  Indian  species  are  not  found  in  Central 
America  and  northern  South  America.  Again,  all  those  in  Cuba 
are  distinct  from  those  in  Jamaica,  except  for  5.  rhobarbarinum. 
This  species  is  indicated  to  be  widely  dispersed  in  Central  Amer- 
ica, tropical  Africa,  and  the  Orient. 

There  is  evidence  that  5.  pseudopedicellatum  and  S.  curtisii, 
common  on  many  native  species  of  trees  and  on  cultivated  ones 
as  well  throughout  the  southeastern  United  States,  may  have  been 
introduced  into  other  lands  with  shipments  of  trees. 

Distribution  of  other  Basidiomycetes.  Some  impressions  have 
been  recorded  of  comparative  distribution  of  agarics  in  North 
America  and  Europe  by  Lange  (1934)  and  of  the  polypores  in 
these  countries  by  Overholts  (1939).  Lange  (1934)  states  that 
70%  of  the  species  that  he  encountered  on  a  tour  across  North 
America  were  known  also  in  Europe.  He  mentions  certain  species 
that  are  common  to  both  continents,  such  as  Psalliota  silvicola  (P. 
arvensis),  Lactarius  deliciosns,  Pamis  stipticus,  Amanita  muscaria, 
A.  caesarea,  Hypholoma  fascicular  e,  Inocybe  geophylla,  Laccaria 
lac  cat  a,  Stropharia  psathyroides  and  Lepiota  cygnea.  The  differ- 
ence between  the  agaric  floras  of  the  two  continents  is  in  no  wise 
as  striking  as  are  differences  on  each  continent  due  to  latitude. 
Stropharia  depilata  is  a  boreal  species  ranging  from  the  Rocky 
Mountains  to  the  Scandinavian  subarctic  zone  [Lange  (1934)]. 
Amanita  caesarea  is  a  temperate  species  and  extends  northward  to 
southern  Denmark  and  northern  Germany.  Lange  (1934)  also 
states  that  certain  species  in  Europe  are  limited  to  the  Mediter- 
ranean region  and  rarely,  if  ever,  extend  beyond  the  Alps.  Spe- 
cies of  Marasmius,  some  of  which  cause  thread  blights,  and  Lenti- 
nus  abound  in  the  subtropics  and  tropics. 

Several  well-known  agarics,  such  as  Clitocycbe  ilhidens,  Armil- 
laria  mucida,  Colly  bia  radicata,  and  Lepiota  procera,  were  noted 
by  Bisby  (1933)  as  being  absent  from  iManitoba  for  some  un- 
known reason. 

Certain  agarics  and  Boletaceae  are  mycorrhizal,  and  some  of 
them  are  known  to  be  restricted  to  certain  species  of  trees.  In 
such  cases  the  range  of  the  tree  is  the  factor  which  governs  the 
distributional  range  of  the  particular  fungus.     (See  Chapter  13.) 


410  GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI 

Another  feature  reeardins  the  distribution  of  Basidiomvcetes 
that  has  impressed  every  mycologist  who  has  intensively  collected 
in  a  given  area  for  a  period  of  years  is  that  certain  species  found 
one  season  mav  be  entirely  absent  in  succeeding  years. 

The  extensive  studies  of  Overholts  (1939)  led  him  to  conclude 
that  of  the  227  species  of  North  American  pileate  Polyporaceae 
at  least  43%  occur  in  the  Eastern  Hemisphere.  Of  the  more  com- 
mon genera,  he  found  that  540/0  of  Fomes  and  of  Trametes  species, 
50%  of  Daedalea  and  of  Lenzites  species,  and  44%  of  Polyporus 
species  are  common  to  North  America  and  the  Old  World.  Cer- 
tain of  them,  such  as  Polyporus  conchifer  and  P.  texam/s,  are 
limited  in  range  to  that  of  their  hosts,  Uhmis  americana  and 
Prosopis  jttliflora,  respectively.  Fomes  applanatus  is  a  cosmopoli- 
tan species.  Polyporus  abietinus  can  utilize  all  species  of  conifers; 
P.  versicolor,  P.  pargamemis,  and  Lenzites  bctid'nw,  many  kinds  of 
hardwoods;  and  all  are  widely  distributed.  Fomes  pint  and  Poly- 
poms  schweinitzii,  both  capable  of  causing  heart  rots  of  conifers, 
are  widely  present  throughout  the  United  States  and  Canada. 

The  Gastromycetes  are  widely  dispersed,  with  little  evidence 
of  being  affected  by  latitude.  An  exception  is  the  Phallales,  which 
are  mostly  tropical,  whereas  the  Lycoperdales  are  temperate. 

DISTRIBUTION  OF  DEUTEROMYCETES 

The  imperfect  fungi  of  most  economic  importance  are  either 
seed-borne  or  soil-borne  or  else  are  dispersed  with  nursery  stock. 

Distribution  of  seed-borne  species.  Many  pathogenic  im- 
perfect fungi,  particularly  those  of  cultivated  plants,  have  been 
demonstrated  to  be  seed-borne  [Orton  (1931)].  This  fact  ac- 
counts for  the  wide  distribution  and  establishment  of  such  fungi 
as  Ascochyta  pisi,  leaf  and  pod  blight  of  pea;  Cercospora  beticola, 
leaf  spot  of  beet;  Cercospora  daizu,  frog-eye  leaf  spot  of  soybean; 
Collet otrichum  gossypii,  cotton  anthracnose;  C.  lagenarium,  water- 
melon anthracnose;  C.  I'mdemuthiamivi,  bean  anthracnose;  Clado- 
sporinm  fulvum,  leaf  mold  of  tomato;  Diplodia  zeae,  ear  rot  of 
corn;  Kabatiella  caidivora,  anthracnose  of  clover;  Helvnntho- 
sporhim  graminenm,  barley  stripe;  Phoma  I'm  gam,  cabbage  black- 
leg; Polyspora  Urn,  flax-stem  break;  Septoria  apii,  celery  blight; 
Septoria  ly coper sic'i,  leaf  spot  of  tomato.  Presumably  each  of 
these  fungi  occurs  wherever  its  hosts  are  cultivated,  and  com- 


DISTRIBUTION  OF  DEUTEROMYCETES  411 

petent  collectors  would  no  doubt  find  them  all  in  regions  from 
which  there  are  now  no  collection  records.  To  mention  a  few 
ranges,  Cercospora  beticola  is  known  to  be  present  in  Korea, 
Japan,  Czechoslovakia,  Hungary,  Ukraine,  Jugoslavia,  Rumania, 
Germany,  Austria,  Italy,  Poland,  Latvia,  Lithuania,  France,  Spain, 
Holland,  Belgium,  Ireland,  Morocco,  Mauritius,  Bermuda,  Cuba, 
Dominican  Republic,  the  United  States,  and  Canada.  Polyspora 
lirii  has  been  noted  on  flax  in  Ireland,  Holland,  Sweden,  Denmark, 
Germany,  Poland,  Latvia,  Russia,  Italy,  New  Zealand,  Canada,  and 
the  United  States.  Septoria  ly  coper  sici  is  known  to  occur  in  the 
United  States,  Canada,  Great  Britain,  France,  Denmark,  Germany, 
Norway,  Esthonia,  Lithuania,  Russia,  Rumania,  middle  Asia,  Cey- 
lon, southern  Australia,  Fiji,  Mauritius,  Kenya,  Morocco,  east 
Africa,  Rhodesia,  Argentina,  Brazil,  Trinidad,  Guatemala,  Ber- 
muda, and  Hawaii. 

Distribution  of  species  dispersed  with  nursery  stock.  Some 
very  important  imperfect  fungi  have  been  widely  disseminated 
with  shipments  of  nursery  stock,  for  example,  Cladospor'mm  car- 
pophiliimi,  causing  scab  and  freckle  of  stone  fruits,  Phyllosticta 
solitaria,  causing  canker,  blotch,  and  leaf  spot  of  apple,  and  Sphace- 
loma  fawcetti,  causing  citrus  scab.  Data  on  the  occurrence  of 
Cladosporhim  carpophilium  outside  the  United  States  and  southern 
Canada  are  not  abundant;  nevertheless  Keitt  (1917)  is  of  the 
opinion  that  this  species  is  present  in  all  countries  where  peach, 
nectarine,  and  cherry  are  grown.  Austria,  Germany,  Bulgaria, 
Holland,  South  Africa,  New  South  Wales,  and  Brazil  are  among 
the  regions  where  C.  carpophilium  is  known  to  occur. 

Phyllosticta  solitaria  has  not  been  given  serious  attention  out- 
side the  central  and  eastern  United  States.  Guba  (1925)  suspected 
that  wild  crabapple,  Pyrus  coronaria,  is  the  original  host  and 
source  of  inoculum.  This  fungus  has  been  reported  from  Argen- 
tina, Rhodesia,  Spain,  and  Holland. 

Sphaceloma  jauccetti  is  believed  [Fawcett  (1926)  ]  to  have  been 
present  in  Japan  since  ancient  times,  but  it  was  given  little  atten- 
tion until  its  discovery  in  Florida  about  1886.  It  occurs  also  in 
China,  India,  the  East  Indies,  Australia,  New  Zealand,  Hawaii, 
Brazil,  and  Argentina. 

Distribution  of  soil-borne  species.  Many  of  the  Moniliales 
are  soil-borne.  The  outstanding  representative  of  this  group  of 
imperfect  fungi  is  Phymatotrichum  omnivorum,  commonly  called 


412  GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI 

the  Texas  root-rot  fungus.  The  appropriateness  of  its  specific 
name  is  indicated  by  the  fact  that  it  is  known  to  attack  more  than 
1 700  species  of  flowering  plants,  more  than  does  any  other  known 
pathogen.  An  appreciation  of  the  destructiveness  of  P.  omni- 
vorum  can  be  gained  from  the  fact  that  a  complete  bibliography 
of  it  would  include  about  300  titles,  and  annual  losses  which  it 
occasions  are  estimated  to  approximate  one  hundred  million 
dollars. 

Its  range  extends  throughout  the  greater  part  of  Texas  and  con- 
tiguous parts  of  Arkansas,  Oklahoma,  New  Mexico,  and  .Mexico. 
It  also  occupies  areas  in  Arizona,  California,  Nevada,  and  Utah. 
Its  existence  outside  this  range  has  been  noted  in  the  Dominican 
Republic,  Hawaii,  and  (doubtfully)  Russia. 

Active  dissemination  is  accomplished  largely  bv  growth  of  the 
fungus  through  the  soil,  where  it  may  hibernate  by  means  of 
sclerotia. 

Various  species  of  Fusarium  that  live  saprophytically  in  the  soil 
for  long  periods  and  cause  wilt  diseases  when  the  appropriate 
crop  is'planted  on  such  a  soil  are  also  included  in  this  group. 
Among  them  are  Fusarium  vasinfectum  on  cotton,  F.  cubense  on 
banana,  F.  oxysporum  on  potato,  F.  lycopersici  on  tomato,  F. 
niveum  on  watermelon,  and  F.  lini  on  flax.  All  are  widely  dis- 
persed in  any  region  where  these  crops  are  grown. 

IMPLICATIONS 

It  is  quite  apparent  that  no  comprehensive  information  regard- 
ing fungus  floras  throughout  the  world  is  available  at  this  time. 
Many  additional  monographic  studies  of  fungal  groups  must  first 
be  made,  and  also  many  more  lists  of  the  type  of  the  Host  Index 
of  the  Fungiof  North  America  [Seymour  ( 1929)],  The  Fungi  of 
Manitoba  [Bisbv,  Buller,  and  Dearness  (1929)],  The  Fungi  of 
India  [Butler  and  Bisby  (1931)],  and  British  Stem  and  Leaf  Fungi 
[Grove  (1935,  1937)]  must  be  prepared.  Seymour's  book  in- 
cludes about  half  of  all  the  known  species  of  fungi,  and  about 
60c  of  the  Canadian  species  listed  by  Bisby  et  al.  (1929)  are  also 
known  to  occur  in  Europe. 

Students  of  the  geographic  distribution  of  fungi  seem  agreed 
that  climate  has  a  controlling  effect  [Bisby  ( 1943)  ],  Diehl  (1937), 
Lind    (1934).     Diehl    (1937)    concluded  that  the   life  zones   of 


IMPLICATIONS  413 

fungus  vegetation  are  bounded  or  delimited  by  climatic  lines  or 
factors.  These  climatic  factors  operate  by  controlling  the  distri- 
bution of  the  particular  substrata,  for  both  endemic  and  exotic 
species.  The  provinces  of  fungi  are  delimited  by  such  natural 
barriers  as  climate,  oceans,  mountains,  deserts,  wind  direction,  and 
vectors,  but  man  has  operated  to  break  down  these  barriers  and 
to  carry  the  fungi  over  them  into  new  sites. 

Lind  (1934)  has  also  emphasized  the  influence  of  climate  as  a 
factor  in  distribution. 

Of  the  422  species  collected  in  the  Arctic,  Lind  indicates  that 
many  occur  also  in  the  Alps  and  are  otherwise  widespread  and 
that  no  genus  in  these  collections  is  endemic  to  the  northern  polar 
region. 

Bisby's  (1943)  opinion  is:  "There  are  perhaps  three  times  as 
many  [species  of]  phanerogams  as  fungi  on  earth."  Moreover 
saprophytic  species  generally  have  a  wider  distribution  than  do 
parasitic  ones,  although  distribution  of  substrata  and  hosts  is  of 
primary  importance  as  a  control  factor. 

The  natural  ranges  and  habitats  of  fungi  tend  toward  the  estab- 
lishment of  stability  and  biological  balance.  Man  has  always  up- 
set this  stability  by  intensive  cultivation  of  a  given  species  of  host 
in  a  limited  area,  bv  constructing  artificial  environments  such  as 
cold  frames  and  greenhouses,  in  which  to  grow  plants,  by  attempts 
to  grow  crops  in  new  areas,  and  by  introducing  fungi  into  areas 
where  the  environment  unfortunately  has  too  frequently  proved 
more  favorable  for  the  fungi  than  did  their  natural  range.  In  re- 
gard to  the  results  of  man's  activities  upon  the  distribution  of 
fungi,  it  is  apparent  that  he  has  indeed  made  his  own  difficulties 
and  problems;  nevertheless  he  seems  to  thrive  in  spite  of  his 
tendency  to  learn  things  the  hard  way. 

There  are  good  reasons  for  believing  that  some  so-called  new 
diseases  of  cultivated  plants  are  not  caused  by  new  species  of  fungi 
but  by  old  ones  long  present  in  a  particular  locality.  As  a  result 
of  the  conditions  that  obtain  under  cultivation,  the  host  may 
succumb  to  attack,  whereas  it  might  be  immune  in  its  natural  or 
native  habitat.  Of  course,  it  must  always  be  remembered  that 
both  the  susceptibility  of  the  host  and  the  aggressiveness  of  the 
parasite  are  influenced  by  environmental  factors  which  may 
eventuate  in  a  modification  of  the  distributional  range  both  of  the 
host  and  of  the  parasite. 


414  GEOGRAPHICAL  DISTRIBUTION  OF  FUNGI 

Because  of  the  enormous  financial  outlay  that  has  become 
necessary  in  connection  with  quarantines  and  with  the  control  and 
eradication  of  fungi  already  introduced,  all  exotics  should  per- 
force be  regarded  as  potentially  undesirable  aliens  and  should  be 
so  treated.  Some  fungi  are  closely  restricted  in  range  and  are 
very  complacently  provincial,  some  can  be  widely  transplanted 
without  becoming  obnoxious,  some  are  exceedingly  noisome  when 
transported  to  new  environments,  and  some  are  naturally  cosmo- 
politan and  international  and,  in  consequence,  have  become  widely 
established. 

LITERATURE  CITED 

Anderson,  A.  P.,  "A  new  Tilletia  parasitic  on  Oryza  sativa"  Botan.  Gaz., 
21: 461-411,  1899. 

Arthur,  J.  C,  et  al.,  The  plant  rusts  (Uredinales) .  446  pp.  John  Wiley 
and  Sons,  New  York.     1929.     (See  Chap.  V,  pp.  161-205.) 

Bisby,  G.  R.,  "The  distribution  of  fungi  as  compared  with  that  of  phanero- 
gams," Am.  J.  Botany,  20:246-254,  1933. 
"Geographical  distribution  of  fungi,"  Botan.  Rev.,  9:  466-482,  1943. 

Bisby,  G.  R.,  and  G.  C.  Ainsworth,  "The  numbers  of  fungi,"  Trans.  Brit. 
Mycol.  Soc,  26:  16-19,  1943. 

Bisby,  G.  R.,  A.  H.  R.  Buller,  and  J.  Dearness,  The  fungi  of  Manitoba. 
viii  +  194  pp.    Longmans,  Green,  and  Co.,  London.     1929. 

Butler,  E.  J.,  and  G.  R.  Bisby,  The  fungi  of  India,  Imper.  Counc.  Agr.  Re- 
search, Sci.  Monograph  I.    xviii  +  237  pp.     1931. 

Carr,  L.  G.,  "A  comparison  of  Mycetozoa  found  in  sandstone  and  limestone 
regions  of  Augusta  County,  Virginia,"  Mycol.,  SI:  157-160,  1939. 

Clayton,  E.  E.,  and  J.  A.  Stevenson,  uPeronospora  tabacina  Adam,  the  or- 
ganism causing  blue-mold  (downy-mildew)  disease  of  tobacco,"  Phyto- 
pathology, 55:  101-113,  1943. 

Clinton,  G.  P.,  "Ustilaginales,"  North  Am.  Flora,  1:  1-82,  1906. 

Clinton,  G.  P.,  and  F.  A.  McCormick,  "Dutch  elm  disease,  Graphium  uhn'u' 
Conn.  Agr.  Expt.  Sta.  Bull.,  389:  707-752,  1936. 

Couch,  J.  N.,The  genus  Septobasidium.  480  pp.  University  of  North 
Carolina  Press.    1938. 

Cunningham,  G.  H.,  The  rust  fungi  of  New  Zealand,  together  with  the 
biology,  cytology,  and  therapeutics  of  the  Uredinales.  xx  +  261  pp. 
J.  .Mclndoe,  Dunedin,  New  Zealand.     1931. 

Diehl,  W.  W.,  "A  basis  for  mycogeography,"  /.  Washington  Acad.  Sci., 
21:  244-254,  1937. 

Faull,  J.  H.,  "Taxonomy  and  geographical  distribution  of  the  genus  Milesia," 
Contrib.  Arnold  Arboretum,  2:5-138,  1932. 
"Taxonomy   and    geographical    distribution    of   the    genus    Uredinopsis," 
Contrib.  Arnold  Arboretum,  11:5-120,  1938. 


LITERATURE  CITED  415 

Fawcett,  H.  S.,  and  H.  A.  Lee,  Citrus  diseases  and  their  control,    xii  +582 

pp.    McGraw-Hill  Book  Co.,  New  York.    1926. 
Fries,  R.  E.,  "Myxomyceten  von  Argentinien  und  Bolivia,"  Ark.  Bot.,  1:  57- 

70,  1903. 
Griffiths,  Marion  A.,  "Experiments  with  flag  smut  of  wheat  and  the  causal 

fungus,  Urocystis  tritici  Kcke,"  /.  Agr.  Research,  27:425-449,  1924. 
Grove,  W.  B.,  British  stem  and  leaf  fungi  (Coelomycetes),  1:  xx  +  488  pp., 

1935;  2:  xi  +  406  pp.,  1937.    Cambridge  University  Press. 
Guba,  E.  F.,  "Phyllosticta  leaf  spot,  fruit  blotch  and  canker  of  the  apple: 

etiology  and  control,"  ///.  Agr.  Expt.  Sta.  Bull.,  255:481-557,  1925. 
Hahn,  G.  G.,  and  T.  T.  Ayers,  "Dasyscyphae  on  conifers  in  North  Amer- 
ica   II.  Dasyscypha  ellisiana,"  My  col.,  26: 167-180,  1934. 
Holton,  C.  S.,  and  F.  D.  Heald,  Bunt  or  stinking  smut  of  wheat  (a  world 

problem).    ii  +  211pp.    Burgess  Publishing  Co.,  Minneapolis.     1941. 
Karling,  J.  S.,  Plasmodiophorales.    ix  +  144  pp.    Published  by  the  author, 

New  York.    1942. 
Keitt,  G.  W.,  "Peach  scab  and  its  control,"  U.  S.  Dept.  Agr.  Bull.,  395: 1-66, 

1917. 

Lange,  J.  E.,  "Mycofloristic  impressions  of  a  European  mycologist  in  Amer- 
ica," My  col,  26:  1-12,  1934. 

Lind,  J.,  "Studies  on  the  geographical  distribution  of  arctic  circumpolar 
micromycetes,"  Kgl.  Danske  Videnskb.  Selskab  Biol.  Medd.,  11  (12):  1- 
152,  1934. 

MacBride,  T.  H.,  "Mountain  Myxomycetes,"  My  col.,  6: 146-149,  1914. 

Martin,  G.  W.,  "The  Myxomycetes,"  Botan.  Rev.,  6:  356-388,  1940. 

McAlpine,  D.,  The  rusts  of  Australia.    349  pp.    1906. 

Orton,  C.  R.,  "Seed-borne  parasites,  a  bibliography,"  West  Va.  Agr.  Expt. 
Sta.  Bull.,  245: 3-47, 1931. 

Overholts,  L.  O.,  "Geographical  distribution  of  some  American  Polypo- 
raceae,"  My  col,  31:  629-652,  1939. 

Salmon,  E.  S.,  "A  monograph  of  the  Erysiphaceae,"  Mem.  Torrey  Botan. 
Club,  9.    292  pp.    1900. 

Seaver,  F.  J.,  The  North  American  cup  fungi  (Operadates) .    284  pp.    Pub- 
lished by  the  author,  New  York.     1928. 
"The  mvcoflora  of  Bermuda,"  Science,  96: 462-463,  1942. 

Seymour,  A.  B.,  Host  index  of  the  fungi  of  North  America,  xiii  +  732  pp. 
Harvard  University  Press.     1929. 

Smith,  E.  C,  "Ecological  observations  on  Colorado  Myxomycetes,"  Tor- 
reya,  37:42-44,  1931. 

Thom,  C,  and  K.  B.  Raper,  "Myxamoebae  in  soil  and  decomposing  crop 
residues,"  /.  Wash.  Acad.  Sci.,  20:  362-370,  1930. 

Tisdale,  W.  H.,  G.  H.  Dugan,  and  C.  E.  Leighty,  "Flag  smut  of  wheat  with 
special  reference  to  varietal  resistance,"  ///.  Agr.  Expt.  Sta.  Bidl,  242:  511- 

537,  1923 
Wehmeyer,  L.  E.,  "A  revision  of  Melanconis,  Pseudovalsa,  Prosthecium,  and 
Titania,"  Univ.  Mich.  Studies,  14.     161  pp.     1941. 


Chapter  18 
MYCOLOGY  IN  RELATION  TO  PLANT  PATHOLOGY 

Plant  materials  constitute  the  substrate  on  which  nearly  all 
fungi  thrive  in  their  natural  habitats.  Relatively  few  utilize  ani- 
mals  or  animal  tissues  as  substrates  of  first  choice.  Furthermore 
many  fungi,  whether  saprogenic  or  pathogenic,  are  quite  closely 
restricted  to  a  particular  plant  species.  The  fundamental  reasons 
for  these  idiosyncrasies  in  the  choice  of  food  are  not  without  sig- 
nificance, but  they  remain  quite  unknown  beyond  the  point  that 
there  is  a  correlation  between  the  enzyme-producing  abilities  of 
each  fungus  and  the  kind  of  substrate  on  which  it  grows. 

The  idea  that  all  fungi  are  either  parasitic  or  saprophytic  has 
had  far-reaching  consequences.  It  has  had  a  deleterious  effect 
primarily  on  understanding  the  activities  of  fungi  and  secondar- 
ily on  appreciating  the  intimate  interdependence  of  mycology 
and  plant  pathology.  It  is  not  uncommon  for  a  plant  pathologist 
to  remark  that  parasitic  fungi  are  of  interest  to  him  but  that 
saprophytic  species  are  of  no  concern.  He  chooses  to  entrust 
saprophytic  species  to  the  tender  care  of  a  mycologist!  In  so  do- 
ing he  may  overlook  the  fact  that  a  particular  species  may  have 
both  a  parasitic  and  a  saprophytic  phase.  Perhaps  the  terms  para- 
sitic and  saprophytic  have  outlived  a  measure  of  their  usefulness. 

A4uch  information  regarding  the  natural  habitats  of  fungi  has 
come  from  studies,  not  of  saprogenic  species,  but  of  pathogenic 
ones  and  has  therefore  been  contributed  by  plant  pathologists.  In 
so  far  as  such  studies  have  emphasized  the  disease  aspect,  including 
disease  prevention  and  control,  they  properly  constitute  the  sub- 
ject matter  of  phytopathology.  On  the  other  hand,  in  so  far  as 
such  studies  pertain  to  the  etiologic  agent  itself,  they  belong  to 
mycology.  The  two  fields  are  therefore  closely  interrelated,  as 
may  be  brought  out  by  consideration  of  their  parallel  develop- 
ment, but  they  have  grown  to  be  quite  distinct.  In  fact,  some 
workers  regard  mycology  as  the  parent  science  and  phytopathol- 

416 


EARLY  CONCEPTS  OF  DISEASE  IN  PLANTS  411 

ogy  as  the  offspring.  The  purpose  of  this  discussion  is  to  bring 
these  interrelations  into  perspective.  To  anyone  who  attempts 
to  do  this  properly,  it  soon  becomes  apparent  that  the  task  is 
herculean,  for  the  reason  that  the  subject  matter  of  each  field  of 
science  is  dispersed  in  a  bewildering  array  of  books,  technical  re- 
ports, and  bulletins.  Manifestly  it  is  impossible  to  accomplish 
such  a  task  within  the  scope  of  a  single  chapter.  Moreover,  to 
date  no  one  has  attempted  a  comprehensive  interpretative  history 
of  mycologic  and  phvtopathologic  development.  Little  more  can 
be  attempted  in  this  discussion  than  to  point  out  a  few  of  the  land- 
marks along  the  pathway,  beginning  with  the  completely  un- 
scientific era  from  which  both  mycology  and  plant  pathology 
emerged  and  ending  with  present-day  concepts.  Both  fields,  as 
was  briefly  indicated  in  Chapter  1,  Vol.  I,  had  their  beginnings 
in  the  dim,  distant  past,  long  before  the  period  of  recorded  his- 
tory. The  development  of  each  has  been  dependent,  as  would 
be  expected,  upon  advances  in  such  fields  as  bacteriology,  medi- 
cine, animal  pathology,  physics,  and  chemistry,  and  especially 
upon  the  improvisation  of  new  methods  or  techniques. 

EARLY  CONCEPTS  OF  DISEASE  IN  PLANTS 

Some  appreciation  of  the  ideas  concerning  disease  in  plants  that 
prevailed  before  1807  may  be  gained  from  a  treatise  by  Re  (1807). 
Later  Smith  (1902,  1929),  Arthur  (1906),  and  Whetzel  (1918) 
sketched  the  background  against  which  present-day  ideas  can  be 
interestingly  evaluated.  As  these  writers  point  out,  man  long 
recognized  the  existence  of  disease,  especially  among  cultivated 
plants,  but  from  earliest  times  such  diseases  were  uniformly  inter- 
preted as  supernatural  phenomena  and  ascribed  to  offended  deities. 
Later  came  the  belief,  generally  accepted  among  scientists,  that 
fungi  were  generated  by  the  host  or  suscept  on  which  they  oc- 
curred. The  works  of  Unger,  Meyen,  and  Hallier  [Whetzel 
( 1918)  ]  are  based  on  this  concept. 

Certain  other  contemporary  writers,  however,  held  a  different 
opinion,  as  is  shown  by  the  observations  of  Fontana,  published  in 
1767,  in  which  he  made  the  following  statement  regarding  grain 
rust:  "We  are  dealing  with  a  great  number  of  hungry  and  in- 
satiable plants  that  live  by  violence,  feeding  at  the  expense  of  the 
tender  green  plant;  they  grow  rapidly,  thanks  to  the  food  that 


418     MYCOLOGY  IN  RELATION  TO  PLANT  PATHOLOGY 

they  steal  from  the  grain,  feeding  in  a  great  number  of  places, 
stopping  entirely  the  flow  of  the  already  prepared  and  digested 
juice,  which  is  to  nourish  the  grain  and  to  be  converted  into  pulp 
and  flour." 

The  mystical  and  ethereal  nature  of  the  cause  of  disease  in  plants 
was  also  refuted  by  Fabricius  in  a  treatise  published  in  1774,  in 
which  he  maintained  that  smut  is  caused  by  "something  origan- 
ized,"  that  is,  something  living,  and  by  Prevost  in  a  dissertation 
published  in  1807,  in  which  he  concluded  that  rust  and  smut  dis- 
eases are  produced  by  "internal  parasitic  plants."  These  ideas  did 
not  gain  acceptance  among  scientists,  however,  and  the  real  turn- 
ing point  in  progress  on  the  nature  of  disease  in  plants  came  with 
the  publication  in  1853  of  Die  Brand  Pilze,  based  on  experimenta- 
tion by  de  Barv.  He  showed  that  the  rust  and  smut  fungi  are 
entities  that  induce  disease  by  growth  within  the  host  tissues,  with 
resultant  modification  of  the  structure  and  the  function  of  the  in- 
fected plants. 

CONTRIBUTORY  ADVANCES  IN  BACTERIOLOGY 

The  impact  of  such  conclusions  from  the  work  of  de  Barv  upon 
mycology  and  plant  pathology  can  be  appreciated  only  if  con- 
sidered in  connection  with  discoveries  that  had  already  been  made 
or  were  made  soon  thereafter  in  other  fields,  especially  bacteriol- 
ogy. It  should  be  remembered  that  for  a  long  time  scientific 
thought  was  permeated  with  the  concept  that  many  kinds  of  liv- 
ing things,  especially  those  of  microscopic  proportions,  originated 
by  spontaneous  generation.  Using  goose-necked  flasks  containing 
fermentable  fluids,  Pasteur  demonstrated  with  finality  that  fermen- 
tations may  be  induced  by  air-borne  bacteria  and  that  during 
fermentation  these  bacteria  generate  other  bacteria  like  them- 
selves.  This  discovery  led  to  his  subsequent  studies,  which  served 
as  the  basis  for  the  establishment  of  the  germ  theory  of  disease 
in  animals,  a  theory  that  soon  came  to  pervade  the  entire  field  of 
medicine.  Concurrently  came  the  development  of  laboratory 
methods  for  the  isolation  and  cultivation  of  organisms  in  pure  cul- 
ture, notably  (1)  the  use  of  semisolid  media,  originating  with  the 
work  of  Koch  on  the  anthrax  bacillus;  (2)  the  use  of  cotton 
stoppers,  interposed  between  the  medium  and  the  open  air  to 
strain    out    organisms    floating    in    the    air,    first    employed    by 


SIGNPOSTS  ALONG  THE  PHYTOPATHOLOG1CAL  PATH      419 

Schroder  and  Dusch;  and  (3)  the  establishment  of  pathogenicity 
by  compliance  with  axiomatic  rules  of  proof,  called  Koch's  rules. 
Gradually  other  techniques  from  procedures  developed  in  bac- 
teriology were  adapted  for  use  in  studying  fungi.  These  tech- 
niques involve  the  influence  of  such  environmental  factors  as  tem- 
perature, food  requirements,  and  hydrogen-ion  concentration  of 
the  medium  and  the  complex  reactions  involved  in  studies  of 
antigenic  properties  of  fungi. 

SIGNPOSTS  ALONG  THE  PHYTOPATHOLOGICAL  PATH 

Certain  outstanding  events  and  discoveries  indicate  the  course 
of  development  in  any  field  of  science.  Those  in  phytopathology, 
as  has  been  stated,  have  been  very  directly  and  quite  uniformly 
related  to  mycology.  The  most  significant  are  categorically  listed 
as  follows: 

1.  The  epiphytotics  of  late  blight  of  potatoes  in  1843,  1844, 
and  1845  in  northern  Europe  and  the  British  Isles.  The  destruc- 
tion of  the  potato  crop  was  so  complete  that  in  Ireland  alone 
approximately  a  quarter  of  a  million  persons  died  of  famine.  As 
a  secondary  consequence  of  the  catastrophe,  attempts  were  made 
to  determine  the  cause  and  control  of  this  potato  disease,  and 
plant  pathology,  as  a  science,  may  properly  be  concluded  to  have 
originated  with  these  studies.  For  the  first  time  the  public  appre- 
ciated the  significance  and  the  necessity  of  plant  pathological 
investigations. 

2.  The  publication  in  1853  of  the  first  textbook  of  plant 
pathology  by  Julius  Kiihn,  who  is  generally  regarded  as  the 
father  of  plant  pathology.  In  this  book  considerable  emphasis 
is  placed  on  the  disease  itself  rather  than  on  its  cause.  This  is 
true  also  of  important  books  that  followed,  such  as  those  by 
Berkeley,  Cooke,  Hartig,  Sorauer,  W.  G.  Smith,  Tubeuf,  Kirch- 
ner,  Ward,  Comes,  Prillieux,  Massee,  and  Viala;  all  of  these,  how- 
ever, are  preponderantly  mycologic. 

3.  The  establishment  of  proof  of  the  heteroecism  of  rusts  by 
de  Bary  in  1864  to  1865.  The  relationship  between  rust  on  wheat 
and  that  on  barberry  had  long  been  suspected  by  farmers.  In 
fact,  they  had  compelled  the  enactment  of  legislation  providing 
for  the  eradication  of  barberry  as  early  as  1660  in  France  and  as 
early  as  1726  in  the  state  of  Connecticut. 


420     MYCOLOGY  IN  RELATION  TO  PLANT  PATHOLOGY 

4.  Outbreaks  of  downy  mildew  on  grapes  in  Europe,  espe- 
cially in  the  vineyards  of  France  and  Italy.  The  causal  fungus, 
Plamwpora  viticola,  indigenous  in  the  United  States,  had  been  in- 
troduced into  Europe  in  1878.  In  order  to  prevent  pilfering  of  his 
grapes,  a  grower  sprinkled  his  vines  with  a  mixture  of  lime  and 
copper  sulphate.  Millardet  noted  that  the  grapes  so  treated  re- 
mained free  from  downy  mildew,  and  as  an  eventual  result  the 
world's  best-known  fungicide,  Bordeaux  mixture,  was  developed. 

5.  The  establishment  of  the  Office  of  Vegetable  Pathology  in 
the  United  States  Department  of  Agriculture  and  the  organization 
of  the  state  agricultural  experiment  stations  under  the  Hatch  act, 
both  in  1887.  Provision  was  thus  made  for  the  first  time  for  the 
initiation  of  organized  research  on  diseases  of  crop  plants.  In 
the  beginning  only  meager  financial  support  was  forthcoming 
for  this  work,  but  the  appropriation  has  increased  throughout  the 
years  in  proportion  to  needs  and  to  growing  appreciation  of  the 
importance  of  such  studies. 

6.  The  publication  of  Saccardo's  Sylloge  Fimgorinn,  a  com- 
pendium containing  descriptions  of  all  known  species  of  fungi. 
This  monumental  work,  the  first  volume  of  which  appeared  in 
1882,  now  contains  twenty-five  volumes.  It  is  truly  a  requisite 
for  the  mycologist  and  phvtopathologist. 

7.  The  introduction  of  two  species  of  alien  fungi,  Endothia 
parasitica,  causing  chestnut  blight,  and  Cronartium  ribicola,  caus- 
ing blister  rust  of  five-needle  pines.  Endothia  parasitica  was  first 
noted  in  the  United  States  in  1904  and  Cronartium  ribicola  in 
1906.  These  two  organisms  became  widely  dispersed  with  rapid- 
ity, and  their  ravages  stimulated  the  general  public  to  an  apprecia- 
tion of  the  destructiveness  of  plant  diseases  and  to  an  interest  in 
problems  of  disease  prevention  and  control. 

8.  The  establishment  of  the  Federal  Plant  Quarantine  Law  in 
1912.  The  enactment  of  this  law  was  the  outgrowth  of  experi- 
ences with  chestnut  blight  and  with  blister  rust  of  white  pines. 
Moreover  it  was  the  first  legalized  effort  by  a  nation  to  exclude 
foreign  pests  and  plant  diseases. 

9.  The  organization  of  departments  of  plant  pathology  at 
Cornell  University  in  1907  and  at  the  University  of  Wisconsin  in 
1909  for  the  training  of  specialists  in  research  and  the  teaching  of 
plant  pathology.    The  emphasis  on  instruction  in  so-called  plant 


DEVELOPMENTS  IN  TERMINOLOGY  421 

pathology  up  to  that  time  had  been  largely  taxonomic  mycology, 
and  in  fact  it  remains  all  too  much  so  to  this  day. 

10.  The  organization  of  the  American  Phytopathological  So- 
ciety in  1909  and  the  publication  of  Phytopathology,  the  official 
organ  of  this  society,  beginning  in  1911.  The  charter  member- 
ship included  130  names,  but  the  membership  has  now  grown  to 
well  over  1000  persons.  These  two  agencies,  the  society  and  the 
journal,  have  been  potent  factors  in  stimulating  interest  and  in 
directing  the  trend  of  phytopathologic  development  not  only 
throughout  the  United  States  but  also  throughout  the  world. 

11.  The  initiation  of  the  abstract  journal,  Review  of  Applied 
Mycology,  at  the  Kew  Gardens  in  1922.  This  journal,  published 
at  regular  intervals  throughout  the  year,  contains  complete  refer- 
ences to  all  current  publications  on  plant  pathology,  together  with 
a  summary  of  the  content  of  each  report.  It  is  absolutely  indis- 
pensable as  a  tool  in  keeping  abreast  of  developments  in  mycology 
and  plant  pathology. 

DEVELOPMENTS  IN  TERMINOLOGY 

Correct  terminology  is  essential  properly  to  express  concepts 
in  any  field  of  learning.  Certain  terms  have  been  used  both  in 
mycology  and  in  phytopathology  without  regard  to  precision 
of  expression,  and,  as  a  consequence,  confusion  and  inaccuracies 
have  appeared.  Fortunately  some  of  these  inaccuracies  have  been 
rectified,  as  inevitably  occurs  during  the  course  of  the  normal 
development  of  a  science.  The  terminology  in  both  fields  could 
be  expected  to  have  much  in  common,  especially  during  their 
formative  periods.  In  fact,  in  the  beginning  the  terminology  of 
mycology  and  phytopathology  reflected  the  influence  of  animal 
pathology  and  medicine,  since  many  of  the  early  workers  in  the 
newer  fields  were  medical  practitioners  or  at  least  had  been 
trained  in  medicine.  This  fact  is  demonstrated  by  the  use  in 
Fabricius'  treatise  of  1774  of  such  terms  as  anasarca,  gangraena, 
tabes,  exulceratio,  polysarcia,  and  carcinoma.  Moreover,  in  the 
period  before  1850,  the  employment  of  such  names  in  connection 
with  diseases  of  plants  as  icterus,  anemia,  phlegmasia,  fluxion  or 
bleeding,  verrucosis,  and  exanthema  is  further  confirmation  of  the 
influence  of  medical  terminology. 


422      MYCOLOGY  IN  RELATION  TO  PLANT  PATHOLOGY 

During  the  latter  half  of  the  nineteenth  century  the  overwhelm- 
ing interest  in  plant  diseases  centered  around  etiology.  In  the 
textbooks  of  this  period,  as  in  nearly  all  recent  textbooks,  plant 
diseases  are  arranged  on  the  basis  of  the  classification  of  the  etio- 
lo^ic  agent.  The  reasons  for  this  situation  are  numerous  and  in- 
clude the  following: 

1.  The  period  of  50  years  after  the  overthrow  of  the  theory  of 
spontaneous  generation,  now  regarded  as  the  "golden  age  of  dis- 
covery" in  bacteriology,  was  also  the  golden  age  of  discovery  in 
fields  pertaining  to  bacteria  and  fungi  as  causes  of  disease  in  plants. 
In  this  period  the  cause  of  a  disease  and  the  disease  itself  were  all 
too  commonly  regarded  as  synonymous.  The  connotation  host- 
parasite,  which  indicates  a  food  relationship,  became  a  common- 
place and  was  used  instead  of  pathogen-suscept,  which  indicates 
the  disease  relationship.  Writers  spoke  of  "spread  of  disease"  and 
"spread  of  infection"  when  they  meant  spread  of  inoculum  or  of 
pathogenic  agents.  These  examples  indicate  the  confusion  of 
ideas  that  have  been  carried  over  from  mycology  to  phyto- 
pathology. 

2.  The  emphasis  in  studies  of  plant-pathogenic  fungi  has  re- 
mained so  overwhelmingly  etiologic  that  even  at  the  present  time 
too  little  recognition  is  being  given  to  the  influence  of  "predispos- 
ing factors,"  as  stressed  by  Sorauer,  and  to  the  morbid  anatomy 
of  diseased  plants,  as  stressed  by  Kiister  (1925)  in  his  first  edition 
of  Phytopathologische  Pflanzenanatomie,  which  appeared  in  1903. 
That  plant  diseases  should  be  classified  on  the  basis  of  the  disease 
processes  themselves  is  cogently  argued  by  Whetzel  (1929).  It  is 
becoming  increasingly  apparent  that  instead  of  stating  that  a 
given  fungus  is  the  cause  of  a  particular  disease  one  should  state 
that  it  is  one  of  the  causes,  because  environmental  factors  may 
exert  a  controlling  influence.  It  is  also  apparent  that  the  classifica- 
tions of  disease  by  Kiister  are  fundamental,  and  future  develop- 
ments must  be  built  on  his  scheme. 

3.  The  investigators  of  this  period  lacked  training  in  phyto- 
pathology, and  in  consequence  their  attention  was  centered  pri- 
marily on  the  pathogen,  with  only  passing  consideration  being 
given  the  diseased  plant.  In  their  scientific  writings  they  em- 
ployed terms  from  fields  of  knowledge  with  which  they  were 
familiar.  As  soon  as  interest  shifted,  a  distinctive  terminology, 
applicable  only  to  plant  pathology,  began  to  develop,  as  exempli- 


FUNGI  AS  ANTIGENS  AND  PLANT  PATHOLOGY  423 

fied  by  such  common  terms  as  wilt,  scorch,  blight,  scald,  stripe, 
die-back,  shot  hole,  leak,  damping-ofT,  chlorosis,  stunt,  dwarf, 
drop,  russet,  intumescence,  curl,  gall,  and  scab,  all  of  which  indi- 
cate characteristic  symptoms  of  disease.  With  the  increase  in 
knowledge  of  changes  in  cellular  structure  and  function  induced 
by  pathogenic  fungi,  technical  terms  have  been  and  are  being 
introduced,  just  as  they  were  in  the  field  of  animal  pathology. 
Also  there  is  an  increasing  tendency  among  plant  pathologists  to 
classify  diseases  as  root-rot  diseases,  fruit  diseases,  leaf  diseases, 
seedling  diseases,  etc.,  terms  analogous  to  respiratory  diseases,  gas- 
trointestinal diseases,  skin  diseases,  etc.,  as  used  by  the  medical 
worker.  There  is  now  a  growing  tendency  to  clarify  terminol- 
ogy as  belonging  to  mycology  or  to  phytopathology  and  to  em- 
ploy terms  that  are  distinctive  in  each  field. 

FUNGI  AS  ANTIGENS  AND  PLANT  PATHOLOGY 

A  very  extensive  literature  on  studies  of  resistance  to  disease 
among  plants  exists  and  has  been  recently  reviewed  by  Wingard 
(1941).  Nearly  all  such  studies  deal  with  natural  immunity,  as 
opposed  to  acquired  immunity.  Experimental  evidence  that  plants 
may  acquire  immunity  after  being  "vaccinated"  and  that  anti- 
body formation  results  was  first  submitted  approximately  40  years 
ago.  Plant  pathologists  generally  have  not  reacted  favorably  to 
this  type  of  research  and  have  given  it  little  credence  for  the  rea- 
son that  plants  lack  a  tissue  system  comparable  with  the  circula- 
tory system  in  animals.  Nevertheless  additional  reports  have  ap- 
peared from  time  to  time  of  studies  that  tend  to  support  the  possi- 
bility of  acquired  immunity  in  plants.  An  excellent  monographic 
review  of  such  studies,  together  with  a  summary  of  their  own 
work,  was  prepared  by  Carbone  and  Arnaudi  (1930).  The  "vac- 
cines" used  were  either  injected  into  plants  or  applied  to  the 
surface  of  seeds  before  planting.  Arnaudi  (1933)  prepared  vac- 
cine of  Thielaviopsis  basicola  from  dried  powdered  mycelial  mat 
or  from  fresh  mycelial  mat  mixed  with  sand  and  triturated  in  a 
mortar.  These  vaccines  were  applied  to  the  tobacco  seed  or  to 
the  soil  with  apparent  protection  of  the  seedlings. 

Series  of  studies  on  immune  reactions  in  plants  were  conducted 
by  Chester  (1932)  and  by  Chester  and  Whitaker  (1933),  which 
snowed  that  the  so-called  "plant  precipitins"  are  in  fact  non- 


424     MYCOLOGY  IN  RELATION  TO  PLANT  PATHOLOGY 

protein  precipitates  arising  from  a  reaction  between  oxalates  and 
calcium.  Their  results  led  them  to  conclude,  "The  published  im- 
munological reactions  in  plants  are  rendered  untenable  because 
of  lack  of  homology  between  the  animal  and  plant  reactions,  and 
because  of  the  wide-spread  occurrence  in  plants  heretofore  used 
of  simple  non-protein  reactions."  Even  though  the  weight  of 
evidence  is  against  the  existence  of  acquired  immunity  against 
pathogenic  fungi  in  plants,  ample  evidence  has  been  accumulated 
to  show  that  fungi  pathogenic  to  man  and  animals  have  antigenic 
properties. 

PRESENT  TRENDS  IN  MYCOLOGIC  AND 
PHYTOPATHOLOGIC  WORK 

Since  the  turn  of  the  present  century  marked  changes  have 
taken  place  in  the  prescribed  disciplines  for  the  training  of  teach- 
ers and  investigators  of  mycology  and  plant  pathology  and  in  the 
kinds  of  research  involving  plant-pathogenic  fungi.  It  is  difficult 
at  this  time  to  determine  or  to  decide  whether  these  changes  have 
always  tended  in  the  direction  of  improvement  over  previous 
studies,  mainly  for  the  reasons  that  not  enough  time  has  elapsed 
to  appraise  them  disinterestedly  and  without  bias  and  to  view 
such  matters  in  perspective.  Improvement  should  have  been  made 
because,  as  must  be  admitted,  present-day  students  of  fungi  are 
better  trained  for  their  tasks  than  were  their  elders.  Additional 
support  for  this  conclusion  is  found  in  the  fact  that  during  the 
first  quarter  of  the  present  century  undue  attention  was  devoted 
to  projects  involving  "spray  schedules"  and  "spray  calendars." 
This  kind  of  project  was  not  sponsored  by  so-called  plant  pathol- 
ogists and  mycologists  alone,  but  also  by  horticulturists,  agron- 

*  -I'll 

omists,  entomologists,  and  botanists,  all  of  whom  vied  with  each 

other  to  acquire  direction  of  such  projects.  Sprays  were  all  too 
commonly  applied,  not  at  critical  times  in  the  development  of  the 
pathogen,  but  on  planned  and  prearranged  dates.  Indeed,  basic 
knowledge  about  the  pathogens  involved  was  extremely  meager, 
and  efforts  to  gain  such  know  ledge  were  regarded  by  some  work- 
ers as  a  "not  practical"  expenditure  of  time.  Determination  of 
not  only  the  most  effective  times  to  spray  but  also  the  proper 
fungicidal  concentrations  was  sought  by  empirical  methods. 
Needless  to  say,  a  body  of  contradictory  and  inexplicable  data  was 


MYCOLOGIC  AND  PHYTOPATHOLOG1C  WORK  425 

assembled  from  such  experimentation,  and  it  is  not  surprising  that 
the  epithet  "squirt-gun  pathologists"  came  to  be  applied  to  such 
workers. 

Although  plant  pathologists  have  gradually  assumed  charge  of 
studies  on  the  prevention  and  control  of  plant  diseases,  some  still 
fail  to  acquire  or  to  utilize  knowledge  of  the  seasonal  cycle  of 
development  of  the  pathogen,  of  its  epiphytology,  and  of  agencies 
of  its  dissemination  as  a  basis  for  instituting  experiments  on  how 
best  to  control  the  given  disease.  Two  obvious  reasons  may  be 
offered  for  this  situation.  It  may  arise  from  lack  of  adequate 
mycological  training  or  else  from  pressure  exerted  by  administra- 
tive officials  for  the  publication  of  experimental  findings.  In  any 
event  the  net  result  is  reflected  in  the  content  of  published  reports 
and  of  papers  presented  at  conferences  or  meetings.  It  is  apparent 
in  many  cases  that  too  little  cognizance  has  been  taken  of  exist- 
ing  knowledge  of  the  disease  and  that  the  materials  presented  are 
preliminary  and  are  fragmentary  rather  than  comprehensive  in 
scope.  For  these  reasons  they  are  intrinsically  limited  in  applica- 
tion and  in  usefulness.  The  validity  of  these  criticisms  is  sup- 
ported by  the  fact  that  many  papers  presented  at  meetings  are 
not  deemed  of  sufficient  merit  for  publication. 

At  present,  plant  pathologists  do  not  occupy  positions  of  re- 
spect and  honor  in  society  comparable  with  those  held  by  medi- 
cal practitioners.  Of  course,  the  difference  in  age  of  the  two 
professions  is  a  causal  factor,  but  several  other  reasons,  such  as 
the  following,  seem  equally  plausible  and  more  fundamental  in  ac- 
counting for  this  state  of  affairs. 

1.  Remuneration  for  services  rendered  by  plant  pathologists  is 
made  from  funds  raised  by  taxation.  Plant  pathologists  are  there- 
fore public  servants  whose  help  and  advice  on  the  problems  of 
diagnosis  and  treatment  of  plant  diseases  must  be  given  gratuitously 
to  all  who  request  aid.  The  public  has  ironically  come  to  feel 
that  the  cost  of  things  and  their* real  value  to  them  as  individuals 
are  either  identical  or  at  least  closely  correlated. 

2.  Reports,  both  those  dealing  with  very  meritorious  research 
on  pathogenic  fungi  and  those  having  little  or  no  value,  are  alike 
published  and  distributed  free  of  charge.  The  public  is  not  al- 
ways able  to  differentiate  between  these  two  types  of  reports 
nor  to  evaluate  them,  and  they  are,  in  consequence,  appraised  as 
though  of  equal  value.    It  is  unfortunate  that  they  should  be  simi- 


426      MYCOLOGY  IN  RELATION  TO  PLANT  PATHOLOGY 

larlv  publicized  or  perhaps  that  either  should  be  given  any  popular 
publicity,  for  they  thereby  partake  all  too  much  of  the  nature  of 
nostrums  for  the  cure  of  human  ailments,  as  advertised  in  news- 
papers and  popular  magazines  or  over  the  radio.  It  should  be 
remembered  that  reputable  physicians  never  sponsor  the  dissemi- 
nation of  panaceas  for  human  diseases.  Neither  do  they  make 
diagnoses  nor  prescribe  treatment  without  first-hand  knowledge 
of  the  patient.  It  seems  altogether  probable,  therefore,  that  the 
plant  pathologist  could  raise  the  esteem  and  respect  with  which  he 
is  regarded  by  emulating  the  medical  practitioner  in  these  respects. 

3.  It  is  patently  a  mistake  for  the  student  of  fungi  to  confine 
himself  to  his  armchair  or  to  the  four  walls  of  his  laboratory  or 
greenhouse.  It  is  equally  fatal  for  best  results  if  he  depends  en- 
tirely upon  observations  made  in  the  field.  Laboratory  experi- 
ments with  fungi  and  observations  on  them  in  the  field  each  have 
a  limited  usefulness,  but  they  can  be  used  to  complement  each 
other.  Results  of  laboratory  experiments  are  intended  to  serve 
as  a  basis  for  field  trials  but  should  never  be  translated  into  definite 
recommendations  for  field  practice  until  after  they  have  been  ade- 
quately tested  under  conditions  that  obtain  in  the  field.  To  do 
otherwise  might  cause  the  reputation  of  the  plant  pathologist  to 
suffer  a  serious  decline;  furthermore  the  mistakes  of  an  individual 
sometimes  reflect  discredit  to  his  associates  and  colleagues  as  well. 
Unfortunately  scientific  theory,  as  developed  from  experiments 
under  controlled  conditions  existing  in  the  laboratory,  and  field 
practice  may  prove  to  be  miles  apart.  All  in  all,  there  clearly 
exists  a  real  need  among  plant  pathologists  and  mycologists  for 
better  acquaintance  with  both  saprogenic  and  pathogenic  fungi 
as  they  occur  in  garden,  orchard,  field,  and  forest.  Such  meetings 
with  fungi  in  their  natural  haunts  would  serve  the  same  function 
to  students  of  mycology  as  does  the  holding  of  clinics  to  the 
physician. 

Gradually  the  interests  of  students  of  fungi  have  become  more 
sharply  delimited,  one  group  being  concerned  primarily  with 
taxonomic  problems  and  the  other  with  disease  problems.  This 
specialization  has  been  carried  to  the  extent  that  it  is  unusual  for 
a  mycologist  to  do  research  in  plant  pathology  and  for  a  phyto- 
pathologist  to  do  research  in  mycology.  The  underlying  reasons 
are  not  difficult  to  discern.  They  may  most  charitably  be  at- 
tributed to  the  frailties  and  limitations  of  the  human  mind  and  to 
the  fact  that  specialization  in  training  and  interest  has  become 


IMPLICATIONS  421 

compulsory  as  a  consequence  of  competition  and  the  desire  to  gain 
recognition  in  a  chosen  field. 

The  control  of  plant  diseases  is  based  mainly  upon  ( 1 )  preven- 
tion and  (2)  natural  resistance.  Prevention  may  be  accomplished 
by  attention  to  sanitary  measures,  rotation  of  crops,  seed  treat- 
ment, establishment  of  quarantines,  application  of  fungicidal 
sprays  and  dusts,  and  other  means.  Natural  resistance  is  sought 
and  isolated  by  selection  and  hybridization.  Little  has  been  done 
in  the  field  of  chemotherapy,  or  the  cure  of  plant  diseases  bv 
chemical  agencies,  especially  by  the  use  of  vaporous  substances, 
although  this  field  of  inquiry  seems  to  offer  inviting  possibilities 
for  development.  The  principle  involved  in  the  use  of  chemicals 
as  therapeutic  agents  is  the  existence  of  a  differential  between 
pathogen  and  suscept  in  tolerance  for  the  chemical  or  drug.  That 
such  studies  have  merit  is  indicated  by  results  from  the  use  of 
benzol  and  related  compounds  in  the  cure  of  tobacco  downy  mil- 
dew. Similarly  the  vapors  of  ethyl  mercury  chloride  and  ethyl 
mercury  phosphate  have  been  found  effective  against  Glomerella 
gossypii  in  cotton-seed  treatment  [Lehman  ( 1943)  ].  It  is  of  more 
than  passing  interest  to  note  that  studies  of  chemotherapy  in  hu- 
man diseases,  beginning  with  the  work  of  Ehrlich,  resulted  in  the 
discovery  of  only  a  few  specifics  until  the  recent  introduction  of 
the  use  of  sulphonamides  and  antibiotics  oroduced  by  certain 
fungi  and  bacteria. 

IMPLICATIONS 

Mycology  and  phytopathology,  parent  and  offspring,  respec- 
tively, have  not  always  worked  together  harmoniously.  '  Seem- 
ingly, parents  have  not  learned  to  accept  gracefully  the  counsel 
and  dictation  of  their  children!  The  offspring  have  become 
numerically  larger  than  the  parent,  and  as  an  outcome  the  irritat- 
ing question  of  their  relative  importance  has  been  raised.  If  their 
relation  were  to  become  synergetic  rather  than  antagonistic,  both 
mycology  and  phytopathology  would  profit.  It  is  indicated  that 
such  a  development  is  in  process  of  accomplishment.  This  end 
could  be  attained  most  effectively  and  most  rapidly  if  teachers 
earnestly  strove  to  impart  instruction  that  not  only  embodied  all 
tradition,  theories,  and  useful  truth  about  fungi  but  also  indicated 
the  relation  of  such  knowledge  to  a  balanced,  well-rounded  edu- 
cation. Moreover,  teachers  with  this  viewpoint  are  true  scientists 
and  cannot  be  nationalistic,  for  science,  like  literature,  music,  and 


428      MYCOLOGY  IN  RELATION  TO  PLANT  PATHOLOGY 

art,  is  international.  Scientists  contribute  their  efforts  and  find- 
ings for  the  betterment  of  mankind  everywhere,  without  regard 
to  race,  creed,  or  political  and  social  affiliations.  Such  scientists, 
as  teachers,  are  not  unduly  concerned  with  the  degree  of  esteem 
and  respect  accorded  them  by  the  public.  They  are  true  human- 
ists, servants  of  their  times,  and  this  in  itself  is  their  all-sufficient 
and  soul-satisfying  reward. 

LITERATURE  CITED 

Arnaudi,  C,  "On  the  vaccination  of  the  tobacco  plant  against  Thielaviopsis 

basicola"  Bull.  Torrey  Botan.  Club,  60:583-597,  1933. 
Arthur,  J.  C,  "History  and  scope  of  plant  pathology,"  Congr.  Arts  Sci., 

St.  Louis,  5:  149-164,  1906. 
Carbone,  D.,  and  C.  Arnaudi,  Vimmuuita  nelle  piante.     Monographic  dell 

Inst.  Sieroterapico  Milanese.    271  pp.     1930. 
Chester,  K.  S.,  "Studies  on  the  precipitin  reaction  in  plants.    I.  The  specifi- 
city of  the  normal  precipitin  reaction,"  /.  Arnold  Arboretum,  13:  52-74, 

1932. 
Chester,  K.  S.,  and  T.  YV.  Whitaker,  "Studies  on  the  precipitin  reaction  in 

plants.    III.  A  biochemical  analysis  of  the  'normal'  precipitin  reaction," 

/.  Arnold  Arboretum,  14:  118-197,  1933. 
Fabricius,   J.   C,    "Attempt   at   a    dissertation   on    the    diseases    of   plants," 

Pbytopath.   Classics,  1.     66  pp.      1926.      (Translated   by   Margaret   K. 

Ravn.) 
Fontana,  Felice,  "Observations  on  the  rust  of  grain,"  Pbytopath.  Classics, 

2.    40  pp.     1932.     (Translated  by  P.  P.  Pirone.) 
Kuster,  Ernst,  Phytopatbologiscbe  Pflanzenanatomie,  3rd  ed.    xii  -+-  558  pp. 

G.  Fischer,  Jena.    1925. 
Lehman,  S.  G.,  "Vapor  action  of  certain  fungicidal  materials  prepared  for 

dusting  cotton,"  Phytopathology,  35:431^148,  1943. 
Prevost,  Benedict,  "Memoir  on  the  immediate  cause  of  bunt  or  smut  of 

wheat,  and  of  several  other  diseases  of  plants,  and  on  preventives  of 

bunt,"  Pbytopath.  Classics,  6.     94  pp.     1939.      (Translated  by  G.  YV. 

Keitt.) 
Re    Fillipo,    Saggio    teorico-pratico    sulle    malattie    delle    piante.      1-437. 

Venezia.     1807. 
Smith,  E.  F.,  "Plant  pathology:  a  retrospect  and  prospect,"  Science,  75: 601— 

612,  1902. 
"Fifty  years  of  pathology,"  Proc.  Intern.  Congr.  Plant  Sci.  Ithaca,  1:  13-46, 

1929. 
Whetzel,  H.  H.,  An  outline  of  the  history  of  phytopathology.     130  pp. 

W.  B.  Saunders  Co.     1918. 
"The  terminologv  of  phytopathology,"  Proc.  Intern.   Congr.  Plant  Sci. 

Ithaca,  2:  1204-1215,  1929. 
Wingard,  S.  A.,  "The  nature  of  disease  resistance  in  plants,"  Botan.  Rev., 

7:59-109,  1941. 


Chapter  19 
SOIL  FUNGI 

In  studies  of  soil  fertility  much  emphasis  has  been  placed  upon 
mineral  composition,  and  all  too  little  attention  has  been  given  to 
microbial  composition  of  soils.  Indeed  Boussingault  and  Lew  y 
(1853)  long  ago  showed  that  the  nitrate  content  of  soils,  if  left 
fallow,  increased,  but  the  causal  relation  of  biologic  factors  was 
not  recognized  at  that  time,  nor  was  it  definitely  established  until 
1877.  Then  Schloesing  and  Miintz  (1877),  in  epoch-making 
studies  involving  the  purification  of  sewage,  established  the  foun- 
dations of  nitrification  and  soil  fertility,  and  their  findings  consti- 
tute the  basis  for  present-day  knowledge  of  relationships  between 
biologic  factors  and  soil  fertility.  An  appreciation  of  these  mat- 
ters can  best  be  gained  from  reading  The  Microorganisms  of  the 
Soil  [Russell  et  al.  (1923)],  Principles  of  Soil  Microbiology 
[Waksman  (1927)],  and  Die  microscopischen  Boden-Pilze 
[Niethammer  (1937)]. 

A  proper  appraisal  of  the  composition  of  soil  must  take  into 
account  its  content  of  microbes,  including  bacteria,  protozoa, 
blue-green  algae,  green  algae,  and  fungi.  It  appears  that  Adametz 
(1886)  was  the  first  to  isolate  fungi  from  the  soil.  No  real  interest 
in  the  fungus  flora  of  the  soil  was  manifest,  however,  until  nearly 
20  years  later,  when  Oudemans  and  Koning  (1902)  isolated  and 
described  45  species  of  soil  fungi.  Subsequent  studies  on  this  sub- 
ject may  be  grouped  into  three  essential  types:  (1)  taxonomic, 
those  concerned  with  the  kind  and  number  of  fungi  in  soils;  (2) 
biochemic,  those  dealing  with  the  physiological  activities  of  soil 
fungi;  and  (3)  epidemiologic,  those  dealing  with  soil-borne  plant 
and  animal  pathogens. 

TAXONOMIC  STUDIES 

Methods.  As  might  be  anticipated,  various  techniques  for  iso- 
lating and  culturing  soil  fungi  have  been  employed.     Oudemans 

429 


430  SOIL  FUNGI 

and  Koning  (1902)  placed  a  fragment  of  humus  in  a  small  vessel 
containing  1  ml  of  sterilized  water.  After  the  humus  has  been 
thoroughly  triturated,  a  platinum  loopful  of  suspension  was  intro- 
duced into  10  ml  of  sterilized  water.  A  small  quantity  of  this  di- 
lute suspension  was  then  poured  upon  the  surface  of  poured  plates 
of  media,  consisting  of  agar  1.5%,  gelatin  10o/o,  and  sucrose  2%, 
with  an  added  quantity  of  wort. 

HaQ-em  (1910)  sprinkled  small  amounts  of  soil  on  the  surface 
of  poured  plates  in  attempts  to  isolate  Alucorales.  By  repeated 
transfer  of  mycelium  and  spores  to  new  substrates  he  secured  pure 
cultures.  Lendner  (1908)  employed  tubes  or  flasks  of  wort 
gelatin  or  of  moist  bread  on  which  small  amounts  of  soil  were 
planted.  Several  other  workers  have  used  a  filtrate  of  soil,  sus- 
pended in  water  for  24  hours,  to  enrich  the  media.  Matters  in- 
volving media  and  methods  of  sampling  and  of  isolating  soil  fungi 
are  discussed  in  an  outline  bv  Waksman  and  Fred  (1922).  They 
recommend  the  use  of  sodium  albuminate  agar,  sodium  caseinate 
agar,  or  soil-extract  agar  and  gelatin. 

Since  fungi  are  tolerant  of  acid  substrates,  whereas  bacteria  and 
actinomycetes  grow  best  on  neutral  or  alkaline  media,  a  reaction 
of  pH  4.0  to  5.0  is  preferable  in  the  isolation  of  fungi. 

Conn  (1922)  proposed  the  use  of  a  technique  by  means  of  which 
the  presence  of  fungus  hvphae  in  soils  could  be  demonstrated  by 
direct  microscopic  examination. 

In  isolating  "water  molds,"  a  small  quantity  of  soil,  along  with 
some  sterilized  water,  is  first  placed  in  a  Petri  dish,  and  then 
boiled  hemp  seeds  are  introduced  as  "bait."  Many  workers,  be- 
ginning with  Harvey  (1925),  have  employed  this  technique. 

Kinds  of  fungi  isolatfd.  Opinion  was  divided  among  earlier 
students  on  whether  funQ-i  are  normal  inhabitants  of  the  soil. 
The  weight  of  evidence,  however,  has  gradually  favored  the  ex- 
istence  of  a  true  fungus  flora  of  the  soil.  The  isolations  of 
Adametz  (1886)  yielded  11  species  of  fungi,  among  which  were 
Aspergillus  gluteus,  Penicillium  glaucum,  Mac  or  vmcedo,  M. 
raceinosus,  and  M.  stolonifer.  These  species  have  been  quite  com- 
monly found  by  all  whose  interest  has  centered  on  the  problem 
of  kinds  of  soil  fungi.  These  investigators  have  included  Oude- 
man  and  Koning  (1902),  Lendner  (1908),  Hagem  (1910),  Beck- 
with  (1911),  Dale  (1912,  1914),  Jensen  (1912)"  Goddard  (1913), 
Werkenthin  (1916),  Paine  (1927),  Gilman  and  Abbott  (1927), 


TAXONOM1C  STUDIES  431 

LeClerg  and  Smith   (1928),  Jensen   (1931),  Cobb    (1932),  and 
Gillman  (1944). 

The  list  of  Oudeman  and  Koning  (1902),  from  Netherlands 
includes  45  species,  9  of  which  are  Alucorales.  Lendner  (1908) 
described  9  new  species  of  Mucorales  among  the  fungi  which  he 
isolated  from  soils  in  Switzerland.  Hagem  (1910)  isolated  18 
species  of  Alucorales  from  field,  meadow,  forest,  and  garden  soils 
in  Norway,  9  of  them  being  new  species. 

Dale  (1912,  1914)  isolated  more  than  100  species  of  fungi  from 
soils  in  England.  Jensen  (1912)  isolated  35  species  in  New  York 
state.  Waksman  (1917)  obtained  from  different  sections  of  the 
United  States  and  Hawaii  25  soil  samples,  from  which  he  isolated 
more  than  200  species,  137  of  which  he  was  able  to  identify. 
Among  the  genera  represented  were  Absidia,  Alucor,  Rhizopus, 
Zygorhynchus,  Saccharomyces,  Hypoderma,  Sordaria,  Sphaero- 
nema,  Monilia,  Oidium,  Papulospora,  Aspergillus,  Penicillium, 
Scopulariopsis,  Rhinotrichum,  Sepedonium,  Botrytis,  Verticil- 
lium,  Acrostalagmus,  Cephalothecium,  Stachybotrvs,  Dematium, 
Cladosporium,  Alternaria,  Macrosporium,  Helminthosporium, 
Stysanus,  and  Fusarium.  The  summary  by  Brierley  (1923)  in 
1923  indicated  that  up  to  that  time  there  had  been  recorded  from 
isolations  from  soils  56  species  in  11  genera  of  Phy corny cetes,  12 
species  in  8  genera  of  Ascomy cetes,  and  197  species  in  62  genera 
of  Fungi  Imperfecti,  including  Actinomycetes.  This  did  not  in- 
clude, of  course,  the  startling  multitude  of  species  of  Basidiomy- 
cetes  that  grow  especially  in  forest  soils.  Later  the  report  by 
Gilman  and  Abbott  (1927)  listed  a  total  of  61  genera,  including 
242  species  from  Iowa  soils.  A  later,  more  comprehensive  report 
by  Gilman  (1944)  contained  a  list  of  198  species  of  Phycomycetes, 
30  Ascomycetes,  and  383  Fungi  Imperfecti.  Paine  (1927)  de- 
scribed as  new  5  among  the  31  species  isolated. 

Beginning  with  the  studies  of  Harvey  (1925),  there  has  been  a 
lively  interest  in  the  occurrence  of  Phycomycetes,  especially  water 
molds  in  soils.  Harvey  isolated  the  following  species:  Brevilegnia 
diclina,  Geolegnia  inflata,  G.  septisporangia,  Leptolegnia  subter- 
ranea,  Saprolegnia  ferax,  hoachlya  eccentrica,  and  Achlya  caro- 
liniana.  Among  other  soil-inhabiting  species  are  Allomyces  arbus- 
cula,  A.  javanicus,  A.  cysto genus  and  A.  moniliformis.  These  spe- 
cies, especially  A.  arbuscula,  appear  to  be  widely   distributed 


432  SOIL  FUNGI 

throughout  the  world,  according  to  Emerson  (1941)  and  Wolf 

(1940. 

Number  of  fungi  in  soils  and  factors  influencing  preva- 
lence. The  quantitative  determinations  of  fungi  in  soils  have  been 
made  by  use  of  dilution-poured  plates,  and  the  results  obtained  do 
not  constitute  an  entirely  satisfactory  estimation.  Anions  the 
factors  that  are  known  to  influence  the  results  are:  (1)  dilution 
of  soil  suspension,  (2)  kind  of  culture  medium,  (3)  reaction  of 
medium,  (4)  kind  of  soil,  (5)  soil  reaction,  (6)  depth  at  which 
sample  was  taken,  (7)  moisture,  (8)  season  of  the  year,  (9)  till- 
age, (10)  manuring  practices. 

If  the  soil  fungi  are  sporulating  in  the  sample  being  examined, 
the  number  of  colonies  will  be  lar^e;  if  they  are  merely  ves;etatin<j;, 
the  investigator  may  get  a  small  count  and  as  a  result  may  infer 
that  few  fungi  are  present. 

Data  presented  by  Brierley  (1923)  show  that  portions  of  the 
same  soil  suspension  plated  on  different  media  yield  strikingly  dif- 
ferent numbers  of  colonies!  Furthermore,  when  the  same  soil 
suspension  is  plated  on  the  same  medium,  adjusted  to  different 
initial  hydroeen-ion  concentrations,  the  number  of  colonies  de- 
veloping  is  very  different.  Brierley 's  observations  from  monthly 
plate  counts  of  fungi  in  soils  at  the  Rothamsted  Experiment  Sta- 
tion led  him  to  conclude  that  there  is  a  seasonal  rhythm  in  the 
number  of  soil  fungi,  ranging  from  approximately  200,000  to 
1,600,000  per  gram.  Jensen  (1931),  using  European  soils  from 
fields,  meadows,  forests,  heaths,  moors,  and  marshes,  secured 
counts  ranging  from  24,300  to  46,000  per  gram  of  soil. 

Accord  exists  among  all  investigators  that  fungi  are  most  abun- 
dant near  the  surface  of  the  soil  and  that  the  number  decreases 
with  depth.  LeClerg  and  Smith  (1928)  found  Aspergillus  mger 
and  Trichoderma  lignorum  in  Colorado  soils  only  at  the  surface. 
Russell  (1923)  isolated  30  species  at  a  depth  of  1  in.  from  the 
surface  of  an  unmanured  grass  plot,  19  species  at  6  in.,  and  1 1  spe- 
cies at  12  in.  Goddard  (1913)  in  .Michigan  and  Werkenthin 
(1916)  in  Texas  found  quite  the  same  uniform  distribution  of 
species  to  a  depth  of  approximately  4  in.  Waksman  (1916)  found 
Z,y gorhynchus  vuilleminii  most  often  in  subsoil  at  depths  of  12 
to  20  in.  Cobb  (1932)  recorded  that  fungi  are  10  times  as  abun- 
dant in  the  top  soil  under  hemlock  trees  as  in  the  subsoil.  The 
data  of  Takahashi  (1919)  showed  590,000  fungi  per  gram  of  soil 


TAXONOMIC  STUDIES  433 

at  a  depth  of  2  cm  and  160,000  at  8  cm.    He  found  Zygorhynchns 
molleri  and  Trichoderma  koningii  at  the  lower  depths. 

Since  the  soil  is  such  a  complex  environment,  there  are  abun- 
dant reasons  for  differences  of  opinion  regarding  kinds  of  soil 
fungi  in  different  soils.  Goddard  (1913)  and  Werkenthin  (1916) 
found  a  constant  and  characteristic  fundus  flora  of  soils,  regard- 
less  of  tillage,  soil  type,  and  manuring.  Dale  (1912,  1914)  found 
certain  species  common  to  chalky,  peaty,  and  black  earth  soils  in 
England.  Waksman  (1916)  obtained  the  same  species  from  culti- 
vated and  uncultivated  soils  in  New  Jersey  but  concluded  that 
each  soil  possesses  a  more  or  less  characteristic  fungus  flora. 
Brown  (1917)  expressed  a  similar  opinion  by  stating  that  different 
soils  have  different  fungus  floras.  Hagem  (1910)  isolated  Alucor- 
ales  from  the  soil  of  meadows,  gardens,  forests,  and  cultivated 
fields  but  observed  that  they  are  most  abundant  in  forest  soils. 
On  the  other  hand,  Jensen  (1931)  found  that  Mucorales  are  most 
abundant  in  field  and  garden  soil,  whereas  species  of  Trichoderma 
are  most  common  in  virgin  soils,  such  as  those  of  forests,  moors, 
and  heaths. 

Cobb  (1932)  was  led  to  conclude  that  species  of  Mucor  and 
Aspergillus  are  scarce  in  forest  soils.  She  also  reported  differences 
in  abundance  between  soils  under  hemlock  trees  and  under  de- 
ciduous trees,  there  being  twice  as  many  in  the  top  soil  under 
hemlocks  as  in  that  under  deciduous  species.  Other  observations 
on  factors  that  modify  the  presence  of  specific  fungi  in  soils  in- 
clude those  of  LeClerg  and  Smith  (1928).  Their  evidence  showed 
that  Rhizopns  nigricans  and  Trichoderma  lignornm  occur  most 
abundantly  in  soils  of  low  mineral  and  low  moisture  content  and 
that  Fenicillium  expansum  is  not  limited  by  soil  moisture  and  oc- 
curs abundantly,  as  does  P.  lilacimim,  in  soils  of  high  mineral 
content. 

Experimentation  involving  the  influence  of  each  of  the  several 
factors  that  modify  the  activities  of  soil  fungi  has  been  limited. 
Coleman  (1916)  employed  sterilized  soils,  with  Aspergillus  niger, 
Trichoderma  koningii,  and  Zygorhynchus  vuilleminii  among  the 
test  organisms  on  which  to  study  the  effects  of  temperature,  aera- 
tion, and  food  supply.  All  grew  best  at  approximately  30°  C, 
but  the  species  differed  in  their  oxygen  and  food  requirements.  At 
any  rate,  there  was  no  interaction  of  one  species  with  another  nor 
with  the  numerous  species  of  soil  microorganisms  that  occur  in 


434  SOIL  FUNGI 

unsterilized  soil,  so  that  the  application  of  Coleman's  findings  to 
conditions  in  the  field  is  difficult  or  even  impossible  of  accom- 
plishment. 

Waksman  (1922)  applied  several  treatments  to  soils  to  determine 
their  influence  upon  the  numbers  of  fungi  and  obtained  the  results 
shown  in  Table  31. 


TABLE 

31 

ence  of  Soil  Amendments  upon  the  Ni 

jmbers  of  Soi 

Soil 

Number  of 

Reaction 

Fungi  per 

Substance  Applied 

(pH) 

Gram  of  Soil 

Minerals  only 

5.6 

37,300 

Heavy  supply  of  manure 

5.8 

73,000 

Sodium  nitrate 

5.8 

46,000 

Ammonium  sulphate 

4.0 

110,000 

Minerals  and  lime 

6.6 

26,000 

Ammonium  sulphate  and  lime         6.2  39,100 

In  general,  it  would  be  expected  that  soils  rich  in  organic  matter 
would  support  the  most  abundant  fungus  population.  Jensen 
(1931)  is  among  those  who  hold  this  belief,  for  he  concluded  that 
the  application  of  barnyard  manure  to  soils  results  in  increased 
numbers  of  fungi. 

The  kind  of  organic  matter,  through  its  correlation  with  the 
kind  of  cleavage  products  resultant  from  decomposition,  may 
well  be  a  factor  of  consequence  in  determining  the  kind  of  fungi 
that  predominate.  Species  of  Penicillium  and  Trichoderma  were 
noted  by  Jensen  (1931)  to  prevail  in  acid  soils.  In  this  instance 
carbohvdrates  may  have  constituted  the  source  from  which  the 
acids  were  derived.  On  the  other  hand,  Jensen  (1931)  also  made 
the  observation  that  My  co gone  nigra  and  Coccospora  agricola 
prevailed  in  alkaline  soils  that  may  be  assumed  to  have  derived 
their  alkalinity  bv  ammonification  of  proteins. 

BIOCHEMICAL  ACTIVITIES  OF  SOIL  FUNGI 

The  purpose  of  this  discussion  is  to  stress  the  role  that  soil  fungi 
play  in  the  transformation  of  organic  matter  into  humus  and  into 
other  material  necessary  for  the  nutrition  of  green  plants.  The 
impact  of  bacteriologic  study  and  teaching  has  resulted  in  estab- 
lishing the  impression  that  bacteria  constitute  the  organisms  most 


BIOCHEMICAL  ACTIVITIES  OF  SOIL  FUNGI  435 

concerned  in  these  important  changes,  when,  as  a  matter  of  fact, 
soil  fungi  are  also  vitally  concerned  in  these  processes.  An  at- 
tempt will  be  made  to  show  that  these  fungi  function  in  three  in- 
terrelated ways:  (1)  in  decomposing  carbohydrates,  (2)  in  am- 
monifying proteins,  and  (3)  in  producing  mineral  transformations. 

Decomposition  of  carbohydrates.  Both  simple  and  complex 
carbohydrates  are  now  known  to  be  fermented  by  various  fungi. 
It  may  be  recalled  that  Hoppe-Seyler  (1886)  long  ago  secured 
evidence  that  filter  paper  is  digested  in  the  presence  of  a  little 
sewage  slime.  He  placed  25.773  grams  of  filter  paper  in  a  flask, 
so  constructed  that  he  could  lead  off  the  gases  for  analyses.  After 
4  years  15  grams  of  the  cellulose  had  been  digested,  with  the  pro- 
duction of  3281  cc  of  carbon  dioxide  and  2571  cc  of  methane. 
This  decomposition  was  established  to  be  induced  by  anaerobic 
bacteria.  Evidence  that  fungi  can  also  function  in  the  decomposi- 
tion of  cellulose  was  first  presented  by  van  Iterson  (1904)  in 
1904.  His  experiments  were  performed  not  with  pure  cultures 
but  with  soil  as  inoculum.  The  medium  consisted  of  filter  paper 
moistened  with  tap  water  in  which  small  amounts  of  ammonium 
nitrate  and  monopotassium  phosphate  had  been  dissolved.  By  this 
procedure  evidence  was  secured  to  show  that  certain  fungi,  includ- 
ing Chaetommm  kunzeanum,  Trichocladium  asperum,  Stachy  bo- 
try  s  altemans,  Sporotrichum  bomby  cinum,  S.  roseolum,  S.  griseo^ 
lum,  Botrytis  sporoideiim^  My co gone  pnccinioides,  and  Clado- 
sporhim  herbarum,  digest  cellulose.  Van  Iterson's  observations 
initiated  a  series  of  studies  on  cellulose  digestion  by  fungi,  among 
them  those  by  Kellerman  and  AIcBeth  (1912),  Daszewska  (1913), 
Scales  (1916),  Waksman  (1918),  and  Henkelekian  and  Waksman 
(1925).  Kellerman  and  McBeth  (1912)  made  use  of  cellulose 
agar,  the  preparation  of  which  they  describe,  and  established  that 
many  species  of  Aspergillus,  Fusarium,  Penicillium,  and  Sporo- 
trichum utilize  cellulose  as  nutrient  in  pure  cultures.  Daszewska 
(1913)  found  that  Sporotrichum  olivaceum,  Verticillium  glau- 
cum,  V.  celhdosae,  and  various  other  Hvphomvcetes  are  more 
important  in  cellulose  decomposition  than  are  bacteria  and  that 
the  color  of  the  humus  formed  is  related  to  that  of  mycelium  and 
conidia.  Among  22  species  of  soil  fungi  tested  by  Waksman 
(1916),  15  were  able  to  decompose  cellulose. 

Henkelekian  and  Waksman  (1925)  have  shown  that  Tricho- 
derma  and  Penicillium  possess  the  ability  to  decompose  cellulose 


436  SOIL  FUNGI 

completely,  with  carbon  dioxide  as  the  only  waste  product. 
Moreover  a  considerable  proportion  of  the  carbon  in  cellulose 
may  be  reassimilated  by  the  fungus  in  building  protoplasm.  This 
observation  on  the  utilization  of  carbon  dioxide  is  elaborated  by 
Foster  et  al.  ( 1941)  in  their  recent  studies  on  this  subject. 

Abundant  evidence,  some  of  which  is  summarized  in  Chapter  3, 
has  been  secured  that  many  Basidiomycetes,  especially  wood- 
rotting  species,  are  capable  of  utilizing  cellulose.  Phycomycetes 
are  generallv  regarded  as  incapable  of  digesting  cellulose.  The 
work  of  Whiffen  (1941),  however,  shows  that  certain  chytrids 
possess  this  ability. 

Manv  fungi  are  known  to  be  capable  of  utilizing  starch.  Among 
22  species  of  soil  fungi  tested  by  Waksman  (1916)  for  diastatic 
abilitv,  6  proved  capable  of  using  starch.  The  Mucorales  have 
been  shown  to  utilize  manv  monosaccharides,  disaccharides,  and 

also  pectins. 

Decomposition  of  proteins.  That  fungi  differ  in  ability  to  use 
elemental  nitrogen  and  nitrogen  complexes  was  given  considera- 
tion in  Chapter  2,  where  it  was  pointed  out  that  some  few  species 
can  assimilate  atmospheric  nitrogen  but  that  most  of  them  prefer 
amino  acids,  nitrate  nitrogen,  or  else  ammonium  salts.  That  soil 
funoi  have  the  power  of  ammonifying  proteins  was  first  demon- 
strated in  1893  by  Miintz  and  Coudon  (1893),  using  Mucor  race- 
mosus  and  Fusarium  miitzii,  and  by  Marchal  (1893),  using  As- 
pergillus terricola  and  Cephalothechtm  roseum.  Numerous  in- 
vestigations of  this  problem  followed,  including  those  of  McLean 
and  \vilson  (1914),  Waksman  (1916),  and  Henkelekian  and 
Waksman  (1925). 

McLean  and  WTilson  (1914)  employed  members  of  the  Mucor- 
aceae,  Aspergillaceae,  Dematiaceae,  and  Moniliaceae,  finding  that 
all  could  produce  ammonia  either  from  dried  blood  or  from  cot- 
tonseed meal.  It  was  observed  that  some  species  are  more  active 
than  others,  but  of  much  more  interest  was  the  finding  that  soil 
fungi  exceed  bacteria  in  ammonifying  power.  Waksman  (1916) 
showed  that  Trichoderma  koningii  is  an  especially  potent  ammoni- 
fier.  Evidence  is  lacking  that  any  species  of  soil  fungi  takes  part 
in  nitrification. 

Henkelekian  and  Waksman  (1925)  observed  a  direct  correla- 
tion between  the  amount  of  nitrogen  transformed  into  ammonia 


IMPLICATIONS  437 

by  species  of  Penicillium  and  Trichoderma  and  the  amount  of 
cellulose  decomposed. 

The  abundance  of  studies  on  protein  decomposition  by  soil 
fungi  has  yielded  data  on  the  various  factors  that  modify  the 
accumulation  of  ammonia.  These  factors  are  known  to  include 
aeration,  soil  moisture,  soil  type,  soil  reaction,  duration  of  the 
incubation  period,  temperature,  nature  of  the  protein  complex, 
and  presence  of  soil  minerals,  especially  phosphates. 

SOIL-BORNE  PATHOGENS 

No  attempt  can  be  made  adequately  to  summarize  the  vast  liter- 
ature on  the  relation  of  soil-inhabiting  fungi  to  disease  in  plants. 
Species  of  Pythium,  Phvtophthora,  Aphanomyces,  Thielaviopsis, 
Fusarium,  Sclerotinia,  Colletotrichum,  Gloeosporium,  Botrytis, 
Rhizoctonia,  Sclerotium,  and  Phymatotrichum  are  among  those 
well-known  to  be  soil-borne  and  to  cause  serious  destruction  of 
crops.  Some  of  them  occur  in  virgin  soils,  and  others  are  intro- 
duced with  the  culture  of  the  host  species.  Unfortunately  many 
of  them,  when  once  introduced  into  a  field,  persist  for  years,  even 
when  susceptible  hosts  are  not  planted  in  these  fields  for  long 
periods.  Pratt  (1918)  isolated  Fusarium  radicicola,  F.  tricho- 
thecioides,  and  Rhizoctonia  solani  from  soils  in  southern  Idaho 
that  had  never  been  cropped  to  potatoes.  Rathbun  (1918)  found 
Fusarium,  a  cause  of  damping-ofl  of  coniferous  seedlings,  in  vir- 
gin seed-bed  soils.  Soils  that  are  "crop  sick,"  on  the  other  hand, 
may  contain  a  variety  of  species  capable  of  producing  infection 
[Beckwith  (1911)]. 

Infection  by  soil-inhabiting  fungi  has  been  shown  to  be  con- 
trolled by  such  factors  as  temperature,  reaction,  and  interaction, 
subjects  given  consideration  in  Chapters  5,  7,  and  12. 

Few  cases  involving  soil-borne  human  pathogens  have  been 
proved.  Emmons  (1942)  determined  that  Coccidioides  immitis, 
the  cause  of  "valley  fever,"  may  be  isolated  from  the  soil  in  re- 
gions where  this  disease  is  endemic. 

IMPLICATIONS 

As  a  result  of  the  transformation  of  organic  materials  into 
humus  by  soil  fungi,  organic  acids  are  produced,  and  these  acids 


438  SOIL  FUNGI 

have  properly  been  assumed  to  account  for  soil  acidity.  Hagem 
(1910)  concluded  that  inorganic  soil  constituents  containing  such 
minerals  as  calcium,  magnesium,  and  phosphorus  are  dissolved 
bv  these  organic  acids  and  thereby  made  available  for  green  plants. 
Soil  fungi  are  therefore  to  be  regarded  as  important  in  soil  fertil- 
ity. Much  remains  to  be  determined,  however,  concerning  the 
indirect  role  of  fungi  in  making  available  iron,  sulphur,  and  the 
many  other  elements  that  green  plants  require  in  small  amounts. 

.Many  soil  fungi,  as  grown  on  artificial  media  or  on  sterilized 
soil,  should  be  studied  intensively  to  increase  our  knowledge  of 
their  biochemical  activities.  Similarly  two  or  more  species,  if 
grown  in  association  in  the  same  culture,  might  yield  valuable 
data.  The  application  of  these  findings  in  explaining  the  activities 
of  fungi  in  normal  soils  would  require  the  exercise  of  incisive 
thinking  and  well-balanced  judgment.  Success  would  be  most 
likely  attained  if  such  studies  were  undertaken  by  a  corps  of  work- 
ers, including  microbiologists,  chemists,  and  physicists,  working 
in  collaboration. 

Means  for  measuring  soil  fertility  continue  to  be  sought  because 
in  the  future  an  adequate  supply  of  food  and  feed  crops  will  come 
more  and  more  to  depend  upon  a  better  knowledge  of  soil  fertility. 
Partly  for  this  reason  the  use  of  Aspergillus  niger  to  test  the  soil- 
potassium  needs  of  a  given  crop,  as  was  proposed  by  Mehlich 
etal.  (1933),  has  intriguing  possibilities  for  application  to  require- 
ments for  other  minerals. 

Undoubtedly  soil  fungi  perform  an  important  role  in  produc- 
ing growth-promoting  substances  that  are  utilized  by  green  plants. 
It  is  a  well-established  fact  that  crop  plants  do  not  grow  as  well 
on  infertile  soil  if  the  fields  are  enriched  with  mineral  fertilizers 
as  if  they  are  enriched  with  manure  or  organic  material  containing 
equivalent  amounts  of  minerals.  The  relationship  of  soil  fungi  to 
the  production  of  growth  regulators  should  be  further  elucidated. 

The  results  of  researches  on  soil  fungi,  if  viewed  in  perspective, 
emphasize  that  soils  are  not  static,  but  dynamic.  The  ever-chang- 
ing balance  between  each  kind  of  soil  microbe  and  the  mineral 
and  non-living  organic  content  of  soils  still  remains  largely  un- 
known.  A  concise  summary  of  these  subjects,  together  with  an 
excellent  bibliography,  is  to  be  found  in  a  paper  by  YVaksman 
(1944). 


LITERATURE  CITED  439 


LITERATURE  CITED 

Adametz,  L.,  "Untersuchungen  iiber  die  niederen  Pilze  der  Ackerkrume," 

Inaugural  dissertation.     78  pp.     Leipzig.     1886. 
Beckwith,  T.  D.,  "Root  and  culm  infections  of  wheat  by  soil  fungi  in  North 

Dakota,"  Phytopathology,  7:169-176,  1911. 
Boussingault,  J.  B.,  and  Lewy,  "Sur  la  composition  de  Fair  confine  dans 

de  terre  vegetale,"  Ann.  chim.  phys.,  Troisieme  Serie,  57:5-50,    1853. 
Brierley,  W.  B.,  "The  occurrence  of  fungi  in  the  soil."     In  E.  J.  Russell, 

Microorganisms  of  the  Soil,  pp.  118-146.     1923. 
Brown,  P.  E.,  "Importance  of  mold  action  in  soils,"  Science,  46:  171-175, 

1917. 
Cobb,  Mary  Jo,  "A  quantitative  study  of  the  microorganic  population  of  a 

hemlock  and  a  deciduous  forest  soil,"  Soil  Sci.,  33:  325-345,  1932. 
Coleman,  D.  A.,   "Environmental  factors  influencing  the   activity  of  soil 

fungi,"  Soil  Sci.,  2:  1-65,  1916. 
Conn,  H.  J.,  "A  microscopic  method  for  demonstrating  fungi  and  actinomy- 

cetes  in  soil,"  So/7  Set.,  14:  149-152,  1922. 
Dale,   E.,    "On   the   fungi   of   the   soil,"    Ann.   My  col,   10:452-477,    1912; 

72:33-62,  1914. 
Daszewska,  W.,  "Etude  sur  la  desagregation  de  la  cellulose  dans  la  terre  de 

bruyere  et  la  trube,"  Bull.  soc.  botan.  Geneve,  Ser.  8,  fasc.  8:  255-316, 

1913. 
Emerson,  Ralph,  "An  experimental  studv  of  the  life  cvcles  and  taxonomy  of 

Allomyces,"  Lloydia,  4:  77-144,  1941. 
Emmons,  C.  W.,  "Isolation  of  Coccidioides  from  soil  and  rodents,"  U.  S. 

Pub.  Health  Rept.,  57:  109-111,  1942. 
Foster,  J.  W.,  S.  F.  Carson,  S.  Ruben,  and  M.  D.  Kamen,  "Radioactive  car- 
bon  dioxide  utilization.     VII.  The  assimilation  of  carbon   dioxide  bv 

molds,"  Proc.  Nat.  Acad.  Sci.,  27:590-596,  1941. 
Gilman,  J.  C,  A  manual  of  soil  fungi.    392  pp.    Iowa  State  College  Press, 

Ames,  Iowa.     1944. 
Gilman,  J.  C,  and  E.  V.  Abbott,  "A  summary  of  the  soil  fungi,"  Ioiva  State 

Coll.  J.  Sci.,  1:  225-343,  1927. 
Goddard,  H.  M.,  "Can  fungi  living  in  agricultural  soil  assimilate  free  nitro- 
gen?" Botan.  Gaz.,  55:249-305,  1913. 
Hagem,  O.,  "Untersuchungen  iiber  Norwegische  Mucorineen.     I,"    Viden- 

skapsselskapets-Skrifter    Mat.-natiirv.    Klasse    Kristiania,    7:  1-50,    1907; 

II,  4:  1-152,  1910. 
"Neue   Untersuchungen   iiber  Norwegische   Alucorineen,"   Ann.  Mycol., 

8:265-286,  1910a. 
Harvey,  J.  V.,  "A  survey  of  the  water  molds  and  Pythium  occurring  in  the 

soils  of  Chapel  Hill?'  /.  Elisha  Mitchell  Sci.  Soc,  41:  151-164,  1925. 
Henkelekian,  H.,  and  S.  A.  Waksman,  "Carbon  and  nitrogen  transforma- 
tion in  the  decomposition  of  cellulose  by  filamentous  fungi,"  /.  Biol. 

Chem.,  66: 323-342,  1925. 


440  SOIL  FUNGI 

Hoppe-Seyler,  F.,  "Uber  Gahrung  der  Cellulose  mit  Bildung  von  Alethan 
und  Kohlensaure,"  Hoppe-Seylefs  Z.  physiol.  Chem.,  70:201-217;  401- 
440,  1886. 

Iterson,  C.  van,  "Die  Zersetzung  von  Cellulose  durch  aerobe  Mikroorganis- 
men,"  Zentr.  Bakt.  Parasitenk.,  II  Abt.,  77:689-698,  1904. 

Jensen,  C.  N.,  "Fungus  flora  of  the  soil,"  Cornell  Agr.  Expt.  Sta.  Bull., 
575:415-501,  1912. 

Jensen,  H.  L.,  "The  fungus  flora  of  the  soil,"  Soil  Sci.,  31:  123-158,  1931. 

Keller.man,  K.  F.,  and  I.  G.  McBeth,  "The  fermentation  of  cellulose," 
Zentr.  Bakt.  Parasitenk.,  II  Abt.,  5-^:485-494,  1912. 

LeClerg,  E.  L.,  and  F.  B.  Smith,  "Fungi  in  some  Colorado  soils,"  Soil  Sci., 
25:433-^41,  1928. 

Lendner,  A.,  Les  Mucorinees  de  la  Suisse.    180  pp.    Berne.     1908. 

.Marchal,  E.,  "Sur  la  production  de  rammonique  dans  le  sol  par  les 
microbes,"  Bull.  acad.  sci.  Belg.,  25:727-771,  1893. 

McLean,  H.  C,  and  G.  AY.  Wilson,  "Ammonification  studies  with  soil 
fungi,"  N.  J.  Agr.  Expt.  Sta.  Bull.,  210.    39  pp.    1914. 

Mehlh  ii.  A.,  E.  Truog,  and  E.  B.  Fred,  "The  Aspergillus  niger  method  of 
measuring  available  potassium  in  soil,"  Soil  Sci.,  55:259-276,  1933. 

.Muntz,  A.,  and  H.  Coudon,  "La  fermentation  ammoniacale  de  la  terre," 
Covipt.  rend.,  116:  395-398,  1893. 

Xiethammer,  A.,  Die  microscopischen  Boden-Pilze,  ihr  Leben,  ihre  rcer- 
breitung,  soivie  ihre  oeconomische  und  pathogene  Bedeutmig.  193  pp. 
W.  Junk,  The  Hague.    1937. 

Oudemans,  C.  A.  J.  A.,  and  C.  J.  Koning,  "Prodrome  d'une  flore  my- 
cologique,  obtenue  par  la  culture  sur  gelatin  preparee  de  la  terre  humeuse 
du  Spanderswould  pres  de  Bussum,"  Arch,  neerland.  sci.,  7:  266-298,  1902. 

Paine,  F.  S.,  "Studies  of  the  fungous  flora  of  virgin  soils,"  My  col.,  19:  248- 
267,  1927. 

Pratt,  O.  A.,  "Soil  fungi  in  relation  to  diseases  of  the  Irish  potato  in  south- 
ern Idaho,"  /.  Agr.  Research,  13:  73-100,  1918. 

Rathbun,  Annie  E.,  "The  fungous  flora  of  pine  seed  beds.  I,"  Phyto- 
pathology, 8:  469-483,  1918. 

Russell,  E.  J.,  et  al.  The  microorganisms  of  the  soil.  188  pp.  Longmans, 
Green  and  Co.,  London.     1923. 

Scales,  F.  M.,  "Studies  on  the  decomposition  of  cellulose  in  soils,"  Soil  Sci., 
7:437-487,  1916. 

Schloesing,  T.,  and  A.  Muntz,  "Sur  la  nitrification  par  les  ferments  or- 
ganises," Compt.  rend.,  84:  301-303,  1877;  85:  1018-1020,  1877. 

Takahashi,  R.,  "On  the  fungus  flora  of  the  soil,"  Ann.  Phytopath.  Soc. 
japan,  12:  17-22,  1919. 

Waksman,  S.  A.,  "Soil  fungi  and  their  activities,"  So/7  Sci.,  2:  103-155,  1916. 
"Is  there  any  fungus  flora  of  the  soil?"  Soil  Sci.,  3:  565-589,  1917. 
"The  importance  of  mold  action  in  the  soil,"  So/7  Sci.,  6:  137-155,  1918. 
"The  growth  of  fungi  in  the  soil,"  So/7  Sci.,  14:  153-158,  1922. 
Principles   of  soil  microbiology,     xix  +  897   pp.     Williams  and  Wilkins 
Co.,  Baltimore.     1927. 


LITERATURE  CITED  441 

Waksman,  S.  A.,  "Three  decades  with  soil  fungi,"  So/7  Set.,  58:  89-114,  1944. 

Waksman,  S.  A.,  and  E.  B.  Fred,  "A  tentative  outline  of  the  plate  method 
for  determining  the  number  of  microorganisms  in  the  soil,"  So/7  Sci., 
14:  27-28,  1922. 

Werkenthin,  F.  C,  "Fungus  flora  of  Texas  soils,"  Phytopathology,  6:  241- 
253,  1916. 

Whiffen,  Alma  J.,  "Cellulose  decomposition  by  the  saprophytic  chytrids," 
/.  Elisha  Mitchell  Sci.  Soc,  51:  321-329,  194L 

Wolf,  Fred  T.,  "A  contribution  to  the  life  history  and  geographical  distri- 
bution of  Allomyces,"  MycoL,  33:  158-173,  1941. 


Chapter  20 

FUNG  US-INSECT  INTERRELA  TIONSHIPS 

The  studies  to  date  on  the  interrelationships  of  fungi  and  in- 
sects may  be  placed  largely  in  one  or  the  other  of  five  categories: 

( 1 )  those  dealing  with  insects  as  vectors  of  plant-pathogenic  fungi, 

(2)  those  concerned  with  fungi  that  produce  diseases  of  insects, 

(3)  those  involving  fungi  as  agencies  in  the  biological  control  of 
insects  injurious  to  crops,  (4)  those  dealing  with  insects  that  make 
it  possible  for  certain  species  of  fungi  to  undergo  their  cyclical 
changes  or  developmental  processes,  and  (5)  those  involving  fungi 
that  are  cultivated  by  insects  for  food.  These  studies  deal  with  a 
laro-e  number  of  species  in  each  group  of  organisms.  For  this 
reason  any  account  that  attempts  a  complete  review  of  the  litera- 
ture and  a  discussion  of  it  would  of  necessity  be  voluminous,  and 
such  an  undertaking  is  beside  the  present  purpose.  Instead  an 
attempt  will  be  made  by  the  use  of  representative  examples  to 
introduce  each  of  these  important  fields  of  interest.  A  much  more 
comprehensive  account  of  these  subjects,  to  which  the  student  is 
referred,  is  contained  in  a  volume  by  Leach  ( 1940). 

INSECTS  AS  VECTORS  OF  PLANT-PATHOGENIC  FUNGI 

This  subject  was  briefly  considered  in  Chapter  8,  and  to  avoid 
repetition  some  details  are  omitted  at  this  point.  Attention  may 
well  be  directed,  however,  to  certain  general  features  of  this 
phase  of  the  fungus-insect  relationship.  It  should  be  appreciated, 
first  of  all,  that  a  background  of  related  evidence  facilitated  ac- 
ceptance  of  the  fact  that  insects  are  instrumental  in  dispersing 
certain  pathogenic  fungi  and  in  implanting  them  within  host 
tissues.  Before  1900  it  had  been  established  that  certain  mos- 
quitoes are  vectors  of  the  nematode  worm,  Wuchereria  bancrofti, 

442 


INSECTS  AS  VECTORS  OF  PLANT-PATHOGENIC  FUNGI      4i3 

causing  elephantiasis  of  man,  that  the  malaria-producing  protozoa 
are  transmitted  by  mosquitoes,  and  that  ticks  transmit  the  Texas 
cattle-fever  organism.  Furthermore  it  had  been  established  that 
the  bacterium  responsible  for  fire  blight  of  pears  and  apples  may 
be  dispersed  by  bees  and  wasps.  From  such  basic  observations  on 
insect  transmission  of  nematodes,  protozoa,  and  bacteria  respons- 
ible for  animal  and  plant  diseases,  interest  in  insects  as  vectors 
increased.  As  an  outcome,  instances  were  found  and  convincing 
proofs  were  submitted  that  viruses  and  plant-pathogenic  fungi 
may  also  be  dispersed  by  insects. 

The  dispersal  of  plant-pathogenic  fungi  by  insects  is  accom- 
plished quite  fortuitously.  Spores  that  adhere  to  the  body  of  the 
vector  may  become  dislodged  on  a  near-by  host.  Leaf-eating  in- 
sects quite  generally  consume  diseased  and  non-diseased  tissues 
indiscriminately,  and  the  spores  may  pass  intact  through  the  ali- 
mentary tract.  Such  spores  in  the  fecal  matter  can  then  serve  as 
inoculum.  Again,  spores  may  be  introduced  or  may  gain  entrance 
into  plant  tissues,  especially  of  fruits  and  twigs,  through  incisions 
made  in  connection  with  oviposition. 

In  general,  all  the  dispersal  of  spores  of  a  given  fungus  is  not 
accomplished  by  one  species  of  insect.  Rather  several  species  of 
insects  serve  as  vectors;  they  may  belong  to  entirely  different 
groups.  Among  the  kinds  of  insects  known  to  be  vectors  of  plant- 
disease-producing  fungi  are  grasshoppers,  crickets,  aphids,  scale 
insects,  beetles,  true  bugs,  flies,  wasps,  and  bees. 

As  might  be  anticipated,  abundance  of  a  given  vector  may  be 
directly  correlated  wTith  the  severity  of  an  outbreak  of  disease 
among  plants.  For  this  reason  insect  control  and  plant-disease 
control  sometimes  become  mutually  interdependent. 

Among  important  plant-pathogenic  fungi  known  to  be  trans- 
ported by  insects  are  the  following:  Endothia  parasitica,  the  chest- 
nut-blight fungus,  Claviceps  purpurea,  the  ergot-producing  organ- 
ism, Phoma  lingam,  the  cause  of  cabbage  blackleg,  Nematospora 
phaseoli,  the  cause  of  pod  spot  of  Lima  bean,  Septoria  ly  coper  sic'u 
the  cause  of  a  leaf  spot  of  tomato,  Sclerotinia  fnicticola,  the 
brown-rot  fungus  of  stone  fruits,  Botrytis  anthophila,  the  cause  of 
clover-blossom  blight,  Ceratostomella  uhni,  the  Dutch  elm  patho- 
gen, and  C.  pilifera  and  related  blue-stain-producing  species  on 
coniferous  wood. 


444  FUNGUS-INSECT  INTERRELATIONSHIPS 

FUNGI  OCCURRING  OX  OR  WITHIN  INSECTS 

The  entomogenous  fungi,  or  fungi  that  naturally  occur  on  or 
within  the  bodies  of  insects,  vary  greatly  in  food  habits.  Some 
utilize  only  living  insects,  whereas  others  subsist  entirely  as  scav- 
engers.  Some  exhibit  a  high  degree  of  specialization;  others  are 
quite  generalized.  Furthermore,  with  the  exception  of  the  La- 
boulbeniales  and  nearly  all  the  Entomophthorales  and  species  of 
Cordvceps,  the  entomogenous  habit  is  not  a  characteristic  pos- 
sessed by  any  large  group  of  closely  related  species.  All  seem 
markedly  influenced  in  their  food  habits  both  by  biotic  and  en- 
vironmental factors. 

.Much  of  our  knowledge  of  these  fungi  comes  from  the  investi- 
gations of  Thaxter  (1888,  1896,  19o{  1924,  1926)  and  Petch 
0914,  1921,  1924,  1925,  1926,  1931,  1932,  1935,  1939).  Thaxter 
devoted  his  attention  to  the  Entomophthorales  and  Laboulbeniales; 
Petch,  to  various  others,  principally  to  Ascomycetes  belonging  to 
Cordvceps,  Hypocrella,  Sphaerostilbe,  Myriangium,  Podonectria, 
and  Xectria,  and  to  members  of  the  Fungi  Imperfecti  belonging 
to  Aspergillus,  Penicillium,  Spicaria  (Isaria),  Aschersonia,  Alicro- 
cera,  Yerticillium,  Acremonium,  Cephalosporium,  Rhinotrichum, 
Cladobotryum,  and  Beauveria.  The  student  of  entomogenous 
fungi  should  also  acquaint  himself  with  the  check  lists  by  Seymour 
(1929,  pp.  698-718)  and  Charles  ( 1941)  to  gain  some  appreciation 
of  the  large  number  of  species  of  fungi  and  insects  involved.  In 
the  following  account  mention  will  be  made  only  of  a  few  of  the 
better-known  ones. 

In  1921  Keilin  (1921)  described  as  Coelomy  ces  stegomyiae  an 
organism  parasitizing  the  larvae  of  the  mosquito,  Stegoviyia  scu- 
tellaris.  Later  Couch  (1945)  found  additional  species  of  Coelo- 
myces  in  larvae  of  other  mosquitoes,  Culex  and  Anopheles,  in 
Georgia,  and  determined  that  the  parasites  belong  among  the 
Blastocladiales. 

Among  the  better-known  species  of  Entomophthora  may  be 
mentioned  E.  vmscae  on  houseflies,  E.  grylii  on  crickets,  and  E. 
sphaerosperma  on  the  caterpillars  of  cabbage  butterflies.  Ento- 
vwphthora  sphaerosperma  was  reported  by  Sawyer  (1929)  as  para- 
sitizing Rhopobota  vacciniaua,  which  attacks  cranberry  vines. 
Speare  (1912)  described  E.  psendococci  as  parasitic  on  mealy  bugs, 


FUNGI  OCCURRING  ON  OR  WITHIN  INSECTS  445 

Fsendococciis  calceolariae,  on  sugar  cane  in  Hawaii.  Petch 
(1926b)  lists,  from  Mysore,  E.  (Empusa)  lecanii  as  the  first  mem- 
ber of  this  genus  found  attacking  a  scale  insect. 

The  "seventeen-year  locust,"  Tibicina  septendecem,  is  very 
commonly  attacked  by  a  peculiar  fungus,  Massospora  cicadina 
[Speare  (1921)].  This  organism  grows  within  the  insect's  body 
and  causes  the  posterior  segments  to  drop  off  while  the  cicada  is 
still  alive.  The  conidia  and  resting  spores  are  then  dispersed  as 
the  cicada  crawls  or  flies. 

In  the  American  tropics  Metarrhiziinn  anisopliae,  called  the 
green  muscardine  fungus,  is  known  to  be  destructive  to  approxi- 
mately 60  species  of  insects.  Some  of  these  insects  are  of  im- 
portance, including  the  sugar-cane  froghopper,  Tomaspis  varia, 
and  May  beetles,  because  they  normally  cause  appreciable  damage 
to  crops. 

Beauvaria  bassiana  is  another  generalized  species,  best  known 
from  its  occurrence  on  chinch  bug,  Blissiis  leucopterus,  and  corn 
borer,  Fyransta  nubilalis.  It  was  first  described  as  a  parasite  of 
silk-worm  larvae  and  given  the  name  Botrytis  bassiana  [Petch 
( 1914)  ] .  Previously  another  species,  Beauveria  globulifera,  which 
has  been  confused  with  B.  bassiana,  was  described  from  France 
and  from  South  America.  In  South  America  it  was  identified  as 
Sporotrichum  globulifernm.  However,  Lefebvre  (1931)  regards 
B.  bassiana  an'd  B.  globulifera  as  distinct  species,  and  his  evidence 
indicates  that  B.  globulifera  is  the  more  virulent  as  a  pathogen 
on  corn  borer. 

Sorosporella  uvella,  a  hyphomycete  pathogenic  to  certain  cut- 
worms and  to  larvae  of  the  sugar-beet  curculio,  Cleonus  pancti- 
ventris,  is  of  peculiar  interest  because  there  is  no  external  evidence 
of  its  presence  in  host  larvae  [Speare  (1920)].  The  fungus  is  an 
obligate  parasite.  Its  resting  spores  are  formed  internally  to  the 
body  wall  and  come  to  fill  the  body  cavity  with  a  brick-red 
powdery  mass.  This  organism  was  first  described  from  Russia, 
where  it  was  given  the  name  Tarichhmi  uvella. 

The  generic  name  Isaria  has  come  to  be  widely  known  among 
mycologists  in  connection  with  conidial  stages  of  Cordyceps  that 
parasitize  various  beetles  and  other  insects.  Petch  (1934)  pro- 
posed, however,  that  the  name  Isaria  be  discarded  in  favor  of 
Spicaria.     Then  the  name  Isaria  farinosa,  as  the  type,  becomes 


446 


FUNGUS-INSECT  INTERRELATIONSHIPS 


Fig.  74.  Various  entomogenous  fungi.  A.  Simple  conidiophores  of  Ccph- 
alosporium  lecanii  on  Lecanium  viride  on  coffee.  B.  Branched  conid  o- 
phore  of  C.  lecanii.    C.  A  head  of  conidia  of  C.  lecanii.    D.  Conidiophore 


FUNGI  OCCURRING  ON  OR  WITHIN  INSECTS  441 

Spicaria  jarinosa.    Spicaria  javanica  attacks  the  cottony  cushion 
scale,  I  eery  a  purehasi,  in  Puerto  Rico. 

According  to  Petch  (1921),  there  are  about  50  valid  species  of 
Hvpocrella,  most  of  them  parasitic  on  scale  insects.  A  consider- 
able number  possess  a  pvenidial  stage  belonging  to  Aschersonia. 
The  first  Aschersonia  to  be  described  was  A.  aleyrodis  on  Aley- 
rodes  citri,  collected  in  Florida,  in  1894. 

Other  parasites  of  scales  are  mostly  species  of  Myriangium, 
Sphaerostilbe,  Nectria,  and  Podonectria.  Of  the  15  species  of 
Myriangium  recognized  by  Petch  (1924a),  4  are  entomogenous, 
namely  M.  duriaei,  M.  curtisii,  M.  montagnei,  and  M.  thueakesii. 

Apparently  the  first  entomogenous  fungus  on  scales  was  col- 
lected in  Normandy  and  given  the  name  Microcera  coccophila  by 
Desmazieres  in  1848  [Petch  (1921)].  This  is  a  conidial  stage,  and 
soon  thereafter  the  Tulasne  brothers  wrongly  attached  this  name 
to  Sphaerostilbe  coccophila.  Petch,  however,  maintains  that  5. 
flammea  is  the  correct  perithecial-stage  name  for  Microcera  cocco- 
phila, which  is  a  widely  distributed  fungus  on  scales  in  North 
America.  The  next  scale  parasite  to  be  recognized  was  collected 
on  orange  twigs  in  Ceylon  and  identified  as  Nectria  aurantiicola. 
Later  Luttrell  (1944)  studied  the  development  of  this  species, 
using  the  name  Sphaerostilbe  aurantiicola,  which  is  widely  present 
in  the  Orient  and  in  the  southeastern  United  States.  Like  5. 
-flammea,  it  possesses  a  similar  conidial  (Microcera)  stage. 

Perhaps  the  most  remarkable  of  the  fungi  that  attack  insects 


of  Spicaria  javanica  with  phialides  and  conidia.    E.  Conidia  of  S.  javanica. 

F.  Conidiophore  and  conidia  of  V erticillhim  heterocladium,  parasitic  on 
Aleyrodes.  G.  Botrvoid  clusters  of  conidiophores  of  Beanveria  bassiana, 
bearing  conidia.  H.  Mature  conidia  of  B.  bassiana.  I.  Germinating  conidia 
of  B.  bassiana.  J.  Flask-shaped  phialides  terminating  conidiophore  branches 
of  B.  bassiana.  K.  Colony  of  young  resting  spores  of  Sorosporella  uvella 
from  diseased  cutworm,  showing  budding.  L.  Mature  resting  spores  of  5. 
uvella  with  remains  of  walls  of  cohering  spores.  M.  Mature  conidia  (sec- 
ondary) of  S.  uvella.  N.  Verticillate  conidiophore  of  5.  uvella,  bearing 
secondary  conidia.  O.  Conidia  (Microcera)  of  Sphaerostilbe  aurantiicola. 
P.  Ascus  of  S.  aurantiicola.    (A,  B,  C,  D,  and  E  after  Petch,  F  after  Fawcett, 

G,  H,  I  and  /  after  Lefebvre,  K,  L,  M  and  N  after  Speare,  and  O  and  P 

after  Luttrell.) 


448  FUNGUS-INSECT  INTERRELATIONSHIPS 

are  species  of  Septobasidium,  a  genus  monographically  treated  by 
Couch  (1938).  Its  members  live  in  mutualistic  association  with 
colonies  of  scale  insects,  using  some  individuals  for  food  and 
giving  shelter  and  protection  to  others. 

BIOLOGICAL  CONTROL  OF  INSECTS 

That  competition  between  organisms  exists  everywhere 
throughout  nature  is  clearly  appreciated  by  biologists.  This  con- 
cept was  crystallized  from  observations  and  incisive  analyses  by 
Darwin,  and  he  expressed  it  by  the  connotation  "the  struggle  for 
existence."  The  discussion  that  follows  is  intended  merely  to 
direct  attention  to  man's  efforts  to  intervene  in  a  struggle  between 
fungi  and  insects  in  order  to  suppress  epidemics  of  insect  pests, 
at  least  to  the  extent  of  bringing  them  under  control. 

The  basic  principles  of  biological  control  of  noxious  insects  by 
microorganisms  (fungi,  bacteria,  viruses,  and  protozoa)  have  been 
given  consideration  by  Sweetman  (1936).  He  indicates  that  the 
following  factors  should  be  given  particular  attention:  (1)  the 
differences  in  receptivity  or  susceptibility  of  the  insect  at  different 
stages  of  development;  (2)  the  environment  most  favorable  to  the 
pathogenic  agent;  (3)  the  virulence  of  the  pathogen  as  modified 
by  environment;  and  (4)  the  necessity  of  having  the  optimum 
conditions  for  attack  by  the  pathogen  coincide  with  the  occur- 
rence of  favorable  abundance  and  developmental  stage  of  the 
insect  to  be  controlled. 

Upon  contemplation  of  these  factors  it  will  become  apparent 
that  little  hope  of  success  should  be  expected  in  controlling  a  par- 
ticular insect  pest  by  use  of  a  given  entomogenous  fungus  unless 
and  until  an  understanding  has  been  gained  of  the  aggressiveness 
or  virulence  of  the  fungus.  For  example,  some  fun^i,  such  as 
species  of  Penicillium,  Alternaria,  and  Cladosporium,  whose  mem- 
bers rarely  attack  living  organisms,  may  be  presumed  when  pres- 
ent to  have  invaded  the  bodies  of  insects  after  they  have  died.  At 
the  opposite  extreme  in  intergradation  of  parasitism  are  such  obli- 
gate parasites  as  Entomophthora  and  Sorosporella,  which  thrive 
only  while  the  insect  remains  alive.  Such  fungi  produce  spores 
during  a  brief  period  before  the  death  of  their  victim  or  immedi- 
ately thereafter,  and  the  spores  remain  dormant  or  fail  to  germi- 
nate unless  they  come  in  contact  with  another  living  insect. 


BIOLOGICAL  CONTROL  OF  INSECTS  449 

Furthermore  weather  factors  are  known  to  influence  the  adores- 
siveness  of  entomogenous  fungi.  Most  of  them,  especially  species 
of  Sphaerostilbe,  Aegerita,  Aschersonia,  and  Beauveria,  are  favored 
by  wet  weather  or  periods  of  high  humidity  coupled  with  high 
temperature.  If  dense  populations  of  insects  occur  at  such  times, 
these  fungi  spread  with  great  rapidity,  and  the  insects  become  dis-  . 
eased  in  epidemic  proportions.  These  factors  may  therefore  be- 
come limiting  in  man's  efforts  toward  artificial  control. 

Beauveria  bassiana,  first  observed  in  1835  by  Bassi  di  Lodi  as 
pathogenic  to  silk-worm  larvae,  is  among  the  better-known  spe- 
cies that  have  been  used  in  efforts  to  secure  control  of  insects. 
Attempts  extending  over  several  seasons  were  made  to  control 
flea  beetles  (Haltica)  in  Algeria,  with  the  result  that  the  adult 
stage  readily  became  infected,  but  the  larvae  seemed  quite  resistant. 
Attempts  were  also  made  over  the  period  1888  to  1896  to  control 
chinch  bug,  Blissus  leucoptenis,  in  Illinois  by  use  of  the  related 
Beauveria  globulifera.  A  measure  of  success  was  obtained  in  these 
trials  but  only  when  the  insects  were  present  in  excessive  abun- 
dance and  when  hot,  wet  weather  prevailed. 

Extensive  attempts  have  been  made  in  Florida  to  utilize  naturally 
occurring  entomogenous  fungi  against  white  flies  and  scale  insects 
in  citrus  groves  [Fawcett  (1907,  1908),  Berger  (1909,  1910),  Mor- 
rill and  Back  (1912)].  In  Florida  citrus  groves,  several  species, 
including  Aegerita  ivebberi,  Aschersonia  aleyrodis,  A.  goldiana, 
V erticilliinn  cinnamomeum,  Sphaerostilbe  aurantiicola,  and  Po- 
donectria  coccicola,  are  of  importance  and  have  been  used  arti- 
ficially. Increase  of  white  flies  and  scale  insects  has  been  stimu- 
lated there  by  the  use  of  Bordeaux  mixture  to  control  citrus  scab, 
Sphacelovm  fawcetti,  and  citrus  melanose,  Diaporthe  citri. 

The  inoculum  for  these  entomogenous  species  consisted  of  spore 
suspensions  sprayed  upon  insect-infested  trees  or  of  fungus-bear- 
ing leaves  or  twigs  tied  to  such  trees.  In  some  instances  the  spore 
suspensions  were  prepared  from  pure  cultures  and  in  others  from 
fungi  removed  from  infested  leaves. 

Under  some  conditions  the  results  in  Florida  and  elsewhere 
show  that  the  artificial  introduction  of  fungi  has  very  materially 
aided  in  the  destruction  of  insects  [Picard  (1914),  Berger  (1921, 
1932),  and  Watson  and  Berger  (1937)]. 

Morrill  and  Back   (1912)   concluded,  however,  that  Aegerita 


450  FUNGUS-INSECT  INTERRELATIONSHIPS 

ivebberi  is  so  effective  in  controlling  white  fly  in  low-lying  ham- 
mock groves  that  artificial  measures  are  unnecessary. 

Aspergillus  parasiticus  has  been  found  effective  against  various 
mealy  bugs  in  Hawaii  [Speare  (1912)],  Puerto  Rico  [Johnston 
(1910)1,  and  California  [Smith  and  Armitage  (1931)]. 

Species  of  Entomophthora  are  not  easily  cultivated  in  pure 
culture  but,  if  artificially  disseminated,  may  aid  in  bringing  epi- 
demics of  plant  lice  under  control.  Entomophthora  sphaero- 
spervia,  for  example,  caused  considerable  reduction  in  the  popu- 
lation of  apple  sucker,  Psyllia  mali  [Sweetman  (1936),  p.  71], 
in  Nova  Scotia  and  in  parts  of  Europe.  Another  species,  E. 
clorojiiaphidis,  was  found  very  destructive  to  walnut  aphis,  Chro- 
viaphis  juglandicola,  in  California.  In  some  seasons  in  Florida  E. 
fresemi  becomes  an  important  factor  in  the  control  of  Aphis 
spiraecola,  especially  on  tangerines. 

Metarrhiziwn  anisopliae,  when  artificially  applied  in  some  lo- 
calities to  corn  leaves,  has  been  found  very  destructive  to  corn 
borer  [Sweetman  (1936),  p.  75]. 

It  becomes  apparent  to  anyone  who  critically  reads  accounts 
dealing  with  attempts  to  use  fungi  to  control  insect  pests  that  the 
results  are  not  always  in  accord,  and  the  conclusions  are  often  con- 
tradictory. Petch  (1921)  summarized  his  pertinent  experiences  as 
follows:  "The  problem  which  has  yet  to  be  solved  by  those  who 
wish  to  control  insects  by  means  of  fungi  is  to  create  an  epidemic 
at  a  time  when  such  an  epidemic  would  not  occur  naturally."  On 
the  basis  of  the  relatively  few  cases  in  which  outstanding  control 
has  been  accomplished  Fawcett  (1944)  suggests  that  more  atten- 
tion should  be  given  to  the  artificial  spreading  of  entomogenous 
fumn  and  to  more  efficient  ways  of  increasing  their  use. 

INSECTS  IX  RELATION  TO   REPRODUCTION   OF   FUNGI 

It  has  long  been  known  that  insects  carry  pollen  and  that  the 
setting  of  seed  and  the  development  of  certain  fruits,  for  example, 
clovers,  apples,  and  peaches,  is  conditioned  by  insect  pollination. 
Similarly  insects  disperse  reproductive  elements  (spermatia) 
among  fungi.  In  support  of  this  conclusion,  Brodie  (1931 )  found 
that  flies  are  agents  of  diploidization  of  Coprimts  lagopi/s,  a  hetero- 
thallic  species.  The  fruit  bodies  of  this  mushroom  do  not  form 
unless  oidia  from  the  plus  mycelium  are  transported  to  the  minus 


FUNGI  CULTIVATED  BY  INSECTS  451 

mycelium,  or  vice  versa,  whereupon  they  germinate,  the  hyphae 
fuse,  diploidization  results,  and  mushrooms  are  developed. 

Craigie  (1931)  showed  that  Puccinia  helianthi  and  P.  graminis 
may  be  diploidized  by  the  agency  of  insects.  The  pycniospores 
of  these  rusts  are  haploid.  Diploidization  occurs  only  if  pycnio- 
spores from  one  pycnium  are  transferred  to  another  of  opposite 
sex,  whereupon  the  process  is  initiated  by  fusion  of  a  germinating 
pycniospore  with  a  receptive  (flexuous)  hypha  that  projects  from 
the  pycnium.  Insects  may  be  essential  agents  in  the  transfer  of 
pycniospores,  and  such  transfer  is  an  essential  condition  in  the 
development  of  dicaryotic  aeciospores.  Subsequent  findings  with 
other  rust  fungi  substantiate  these  observations.  Spermatization 
of  certain  ascomycetes  also  is  known  to  result  from  insect  trans- 
fer of  spermatia. 

FUNGI  CULTIVATED  BY  INSECTS 

Much  of  our  knowledge  on  this  topic  involves  "ambrosia" 
beetles  (timber-boring  Scolytidae,  including  engraver  beetles  and 
bark  beetles  that  tunnel  and  breed  in  bark  and  sapwood),  leaf- 
cutting  ants,  and  termites.  Such  relationship  of  insect  and  fungus 
is  termed  an  ectosvmbiotic  one  bv  Buchner  (1930).  By  ectosym- 
biosis,  in  this  instance,  is  meant  an  association  in  which  the  fungus 
occurs  chiefly  outside  the  body  of  the  insect. 

Beetles  and  fungi.  Many  species  of  Scolytid  beetles  are  asso- 
ciated with  fungi;  the  better-known  ones  belong  to  Scolytus, 
Dendroctonus,  Ips,  and  Hvlurgopinus.  Their  relationship  with 
specific  fungi  seems  none  too  well  understood  in  most  cases,  al- 
though the  phenomenon  of  fungus-insect  association  was  first  ob- 
served about  a  hundred  years  ago.  As  indicated  in  Buchner's 
treatise  (1930),  Thomas  Hartig  in  1844  recognized  that  the  am- 
brosia of  Xyle  bonis  dispar  in  Ahms  cor  data  is  a  fungus,  which  he 
named  Monilia  Candida.  Subsequent  investigations  have  shown 
that  there  are  many  other  species  of  ambrosia  fungi.  Leach 
(1940)  emphasizes,  however,  that  ".  .  .  taxonomic  studies  of  am- 
brosia fungi  are  conspicuous  by  their  absence." 

Ambrosia  fungi  in  general  permeate  the  wood  and  enter  into 
the  burrows  and  brood  galleries  made  by  the  beetles.  The  my- 
celium and  spores  that  protrude  into  the  galleries  are  eaten  by  the 


452  FUNGUS-INSECT  INTERRELATIONSHIPS 

beetles,  and  spores  either  may  be  regurgitated  or  may  resist  diges- 
tion and  then  be  yoided  in  the  excrement. 

A  great  deal  of  interest  in  ambrosia  fungi  has  centered  on  those 
species  associated  with  the  staining  of  wood,  since  such  wood 
staining  is  of  so  much  economic  importance  to  the  lumber  indus- 
try. The  work  of  Rumbold  (1936)  shows  that  Ceratostomella 
ips,  C.  pilifera,  and  C.  pint  occur  in  pines,  C.  piceaperda  in  spruce 
in  eastern  Canada,  C.  pseudotsugae  in  Douglas  fir  and  larch  in  the 
Northwest,  and  C.  pluriannulata  in  hardwoods.  In  white  fir 
damaged  by  seyeral  species  of  Scolytus,  Wright  (1935,  1938) 
noted  two  wood-staining  species,  Trichospor'nim  symb'wt'icum 
and  Spicaria  anomala. 

Ceratostomella  ulvii,  which  attacks  elms,  is  always  associated 
with  galleries  produced  by  Scolytus  scolytus  and  5.  vmltistriatus. 

Seyeral  other  species  of  fungi  are  associated  with  wood  staining, 
but  their  relationship  to  insects  remains  unknown.  These  species 
include  Endocon'uiiophora  coemlescens,  E.  moniliformis,  Diplodia 
natalensis,  Graphiinn  rigidum,  Lasiosphaeria  peziztda,  Pemcill'unn 
divaricatum,  P.  roseum,  P.  aureum,  Chlorospleminn  aeriig'nwsinih 
Fusarium  moniliforme,  F.  viride,  F.  roseum,  Demathnu  pulli/lans, 
and  seyeral  species  of  Cadophora,  Hormodendrum,  and  Alternaria. 
It  seems  probable  that  all  of  them  are  not  cultivated  by  wood- 
boringr  beetles. 

Ants  and  fungi.  Approximately  a  hundred  species  of  tropical 
and  subtropical  myrmicine  ants  have  the  remarkable  habit  of  culti- 
vating and  feeding  upon  fungi.  These  ants  live  in  large  colonies 
in  underground  nests.  They  cut  out  bits  of  leaves  and  carry  them 
into  these  nests.  The  plant  tissues  are  then  built  into  spongy 
masses  that  serve  as  a  culture  medium  upon  which  the  ants  im- 
plant spores  and  mycelium.  Such  inoculum  is  transported  within 
the  infrabuccal  pouch,  especially  by  the  queens.  The  fungi  grow 
in  these  "ant  gardens"  and  produce  bromatia,  swollen,  roundish 
hvphal  tips,  which  are  consumed  by  the  ants.  New  crops  of  bro- 
matia continue  to  replace  those  that  have  been  eaten. 

Divergent  opinions  have  been  expressed  on  the  identity  of  the 
fungi  involved.  Moller  (1893)  found  in  the  nests  of  Acromyrex 
disciger  a  gill  fungus  that  he  named  Rozites  gonglyophora  (the 
termination  "ites"  should  be  reserved  for  fossil  fungi).  Xylaria 
mi  crura  was  identified  in  the  nest  of  Acromyrex  lundi  by  Spegaz- 
zini.    Cladosporimn  myrmecophilwn  is  cultivated  by  Lasius  fiilig- 


FUNGI  CULTIVATED  BY  INSECTS 


453 


inosus,  and  Hormisciinn  pithy ophilum  by  Lashis  umbratus.  The 
fungus  cultivated  by  Atta  cephalotes  was  identified  by  Weber 
(1938)  as  Lentinus  atticohis.  Spores  of  several  unidentified  species 
from  infrabuccal  pouches  are  represented  in  the  illustrations  that 
accompany  the  report  by  Bailey  (1920). 


Fig.  75.  Fungi  used  as  food  by  insects.  A.  Globular  hyphal  tips  (bromatia) 
of  a  fungus  cultivated  by  ants.  (Adapted  from  Wheeler.)  B.  Aloniliod 
fungus  in  artificial  culture.  The  ambrosia  beetle,  Trypodendron  betnlae, 
uses  this  fungus.     (Adapted  from  Leach,  Hodson,  Christiansen,  and  Chilton.) 

Some  workers  have  maintained  that  the  associated  fungus  oc- 
curs in  "pure  culture,"  a  claim  which  is  denied  by  Goetsch  and 
Stoppel  [Uphof  (1942),  p.  584].  These  investigators  isolated  the 
following  fungi  from  the  nests  of  Atta  sexdens:  Hypomyces  ipo- 
moeae,  Fusarium  oxysporinn,  F.  angustum,  F.  equiseti,  Verticil- 
lium  candidum,  and  Clonostachys  araucariae;  from  nests  of  Acro- 
myrex  they  isolated  Mucor  racemosus,  Actinomiicor  re  pens, 
Moniliopsis  aderholdii,  Rhizopns  nigricans,  Trichoderma  sp.,  and 
Penicillium  sp. 


454  FUNGUS-INSECT  INTERRELATIONSHIPS 

Interest  in  such  problems  involving  ants  as  growers  of  fungi 
should  be  stimulated  bv  perusal  of  the  reports  of  Aloller  (1893), 
Wheeler  (1907),  Elliott  (1915),  Bailey  (1920),  Spegazzini  (1922), 
and  Weber  (1938). 

Termites  and  fungi.  One  group  of  the  termites  cultivates 
fungi  in  "gardens"  for  use  as  food.  Such  termites  are  colonial  and 
live  either  in  lar^e  nests  (termitaria)  built  underground  or  in 
mounds  above  ground.  Within  these  nests  are  compartments  in 
which  the  fungi  are  cultivated  on  termite  excrement.  The  fungi 
grown  are  eaten  by  the  young  and  constitute  essentially  the  only 
food  used.  In  spite  of  the  fact  that  naturalists  found  fungi  in  ter- 
mite nests  nearly  200  vears  ago,  little  is  yet  known  regarding  the 
identitv  of  such  fungi,  as  is  indicated  bv  the  accounts  of  Holter- 
man  (1898),Petch  (i906,  1913),  Brown  (1918),  Bose  (1923),  and 
Uphof  (1942).  Uphof  states  that  Berkeley  in  1869  described  a 
fungus  taken  from  white-ant  nests  as  Agaricas  terviitigina,  prob- 
ably identical  with  Lentimts  cartilagineus.  He  further  states  that 
Cesati  in  1870  regarded  Tricholoma  snbgavibosnm,  which  occurs 
in  Cevlon,  Java,  Singapore,  and  Borneo  as  a  termite  fungus. 
Fungi  identified  as  Pint  ens  tennitus  and  Xylaria  m gripes  have  been 
taken  from  termite  nests  in  Brazil.  In  India  Bose  (1923)  found 
that  termites  cultivate  Colly bia  albnminosa  but  "weed  out"  the 
stromata  of  Xylaria  nigripes.  Petch  (1906)  made  the  observation 
that  Agaricus  sp.  does  not  grow  in  the  soil  surrounding  the  nest 
but  onlv  on  the  "comb"  in  compartments  while  the  nests  are  in- 
habited. After  the  nests  have  been  abandoned,  Peziza  epispadia, 
Podaxon  sp.,  and  other  fungi  develop  on  the  comb. 

In  addition  to  the  cases  of  ectosvmbiosis  involving  fungi  and 
insects  which  have  been  enumerated,  attention  may  be  directed 
to  the  existence  of  endosvmbiosis.  The  best  known  of  these  endo- 
biotic  relations  involve  termites  that  digest  wood  but  are  able  to 
do  so  onlv  through  the  agency  of  svmbiotic  protozoa  that  live 
within  their  intestines.  The  claim  has  been  made  by  Koch  ( 193 1 ) 
that  an  unnamed  fundus,  which  is  endobiotic,  lives  in  the  fat 
bodies  of  the  saw-tooth  grain  weevil,  Oryzaephilus  snrinamensis, 
and  in  some  manner  contributes  to  fat  metabolism.  This  relation- 
ship is  maintained  from  generation  to  generation  by  invasion  of 
the  eggs. 


IMPLICATIONS  455 

IMPLICATIONS 

It  appears  that  problems  of  interrelationship  of  fungi  and  insects 
are  basically  ecological,  and  more  emphasis  should  be  placed  on 
approaching  them  from  this  viewpoint.  To  this  end  closer  co- 
operation between  mycologists  and  entomologists  is  required. 
The  usefulness  of  these  scientists'  findings  should  be  enhanced  if 
natural  rather  than  artificial  environments  can  be  employed  for 
their  experimentation.  The  resistance  of  seed  plants  to  attack  bv 
the  noxious  insect  should  in  any  event  be  regarded  as  an  essential 
phase  of  such  ecologic  problems. 

LITERATURE  CITED 

Bailey,  I.,  "Some  relations  between  ants  and  fungi,"  Ecology,  1:  174-189, 

1920. 
Berger,  E.  W.,  "White  fly  studies  in  1908,"  Fla.  Agr.  Expt.  Sta.  Bull.  91: 43- 

71,  1909. 
"White  fly  control,"  Fla.  Agr.  Expt.  Sta.  Bull.,  103:  1-28,  1910. 
"Natural  enemies  of  scale  insects  and  white  flies  in  Florida,"  Fla.  Sta. 

Plant  Bd.  Quart.  Bull.,  5:  141-154,  1921. 
"The  latest  concerning  natural  enemies  of  citrus  insects,"  Fla.  State  Hort. 

Soc.  Proc,  45:  131-136,  1932. 
Bose,  S.  R.,  "The  fungi  cultivated  by  the  termites  of  Barkuda,"  Rec  Indian 

Mus.,  25:  253-258,  1923. 
Brodie,  H.  J.,  "The  oidia  of  Coprinus  lagopus  and  their  relation  with  insects," 

Ann.  Botany,  45:315-344,  1931. 
Brown,  W.  H.,  "The  fungi  cultivated  by  termites  in  the  vicinity  of  Manila 

and  Los  Banos,"  Philip.  J.  Sci.,  Ser.  C.  (Bot.),  75:223-231,  1918. 
Buchner,  P.,  Tier  und  Pflanze  in  Symbiose.    Gebruder  Borntrager,  Berlin. 

1930. 
Charles,  Vera  K.,  "A  preliminary  check  list  of  the  entomogenous  fungi  of 

North  America,"  U.  S.  Dept.  Agr.,  Bur.  Plant  Indus.,  Insect  Pest  Survey 

Bull,  21:  770-785,  1941. 
Couch,  J.  N.,  The  genus  Septobasidium.    480  pp.    Chapel  Hill,  N.  C.    1938. 
"Revision  of  the  genus  Coelomvces,  parasitic  in  insect  larvae,"  /.  Elisha 

Mitchell  Sci.  Soc,  61:  124-136,  1945. 
Craigie,  J.  H.,  "An  experimental  investigation  of  sex  in  the  rust  fungi," 

Phytopathology,  21:  1001-1040,  1931. 
Elliott,  J.  S.,  "Fungi  in  the  nests  of  ants,"  Trans.  Brit.  My  col.  Soc,  5:  138 

142,  1915. 
Fawcett,  H.  S.,  "Fungi  parasitic  on  the  Citrus  white  fly,"  Fla.  Agr.  Expt. 

Sta.  Kept.,  1901:  47-49,  1907. 


456  FUNGUS-INSECT  INTERRELATIONSHIPS 

Fawcett,  H.  S.,  "Fungi  parasitic  upon  Aleyrodes  citri,"  Univ.  Fla.  Spec. 

Studies,  1:  1-41,  1908. 
"Fungus  and  bacterial  diseases  of  insects  as  factors  in  biological  control," 

Botan.  Rev.,  10:  327-348,  1944. 
Holterman,  C,  Mykologische  Untersuchungen  aus  den  Tropen.     107  pp. 

1898. 
Johnston,  J.  R.,  "The   entomogcnous  fungi   of  Porto  Rico,"   Porto  Rico 

Bd.  Covnns.  Agr.  Bull.,  10:  1-33,  1910. 
Keilin,  D.,  "On  a  new  type  of  fungus,  Coeloviyces  stegoviyiae,  n.g.,  n.sp., 

parasitic    in    the    body    cavity    of    the    larva    of   Stegomyia   scutellaris 

Walker,"  Parasitology,  13: 225-234,  1921. 
Koch,   A.,   "Die   Svmbiose   von   Oryzaephilus  surincnnensis  L.    (Cucujidae, 

Coleoptera),"  Z.  Morphol.  Okol.  Tiere,  23:  389-424,  1931. 
Leach,  J.  G.,  Insect  transmission  of  plant  diseases,    ix  +  615  pp.  McGraw- 
Hill  Co.,  New  York.     1940. 
Lefebvre,   C.   L.,   "Preliminary   observations   on   two   species   of   Beauveria 

attacking  the  corn  borer,  Pyrausta  nubilalis  Hiibner,"  Phytopathology, 

21:  1115-1128,  1931. 
Luttrell,  E.  S.,  "The  morphologv  of  Sphaerostilbe  aurantiicola    (B.  and 

Br.)  Petch,"  Bull.  Torrey  Botan.  Club,  27:599-619,  1944. 
Moller,  A.,  "Die  Pilzgarten  einiger  Siidamerkanischen  Ameisen,"  Schimper's 

Bot.  Mitt,  aus  Trope?!.,  6:  1-127,  1893. 
Morrill,  A.  W.,  and  E.  A.  Back,  "Natural  control  of  white  flies  in  Florida," 

U.  S.  Dept.  Agr.,  Bur.  Entom.  Bull,  102:  1-73,  1912. 
Petch,  T.,  "The  fungi  of  certain  termite  nests,"  Ann.  Roy.  Botan.  Garden, 

Peradeniya,  3:  185-270,  1906. 
"Termite  fungi,  a  resume,"  Ann.  Roy.  Botan.  Garden,  Peradeniya,  5:  303- 

341,  1913. 
"The  genera  Hvpocrella  and  Aschersonia,"  Ann.  Roy.  Botan.  Garden, 

Peradeniya,  5:52 1-537,  1914. 
"Fungi  parasitic  on  scale  insects,"  Trans.  Brit.  My  col.  Soc,  7:  18-40,  1921. 
"Studies  in  entomogenous  fungi.     I.  The  Nectriae  parasitic  on  scale  in- 
sects," Trans.  Brit.  Mycol.  Soc,  7:89-167,  1921a. 
II.  "The  genera  Hvpocrella  and  Aschersonia,"  Ann.  Roy.  Botan.  Garden, 

Peradeniya,  7:167-278,  1921b. 

IV.  "Some  Cevlon  Cordyceps,"  Trans.  Brit.  Mycol.  Soc,  10:  28-45,  1924. 

V.  "Mvriangium,"  Trans.  Brit.  Mycol.  Soc,  70:45-80,  1924a. 

VI.  "Cephalosporium   and   associated    fungi,"    Trans.   Brit.   Mycol.   Soc, 
10:  152-182,  1925. 

VII.  "Spicaria,"  Trans.  Brit.  Mycol.  Soc,  10:  183-189,  1925a. 

VIII.  "Notes  on  Beauveria,"  Trans.  Brit.  Mycol.  Soc,  70:244-271,  1926. 

IX.  "Aegerita,"  Trans.  Brit.  Mycol.  Soc,  11:  50-66,  1926a. 

XI.  "Empusa  lecanii  Zimm,"  Trans.  Brit.  Mycol.  Soc,  77:254-258,  1926b. 

"Notes  on  entomogenous  fungi,"  Trans.  Brit.  Mycol.  Soc,  16:55-75,  1931; 
76:209-245,    1932;    7£:  48-75,    1933;    7 9:  34-38,    1934;    20:161-194,    1935; 
23:  127-148,  1939. 
Picard,  F.,  "Les  champignons  parasites  des  insects  et  leur  utilization  agri- 
cole,"  Ann.  ecole  nat.  agr.  Montpellier,  13:  121-248,  1914. 


LITERATURE  CITED  451 

Rumbold,  Caroline  T.,  "Three  blue-staining  fungi,  including  two  new  spe- 
cies associated  with  bark  beetles,"  /.  Agr.  Research,  53:  419^-37,  1936. 
Sawyer,  W.   H.,   "Observations  on  some   entomogenous   members   of  the 

Entomophthoraceae   in   artificial   culture,"   Am.   J.   Botany,   16: 87-121, 

1929. 
Seymour,  A.  B.,  Host  index  of  the  fungi  of  North  America,    xiii  +  718  pp. 

Cambridge,  Alass.     1929. 
Smith,  H.  S.,  and  H.  M.  Armitage,  "The  biological  control  of  mealy  bugs 

attacking  citrus,"  Calif.  Agr.  Expt.  Sta.  Bull.,  509:  1-74,  1931. 
Speare,    A.    T.,    "Fungi    parasitic    upon    insects    injurious    to    sugar    cane," 

Hawaiian  Sugar  Planters  Assoc,  Expt.  Sta.  Bull.,  12:  1-62,  1912. 
"Further  studies   of  Sorosporella  uvella,   a   fungous   parasite   of  noctuid 

larvae,"  /.  Agr.  Research,  18:  399-440,  1920. 
uMassospora  cicadina  Peck,  a  fungus  parasite  of  the  periodical  cicada," 

My  col,  13:72-82,  1921. 
Spegazzini,  C,  "Description  de  Hongos  Alirmecofilos,"  Rev.  museo  de  la 

Plata,  26:  166-173,  1922. 
Sweetman,  H.  L.,  The  biological  control  of  insects.     461  pp.     Comstock 

Publishing  Co.,  Ithaca,  N.  Y.     1936. 
Thaxter,  R.,  "The  Entomophthoraceae  of  the  United  States,"  Mem.  Boston 

Soc.  Nat.  Hist.,  4:  133-201,  1888. 
"Contributions  toward  a  monograph  of  the  Laboulbeniaceae.     I,"  Mem. 

Am.  Acad.  Arts  Sci.,  12:  189-429,  1896;  II,  75:219-469,  1908;  III,  74:313- 

414,  1924;  IV,  75:431-580,  1926. 
Uphof,  J.  C.  Th.,  "Ecological  relations  of  plants  with  ants  and  termites," 

Botan.  Rev.,  8:  563-598,  1942. 
Watson,  J.  R.,  and  E.  W.  Berger,  "Citrus  insects  and  their  control,"  Univ. 

Fla.  Agr.  Ext.  Bull.,  88:  1-135,  1937. 
Weber,  N.  A.,  "The  biology  of  the  fungus-growing  ants.     III.  The  sporo- 

phore  of  the  fungus  grown  by  Atta  cephalotes  and  a  review  of  other 

reported  sporophores,"  Rev.  Entomologia,  8:  265-272,  1938. 
Wheeler,  W.  M.,  "The  fungus-growing  ants  of  North  America,"  Bull.  Am. 

Mus.  Nat.  Hist.,  23:  669-807,  1907. 
Wright,  Ernest,  "Trichosporium  symbioticum,  n.sp.:  a  wood-staining  fungus 

associated  with  Scolytus  ventralis^  J.  Agr.  Research,  50:525-538,  1935. 
"Further  investigations  of  brown-staining  fungi  associated  with  engraver 

beetles  (Scolytus)  in  white  fir,"  /.  Agr.  Research,  51:  759-774,  1938. 


Chapter  21 
MARINE  FUNGI 

Among  students  of  fungi  and  of  marine  biology  generally,  a 
knowledge  of  marine  fungi  is  largely  non-existent.  The  under- 
lying  reasons  for  this  strange  state  of  affairs  are  not  apparent  in 
view  of  the  enormous  volume  of  work  dealing  with  marine  life 
that  has  been  accomplished.  Biologists  quite  generally  concede 
that  the  ocean  is  the  ancestral  home  of  life  and  that  the  progenitors 
of  present-day  land  animals  and  plants  came  from  the  ocean. 
With  similar  reasoning  fungi  may  be  assumed  to  have  originated 
within  the  ocean.  It  might  be  anticipated,  moreover,  that  marine 
fungi  would  constitute  favorable  materials  for  studies  on  phylog- 
eny  and  on  the  place  which  such  organisms  occupy  in  the 
economy  of  life  in  oceans. 

Terrestrial  fungi  and  bacteria  are  well  known  to  be  responsible 
for  the  decomposition  of  organic  debris  of  all  sorts,  and  it  may 
reasonably  be  assumed  therefore  that  organisms  of  these  types 
play  a  similar  role  in  the  ocean.  This  assumption  is  not  supported, 
however,  by  any  body  of  observational  and  experimental  data  of 
appreciable  magnitude.  Similarly,  relatively  little  appears  to  be 
known  about  the  activities  and  life  histories  of  any  species  of 
marine  fungi  and  bacteria,  although  marine  bacteria  have  been 
studied  somewhat  intensively  and  extensively. 

Students  of  the  phytogeny  of  the  fungi  regard  the  Archimy- 
cetes  as  the  ancestral  and  the  most  primitive  group.  Among 
Archimvcetes  the  asexual  spores  and  both  kinds  of  gametes  or 
those  of  one  sex  only  may  be  motile,  whereas  among  present-day, 
higher,  terrestrial  Phvcomvcetes  and  anions  all  Ascomvcetes  and 
all  Basidiomvcetes  motility  is  lacking.  This  fact  might  be  inter- 
preted to  indicate  that  all  these  present-day,  non-motile  forms 
were  derived  in  a  monophyletic  line  from  terrestrial  progenitors 
after  the  land  habit  had  once  become  established.  It  is  conceiv- 
able too  that  the  higher  marine  fungi  of  the  present  day  may 

458 


HISTORICAL  BACKGROUND  459 

have  evolved  on  land  and  thereafter  migrated  from  the  land  to 
the  ocean.  On  the  other  hand,  those  who  would  derive  the 
Ascomvcetes  from  Florideae  regard  the  fungi  as  polvphyletic. 
They  emphasize  as  a  basis  of  relationship  similarities  between  sex- 
ual reproductive  structures  rather  than  the  phenomenon  of  mo- 
tility. Regardless  of  whether  fungi  are  mono-  or  polvphyletic, 
there  do  not  seem  to  be  adequate  explanations  to  account  for  the 
paucity  of  Phycomycetes  and  Ascomycetes  within  the  oceans. 
There  should  be  an  abundant  population  of  marine  fungi,  primar- 
ily because  the  ocean  constitutes  a  relatively  stable  environment 
which  should  be  favorable  for  the  continuous  maintenance  cf  spe- 
cies, without  major  adaptative  modification,  even  of  those  whose 
origin  dates  back  into  remote  ^eolomc  time.  This  environmental 
stability  may  in  itself  be  used  to  account  for  the  lack  of  evolutional 
development  of  new  or  different  species.  If  numerous  kinds  of 
marine  fungi  exist,  the  fact  is  not  revealed  by  publications.  In- 
stead the  literature  on  marine  fungi  conveys  the  definite  impres- 
sion that  the  oceans  do  not  constitute  the  natural  habitat  of  di- 
verse fungi,  nor  are  they  at  any  place  densely  populated  by  any 
given  species. 

HISTORICAL  BACKGROUND 

Evidently  many  of  the  early  students  of  marine  animals  and 
plants  failed  to  recognize  the  presence  of  fungi  among  their  col- 
lections or  else  interpreted  the  fungi  as  structures  possessed  by  the 
animals  or  plants  themselves.  Nevertheless  occasional  observers 
noted  hyaline  objects  which  were  interpreted  to  be  fungoid.  In 
1858  Wedl  [Bornet  and  Flahault  (1889)]  observed  that  corals 
from  the  littoral  zone  down  to  a  depth  of  1095  fathoms  are  fre- 
quently invaded  by  filaments  that  lack  septations  and  are  termi- 
nated by  clavate  cells  resembling  sporangia  of  the  Saprolegniaceae. 
Kolliker  (1859-1860)  made  similar  observations  in  his  examination 
of  animals  possessing  calcareous  shells.  Stirrup  (1872)  observed 
fungoid  growths  within  the  shells  of  molluscs,  and  Duncan  (1876- 
1877)  identified  as  Achlya  penetrans  and  Saprolegnia  ferax  two 
water  molds  within  the  canals  of  Caryophyllia  smithii,  one  of  the 
Aladreporia.  Since  these  two  species  have  not  been  found  subse- 
quently in  salt  water,  their  identification  must  be  questioned.  The 
solvent  action  of  carbon  dioxide  produced  by  the  hyphal  tips 
made  possible  the  penetration  of  the  shells.    Bornet  and  Flahault 


460  MARINE  FUNGI 

(1889)  identified  the  fungi  which  they  found  in  molluscan  shells 
as  Ostraco blade  implexa,  presumably  a  saprolegniaceous  form,  and 
Lithopytbiinn  gangliiforme,  a  pythiaceous  species. 

Evidently  non-filamentous  Phycomycetes  are  more  abundant 
among  marine  species  than  are  Saprolegniaceae  and  Pythiaceae. 
The  work  of  Petersen  (1905)  in  Denmark  and  the  more  recent 
studies  by  Sparrow  in  Denmark  and  along  the  New  England  coast 
(1934,  1936)  on  marine  Chytridiales  should  be  considered  in 
orienting  one's  knowledge  of  this  group. 

Barghoorn  and  Linder  (1944)  and  Linder  (1944)  gave  special 
consideration  to  marine  fungi  on  wood  and  cordage.  Nearly  all 
of  the  10  imperfect  species  and  18  Pyrenomycetes  which  they 
isolated  had  not  been  described  previously.  Seven  of  the  Pyreno- 
mycetes tolerated  well  the  salinity  of  sea  water  and  were  able  to 
utilize  cellulose,  pectin,  and  starch. 

For  a  period  of  years  no  one  seems  to  have  devoted  himself  to 
a  study  of  marine  Ascomycetes.  The  reports  by  Reed  (1902) 
from  collections  on  the  California  coast  and  of  Cotton  (1907) 
and  Sutherland  (1914,  1915,  and  1915a)  on  the  English  coast  are 
among  those  of  most  importance. 

Knowledge  of  the  imperfect  fungi  of  the  sea  is  very  meager,  as 
is  that  of  the  Alyxomycetes,  except  for  a  few  species  in  the  aber- 
rant order  Labyrinthulales.  The  best  known  of  these  is  Laby- 
rinthula  viacroystis,  associated  with  the  "wasting  disease"  of  eel 
grass,  Zostera  spp. 

In  the  account  that  follows  each  of  these  four  major  groups  of 
fungi  will  be  considered  to  a  degree  consonant  with  available 
knowledge  and  with  its  importance. 

MARINE  PHYCOMYCETES 

One  of  the  first  chytrids  to  be  studied  is  Ewychasma  dicksonii, 
parasitic  upon  Ectocarpus.  Wright  (1879)  named  this  parasite 
Rhizophydhmi  dicksonii,  a  name  which  was  subsequently  changed 
to  Olpidinm  dicksonii  by  the  algologist  Wille  and  then  to  Enry- 
chasvia  dicksonii  by  Mansmus.  Information  on  its  structure  and 
parasitism  appears  in  the  accounts  by  Lowenthal  (1905)  and 
Dangeard  (1934).  Lowenthal  (1905)  states  that  at  maturity  the 
thallus  contains  a  large  vacuole  with  a  peripheral  segmentation 
of  this  layer.     Petersen  (1905)   traced  zoosporogenesis  also  and 


MARINE  PHYCOMYCETES  461 

found  that  numerous  vacuoles,  separated  bv  thin  layers  of  cyto- 
plasm, function  in  zoospore  formation.  Once  formed,  they  are 
active  for  a  brief  period  and  then  encyst  within  the  sporangium, 
giving  it  a  reticulate  appearance.  Encystment  within  the  spo- 
rangium seems,  however,  to  be  abnormal.  ScherfTel  (1925)  be- 
lieves that  these  methods  of  zoosporogenesis  in  Eurychasma  are 
not  those  of  true  chytrids  but  of  Saprolegniaceae,  and  he  would 
therefore  place  it  in  this  group. 

Reports  of  chytrids  from  the  Pacific  coast  briefly  describe 
Chy iridium  alar  him  [Kibbe  (1916)]  on  Alarm  fistnlosa  and  C. 
codicola  and  Rhizophy diitm  codicola  on  C odium  miicronatum 
[Zeller  (1918)].  In  a  brief  note  Martin  (1922)  calls  attention  to 
the  fact  that  Polysiphonia  sp.  along  the  New  Jersey  coast  is  para- 
sitized bv  Chytridhim  (Rhizophid'mm)  polysiphoniae,  and  Spar- 
row (1936)  records  the  occurrence  of  this  same  chytrid  on  Poly- 
siphonia fibrillosa  and  Ceraminm  rubrum  in  the  vicinity  of  Woods 
Hole,  Massachusetts.  This  pathogen  is  in  turn  parasitized  by  the 
chytrid  Pleolpidhnn  (Rozella)  marinum  [Sparrow  (1936)].  All 
other  known  species  of  this  genus  occur  in  fresh  water. 

Among  the  15  species  of  chytrids  collected  by  Sparrow  (1936) 
in  the  waters  near  Woods  Hole,  2  are  especially  noteworthy. 
One,  Peter senia  (Olpidiopsis)  andreei,  occurs  on  Ectocarpus  sili- 
cidosiiSj  upon  which  it  may  be  pathogenic.  Its  zoospores  are  later- 
ally biciliate,  as  was  first  pointed  out  by  Petersen  (1905)  and  con- 
firmed by  Sparrow  (1936).  The  other  species,  Thransto chytri- 
dhim proltferum,  occurring  saprophytically  upon  Ceramium  dia- 
phamim  and  Bryopsis  plumosa,  is  described  as  a  new  generic  type. 
Its  sporangia  are  Thraustotheca-like  in  their  discharge  of  zoo- 
spores and  sporangial  proliferation.  At  the  time  of  discharge  the 
zoospores  lack  cilia,  but  each  may  later  come  to  have  a  single 
anterior  flagellum. 

In  Karling's  (1943)  account  mention  is  made  of  an  organism 
collected  near  Beaufort,  North  Carolina,  which  is  parasitic  on 
Ectocarpus  mitchellae  and  E.  siliculosns  and  is  Olpidium-like  in 
structure  and  development  but  possesses  anteriorly  uniflagellate 
zoospores.  Karling  described  it  as  Amsolpidium  ectocarpii  and 
placed  it  in  the  family  Anisolpidiaceae,  which  was  to  include  2 
other  genera  and  5  other  species,  each  having  zoospores  with  a 
single  flagellum  that  rises  anteriorly.  Furthermore  he  believed 
that  the  members  of  this  family  and  those  of  the  Rhizidiomyce- 


462 


MARINE  FUNGI 


taceae  and  Hyphochytriaceae  should  together  be  placed  in  the 
new  order  Anisochvtridiales. 

Among-  the  collections  by  Petersen  (1905)  and  Sparrow  (1934) 
from  the  coast  of  Denmark  are  listed  22  species  of  chytrids.  Their 
studies  indicate  that  chytrids  are  the  most  abundant  members  of 


the  marine  fungus  flora. 


h  <3 


'•  •     v'"<   r 
i  -  ■     V^W 


Fig.  76.  Various  marine  chytrids.  (After  Sparrow.)  A-D.  Developmental 
stages  of  Thraustochytridhim  proliferum  on  Bryopsis  plumosa.  E.  Chytrid- 
ium  polysiphoneae  in  thallus  of  Polysiphonia.  F.  Pleolpidium  (Rozella) 
marimtm,  discharging  its  spores  within  the  thallus  of  Chytridium  polysi- 
pkonieae.  G.  Sporangium  of  Petersenia  andreei  in  Ectocarpus.  H.  P. 
andreei,  mature  resting  spore  with  empty  male  cyst  attached. 

Perhaps  the  most  singular  member  of  this  group  that  has  been 
described  is  Ichthyophomis  hoferi,  first  mentioned  in  1904  as  a 
parasite  of  certain  fishes  by  Hofer  and  later  studied  by  Plehn  and 
Alulsow  (191 1)  and  Daniel  (1933).  This  species  causes  enormous 
losses  to  marine  fish,  particularly  herring  and  trout.  Plehn  and 
Mulsow  (1911)  described  and  named  the  organism,  placing  it 
anions  the  Chytridiales.  Daniel  (1933)  made  a  rather  detailed 
study  of  the  pathogen  as  it  occurs  in  the  sea  herring,  Clupea 
harengus.    The  spores  are  non-motile  and  usually  multinucleate 


MARINE  PHYCOMYCETES 


463 


and  escape  from  the  apex  of  a  thick  exit-tube-like  hypha.  During 
transformation  of  the  spore  into  a  globular  thallus  nuclear  division 
is  accompanied  by  an  increase  in  the  volume  of  the  thallus. 

An  earlier  account  by  Neresheimer  and  Clodi  (1914)  deals  com- 
prehensively with  the  morphology,  life  history,  and  pathogenicity 
of  Ichthy ophonus  hoferi.    The  later  study  by  Fish  (1934)  em- 


Fig.   77.     Schematic   life   cycle   of  Icthyophomts   hoferi,  which   parasitizes 

fishes.     (Adapted  from  Daniel.) 

ploys  the  name  Ichthy  osporidhnn  hoferi  for  the  pathogen,  which 
Fish  encountered  in  sea  herring,  ale  wife  (Pomobohis  pseudo- 
harengus),  and  flounder  (Pseudoplenronectes  americanus) 
throughout  the  Gulf  of  jMaine.  He  concluded  that  fishes  become 
infected  by  way  of  the  alimentary  canal.  Association  of  these 
species  and  cannibalistic  food  habits,  especially  of  flounder,  which 
eats  herring,  account  for  acquisition  of  the  pathogen. 

Several  saprolegniaceous  parasites  of  marine  animals  have  been 
observed.  Apstein  (1910)  noted  that  Synchaeta  monopus,  a  roti- 
fer occurring  in  brackish  waters  along  the  Baltic  Sea,  may  be  in- 
vaded by  mycelia  of  an  organism  that  he  named  Synchaetophagns 
balticus.  The  hvphae  may  more  or  less  completely  occupy  the 
body  cavity,  destroying  the  organs  and  leaving  only  the  outer 


464  MARINE  FUNGI 

body  membrane.  Eventually  an  isolated  branch  or  the  entire 
mycelium  is  transformed  into  sporangia  that  liberate  motile  zoo- 
spores 5  to  8  /x  in  diameter.  Apstein  also  observed  structures 
which  he  doubtfully  referred  to  as  oogonia. 

In  England  Atkins  (1929)  found  that  pea  crabs  (Pinnotheres) 
are  killed  by  one  of  the  Saprolegniaceae.  Infection  is  indicated 
by  whitish  patches  that  show  through  the  body  wall  in  the  region 
of  the  gills  and  along  the  junctions  of  the  abdominal  segments. 
Intricately  branched  hyphae  occupy  the  tissues  of  the  gills  and 
those  between  the  gill  chamber  and  the  dorsal  surface  of  the 
carapace.  Hyphae  do  not  appear  at  the  exterior.  The  sporangia, 
which  are  confined  to  the  gills  and  pleopods,  form  at  hyphal  tips 
and  are  cut  off  by  septa.  They  are  of  the  same  diameter  as  the 
assimilatory  hyphae.  The  zoospores  are  pyriform  and  bicilate. 
After  a  brief  period  of  motility  they  encyst  and  may  undergo  a 
second  motile  phase.  Atkins'  evidence  for  diplanetism,  however, 
is  not  conclusive.  Its  identity  among  Saprolegniaceae  is  not  estab- 
lished beyond  the  fact  that  it  differs  from  all  other  members  of 
this  family,  mainly  in  its  occurrence  wholly  within  the  body  of 
the  animal. 

Two  other  parasites  of  marine  animals,  described  by  Niezabitow- 
ski  (1913),  are  of  interest,  Thalassoviyces  spizakovii  and  T.  batei. 
He  placed  them  in  the  new  family,  Thalassomycetineae,  among 
the  Oomycetes.  ThalassoiJiyces  spizakovii  occurs  on  the  deep-sea 
decapod,  Pasiphaea  sivado,  in  the  Mediterranean,  and  T.  batei  on 
P.  cristata  on  the  coast  of  the  Fiji  Islands.  Evidence  of  infection 
is  the  presence  of  clusters  of  colorless  hyphae  on  the  underside 
of  the  crustacean's  body.  Apparently  the  assimilatory  mycelium 
lives  wholly  within  the  interior  of  the  body,  and  the  reproductive 
hyphae  constitute  the  external  hyphal  tufts.  The  non-septate, 
external  hyphae  consist  of  a  stalk  cell  that  divides  dichotomously 
one  or  more  times,  and  each  tip  eventually  becomes  segmented  to 
form  a  row  of  three  cells,  which  are  liberated  as  conidia.  Nieza- 
bitowski  (1913)  places  Thalassomyces  near  the  Saprolegniaceae 
and  Monoblepharidaceae. 

In  the  vicinity  of  Beaufort,  North  Carolina,  mud  crabs,  Pano- 
pens  herbstii,  and  mole  crabs,  Emerita  talpoida,  are  commonly 
parasitized  by  a  species  of  Enterobryus,  apparently  unnamed. 
The  organism  consists  of  thick-walled,  cvlindrical  filaments  of  uni- 
form diameter  that  are  about  2  to  3  mm  long  and  15  to  20  fx  wide. 


MARINE  PHYCOMYCETES 


465 


These  filaments  are  straight  or  coiled  and  are  non-septate.  They 
are  attached  by  disk-shaped  holdfasts  to  the  intestinal  wall  and 
project  as  a  tuft  of  white  hairs  from  the  anal  opening.  At  matur- 
ity a  series  of  three  or  four  cylindrical  cells  of  the  same  diameter 
as  the  hypha  is  formed.    These  cells  appear  to  be  spores.    When 


Fig.  78.  An  eccrinid,  presumably  a  species  of  Enterobryus  from  mud  crab, 
Pajiopeus  herbstii.  A.  Apex  of  hypha,  showing  endogenously  formed  spore. 
B.  Basal  portion  of  hypha  with  disk,  by  means  of  which  the  eccrinid  is 
attached  to  intestinal  wall.     C.  Entire  plant,  unbranched  and  unsegmented. 

the  apex  of  the  hypha  ruptures,  the  spores  are  freed  seriatim  by 
growth  and  pressure  from  below.  All  efforts  to  cultivate  this 
organism  on  artificial  media  have  failed.  It  is  strictly  parasitic,  as 
are  related  species. 

Little  is  known  about  the  taxonomy  and  systematic  position  of 
Enterobryus,  and  it  is  not  included  in  Saccardo's  Sylloge  Fungo- 
rum,  even  though  a  considerable  number  of  species  have  been 
described.  The  Genus  Enterobryus  was  founded  by  Leidy  (1849, 
1853)  from  observations  of  several  entophytous  species. 


466  MARINE  FUNGI 

In  1895  Hauptfleisch  (1895)  described  as  a  new  genus  and  spe- 
cies Astreptonema  longispora,  occurring  in  the  intestine  of  Gam- 
marus  locust  a.  He  regarded  it  as  among  the  Saprolegniaceae,  but 
Saccardo  {Sylloge  Fungomm,  14:  446)  placed  it  among  the  chy- 
trids.  In  1920  Thaxter  (1920)  found  a  closely  related  organism 
growing  exposed  on  the  anal  plates  of  beetle,  Passalus  sp.,  and 
properly  assigned  it  the  name  Enter obryus  compressus.  He  was 
of  the  opinion  that  the  organism  described  by  Hauptfleisch  is  an 
Enterobryus  and  that  it  belongs  among  the  Phycomycetes,  near 
the  Saprolegniaceae. 

The  ordinal  name  Eccrinales  has  been  employed  to  include 
Enterobryus  and  several  related  genera,  all  of  which  have  the 
same  growth  habit  and  form  endogenous  non-motile  spores.  None 
of  them  is  genuinely  aquatic,  although  some  species,  such  as 
Eccrinopsis  hydropilontni,  parasitize  aquatic  beetles.  No  accord 
has  been  reached  on  the  relationship  of  the  Eccriniales  to  other 
fungi,  but  presumably  they  are  related  to  the  Saprolegniales.  The 
reports  by  Leger  and  Duboscq  (1916)  and  Poisson  (1929)  will 
introduce  the  reader  to  the  status  of  this  strange  order  of  fungi. 

Only  one  species  of  Pvthium  having  a  marine  habitat  has  been 
recorded.  Sparrow  (1934)  obtained  it  from  Ceramium  rubruvi 
and  described  it  as  Pythium  mar  mum. 

MARINE  ASCO.MYCETES  * 

Representatives  of  the  Sphaeriales,  Dothidiales,  and  Hysteriales 
have  been  found  on  marine  plants  and  animals.  Most  of  the  known 
species  occur  on  marine  algae.  Among  the  35  species  of  marine 
seed  plants,  included  in  8  genera,  all  monocotyledonous,  only 
Zostera  and  Posidonia  are  known  to  serve  as  hosts  for  ascomyce- 
tous  fungi.  Ophiobolus  halimus  on  Zostera  marina  is  associated 
with  the'so-called  "wasting  disease,"  which  has  wrought  so  much 
havoc  with  this  valuable  marine  species.  Amphisphaeria  posi- 
doniae  has  long  been  known  on  Posidonia  Oceania. 

Of  most  interest,  perhaps,  are  those  species  that  are  thought 
to  be  symbiotic.  Reed  (1902)  found  that  the  Guignardia  alas- 
kana-Prasiola  borealis  complex  approaches  that  of  an  ordinary 
terrestrial  lichen.  The  fronds  are  entirely  dissimilar  to  those  of 
normal  Prasiola.  In  the  Uha  calif ornica-Guignardia  ulvae  com- 
plex, how  ever,  thickenings  appear  in  the  tissues  surrounding  the 


MARINE  ASCOMYCETES 


461 


Fig.  79.    Ophio  bolus  halimus  on  Zoster  a  marina.    A.  Perithecium  in  vertical 
section.    B.  Ascospores.    C.  Hyphae  in  tissue  of  rhizome.    D.  Appendaged 

tips  of  ascospores. 


468 


MARINE  FUNGI 


perithecia,  but  thev  are  otherwise  quite  normal,  although  Ulva 
does  not  fruit. 

Sutherland  (1915)  regards  Mycosphaerella  pehetiae  as  a  symb- 
biont  with  Pelvetia.  In  this  case  the  perithecia  and  the  host  con- 
ceptacles  mature  coincidentallv. 

Didymella  conchae  is  of  particular  interest  because  of  its  ability 
to  decalcify  the  shells  of  certain  limpets,  molluscs,  and  barnacles, 


Fig.  80.  Gu'ignardia  ulvae  on  Ulva  califoriiica.  (After  Reed.)  A.  Habit 
sketch,  indicating  swollen  areas  in  which  the  perithecia  are  embedded.  B. 
Section  of  thallus  and  perithecium.    C.  Ascus  of  G.  ulvae.    D.  Ascospores. 

E.  Germination  of  ascospores. 

including  Acmea  digitalis,  A.  fene strata,  A.  limatula,  A.  pelt  at  a,  A. 
scabra,  A.  scutum,  Balamis  glandulosa,  Littorina  planacis,  Mitella 
polyvierns,  and  Tegula  fwiebralis  [Bonar  (1931)]. 

If  further  acquaintance  with  this  group  is  sought,  it  may  be 
obtained  by  study  of  the  species  assembled  in  Table  32.  This  list, 
however,  does  not  include  all  the  Ascomycetes  found  on  marine 
algae  and  seed  plants. 


MARINE  FUNGI  IMPERFECTI 

Know  ledge  of  these  fungi,  which  is  limited  to  a  few  saprophytic 
species,  has  come  from  direct  examination  of  decaying  algae  and 


MARINE  ASCOMYCETES 


469 


TABLE  32 

Some  Ascomycetes  Formed  on  Marine  Plants 


Organisms 
Amphisphaeria  posidoniae 

Didymella  conchae 

Didymosphaeria  fucicola 
Didy?nosphaeria  pelvetiana 
Dothidella  laminariae 
Dothidella  pelvetiae 
Guignardia  alaskana 
Guignardia  {Sphaerella) 

chondri 
Guignardia  irritans 

Guignardia  uhae 

Hypoderma  laminariae 

Leptosphaeria  chondri 
(identical  with 
Sphaerella  chondri) 

Maireomyces  peyssonelia 

Mycaureola  dilseae 

My co sphaerella  as cop hy  Hi 
My co sphaerella  pelvetiae 
Ophiobolus  halimus 

Ophiobolus  laminariae 
Orcadia  ascophylli 
Orcadia  pelvetiana 
Pharcidia  pelvetiae 
Phyllachorella  oceanica 

Pleospora  pelvetiae 
Stigmatea  pelvetiae 
Trailia  ascophylli 
Zignoella  calospora 
Zignoella  enormis 


Hosts 
Posidonia  Oceania 

Acmea,  Balanus,  Littorina, 

Mitella,  Tegula 
Fucus  vesiculosus 
Pelvetia  canaliculata 
Laminaria  sp. 
Pelvetia  canaliculata 
Prasiola  borealis 
Chondrus  crispus 

Cystoseira  osmundacea, 

Halidrys  dioica 
Ulva  californica, 

Enteromorpha  mimima 
Laminaria  saccharina 
Chondrus  crispus 


Peyssonelia  squamaria 
Dilsea  edulis 

Ascophyllum  nodosum 
Pelvetia  spp. 
Zostera  marina 

Laminaria  digitata 
Ascophyllum  nodosum 
Pelvetia  canaliculata 
Pelvetia  spp. 
Sargassum  sp. 

Pelvetia  spp. 
Pelvetia  spp.  " 
Ascophyllum  nodosum 
Castagnea  chordariaeformis 
Styptocaulon  scoparum 


Authority  for 
Name  of  Fungus 

Cesati    and   de   Notrais 

(1863)* 
Bonar  (1931) 

Sutherland  (1915) 
Sutherland  (1915) 
Rostrup  (1891)* 
Sutherland  (1914) 
Reed  (1902) 
Jones  (1898) 

Estee  (1913) 

Reed  (1902) 

Sutherland  (1914) 
Cotton  (1907) 


Feldmann  (1940) 
Maire  and  Chemin 

(1922) 
Cotton  (1908) 
Sutherland  (1915) 
Mounce  and  Diehl 

(1934) 
Sutherland  (1914) 
Sutherland  (1914) 
Sutherland  (1915) 
Sutherland  (1915) 
Ferdinandsen  and 

Winge  (1920) 
Sutherland  (1915) 
Sutherland  (1915) 
Sutherland  (1914) 
Patouillard  (1897) 
Patouillard  and  Hariot 

(1903) 


See  Saccardo,  Sylloge  Fungormn,  1:729  (1882). 


410  MARINE  FUNGI 

from  attempts  to  isolate  in  culture  fungi  obtained  in  samples  of 
mud  from  the  ocean  bottom  at  various  depths.  This  second  pro- 
cedure has  yielded  no  typically  marine  species,  all  isolates  being 
common  species  of  Aspergillus,  Penicillium,  and  similar  genera 
[Sparrow  (1937)1.  By  direct  examination  of  decaying  algae, 
largely  through  the  work  of  Sutherland  (1916),  however,  a  num- 
ber of  species  have  been  identified.  These  include  Alternaria 
maritima,  Blodgettia  confervoides,  Cladosporium  algarnm,  Cerco- 
spora  salinia,  Diplodina  I  ami  n  avian  a,  Epicocann  viavitivnmi,  Ma- 
crosporium  laminarium,  Monosporium  maritimum,  Sporotrichinu 
viarit'nmnn,  and  Steviphyliinn  codii.  Feldmann  (1940)  described 
Macro phoma  gyumogongri  as  a  parasite  on  Gyrnnogongrus  norve- 
gicns. 

MARINE  SLIME  MOLDS 

The  most  important  among  the  several  species  of  marine  slime 
molds  is  that  within  diseased  leaves  of  Zostera  marina.  It  has,  with 
uncertainty,  been  identified  as  Labyrinthula  macrocystis,  an  or- 
ganism consisting  of  net-like  aggregates  of  individuals  connected 
by  pseudopodia.  The  individuals  are  spindle-shaped  and  glide 
along  this  interconnecting  pseudopodial  network. 

Affected  leaves  of  Zostera  bear  dark  streaks  and  splotches. 
Often  the  cuticle  and  cortex  of  the  stems  are  also  irregularly 
spotted  with  dark  brown  or  black  areas.  Affected  leaves  slough 
off;  the  stem  may  persist  for  a  year  or  two  and  form  new  shoots, 
but  eventually  the  reserve  food  is  exhausted,  the  plants  waste 
away,  and  the  roots  decompose. 

Among  those  who  have  studied  this  eel-grass  disease  are  Peter- 
sen (1935),  Renn  (1936,  1937),  and  Young  (1938).  Accord  has 
not  been  reached  concerning  its  etiology,  but  Renn  and  Young 
interpret  their  evidence  as  showing  that  Labryinthula  is  the  patho- 
genic agent.  Among  the  causes  assigned  by  others  are  the  pyre- 
nomycete  Ophiobohis  halimus,  bacteria,  unfavorable  light,  un- 
favorable temperature,  and  accumulation  of  industrial  wastes  and 
oil. 

IMPLICATIONS 

It  is  of  more  than  passing  interest  to  note  that,  with  the  excep- 
tion of  the  disease  on  Zostera,  fungus  diseases  of  marine  plants 
sufficiently  abundant  and  widespread  to  be  regarded  as  epidemics 


IMPLICATIONS  411 

are  unknown.  If  a  plausible  reason  assigned  bv  investigators  or 
arising  from  contemplation  of  the  data  is  sought,  nothing  signifi- 
cant comes  to  light. 

Again,  all  the  known  marine  fungi  are  quite  like  those  occurring 
in  fresh  water  or  on  land.  None  appears  to  have  any  structural 
modifications  of  either  the  assimilatory  or  the  reproductive  parts 
that  can  be  correlated  with  adaptation  to  halophytism.  On  the 
other  hand,  they  cannot  be  regarded  as  "living  fossils,"  nor  as 
evidence  either  for  or  against  the  concept  that  the  ocean  is  the 
ancestral  home  of  the  Fungi. 

Since  the  ocean  is  so  stable  an  environment  and  contains  so 
many  plants  and  animals  that  might  serve  as  food,  it  becomes  of 
interest  to  speculate  on  the  reasons  for  the  paucity  of  species 
among  marine  fungi. 

The  role  of  marine  fungi  in  the  decomposition  of  seaweeds 
constitutes  an  almost  completely  neglected  field  of  inquiry.  In 
all  likelihood  some  of  them  are  capable  of  digesting  agar  and 
chitin,  as  marine  bacteria  are  known  to  do  [Stanier  (1941)].  Sea- 
weeds cast  up  on  beaches  no  doubt  serve  as  food  for  both  ter- 
restrial and  marine  fungi. 

LITERATURE  CITED 

Apstein,  C,  uSynchaetophagus  balticus,  ein  in  Synchaeta  lebender  Pilz," 

Wiss.  Meersuntersiichimgen,  Abt.  Kiel,  n.f.,  12:  163-166,  1910. 
Atkins,  D.,  "On  a  fungus  allied  to  the  Saprolegniaceae  found  in  the  pea 

crab,  Pinnotheres,"  /.  Marine  Biol.  Ass.  United  Kingdom,  25:203-219, 

1929. 
Barghoorn,  E.  S.,  and  D.  H.  Linder,  "Marine  fungi:   their  taxonomy  and 

biology,"  Farloivia,  1:  395-401,  1944. 
Bonar,  L.,  "An  unusual  Ascomycete  in  the  shells  of  marine  animals,"  Univ. 

Calif.  Pub.  Bot.,  19:  187-194,  1936. 
Bornet,  E.,  and  C.  Flahault,  "Sur  quelcjues  plants  vivant  dans  le  test  cal- 

caire  des  Alollusques,"  Bull.  soc.  bot.  France,  36:  cxlvii-clxxvii,  1889. 
Cotton,  A.  D.,  "Notes  on  marine  Pvrenomycetes,"  Trans.  Brit.  My  col.  Soc, 

3:  92-99,  1907. 
Dangeard,   P.,    "Sur  la   presence   a   Roscoff   d'une   chytridiale   parasiti    des 

Ectocarpees,    YEurychasnia    dicksonii    (Wright)    Magnus,"    Ami.    Pro- 

tistenk.,  4:  69-72,  1934. 
Daniel,  G.  E.,  "Studies  on  lchthy ophonus  hoferi,  a  parasitic  fungus  of  the 

herring,  Clupea  harengus.    I.  The  parasite  as  it  is  found  in  the  herring," 

Am.  J.  Hyg.,  11:  262-276,  1933. 


412  MARINE  FUNGI 

Duncan,  P.  Martin,  "On  some  thallophytcs  parasitic  within  Madreporia," 

Froc.  Roy.  Soc.  London,  25:  238-257,'l876-1877. 
Estee,  Lula  M.,  "Fungus  galls  on  Cystoseira  and  Halidrys,"   Univ.  Calif. 

Pub.  Bot.,  4:305-316,  1913. 
Feldmann,  Jean,  "Maireomyces,  nouveau  genre  du  Pyrenomycete  marin," 

Bull.  soc.  hist.  nat.  Afrique  du  Nord,  31:  163-166,  1940. 
"Une  nouvelle  espcce  de  Spheropsidee  parasite  d'une  algue  marin,"  Bull. 

soc.  hist.  nat.  Afrique  du  Nord,  31:  167-169,  1940. 
Ferdinandsen,  C,  and  O.  Wince,  "A  Phyllachorclla  parasitic  on  Sargassum," 

Mycol.,  12:  102-103,  1920. 
Fish,  F.  T.,  "A  fungus  disease  in  fishes  of  the  Gulf  of  Maine,"  Par  ash., 

26:  1-16,  1934. 
Hauptfleisch,  P.,  uAstreptonema  longispora,  n.  g.,  n.  sp.,  eine  neue  Sapro- 

leginacee,"  Ber.  deutsch.  botan.  Ges.,  13:  83-88,  1895. 
Jones,  Herbert  L.,  "A  new  species  of  Pyrenomycete  parasitic  on  an  alga," 

Bull.  Oberlin  Coll.  Lab.,  9:  3,  1898. 
Karling,  J.  S.,  "The  life  history  of  Anisolpidium  ectocarpii,  gen.  nov.  et  sp. 

now,  and  a  synopsis  and  classification  of  other  fungi  with  anteriorly 

uniflagellate  zoospores,"  Am.  J.  Botany,  50:637-648,  1943. 
Kibbe,  Alice,  uChytridiimi  alarium  on  Alaria  fistulosa,'''  Pub.  Puget  Sound 

Marine  Sta.,  7:221-226,  1916. 
Kolliker,  A.,  "On  the  frequent  occurrence  of  vegetable  parasites  in  the  hard 

structure  of  animals,"  Proc.  Roy.  Soc.  London,  10:95-99,  1859-1860. 
Leger,  L.,  and  O.  Duboscq,  "Sur  les  Eccrinides  des  Hydrophilides,"  Arch. 

zool.  expt.  gen.,  56:21-31,  1916. 
Leidy,  Joseph,  "On  the  existence  of  Entophyta  in  healthy  animals  as  a  natural 

condition,"  Proc.  Acad.  Nat.  Sci.  Phifa.,  4:  225-233,  1849. 
"A  flora  and  fauna  within  living  animals,"  Pub.  Smithsonian  Inst.,  5:  2-67, 

1853. 
Linder,  D.  H.,  "I.  Classification  of  the  marine  fungi,"  Farloivia,  7:401-420, 

1944. 
Lowenthal,  W.,  "Weitere  Untersuchungen  an  Chytridiaceen,"  Arch.  Pro- 

tistenk.,  5:221-239,  1905. 
M aire,  R.,  and  E.  Chemin,  "Un  noveau  pyrenoinvcete  marin,"  Compt.  rend., 

775:319-321,  1922. 
Martin,  G.  W.,  uRhizophidium  polysiphoniae  in  the  United  States,"  Botan. 

Gaz.,  75:236-238,  1922. 
Mounce,  I.,  and  W.  W.  Diehl,  "A  new  Ophiobolus  on  eel  grass,"  Can.  J. 

Research,  11:  242-256,  1934. 
Neresheimer,  E.,  and  C.   Ci.odi,    ulchthyophonus  hoferi  Plehn  und  Mul- 

sow,  der  Erreger  der  Traummelkrankheit  der  Salmoidcn,"  Arch.  Pro- 

tistenk.,  34:  217-248,  1914. 
Niezabitowski,  E.  L.,  "Die  pflanzlichcn  Parasiten  der  Tiefsee-Decapoden- 

Gattung  Pasiphaera,"  Kosmos  {Livoiv),  5#:  1563-1572,  1913. 
Patouillard,  N.,  "ZigJioella  calospora"  }.  Bot.,  11:  242,  1897. 
Paiouii  i.ard,  X.,  and  P.  Hariot,  "Une  algue  parasitee  par  une  Sphaeriacee," 
/.  Bot.,  77:228,  1903. 


LITERATURE  CITED  413 

Petersen,  H.  E.,  "Contributions  a  la  connaissance  des  Phycomycetcs  marins 

(Chytridinae    Fischer),"    Oversigt,    Kgl.    Danske     Videnskab.    Selskab 

Forhandl.,  1905:  440-488,  1905. 

"Preliminary  report  on  the  disease  of  eel  grass  (Zostera  marina  L.),"  Rept. 

Danish  Biol.  St  a.,  40:  1-8,  1935. 

Plehn,  A  I.,  and  Al.  Mulsow,  "Der  Erregcr  der  'Taumelkrankheit'  der  Sal- 

moniden,"  Zentr.  Bakt.  Parasitenk.,  52:63-68,  1911. 
Poisson,   R.,   "Recherches  sur  quelques   Eccrinides   parasites   de   Crustaces, 

Amphipodes  et  Isopodes,"  Arch.  zool.  expt.  gen.,  69:  179-216,  1929. 
Reed,  AIinnie,  "Two  new  ascomycetous  fungi  parasitic  on  marine  algae," 

Univ.  Calif.  Pitb.  Bot.,  1:  141-164,  1902. 
Renn,  C.  E.,  "The  wasting  disease  of  Zostera  marina.    I.  A  phytological  in- 
vestigation of  the  diseased  plant,"  Biol.  Bull,  10:  148-158,  1936. 
"The    eel-grass    situation    along    the    middle    Atlantic    coast,"    Ecology, 
18:  323-325,  1937. 
Scherffel,  A.,  "Zur  Sexualitat  der  Chytrideen,"  Arch.  Protistenk.,  53:  1-58, 

1925. 
Sparrow,  F.  K.,  "Observations  on  marine  phycomycetes  collected  in  Den- 
mark," Dansk  Bot.  Arkiv,  8:  1-24,  1934. 
"Biological  observations  on  the  marine  fungi  of  Woods  Hole  waters," 

Biol.  Bull.,  10:  236-263,  1936. 
"The    occurrence    of   saprophytic    fungi    in    marine    muds,"    Biol.    Bull., 
75:242-248,  1937. 
Stanier,  R.  Y.,  "Studies  on  marine  agar-digesting  bacteria,"  /.  Bact.,  42:  527- 

560,  1941. 
Stirrup,  A  I.,  "On  shells  of  mollusca  showing  so-called  fungoid  growths," 

Proc.  Lit.  Phil.  Soc.  Manchester,  11:  173,  1872. 
Sutherland,  G.  K.,  "New  marine  Pyrenomycetes,"  Trails.  Brit.  My  col.  Soc, 
5:  147-154,  1914. 
"New  marine  fungi  on  Pelvetia,"  New  Phytol.,  14:  33^2,  1915. 
"Additional  notes  on  marine  Pyrenomycetes,"  New  Phytol.,  14:  183-193, 

1915a. 
"Marine  Fungi  Imperfecti,"  New  Phytol.,  15:  35-48,  1916. 
Thaxter,  R.,  "Second  note  on  certain  peculiar  fungus  parasites  of  living  in- 
sects," Botan.  Gaz.,  69:  1-27,  1920. 
Wright,  E.  P.,  "On  a  species  of  Rhizophydium  parasitic  on  a  species  of 
Ectocarpus,  with  notes  on  the  fructification  of  the  ectocarpi,"  Trans. 
Roy.  Irish  Acad.  Sci.,  26:  369-379,  1879. 
Young,  E.  L.,  "Labvrinthula  on  Pacific  coast  eel  grass,"  Can.  J.  Research, 

16:  115-117,  1938. 
Zeller,  S.  Al.,  "Fungi  found  on  Codium  mucronatum"  Pub.  Puget  Sound 
Marine  Sta.,  2:  121-126,  1918. 


Chapter  22 

FOSSIL  FUNGI 

At  first  thought  fossil  fungi  might  be  regarded  as  outside  the 
field  of  interest  of  the  student  of  fungi  and  of  little,  if  anv,  innate 
value  to  him.  It  must  be  admitted  that  in  the  past  few  contribu- 
tions to  our  knowledge  of  fossil  fungi  have  been  made  by  mycolo- 
gists.  This  field  of  inquiry  has  been  left  to  geologists,  whose 
knowledge  of  fungi,  it  is  to  be  hoped,  exceeds  the  mycologists' 
acquaintance  with  geology.  There  are  doubtless  few  mycologists 
who  have  ever  seen  any  fossil  fungi,  and  until  an  occasional  worker 
comes  to  have  some  first-hand  knowledge  of  them,  there  can  be 
no  lively  interest  in  objects  so  long  dead  and  buried.  The  reason 
for  discussing  fossil  fungi  in  this  work  is  that  a  better  acquaintance 
with  the  geological  history  of  fungi  will,  it  is  hoped,  contribute  to 
a  greater  appreciation  of  the  present  place  of  these  plants  in  the 
economy  cf  nature. 

GEOLOGICAL  TIME 

Rocks  have  been  truly  said  to  constitute  the  documentary 
source  books  of  geological  history7.  By  using  the  evidence  ex- 
hibited by  rocks,  that  is,  their  kind,  their  composition,  their  posi- 
tion, and  their  content  of  minerals  and  fossils,  geologists  are  able 
to  interpret  the  past  developmental  history  of  the  earth  and  to 

forecast  the  future.    In  so  doing  they  denote  segments  of  geologi- 
es O  C1  o 

cal  time  as  eras,  periods,  epochs,  and  stages,  which  in  point  of  view 
of  time  are  not  sharply  delimited  one  from  the  other.  If,  since 
the  beginning  of  geological  time,  there  had  not  been  inequalities 
in  the  amount  of  heat  received  from  the  sun  by  different  regions 
of  the  earth's  surface,  and  if  rock  formation  had  everywhere  pro- 
ceeded uniformly  and  without  interruption,  a  geologist  could 
examine  a  vertical  section  of  the  earth's  crust  anywhere,  and  the 
whole  monotonous  course  of  events  would  be  in  evidence.     Cli- 

414 


GEOLOGICAL  TIME  415 

mate,  however,  must  always  have  been  zonal,  as  it  now  is.  Fur- 
thermore the  earth's  crust  was  not  uniformly  constructed  nor  is 
it  uniformly  constituted,  as  is  shown  by  its  stratification.  It  be- 
comes necessary  therefore  to  segment  geological  time  into  intervals 
to  indicate  the  periods  during  which  the  different  strata  were 
formed.  It  would  also  be  anticipated  that  under  these  conditions 
the  same  kinds  of  strata  would  not  be  encountered  everywhere 
that  examination  was  made  of  a  vertical  section  of  the  earth's 

crust. 

The  student  must  also  be  prepared  to  accept  the  conclusion 
that  the  same  kinds  of  strata  do  not  occur  everywhere  in  the  same 
relative  positions.  Evidence  is  furnished  by  exposed  rocks  in 
such  situations  as  mountainsides,  canyon  walls,  mine  shafts,  escarp- 
ments, and  tunnels.  Here  the  strata  may  be  observed  to  be  vari- 
ously folded,  buckled,  and  jumbled.  Moreover,  sedimentary 
rocks  are  found  in  some  places  to  be  deeply  covered  by  basaltic 
lava  and  volcanic  ash.  In  certain  localities  layers  of  rock  have 
slipped  past  each  other  and  been  reshuffled  in  the  reverse  order  of 
that  in  which  they  were  formed.  In  others  great  beds  of  coal, 
lignite,  or  peat  occur.  Extensive  deposits  of  salt,  sulphur,  gypsum, 
limestone,  phosphate,  and  various  minerals  are  found  in  other 
localities.  There  is  evidence  that  certain  parts  of  the  earth  were 
inundated  for  long  periods  and  that  long  ago  these  areas  were 
raised  up  out  of  the  sea.  Faunas  and  floras  existed  that  were  very 
different  from  those  present  anywhere  today.  Catastrophic 
changes  in  climate  evidently  occurred.  The  earth's  crust  must 
have  been  in  convulsion  when  the  mountains  were  formed.  It  is 
from  evidence  of  this  kind,  gathered  from  various  localities,  that 
geologists  have  been  able  to  piece  together  and  to  formulate  a 
plausible  conception  of  the  sequence  of  geological  events  and  to 
approximate  the  duration  of  the  different  segments  of  geological 

time. 

Estimates  of  the  age  of  the  earth  do  not  agree  closely,  partly 
because  they  are  based  upon  different  kinds  of  evidence.  From 
Biblical  evidence  Archbishop  Ussher  placed  the  age  of  the  earth 
at  approximately  4000  years.  If  calculations  of  the  duration  of 
geological  time  are  based  upon  the  rate  of  dissipation  of  the  earth's 
initial  store  of  heat  energy,  however,  a  figure  of  about  100  million 
years  is  deduced. 


416 


FOSSIL  FUXG1 


Several  years  ago  a  more  exact  method  of  estimating  the  earth's 
age  was  provided  from  observations  involving  radioactive  rocks, 
which  showed  that  atoms  of  uranium  spontaneously  decompose 
into  atoms  of  lead  and  helium,  thus  liberating  radiations.    By  de- 


Fig.  81.    Dial  of  geologic  time  clock.    The  proportion  of  time  in  each  era 
and  of  the  most  important  divisions  of  each  is  indicated. 

termininp;  the  amount  of  uranium  in  uranium-containing  rocks,  to- 
gether  with  the  amount  of  lead  associated,  Professor  A.  Holmes 
concluded  that  the  Pre-Cambrian  period  began  1580  million  years 
ago.  The  primeval  crust  of  the  earth  was  formed  earlier;  hence 
it  may  be  concluded  that  2000  million  years  constitutes  a  con- 
servative estimate  of  the  earth's  antiquity.  As  shown  by  the 
geological  time  clock,  the  age  of  the  earth  has  been  set  at  500 
million  years  as  a  minimum.    Whether  the  earth's  age  is  assumed 


AGE  OF  FOSSIL  FUNGI  411 

to  be  500  million  years  or  2000  million  years  is  certainly  of  little 
consequence  to  the  mycologist. 

AGE  OF  FOSSIL  FUNGI 

Seward  (1933),  one  of  the  world's  foremost  students  of  fossil 
plants,  writes  as  follows  on  this  subject:  "One  thing  is  certain: 
from  the  Devonian  period  onwards  and  even  from  a  more  remote 
age  there  were  parasitic  and  saprophytic  fungi  .  .  .  which  so  far 
as  we  can  tell  differed  in  no  essential  respects  from  living  represen- 
tatives of  this  class.  We  can  safely  assume  that  bacteria  and  many 
other  fungi  are  entitled  to  be  included  among  the  most  ancient 
members  of  the  plant  kingdom."  James  (1893)  has  expressed  the 
opinion  that  evidences  of  fungi  need  not  be  looked  for  until  the 
Devonian  period. 

Indirect  evidence  must  be  employed  in  determining  how  long 
before  the  Devonian  period  plants  could  have  existed.  The  seas 
during  the  Cambrian  period  contained  an  abundance  of  animals, 
and  fossils  in  Cambrian  rocks  reveal  something  of  the  multitude 
and  variety  of  these  animals.  Since  fossil  plants  are  lacking,  how- 
ever, it  must  be  assumed  that  plants  existed  to  serve  as  food  for 
the  multitude  of  animals.  Then,  as  one  descends  in  time  toward 
and  into  the  Pre-Cambrian  period  in  an  effort  to  find  a  common 
"dawn  of  life"  for  plants  and  animals,  the  tracery  terminates,  and 
he  is  compelled,  as  Seward  (1933)  has  been,  to  the  following  con- 
clusion: "We  do  not  know  when  and  how  life  began;  we  cannot 
measure  the  rate  of  the  early  stages  of  evolution,  nor  can  we  ac- 
cept as  proof  of  the  existence  of  plants  much  of  the  evidence  that 
has  been  adduced,  and  not  infrequently  presented  with  a  confi- 
dence worthy  of  a  better  cause." 

If  one  ascends  in  time  from  the  Devonian  period,  fossil  plants, 
including  fungi,  would  be  anticipated  in  all  subsequent  periods. 
They  have  been  found  to  exist,  "perhaps  most  abundantly  in  Car- 
boniferous rocks  formed  during  the  Pennsvlvanian  and  Permian 
periods,  when  ferns,  fern  allies,  and  pteridosperms  flourished. 
Fossil  plants  occur  throughout  the  rocks  of  the  Triassic  and 
Jurassic  periods,  when  gymnosperms  predominated,  and  through- 
out the  Cretaceous  and  Tertiary  periods,  when  angiosperms  came 
into  ascendancy.  Species  from  the  early  Mesozoic  period  sur- 
vived and  developed,  as  is  indicated  by  fossils  in  all  subsequent 


418  FOSSIL  FUXGI 

periods,  and  their  offspring  persisted  to  become  the  varied  as- 
semblage of  species  that  constitute  our  present  living  fungi. 

In  the  ascending  order  the  Tertiary  period  includes  the  Eocene, 
Oligocene,  and  Miocene  and  grades  into  the  Quaternary,  includ- 
ing  the  Pliocene  and  Recent  Glacial.  The  Tertiary  and  Quater- 
nary  comprise  the  Cenozoic  era. 

THE  NATURE  OF  FOSSILIZED  FUNGI 

It  has  been  possible  with  a  considerable  degree  of  certitude  to 
relate  fossil  fungi  with  members  of  each  of  the  classes  employed 
in  classification  of  present-day  forms.  Some  fungi,  as  is  well 
known,  are  extremely  ephemeral;  others,  because  of  their  corky, 
leathery,  or  woody  texture,  can  be  kept  indefinitely.  Since  fossils 
both  of  ephemeral  species,  for  example,  phycomycetous  forms, 
and  of  resistant  species,  resembling  Polyporus,  occur,  the  paucity 
of  fossil  fungi  cannot  be  attributed  solely  to  the  constitution  of 
the  fungi  themselves. 

The  fossilization  of  fungi  is  in  no  way  different  from  that  of 
other  plants.  Ordinarily  the  term  fossil  implies  that  petrification, 
a  process  in  which  living  tissues  are  replaced  by  mineral  matter, 
has  taken  place.  Sometimes  in  fossilization  the  replacement  is 
made  with  calcareous  materials,  as  is  the  case  with  fossils  found 
in  so-called  "coal  balls."  These  nodular  concretions,  sometimes 
several  inches  in  diameter,  consist  mainly  of  carbonates  of  calcium 
and  magnesium,  together  with  oxides  and  sulphides  of  iron. 

Carbonaceous  matter  may  also  replace  the  original  tissues  in  the 
formation  of  fossils. 

Perhaps  the  most  common  kind  of  fossil  is  formed  by  incrusta- 
tion with  calcium  carbonate.  Sometimes  leaves  and  stems,  to- 
gether with  the  fungi  which  inhabit  them,  leave  impressions  in 
argillaceous  or  arenaceous  shales  or  in  travertine.  These  impres- 
sions begin  to  form  when  the  plant  part  is  deposited  in  the  siliceous 
or  calcareous  matrix  while  it  is  still  soft.  Gradually  the  matrix 
hardens  and  sets,  and  the  impressions  often  portray  the  tissues 
in  great  delicacy  of  detail. 

Sometimes  fungi  are  found  sealed  up  in  masses  of  Baltic  amber 
and  are  thus  preserved  in  a  high  degree  of  perfection.  Baltic 
amber,  also  called  true  amber,  consists  of  hardened  resinous  secre- 
tions that  exuded  from  conifers  and  other  trees  during  the  Oligo- 


CLASSIFICATION  OF  FOSSIL  FUNGI  419 

cene  era.    Other  kinds  of  amber  are  more  recent  and  may  contain 
the  remains  of  various  fungi. 


PREPARATION  OF  FOSSILS  FOR  STUDY 

Several  methods  have  been  developed  for  the  study  of  fossilized 
funo-i.  The  choice  of  method,  as  Seward  (1933)  has  indicated, 
depends  upon  the  nature  of  the  fossil.  Sometimes  fossil  leaves 
and  fructifications  of  fungi  growing  upon  them  are  preserved  in 
carbonized  films,  especially  on  the  surface  of  hardened  mud.  If 
fragments  of  these  carbonized  films  can  be  peeled  off,  they  may 
be  bleached  in  potassium  chlorate  and  nitric  acid,  washed  in  am- 
monia, and  then  mounted  in  Canada  balsam  for  direct  examina- 
tion. If  the  carbonized  film  cannot  be  detached,  the  specimen 
is  first  covered  with  cellulose  acetate  dissolved  in  amyl  acetate. 
After  this  solution  has  dried,  the  specimen  is  covered  with  hot 
Canada  balsam  and  then  with  melted  paraffin,  after  which  it  is 
placed  in  hydrofluoric  acid.  This  acid  dissolves  the  matrix  and 
leaves  the  fossil  intact.  If  the  paraffin  is  then  removed,  the  fossil 
can  be  examined  directly. 

In  preparing  fossils  in  coal  balls,  either  thin  sections  are  cut  by 
special  machinery,  or  else  sections  can  be  ground  down  to  a  suit- 
able thinness.  As  an  alternative,  the  smooth,  cut  surface  of  the 
coal  ball  may  be  etched  by  immersion  in  hydrofluoric  acid,  where- 
upon  the  actual  plant  substance  is  left  in  relief.  After  the  etched 
surface  has  been  washed  and  dried,  a  film  of  gelatin  or  of  some 
cellulose  ester  is  poured  over  it;  when  this  film  hardens,  it  may  be 
peeled  off  and  mounted.  This  simple  method  makes  it  possible  to 
get  a  score  or  more  of  reproductions  from  the  same  etched  surface. 

CLASSIFICATION  OF  FOSSIL  FUNGI 

It  is  apparent  that  fossil  fungi  cannot  be  classified  on  the  basis  of 
developmental  morphology,  as  can  living  species.  Their  fossil- 
ized remains  must  therefore  be  compared  structurally  with  pres- 
ent-day forms  and,  on  the  basis  of  evidence  which  is  at  best 
merely  fragmentary,  must  be  placed  in  modern  families.  When 
this  is  done,  some  appear  to  resemble  living  forms  closely,  and 
others,  as  might  be  expected,  do  not  exhibit  such  affinities.  By 
use  of  the  generic  termination  "ites"  the  resemblance  of  fossils 


480  FOSSIL  FUNGI 

to  present-day  genera  may  be  indicated.  If  this  were  the  sole 
difficulty  in  classification,  a  fairly  stable  taxonomic  status  might 
be  achieved.  There  remains,  however,  the  vexatious  and  ever- 
present  problem  of  specific  identity.  Are  specimens  in  rocks  from 
one  locality  identical  with  those  from  another?  Are  specimens  in 
non-contemporaneous  rocks  specifically  alike?  Are  specimens  on 
different  hosts  specifically  distinct?  These  are  only  typical  of  the 
questions  that  arise  and  cannot  be  answered  satisfactorily.  Other 
difficulties  just  as  serious  will  appear  in  the  account  that  follows. 

Several  extensive  classifications  of  fossil  fungi  have  appeared, 
including  Meschinelli's  (1892)  "Fungi  Fossiles"  in  1892  in  Sac- 
cardo's  Sylloge  Fwigorwn.  It  contains  a  list  of  slightly  more 
than  300  named  species  and,  as  maintained  by  Seward  (1898), 
".  .  .  includes  certain  species  which  .  .  .  should  have  no  place  in 
any  list  that  claims  to  be  authentic."  Meschinelli's  lconographia 
(1902),  which  appeared  10  years  later,  is  to  be  regarded  as  the 
most  useful,  complete,  and  well-illustrated  compilation  up  to  that 
date. 

The  most  comprehensive  modern  treatise  on  fossil  fungi  is  that 
by  Pia  in  Hirmer's  Handbuch  der  Palaobotairik  (1927).  Pia's 
compilation  recognizes  fossil  fungi  that  bear  resemblance  to  mem- 
bers of  39  present-day  families.  The  account  that  follows  is  taken 
from  Pia's  report  with  certain  additions  and  omissions  and  with 
comments  and  criticisms. 

I.  Myxomycetes 

A  single  species  of  slime  mold,  Myxomycetes  mangini  Renault, 
in  the  cortex  of  some  vascular  plant  in  the  Coal  Measures  has  been 
described. 

II.  Phycomycetes 

Eleven  species  of  Phycomycetes  are  mentioned  in  Meschi- 
nelli's Iconographia,  and  Ellis  (1915,  1918)  is  authority  for  the 
statement  that  four  have  been  described  since:  Falaeomyces  bacil- 
loides,  among  the  Saproleginaceae,  and  Fhy  corny  cites  froding- 
hamii  by  Ellis,  Urophlyctites  stigmaviae  by  Weiss  (1904),  and 
Peronosporites  palmi  by  Berrv  (1916).  Porter  and  Zebrowski 
(  1937)  identified  fungi  occurring  in  sands  from  Australia,  China, 
Africa,  Texas,  North  Carolina,  and  the  West  Indies  as  Phycomy- 


CLASSIFICATION  OF  FOSSIL  FUNGI  481 

cetes  in  the  Cladochytriaceae.  These  fungi  occurred  in  shell  frae;- 
ments  of  Mollusca,  Foraminifera,  and  Ostracoda  and  in  sponge 
spicules  of  species  that  date  back  to  the  Cambrian.  Renault  and 
Bertrand  (1885)  would  include  their  chytridiaceous  Grilletia 
sphaerospermii  in  this  class. 

1.  Oochytriaceae 

Oochytrium  *  lepidodendri  Renault,  in  twigs  of  Lepidoden- 
dron,  like  the  present-day  chytrid  genus  Urophlyctites  oliverianus 
Magnus  (1903),  is  parasitic  in  leaves  of  Alethopteris  aquilina. 
Urophlyctites  stigmariae  Weiss  is  parasitic  in  rootlets  of  Stigmaria. 

2.  Pythiaceae 

Pythites  dysodilis  Pamp.,  fossil  remains  from  the  Miocene,  show 
mycelia  and  spores. 

3.  Peronosporaceae 

Peronosporites  antiquarius  W.  Smith,  in  tracheids  of  Lepido- 
dendron  from  the  English  Coal  Measures,  is  one  of  the  best- 
known  fossil  fungi.  Peronosporites  gracilis  Renault  was  first 
described  as  Palaeomyces  gracilis.  Ellis  (1918)  noted  its  intracel- 
lular hyphae  in  parenchyma  cells  of  stem  and  roots  of  Lepido- 
dendron  acideatum  and  Ly  ginodendron  old  hafnium.  Peronospo- 
rites  miocaenicns   Pamp.    and   P.   siculus   Pamp.    are    from   the 

Miocene. 

4.  Mucoraceae 

Mucorites  cambrensis  Renault  from  the  Paleozoic  lacks  repro- 
ductive structures;  hence  its  relationship  is  unsatisfactorily  known. 

Phy  corny  cites  frodinghamii  Ellis  from  the  Jurassic  is  interpreted 
as  having  had  a  chemotactic  affinity  for  iron,  as  have  modern  iron 
bacteria. 

III.    ASCOMYCETES 

Approximately  100  species  of  Sphaerites  are  included  in  Meschi- 
nelli's  "Fungi  Fossiles,"  a  fact  which  gives  an  indication  of  the 
abundance  of  fossil  Ascomycetes  and  at  the  same  time  may  be  pre- 
sumed to  demonstrate  the  difficulty  of  making  specific  identifi- 
cations. It  is  reasonable  to  assume  that  certain  of  this  assemblage 
may  not  be  distinct  species.    There  is  reason  to  believe  also  that 

*  Some  palaeontologists  have  not  chosen  to  employ  the  termination  "ites." 


482 


FOSSIL  FUNGI 


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CLASSIFICATION  OF  FOSSIL  FUNGI  483 

structures  interpreted  to  be  fossil  perithecia  may  not  be  perithecia, 
since  asci  and  paraphyses  are  rarely  preserved.  This  fact  is  illus- 
trated by  Salmon's  (1903)  comments.  He  stated  that  the  globoid 
bodies  which  Pampaloni  (1902)  described  as  appendaged  perithe- 
cia of  Uncinulites  and  Erysiphites,  and  which  he  examined,  are 
merely  spiny  spores. 

1.  Protomycetaceae 

Frotomy  cites  proto genes  W.  Smith  occurs  on  Lepidodendron 
roots  from  the  Coal  Measures. 

2.  Erysiphaceae 

Erysiphites  metilli  Pamp.,  E.  protogaens  Schmalhausen,  and  Un- 
cinulites baccarinii  Pamp.  are  said  to  occur  in  the  Miocene,  but 
Salmon  (1902)  thinks  they  are  from  the  Eocene. 

3.  Perisporiaceae 

The  Genus  Perisporites,  with  three  species,  was  created  by  Felix 
from  Eocene  and  Miocene  rocks. 

4.  Microthyriaceae 

Fhragmothy rites  eocenica  Edwards,  Microthy rites  dy sod His 
Pamp.,  which  looks  like  an  Asterina,  and  Xylomites  asteriformis. 
Braun,  occurring  on  some  cycad-like  plant,  represent  this  family. 

5.  Aspergillaceae 

Fenicillites  curtipes  Berk,  occurs  as  a  well-preserved  fungus  in 
amber  from  the  Eocene. 

6.  Hysteriaceae 

This  family  is  represented  by  Hysterites  ancinitis  Matth.  from 
the  upper  Devonian  and  H.  cordiatis  Matth.  from  the  Permian 

and  Carboniferous. 

7.  Phacidiaceae 

Approximately  50  species  of  leaf-inhabiting  species  assigned  to 
Meschinelli's  genera  Phacidites  and  Rhytismites  from  the  Tertiary 
and  Quaternary  have  been  described. 

8.  Stictidiaceae 

Stegites  poacitum  A.  Br.,  described  from  the  Miocene,  occurs 
in  flecks  on  grass  leaves. 


484  FOSSIL  FUNGI 

9.  Pezizaceae 

Pezizites  candidus  Gopp  et  Ber.  occurs  as  well-preserved  mate- 
rial on  insects  in  amber. 

10.  Cenansnaceae 

Cemvigites  piri  Ludw.  from  the  Miocene  externally  resembles 
modern  Cenansnum. 

11.  Hvpocreaceae 

Melanosporites  stefani  Pamp.   from  the   Miocene   consists  of 
perithecia  and  ascospores. 

12.  Dothideaceae 

Included  in  this  family  are  8  species  of  leaf-inhabiting  fungi 
belonging  to  Dothidites  Bur.  et  Pot. 

13.  Chaetomiaceae 

Chaetomites  intricatus  Pamp.  from  the  Miocene  shows  hairy 
perithecia  like  those  of  Chaetomium. 

14.  Sordariaceae 

From  the  Miocene  came  fossilized  ascospores  resembling  those 

of  Sordaria. 

15.  Sphaenaceae 

A  large  number  of  leaf-  and  bark-inhabiting  species  represent- 
ing this  family  from  the  Permian  have  been  described  in 
Sphaerites,  established  by  linger.  Representative  forms  include 
Sphaerites  sitessi  Ettingh.  on  Rhamnus,  Rosellinites  Beyschlagii 
Pot.,  R.  congestus  Beck,  R.  schusteri  Rehm.,  Petrosphaeria  japon- 
ic a  Stopes  et  Fujii,  and  Chaetosphaerites  bily  chnis  Felix. 

16.  Amphisphaeriaceae 
Trematosphaerites  lignitum  is  from  the  Oligocene. 

17.  Mycosphaerellaceae 
Laestadites  nathorstii  Mesch.  is  from  the  Quaternary. 

18.  Pleosporiaceae 

On  the  leaves  of  Cryptomeriopsis  mesozoica  occurs  a  species, 
that  shows  perithecia  containing  asci  and  paraphyses  and  that  has 


CLASSIFICATION  OF  FOSSIL  FUNGI  485 

been  identified  as  Pleosporites  shirianus  Suzuki.  Other  represen- 
tatives include  Didymosphaerites  bethel ii  Cockerell  on  Tvpha 
leaves  from  the  Miocene  and  Leptosphaerites  lemoinii  Richon. 


IV.  Basidiomycetes 

Among  the  fossilized  Basidiomycetes  are  two  of  outstanding 
interest.  One  was  described  by  Conwentz  [Seward  (1898)]  from 
petrified  wood  preserved  in  amber  and  identified  as  Polyporus 
vapor arins  Fr.  f.  siiccinea.  The  other,  a  beautifully  silicified  shelf 
fungus,  was  collected  in  the  site  of  the  dinosaur  beds  from  the 
lower  Cretaceous  of  Montana  by  Wieland  (1934)  and  identified 
by  him  as  Poly pontes  brovonii. 

As  is  the  situation  in  other  classes  of  fossil  fungi,  identifications 
have  been  questioned.  Poly  pontes  bovcmanii  Lindley  et  Hutton 
from  the  Carboniferous  of  England  may  be  a  ganoid  fish  scale. 
James  (1893)  suggests  that  Rhizomorpha  sigillariae  Lesquereux 
bears  a  strong  resemblance  to  insect  burrows,  like  those  of  Bostry- 
chus.  Renault's  Teleutosporites  milloti  from  the  Permo-Carboni- 
ferous,  in  the  macrospores  of  Lepidodendron,  is  rejected  by 
Seward  (1898)  as  a  fossil  Puccinia. 

1.  Tilletiaceae 

Spores  from  coal  resemble  those  of  modern  Tilletia  and  Uro- 

cystis. 

2.  Coleosporiaceae 

Coleosporium-like  spores  have  been  identified  in  coal. 

3.  Pucciniaceae 

From  the  upper  Cretaceous  come  Puccinites  lanceolatus  Et- 
tingsh.,  P.  cretaceous  Velen.,  and  P.  Whitfordi  Knowlt.  Whit- 
ford  (1916)  described  P.  cretacewn  from  Cretaceous  leaf  tissue  as 

new. 

4.  Hypochnaceae 

Meschinelli  has  described  a  species  of  Hypochnites  on  wood 
overlain  with  amber. 

5.  Clavariaceae 

From  the  Quaternary  has  been  described  the  little-known  spe- 
cies Clavaria  turbinata  Murr. 


486  FOSSIL  FUNGI 

6.  Hydnaceae 
Only  a  single  species,  Hydnites  argillae  Ludw.,  has  been  listed. 

7.  Polyporaceae 

Fossil  poly  pores  include  Folyporites  foliatits  Ludw.  on  Tertiary 
wood,  P.  brownii  YVieland  from  the  lower  Cretaceous,  Pseudo- 
poly  poms  carbonicus  [Hollick  (1910)]  from  the  Carboniferous, 
and  Lenzitites  gastaldii  Heer  from  the  Tertiary. 

8.  Agaricaceae 

Agariciies  Wardianus  Alesch.  is  a  representative  agaric. 

9.  Lycoperdaceae 

From  the  Miocene  in  Colorado  comes  Geasterites  florissantensis 
Cockerell,  an  earth-star-like  species. 

V.  Deuteromycetes  (Fungi  Lmperfecti) 

A  rather  wide  range  of  fossilized  Deuteromycetes,  many  from 
amber,  have  been  discovered. 

1.  Sphaerioidaceae 

Depazites  rabenhorsti  Gein.  occurs  on  Carboniferous  fern  leaf. 

2.  Aielanconiaceae 
Pestalozzites  sabalana  Berry  is  found  on  palm  leaves. 

3.  Mucedinaceae 

In  amber  have  been  found  Acremonites  sitccineus  Gasp.,  Gona- 
tobotrytis  primigennis  Gasp.,  Monilites  albida  Pamp.,  Ravntlarites 
oblongispoms  Gasp.,  and  Sporotrichitcs  heterospenmts  Gopp. 
Ovularites  barbouri  Whit,  occurs  in  leaf  tissue  from  the  Cretaceous 

[Whitford  (1916)].  _ 

4.  Dematiaceae 

Among  dark-spored  Moniliales  are  Cladospitcs  bipartitus  Felix, 
C.  fasciciilatus  Berry,  C.  oligocaemcuvi  Berry,  Macrosporites 
ropaloides  Ren.,  M.  subtrichellus  Ren.,  and  Tondites  moniliformis 
.Menge. 


FOSSIL  MYCORRHIZAE  481 

5.  Stilbaceae 
Stilbites  coniventzi  Felix  is  among  the  coremioid  species. 

6.  Tuberculariaceae 

On  Tertiary  wood  occurs  a  form  identified  as  Spegazzinites 
cruciformis  Felix. 

At  the  end  of  his  list  of  classified  fossils  Pia  has  assembled  a 
group  that  does  not  fit  among  present-dav  genera,  and  therefore, 
their  classification  is  uncertain.  This  list  includes  Palaeomyces 
gordoni  Kidst.,  P.  majus  Ren.,  Fnngites  jenensis  Hallier  on  mussels, 
Xylomites  polaris  Heer  from  the  upper  Triassic,  X.  zamitae  Gopp. 
from  the  Carboniferous,  Caenomyces  sapotae  Berry  from  the 
Eocene,  Nyctomyces  entoxy linns  Ung.,  Anthracomyces  cannal- 
lensis  Ren.,  A.  rochei  Ren.,  Sclerotites  brandonianiis  JefTr.  et 
Chrvsl.  in  Tertiary  lignite,  Phellomyces  dnbhis  Ren.,  Rhizomor- 
phites  intertextns  Sternb.,  and  R.  polymorphic  Matth. 

FOSSIL  MYCORRHIZAE 

Seward  (1933)  expressed  the  opinion,  "From  very  early  times 
there  have  been  two  kinds  of  associations  between  higher  plants 
and  fungi:  fungi  preying  upon  their  hosts  and  others  beneficial 
to  the  hosts  in  which  they  lived."  In  the  beneficial  category  are 
the  mycorrhizal  associates.  It  is  exceedingly  interesting  that  this 
peculiar  symbiotic  relationship  extends  so  far  into  antiquity  as 
the  lower  Coal-Measures  period.  Some  appreciation  of  the  my- 
corrhizal habit  can  be  obtained  from  the  accounts  of  Weiss  (1904), 
Lignier  (1906),  and  Osborn  (1909).  Weiss  (1904)  observed  my- 
corrhizae  in  coal  balls.  He  says  of  them,  "The  excellent  preserva- 
tion of  both  the  fungus  and  the  host  and  the  specialization  of  the 
cortex  into  two  layers  comparable. with  similar  structures  in  recent 
mycorrhizae  suggest  that,  as  in  the  case  of  the  latter,  the  host 
plant  is  deriving  some  benefit  from  the  presence  of  the  fungus." 
Lignier  (1906)  identified  the  fungal  component  on  some  Sequoia- 
like tree  root  as  Radicidites  reticidatns.  The  mycorrhizae  ob- 
served by  Osborn  (1909)  involved  the  roots  of  Amyelon  rad'icans. 


488  FOSSIL  FUNGI 

IMPLICATIONS 

The  habit  of  procuring  a  livelihood  by  appropriating  it  from 
other  organisms  or  bv  scavenging  is  usually  considered  to  be  de- 
grading  to  both  the  individual  and  the  race,  and  it  may  lead 
to  extinction.  The  habit  of  obtaining  food  by  parasitism,  sapro- 
phvtism,  or  symbiosis  among  fungi  therefore  becomes  of  interest 
because  of  its  antiquity.  In  spite  of  this  habit  the  race  has  sur- 
vived with  little  modification,  as  is  shown  by  the  resemblance  be- 
tween fossilized  species  and  present-day  forms.  In  contrast,  vast 
faunas  and  autotrophic  floras  have  been  unable  to  survive  compe- 
tition and  the  vicissitudes  of  geological  climatic  changes.  The 
extinction  of  dinosaurs  and  of  the  progenitors  of  modern  seed 
plants  bears  witness  to  this  fact.  No  evidence  is  at  hand  to  show- 
that  the  rapacity7  of  parasitic  fungi  can  be  used  to  account  for  the 
disappearance  of  any  races  of  plants  or  animals.  From  the  be- 
ginning their  motto  seems  to  have  been,  "Live  and  let  live."  This 
adjustment  by  fungi  to  their  environment,  therefore,  must  be 
pronounced  a  successful  one  of  a  high  order  by  any  standard  of 
measurement  that  can  be  applied. 

The  antiquity  of  fungi  also  raises  again  the  question  of  their 
origin,  whether  they  came  from  the  Algae  or  from  one  or  more 
separate  and  distinct  phylogenetic  lines.  The  sum  of  geological 
evidence  appears  to  favor  the  conclusion  that  they  have  been  dis- 
tinct from  the  beginning  and  should  not  be  placed  in  the  same 
phylum  with  the  algae. 

LITERATURE  CITED 

Berry,  E.  YV.,  "Remarkable  fossil  fungi,"  MycoL,  8:  73-79,  1916. 

Ellis,  D.,  "Fossil  micro-organisms  from  the  Jurassic  and  Cretaceous  rocks 

of  Great  Britain,"  Proc.  Roy.  Soc.  Edinburgh,  35:  110-132,  1915. 
"Phvcomvcetous  fungi  from  the  English   Lower  Coal  Measures,"  Proc. 

Roy.  Soc.  Edinburgh,  38:  130-145,  1918. 
Hirmer,  Max  (with  the  collaboration  of  Julius  Pia  and  William  Troll), 

Handbuch  der  Palaobotanik,     Vol.  I.     708  pp.     1927.     (Vide  pp.  43, 

112-131.) 
Hollick,  A.,  "A  new  fossil  polvpore,  Pseudopolyporus  carbonicus,  gen.  et  sp. 

nov.,"  MycoL,  2:93-94,  1910. 
James,  J.  F.,  "Notes  on  fossil  fungi,"  /.  MycoL,  7;  268-273,  1893. 


LITERATURE  CITED  489 

Lignier,  O.,  "Radiculites  reticulata,  radicelle  fossile  de  Sequoinee,"  Bull. 

soc.  bot.  France,  53:  193-201,  1906. 
Magnus,  P.,  "Ein  von  F.  W.  Oliver  nachwiesener  parasitischer  Pilz,"  Ber. 

deut.  botan.  Ges.,  27:248-250,  1903. 
Meschinelli,  A.,  "Fungi  fossiles."    In  Saccardo's  Sylloge  fungorum  omnium 

hucusque  cognitorum,  10:  741-805,  1892. 
fungorum  fossilium  omnium  hucusque  cognitorum,  Iconographia.     144 

pp.     1902.     (Vicetia.) 
Osborn,  T.  G.  B.,  "Lateral  roots  of  Amyelon  radicans  and  their  mycorrhiza," 

Ann.  Botany,  25:603-611,  1909. 
Pampaloni,  L.,  "Microflora  e  microfauna  nel  disodile  di  Melille  in  Sicilia," 

Atti.  accad.  Lincei,  11:  sem.  2,  248-251,  1902. 
Porter,  C.  L.,  and  George  Zebrowski,  "Lime-loving  molds  from  Australian 

sands,"  My  col,  29:  252-257,  1937. 
Renault,  B.,  and  C.  E.  Bertrand,  "Grilletia  sphaerospermii,  Chytridiacee 

fossile  du  terrain  houiller  superieur,"  Compt.  rend.,  100:  1306-1308,  1885. 
Salmon,  E.  S.,  "Cercosporoites  spec,  a  new  fossil  fungus,"  /.  Botany,  41:  127- 

130,  1903. 
Seward,  A.  C,  Fossil  plants,  Vol.  1,  pp.  207-222.     Cambridge  University 

Press.     1898. 
Plant  life  through  the  ages,  a  geological  and  botanical  retrospect.    603  pp. 
Cambridge  University  Press.     1933. 
Weiss,  F.  E.,  "A  probable  parasite  of  Stigmarian  rootlets,"  New  PhytoL,  3:  63- 

68,  1904. 
"Mycorrhiza  from  the  Lower  Coal  Measures,"  Ann.  Botany,  18:  255-265, 

1904a. 
Whitford,  A.  C,  "A  description  of  two  new  fossil  fungi,"  Nebr.  Geol. 

Survey,  7:  85-92,  1916. 
Wieland,  G.  R.,  "A  silicified  shelf  fungus  from  the  lower  Cretaceous  of 
Montana,"  Am.  Museum  Novitates,  125: 1-13,  1934. 


AUTHOR  INDEX 


Aamodt,  O.  S.,  260,  272 

Abbott,  E.  V.,  430,  439 

Abe,  T.,  219,  234 

Abraham,  E.  P.,  87,  89,  284,  293 

Adametz,  L.,  429,  430,  439 

Ainsworth,  C.  G.,  395,  397,  403,  414 

Albertini,  J.  B.  de,  189,  206 

Allen,  Al.  C,  287,  293 

Allen,   Ruth  F.,   131,   134,   148,   239, 

250,  253,  254 
Allison,  C.  C,  260,  272,  329,  336 
Allison,  F.  E.,  24,  31 
Ames,   Adeline,    111,    119,    223,   225, 

226,  228,  233 
Ames,  L.  M.,  320,  321,  322,  336 
Andersen,  Emma  N.,  203,  205,  209 
Anderson,  A.  P.,  405,  414 
Angell,  H.  R.,  245,  255 
Apstein,  C,  463,  464,  471 
Armitage,  H.  M.,  450,  457 
Armstrong,  G.  M.,  4,  31 
Armstrong,  J.  I.,  158,  164 
Arnaudi,  C,  423,  428 
Aronescu,  Alice,  238,  239,  248,  249, 

253,  254 
Arrillaga,  J.  G.,  281,  282,  291,  293 
Arthur,  J.  C,  166,  168,  173,  174,  177, 

179,   206,   406,   407,   408,  414,  417, 

428 
Ashton,  M.  R.,  145,  149 
Aso,  K.,  11,  31 
Asthana,  R.  P.,  291,  293 
AtanasofT,  D.,  192,  206,  354,  362 
Atkins,  D.,  464,  471 
Ayers,  T.  T.,  404,  415 

Back,  E.  A.,  445,  456 
Backus,  M.  P.,  137,  148 
Bailey,  A.  A.,  144,  149 
Bailey,  D.  L.,  260,  273,  277 
Bailey,  L.,  453,  454,  455 
Baker,  E.  E.,  368,  391 
Baker,  R.  D.,  365,  372,  391,  393 
Baldwin,  M.  E.,  159,  164 


491 


Ball,  E.  D.,  173,  208 
Bamberg,  R.  H.,  285,  293 
Barger,  G.,  354,  356,  358,  362 
Barger,  W.  R.,  108,  120 
Barghoorn,  E.  S.,  460,  471 
Barnes,  B.,  270,  273 
Barrett,  J.  T.,  170,  206 
Barrows,  Florence  L.,  304,  314 
Barrus,  M.  F.,  260,  273 
Bartetzko,  H.,  106,  119 
Bartlett,  H.  H.,  260,  275 
Bary,  A.  de,  181,  190,  191,  202,  206, 

230,   231,   233,   236,   237,   238,   239, 

254,  289,  293 
Bavendamm,  W.,  44,  51 
Bayliss,  J.  S.,  46,  51 
Beach,  W.  S.,  260,  273 
Beck,  M.  Dorothy,  367,  393 
Beckwith,  T.  D.,  430,  437,  439 
Becquerel,  P.,  106,  119 
Benecke,  W.,  2,  3,  13,  31 
Benham,  Rhoda  W.,   369,   377,   378, 

388,  391,  392 
Bennett,  C  W.,  4,  7,  22,  36 
Bennett,  F.  T.,  105,  119 
Bensaude,  M.,  325,  336 
Bergel,  F.,  87,  89 
Berger,  E.  W.,  449,  454,  457 
Bernard,  N.,  308,  309,  310,  312,  313, 

314 
Bernhauer,  K.,  15,  31,  70,  72,  73,  74, 

81,  89,  90 
Berry,  E.  W.,  480,  488 
Bertrand,  C.  E.,  481,  489 
Beurmann,  L.,  375,  377,  397 
Bever,  W.  M.,  215,  235 
Bilbroth,  T.,  257,  273 
Birkinshaw,  J.  H.,  70,  76,  78,  81,  84, 

85,  90 
Bisby,  G.  R.,  114,  119,  128,  148,  395, 

399,  403,  404,  409,  412,  413,  414 
Bjorkman,  Erik,  297,  308,  314 
Blaauw,  A.  H.,  129,  148 
Blackman,  F.  F.,  98,  119 


492 


AUTHOR  INDEX 


Blackman,  V.  H.,  220,  230,  233,  238, 

240,  254 
Blakeslee,  A.  F.,  319,  336 
Blank,  L.  M.,  7,  35 
Blumer,  B.,  260,  273 
Boas,  F.,  22,  31,  79,  90 
B6ckl,  N.,  73,  89 
Boeseken,  J.,  16,  31 
Bonar,  L.,  264,  273,  468,  469,  471 
Bonner,  James,  27,  31 
Bornet,  E.,  459,  471 
Bortels,  H.,  11,  13,  15,  31 
Bose,  S.  R.,  43,  46,  51,  454,  455 
Bourquelot,  E.,  43,  51 
Boussingault,  J.  B.,  429,  439 
Boyle,   C,   238,   239,   244,   255,   283, 

293 
Brannon,  J.  M.,  18,  31 
Bressman,  E.  N.,  260,  273 
Brewbaker,  H.  E.,  260,  277 
Brian,  P.  W.,  88,  90 
Brierley,  W.  B.,  264,  265,  273,  431, 

432,  439 
Briton-Jones,  H.  R.,  260,  273 
Broadfoot,  W.  C,  281,  286,  292,  293, 

296 
Brodie,  H.  J.,  174,  206,  219,  233,  450, 

455 
Brooks,  Charles,  103,  115,  119,  120 
Brown,  A.  M.,  270,  274,  276 
Brown,  H.  B.,  358,  362 
Brown,  P.  E.,  433,  439 
Brown,  W.  H.,  454,  455 
Brown,  William,   128,   148,  216,  231, 

233,  236,  237,  238,  243,  244,  255 
Brumpt,  E.,  367,  372,  391 
Brunswik,  H.,  328,  331,  336 
Buchner,  P.,  451,  455 
Budde,  A.,  260,  273 
Budcr,  J.,  130,  148 
Bugie,  Elizabeth,  87,  94 
Buller,   A.   H.  R.,  46,  51,   105,   106, 
120,    125,    126,    131,    132,    133,    135, 
137,    138,    148,    172,    176,    182,    183, 
189,    190,    194,    195,    196,    197,    198, 
199,   200,   201,   203,   206,   286,   294, 
328,    333,    336,   385,   391,   397,  403, 
412,  414 
Bulliard,  P.,  189,  206 
Bulloch,  William,  54,  55,  67 
Bunker,  H.  J.,  50,  52 
BurgefT,  H.,  240,  241,  255,  319,  336 
Burgert,  Irma  A.,  216,  223,  233 


Burges,  A.,  298,  308,  314 
Burkhardt,  E.,  359,  363 
Burkholder,  P.  R.,  27,  28,  31 
Burkholder,  W.  H.,  260,  273 
Burrill,  T.  J.,  170,  206 
Burt,  E.  A.,  202,  206 
Busgen,  M.,  239,  255 
Butkewitsch,  W.  S.,  70,  71,  72,  73, 

75,  90 
Butler,  E.  J.,  404,  412,  414 
Butler,  Ellys  T.,  188,  192,  206 

Caesar,  L.,  173,  208 
Cagniard-Latour,  Charles,  54,  67 
Caley,  D.  ML,  284,  294 
Calfee,  R.  K.,  13,  14,  33 
Callow,  R.  K.,  81,  90 
Calloway,  J.  L.,  365,  391 
Calvery,'H.  O.,  41,  51 
Cameron,  A.  T.,  105,  120 
Camp,  A.  F.,  19,  31 
Campbell,  W.  G,  44,  51 
Carbone,  D.,  423,  428 
Carr,  L.  G.,  398,  414 
Carrion,  A.  L.,  372,  391,  392 
Carson,  S.  F,  19,  32,  463,  439 
Carter,  J.  C,  280,  295 
Cartwright,  K.  St.  G.,  98,  102,  120 
Cassell,  R.  S.,  169,  208 
Castle,  E.  S.,  131,  148 
Chain,  E.,  86,  87,  89,  90,  284,  293 
Challenger,  F.,  88,  90 
Charles,  Vera  K,  444,  455 
Chaudhuri,  H.,  97,  99,  113,  117,  120 
Chemin,  E.,  469,  472 
Chester,  K.  S.,  423,  428 
Chibnall,  A.  C,  21,  32 
Chilton,  S.  J.  P.,  325,  337 
Christiansen,  C,  259,  265,  273 
Christiansen,  J.  J.,  171,  206,  260,  264, 
265,   267,   273,   274,   277,   321,   336, 
327,  329,  330,  338,  360,  361,  362 
Christman,  A.  H.,  227,  233 
Christopher,  W.  N.,  169,  208 
Chrzaszcz,  T.,  13,  15,  31,  70,  71,  73, 

79,  90,  91 
Chupp,  C,  159,  161,  164 
Church,  M.  B.,  74,  92 
Ciferri,  R.,  260,  274 
Clark,  A.  B.,  74,  93 
Clark,  E.  D.,  341,  350,  362 
Clark,  J.  F.,  151,  164 
Clark,  W.  M.,  151,  164 


AUTHOR  INDEX 


493 


Clayton,  C.  N.,  219,  233 

Clayton,  E.  E.,  401,  414 

Clegg,  M.  T.,  375,  393 

Clemmer,  H.  J.,  260,  266,  279 

Clinton,  G.  P.,  404,  405,  414 

Clodi,  C,  463,  472 

Clutterbuck,  P.  W.,  84,  88,  90,  284, 
294 

Cobb,  Mary  Jo,  431,  432,  433,  439 

Coblentz,  W.  W.,  141,  148 

Coghill,  R.  D.,  146,  149 

Cohen,  Clara,  70,  91,  93 

Coleman,  D.  A.,  433,  434,  439 

Committee  on  apparatus  in  aero- 
biology,  171,  206 

Conant,  G.  H.,  246,  255 

Conant,  N.  F.,  365,  370,  372,  384, 
391,  393 

Conn,  H.  J.,  430,  439 

Connstein,  W.,  77,  91 

Constintin,  J.,  313,  314 

Cooley,  J.  S.,  103,  115,  119,  120 

Coons,  G.  H.,  199,  206 

Copping,  Alice  M.,  25,  31 

Cotter,  R.  U.,  260,  266,  274,  277 

Cotton,  A.  D.,  460,  469,  471 

Couch,  J.  N.,  409,  414,  444,  448,  455 

Coudon,  H.,  436,  440 

Coyne,  F.  P.,  79,  91 

Crabill,  C  H.,  43,  51 

Craigie,  J.  H.,  170,  174,  206,  245, 
256,  266,  274,  333,  336,  451,  455 

Crosier,  Willard,   113,   120,  222,  233 

Cunningham,  G.  H.,  406,  407,  414 

Curran,  C.  G.,  169,  208 

Currie,  J.  N.,  71,  72,  91 

Curtis,  K.  M.,  240,  246,  255 

Curtis,  P.  J.,  88,  90 

Czapek,  F.,  21,  31,  43,  51 

Czurda,  V.,  131,  135,  149 

D'Aeth,  H.  R.  X.,  280,  281,  294 
Dale,  E.,  430,  431,  433,  439 
Dammann,  E.,  66,  61 
Dangeard,  P.,  460,  471 
Daniel,  G.  E.,  462,  471 
Darkis,  F.  R.,  108,  122,  170,  209 
Daszewska,  W.,  435,  439 
Davidson,  A.  M.,  385,  389,  391 
Davis,  A.  R.,  23,  24,  31 
Davis,  W.  H.,  214,  223,  233 
Davison,  F.  R.,  48,  51 
Davison,  W.  C,  38,  52 


Dearness,  J.,  397,  403,  412,  414 
Demerec,  M.,  139,  140,  146,  150 
Devese,  P.,  388,  393 
Dev,  P.  K.,  239,  244,  255 
Dickson,  E.  C,  367,  393 
Dickson,  Hugh,  146,  148 
Dickson,  J.  G.,  109,  120,  121 
Dickson,  S.,  329,  330,  331,  337 
Diedicke,  H.,  260,  274 
Diehl,   W.   W.,   205,    206,   412,   414, 

469,  472 
Dietel,  P.,   199,  206 
Dietz,  S.  M.,  260,  276 
Dillon-Weston,  W.  A.  R.,  143,  148, 

231,  233 
Dimock,  A.  W.,  266,  274,  323,  337 
Dimond,  Albert,  141,  148 
Dixon,  L.  F.,  108,  111,  113,  122,  170, 

189,  206,  209 
Doak,  K.  D.,  299,  300,  301,  309,  314 
Dodge,  B.  O.,  200,  206,  264,  266,  274, 

290,    294,    321,    322,    323,    324,    326, 

327,  331,  335,  336,  337,  338 
Dodge,   C.   W.,    364,    367,    377,    379, 

383,  384,  389,  391 
Doran,    W.    L.,    161,    164,    218,    223, 

228,  231,  233 
Dowding,  E.  S.,  321,  323,  337,  384, 

385,  391 
Dox,  A.  W.,  79,  91 
Duboscq,  O.,  466,  472 
Dudley,  H.  W.,  359,  362 
Dugan,  G.  H.,  406,  415 
Duggar,  B.  M.,  23,  24,  31,  141,  148, 

230,  233 
Dujarrac  de  la  Riviere,  D.,  341,  362 
Duncan,  P.  Martin,  459,  472 
Durham,  O.  C,  171,  206 
Durrell,  L.  W.,   221,   222,   230,   231, 

234 
Dutcher,  J.  D.,  284,  294 

Eakin,  R.  E.,  28,  36 

Eastcott,  E.  V.,  288,  294 

Edgerton,  C.  W.,  99,  109,   120,  325, 

337 
Edson,  H.  A.,  99,  118,  120 
Ehrlich,  John,  173,  206 
Fide,  C.  J.,  260,  277 
Elliott,  J.  S.,  454,  455 
Ellis,  D.,  480,  481,  488 
Ellis,  L.,   88,  90 
Emerson,  O.  H.,  284,  296 


494 


AUTHOR  INDEX 


Emerson,  Ralph,  84,  91,  432,  439 
Emmerie,  A.,  11,  14,  36 
Emmerling,  O.,  78,  91 
Emmons,  C.  AY.,   140,  146,  148,  149, 

371,   373,   374,   377,   383,   384,   386, 

391,  392,  437,  439 
Endo,  S.,  281,  294 
Erickson,  James,  26,  31 
Eriksson,  J.,  258,  260,  274 
Errera,  L.,  205,  207 
Estee,  Lula  A  I.,  469,  472 
Ewert,  R.,  227,  233 

Fabbrioni,  Adamo,  53,  55,  67 
Fabricius,  J.  C,  418,  421,  428 
Falck,  R.,  99,  120,  189,  207,  356,  362 
Faris,  J.  A.,  260,  274 
Faull,  J.  H.,  106,  108,  120,  406,  414 
Fawcett,  H.  S.,  98,  99,  108,  116,  120, 
280,   285,   291,   294,   296,  402,   411, 
415,  447,  449,  450,  455,  456 
Fedoroff,  AI.  W.,  71,  73,  75,  90 
Fcldmann,  Jean,  469,  470,  472 
Fellows,  H.,  22,  31,  158,  165 
Ferdinandsen,  C,  469,  472 
Findlav,  W.  P.  K.,  98,  102,  120 
Finn,  R.  F.,  308,  315 
Fischer,  E.,  203,  207 
Fischer,  G.  W.,  335,  337 
Fischmann,  C.  F.,  81,  90 
Fish,  F.  T.,  463,  472 
Fisher,  R.  A.,  213,  233 
Fisher,  W.  R.,  189,  206 
Fitz,  A.,  76,  77,  91 
Flahault,  C,  459,  471 
Fleming,  A.,  86,  91 
Fletcher,  C.  AI.,  87,  89,  284,  293 
Flor,  H.  H.,  260,  264,  274,  329,  330, 

337 
Folkers,  K.,  28,  32 
Fontana,  Felice,  417,  428 
Ford,  W.  AY.,  341,  342,  350,  362,  363 
Foster,  J.  W.,  11,  13,  14,  16,  19,  32, 

36,  76,  94,  436,  439 
Fox,  D.  L.,  84,  91 
Frank,  A.  B.,  238,  255,  297,  299,  301, 

305,  306,  314 
Fred,  E.  B.,    19,   22,   36,  81,   82,  93, 

430,  438,  440,  441 
Freeman,  Walter,  369,  392 
Frenzel,  H.,  260,  274 
Fricke,  C.  H.,  260,  276 
Fries,  Elias,  356,  362 


Fries,  N.,  26,  32,  288,  295 
Fries,  R.  E.,  398,  415 
Fromme,  F.  D.,  138,  148 
Fulmer,  E.  J.,  289,  296 
Fulton,  H.  R.,  141,  148,  242,  255 
Funke,  G.  L.,  48,  51 

Gaines,  E.  F.,  260,  274 
Gardner,  A.  D.,  87,  89,  284,  293 
Gardner,  M.  W.,  173,  176,  207,  208 
Garren,  K.  H.,  47,  51 
Garrett,  S.  D.,  287,  294 
Gaumann,  E.,  260,  267,  274 
Gehenio,  P.  M.,   107,   120,   121,  227, 

234 
Gilbert,  E.  AI.,  260,  274 
Gilchrist,  T.  C,  368,  393 
Gillispie,  J.  L.,  161,  164 
Gilman,  J.  C,  109,  120,  430,  431,  439 
Glasgow,  O.  E.,  298,  315 
Goddard,  D.  R.,  216,  217,  234,  390, 

392 
Goddard,  H.  AT.,  430,  432,  433,  439 
Goldschmidt,  V.,  260,  274 
Gorcica,  H.  J.,  82,  91,  93 
Gordon,  XV.  L.,  260,  274 
Gottschalk,  A.,   58,  67,  74,  91 
Gougerot,  H.,  375,  377,  391 
Gould,  B.  S.,  84,  91 
Goulden,  C.  H.,  270,  274 
Graff,  P.  W.,  254,  255 
Graham,  T.  W.,  260,  273 
Gravatt,  G.  F.,  176,  207 
Graves,  A.  H.,  242,  255 
Greaney,  F.  J.,  146,  148,  287,  294 
Greene,  H.  C,  82,  93 
Gregory,  P.  H.,   172,  207,  364,  387, 

388,  389,  391,  392 
Grevel,  F.  K.,  260,  275 
Griffiths,  D.,  191,  207 
Griffiths,  Alarion  A.,  406,  415 
Grigoraki,  L.,  383,  392 
Grove,  W.  B.,  412,  415 
Guba,  E.  F.,  388,  393,  411,  415 
Guerra,  P.,  377,  392 
Gyorgy,  Paul,  289,  296 

Haenseler,  C.  AI.,  5,  12,  32,  287,  293 

Hafstad,  G.  E.,  264,  278 

Hagem,  O.,  430,  431,  433,  438,  439 

Harm,  G.  G.,  404,  415 

Hainan,  E.  T.,  143,  148 

Hammarlund,  C,  260,  262,  275 


AUTHOR  INDEX 


495 


Hanna,  W.  F„  329,  337 

Hansen,  H.  N.,  264,  265,  275 

Harden,  A.,  58,  67 

Hariot,  P.,  469,  472 

Harrington,  J.  B.,  269,  275 

Harris,  G.  C.  A  I.,  88,  94,  95 

Harris,  S.  A.,  28,  32 

Harsch,  R.  M.,  127,  149 

Hart,  Helen,  215,  223,  234 

Hartelius,  V.,  23,  33 

Harter,   L.   L.,    18,   36,  48,   51,    102, 

122,  224,  235,  260,  275 
Hartman,  R.  E.,  109,  120 
Harvey,  C.  C,  243,  244,  255 
Harvey,  E.  Newton,   137,  148 
Harvey,  J.  V.,  430,  431,  439 
Harvey,  R.  B.,  245,  246,  255 
Harz,  C.  O.,  374,  392 
Haskins,  C.  P.,  145,  149 
Hasselbring,  H.,  239,  255 
Hatch,  A.  B.,  178,  207,  297,  299,  300, 

301,  306,  307,  308,  311,  312,  314 
Hauptfleisch,  P.,  466,  472 
Hawker,  Lilian  E.,  25,  26,  32,  66,  67, 

291,  293 
Hawkins,  L.  A.,  18,  29,  32,  245,  246, 

255 
Haworth,  W.  N.,  88,  90 
Heald,  F.  D.,  29,  32,   167,   170,   173, 

176,  207,  291,  294,  405,  415 
Heatlev,  N.  G.,  87,  89,  284,  293 
Hedgcock,  G.  G.,  127,  149 
Heim,  Roger,  341,  362 
Hellback,  R.,  74,  92 
Hemmi,  H.,  219,  234 
Hemming,  H.  G.,  88,  90 
Hendree,  Esther  C,  175,  207 
Henkelekian,  H.,  435,  436,  439 
Henrv,  A.  W.,  169,  208 
Herissev,  H.,  43,  51 
Hermann,  W.  W.,  369,  373 
Herrick,  H.  T,  16,  32,  74,  75,  78,  92, 

94 
Herrick,  J.  A.,  103,  120,  155,  164 
Herriott,  R.  M.,  41,  51 
Hev,  A.,  260,  275 
Higginbottom,  C,  88,  90 
Higgins,  B.  B.,  49,  52,  237,  238,  255 
Hines,  L.,  260,  266,  277 
Hirmer,  Max,  480,  488 
Hodgetts,  W.  J.,   192,  207 
Hoerner,  G.  R.,  260,  275 
Hoffman,  H.,  212,  224,  234 


Hohnk,  W.,  168,  207 
Hollaender,  A.,  139,  146,  150 
Hollick,  A.,  486,  488 
Holterman,  C,  454,  456 
Holton,  C.  S.,  260,  275,  405,  415 
Honn,  J.  M.,  289,  296 
Hoover,  S.  R.,  24,  31 
Hopkins,  J.  G.,  388,  392 
Hopkins,  S.  J.,  21,  32 
Hoppe,  P.  E.,  285,  295 
Hoppe-Seyler,  F.,  435,  440 
Hopper,  Mary  E.,  365,  392 
Horner,  G.  R.,  215,  227,  234 
Horr,  W.  W.,  18,  32 
Howe,  Mary  E.,  231,  234 
Howell,  Arden,  370,  392 
Huang,  P.  T.,  373,  393 
Humphrey,  C.  J.,  102,  120 
Hutchinson,  A.  H.,  143,  145,  149 

Ingold,  C.  T.,  136,  137,  149,  185,  186, 
187,  188,  190,  191,  192,  193,  196, 
197,  207 

Isenbeck,  K.,  260,  272 

Iterson,  C.  van,  435,  440 

IwanorT*,  N.  M.,  69,  73,  82,  85,  86, 
92,  352,  362 

Jackson,  H.  S.,  260,  276 
Jackson,  L.  W.  R.,  155,  164 
Jahn,  E.,  220,  234 
James,  J.  F.,  477,  488 
Jamieson,  S.  G.,  80,  94 
javillier,  M.,  11,  16,  32 
Jennings,  M.  A.,  87,  89,  284,  293 
Jensen,  C.  N.,  430,  431,  440 
Jensen,    H.    L.,    431,    432,    433,    434, 

440 
Johnson,  Burt,  242,  255 
Johnson,  C.  O.,  260,  275,  276 
Johnson,  Delia,  285,  295 
Johnson,  E.  C,  223,  234 
Johnson,  E.  M.,  264,  275 
Johnson,  H.  W.,  155,  164 
Johnson,  James,  109,  120,  121 
Johnson,  T,  260,  264,  267,  276,  328, 

331,  334,  337,  338 
Johnston,  J.  R.,  450,  456 
Jolivette,  H.  D.,  131,  134,  148 
Jones,  C.  P.,  89,  92,  377,  378,  393 
Jones,  Edith  S.,  220,  221,  223,  234 
Jones,  Herbert  L.,  469,  472 
Jones,  L.  R.,  105,  109,  110,  121 


496 


AUTHOR  INDEX 


Kadisch,  E.,  106,  121 
Kamen,  M.  D.,  19,  32,  436,  439 
Kardo-Ssvsojewa,  E.,  75,  92 
Karling,  j.  S.,  398,  415,  461,  472 
Karrer,  Joanne  L.,  159,  164 
Kavanauejh,  F.,  26,  27,  28,  34 
Keilin,  D.,  444,  456 
Keitt,  G.  W.,  171,  207,  411,  415 
Kellerman,  K.  F.,  435,  440 
Kelly,  A.  P.,  305,  315 
Kernkamp,  H.  C.  H.,  360,  361,  362 
Kernkamp,  M.  F.,  329,  331,  337 
Kersten,  Beatrice,  375,  391 
Kharasch,  M.  S.,  359,  363 
Kibbe,  Alice,  461,  472 
Kiessling,  W.,  58,  61,  67 
Killian,  Charles,  356,  363 
Kin?,  H.,  359,  363 
Kina,  T.  H.,  331,  338 
Kinierv,  L.  K.,  4,  15,  19,  25,  33 
Kinnear,  J.,  389,  392 
KirchhofT,  H.,  356,  363 
Klebahn,  H.,  169,  199,  207 
Klein,  R.,  87,  89 
Klotz,  L.  J.,  22,  32 
Kniep,  H.,  325,  328,  337 
Knudson,  L.,  310,  311,  315 
Koch,  A.,  454,  456 
Kocholatv,  W.,  87,  92 
Kogl,  F.,  26,  32,  82,  92,  288,  295 
Kolk,  Laura  A.,  260,  277 
Kolliker,  A.,  459,  472 
Koning,  C.  J.,  429,  430,  431,  440 
Kostermans,  D.  G.,  82,  92 
Kostytchew,  S.,  57,  58,  67,  72,  92 
Krause,  A.  W.,  113,  121 
Kusano,  S.,  304,  315 
Kiister,  Ernst,  422,  428 

LaFuze,  H.  H.,  45,  52 

Lamater,  E.  D.  de,  388,  392 

Lamb,  J.  H.,  377,  378,  392 

Lamb,  Margaret  L.,  377,  378,  392 

Landen,  E.  W.,  143,  149 

Lange,  J.  E.,  409,  415 

Langeron,    M.,    377,    383,    386,    387, 

392,  393 
Lanphere,  W.  M.,  47,  52 
LaRue,  C.  D.,  260,  261,  265,  275 
Latham,  M.  E.,  23,  32 
Lauritzen,  J.  I.,  99,  103,  121,  224,  234 
Lavoisier,  A.  L.,  54,  67 


Leach,  J.  G.,  173,  175,  207,  260,  275, 

442,  451,  456 
LeClerg,  E.  L.,  431,  432,  433,  440 
Lee,  H.  A.,  402,  415 
Lee,  L.  E.,  377,  378,  393 
Lefebvre,  C.  L.,  445,  447,  456 
Legault,  R.  R.,  359,  363 
Leger,  L.,  466,  472 
Lehman,  S.  G.,  108,  121,  427,  428 
Lcidv,  Joseph,  465,  472 
Leightv,  C.  E.,  406,  415 
Lendner,  A.,  430,  431,  440 
Lentze,  F.  A.,  375,  392 
Leonian,  L.   H.,  4,   22,  27,   32,   260, 

265,  268,  275,  289,  295 
Letcher,  H.,  77,  92 
Leveille,  J.  H.,  356,  363 

Levine,   M.   N.,   260,   266,   267,   274, 
275,  277 

Levisohn,  I.,  185,  208 

Lewis,  George  A  I.,  364,  373,  392 

Liebig,  J.  von,  54,  55,  67 

Lignier,  O.,  487,  489 

Lilly,  V.  G.,  4,  22,  27,  32,  289,  295 

Lin',  C.  K.,  213,  234 

Lind,   J.,  412,  413,  415 

Lindbenx,  Charles  A.,  171,  208 

Lindegren,  C.  C,  321,  323,  325,  337, 
338^ 

Linder,  D.  H.,  460,  471 

Lindgren,  R.  M.,  99,  121,  162,  164 

Lindner,  J.,  106,  121 

Ling,  Lee,  223,  230,  234 

Link,  H.  F.,  182,  208 

Link,  K.  P.,  245,  255 

Lipman,  C.  B.,   106,  107,  121 

Livingston,  B.  E.,  112,  117,  121 

Lockwood,  L.  B.,  15,  16,  32,  70,  80, 
92,  94,   146,   149 

Long,  W.  H.,  127,  149 

Longree,  K.,  113,  121 

Lowell,  R.,  284,  294 

L6\venthal,  W.,  460,  472 

Lucas,  G.  B.,  325,  337 

Ludecke,  K.,  77,  91 

Lutman,  B.  F.,  61,  63,  67,  313,  315 

Luttrell,  E.  S.,  254,  255,  447,  456 

Lutz,  O.,  283,  295 

Luvet,  B.  F.,  107,  120,  121,  146,  150, 
227,  234 

Ala,  Roberta,  25,  28,  34 
MacBride,  T.  H.,  397,  415 


AUTHOR  INDEX 


491 


Machacek,  J.  E.,  146,  148,  287,  294, 

295 
Maclnnes,  Jean,  160,  164 
MacKee,  G.  M.,  373,  392 
Mackinnon,  J.  E.,  25,  34 
Macrae,  Ruth,  329,  338 
Magnus,  P.,  481,  489 
Magrou,  J.,  313,  314,  315 
Mains,  E.  B.,  260,  275,  276 
Maire,  E.,  469,  472 
Maneval,  W.  E.,  214,  234 
Mann,  Mary  L.,  7,  32 
Marchal,  E.',  260,  276,  436,  440 
Marczynski,  M.,  26,  33 
Margarot,  J.,  388,  393 
Marfoth,  R.  H.,  163,  164 
Marshall,  R.  P.,   176,  207 
Martin,  D.  S.,  89,  92,  365,  372,  377, 

378,  391,  393 
Martin,  G.  W.,  397,  415,  461,  472 
Martin,  W.  J.,  331,  338 
Masui,  Koki,  303,  308,  315 
Matsumoto,  T.,  260,  276 
May,  O.  E.,   15,   16,   32,  74,  75,  78, 

92,  94 
Mayo,  J.  K.,  47,  52 
McAlpine,  D.,  407,  415 
McBeth,  I.  G.,  435,  440 
McCallan,  S.  E.  A.,  212,  234 
McCormick,  Florence  A.,  291,  295, 

404,  414 
McDonald,  J.  A.,  47,  52 
McDousall,  W.  B.,  298,  308,  315 
McGowan,  J.  C,  88,  90 
McHargue,  J.  S.,  13,  14,  33 
McKay,  M.  B.,  248,  256 
McLean,  H.  C,  436,  440 
McLean,   Ruth,    108,    111,    113,    122, 

170,  209 
McVeigh,  Ilda,  27,  28,  31 
Meacham,  M.  R.,  155,  164 
Medlar,  E.  M.,  371,  393 
Meier,  F.  C,   171,  208 
Melander,  L.  W.,  245,  256 
Melchers,  L.  E.,  260,  266,  276,  279 
Melhus,  I.  E.,  221,  222,  230,  231,  234 
Melich,  A.  E.,  438,  440 
Melin,  Elias,  299,  301,  303,  311,  315 
Melville,  D.  B.,  289,  296 
Mendel,  L.  B.,  351,  352,  363 
Menon,  K.  P.  V.,  48,  52 
Meschinelli,  A.,  480,  481,  489 
Metz,  O.,  14,  15,  33 


Meyen,  F.  J.  B.,  356,  363 

Meyer,  Helen,  166,  208 

Meyer,  Karl,  87,  92 

Meyer-Hermann,  K.,  160,  161,  164 

Meyerhoff,  O.,  58,  61,  67 

Micheli,  P.  A.,  189,  203,  207,  208 

Milchochevitch,  S.,  383,  386,  392 

Millard,  W.  A.,  286,  295 

Miller,  T.  E.,  86,  92 

Mitchell,  H.  F.,  308,  315 

Miyoshi,  ML,  241,  256 

Modess,  O.,  312,  315 

Moir,  J.  C,  359,  362 

Molisch,  H.,  3,  4,  13,  33 

Moller,  A.,  452,  454,  456 

Molliard,  M.,  18,  29,  33,  72,  92,  291, 

295 
Monbreun,  W.  A.  de,  369,  393 
Montgomery,  H.  B.  S.,  47,  52 
Moore,  C.  N.,  145,  149 
Moore,  Elizabeth  J.,  19,  33 
Moore,  M.,  367,  373,  376,  393 
Moreau,  F.,  127,  149,  290,  295 
Morrill,  A.  W.,  449,  456 
Morris,  H.  J.,  24,  31 
Morrison,  A.  L.,  87,  89 
Moruzi,  M.  C,  290,  295 
Moss,  A.  R.,  87,  89 
Moss,  E.  H.,  166,  208 
Mosher,  W.  A.,  4,  15,  19,  25,  33 
Mounce,  I.,  469,  472 
Moyer,  A.  J.,  70,  74,  78,  92,  146,  149 
Mozingo,  R.,  28,  32 
Mrak,  E.  M.,  368,  391 
Muhleman,  G.  W.,  48,  52 
Mull,  Robert  P.,  80,  82,  93 
Mulsow,  M.,  462,  473 
Miintz,  A.,  429,  436,  440 
Musgrove,  W.  E.,  375,  393 

Nadson,  G.  A.,  145,  149 
Naegeli,  C.  von,  2,  3,  19,  33 
Nannizzi,  A.,  385,  393 
Neidig,  R.  E.,  79,  91 
Nerescheimer,  E.,  463,  472 
Neuberg,  C,  58,  67,  70,  93 
Neufeld,  C.  C,  219,  233 
Newton,  D.,  143,  149 
Newton,  M.,  260,  264,  267,  270,  274, 

276,  328,  331,  334,  337,  338 
Nickerson,  W.  J.,  290,  295 
Niederlander,  K.,  82,  94 
Nielsen,  E.,  23,  28,  33 


498 


AUTHOR  INDEX 


Niethammer,  A.,  15,  33,  429,  440 

Niezabitowski,  E.  L.,  464,  472 

Nikitinskv,  J.,  282,  295 

Niklas,  H.,  30,  33 

Noack,  R.,  303,  315 

Noble,  R.  J.,  223,  234 

Noecker,  N.  L.,  26,  33 

Xoelle,  YV.,  301,  315 

Nord,  F.  F.,  38,  39,  52,  63,  67,  80, 

82,  93 
Northrop,  J.  L.,  41,  51,  52 
Xutman,  F.  J.,  45,  47,  52 

O'Neill,  H.  T.,  16,  32,  80,  92 

Orr,  H.,  384,  391 

Orton,  C.  R.,  178,  208,  410,  415 

Osborn,  T.  C.  B.,  487,  489 

Oster,  R.  H.,  140,  147,  149 

Ota,  M.,  373,  383,  393 

Oudemans,    C.    A.   J.    A.,   429,    430, 

431,  440 
Overholts,  L.  O.,  409,  410,  415 
Oxford,  A.  E.,  87,  91,  93 

Padv,  S.  M.,  252,  256 

Paine,  F.  S.,  430,  431,  440 

Palladin,  W.,  58,  67 

Pampaloni,  L.,  483,  489 

Parr,  Rosalie,  131,  132,  149 

Pasteur,  Louis,  55,  67,  68 

Patouillard,  N.,  469,  472 

Pearson,  L.  K.,  80,  93 

Peltier,  G.  L.,  237,  250,  251,  256 

Pennington,  L.  H.,  23,  33,  169,  208 

Penser^H.,  260,  276 

Petch,  T.,  444,  445,  447,  450,  454,  456 

Petersen,  H.  E.,  460,  462,  470,  473 

Peterson,  W.  H.,  19,  22,  36,  80,  82, 

91,  93,  94 
Peturson,  B.,  260,  269,  276,  277 
Pevros,  E.,  13,  15,  31 
PferTer,  W.,  16,  33 
Pfister,  R.,   260,   276 
Pfundt,  R.,  82,  94 
Philippov,  G.,  145,  149 
Pichler,  F.,  145,  149 
Pickard,   F.,  449,  456 
Piemcisel,  F.  J.,  260.  278 
Pierce,  W.  D.,  173,  208 
Pieters,  A.  J..  19,  33 
Pinckard,  J.  A.,  181,  208 
Pirschle,  K.,  16.  23,  33,  34 
Plakidas,  A.  G.,  253,  256 


Platz,  G.  A.,  231,  234 

Plehn,  Al.,  462,  473 

Plowright,  C.  B.,   189,  208 

Poisson,  R.,  466,  473 

Polk,   M.,   375,   393 

Pool,  V.  W.,  29,  32,  248,  256,  291, 

294 
Popham,  W.  L.,  169,  208 
Porges,  N.,  15,  34,  72,  93 
Porter,  C.  L.,  280,  281,  295,  480,  489 
Potzelt,  G.,  81,  89 
Pratt,  Clara  A.,  283,  295 
Pratt,  E.  F.,  66,  68 
Pratt,  O.  A.,  437,  440 
Pratt,  R.,  9,  34,  221,  235 
Preuss,  L.  A  I.,  81,  93 
Prevost,  Benedict,  418,  428 
Prill,  E.  A.,  80,  93 
Prince,  A.  E.,  199,  208 
Pringsheim,  E.  G.,  131,  135,  149 
Prin^sheim,  N.,  192,  208 
ProcW,  B.  E.,  172,  208 

Quantz,  L.,  26,  27,  34 

Raciborski,  H.,  29,  34 
Rackemann,  F.  Al.,  388,  393 
Radulescu,  E.,  260,  276 
Raeder,  J.  Al.,  215,  235 
Raistrick,  H.,   18,  34,  69,  70,  74,  75, 

76,  77,  78,  79,  83,  84,  85,  87,  88,  90, 

91,  93,  94,  284,  294,  295 
Ramsbottom,  J.,  364,  393 
Ramsey,  G.  B.,  144,  149 
Rancki  E.  Al,  358,  362 
Rand,  F.  V.,  173,  208 
Randolph,  T.  G.,  388,  393 
Raper,  K.  B.,  80,  93,    146,   149,  398, 

415 
Raper,  J.  R.,  290,  295,  296 
Rathbun,  Annie  E.,  437,  440 
Rathbun-Gravatt,   A.,   214,   225,   235 
Raulin,  J.,  2,  3,  10,  13,  34 
Ravner,   Al.   C,    297,   298,   299,    302, 

303,  304,  307,  308,  311,  315,  316 
Ravss,'T.,  268,  277 
Re',  Fillipo,  417,  428 
Reed,  G.  Al.,  260,  263,  267,  272,  276, 

277 
Reed,  H.  S.,  43,  48,  51,  52 
Reed.  Alerton,  26,  33 
Reed,  Alinnie,  460,  466,  468,  469,  473 
Reid,  R.  D.,  86,  94 


AUTHOR  INDEX 


499 


Reidemeister,  W.,   127,  128,  149 
Reindel,  F.,  82,  94 
Renault,  B.,  481,  489 
Renn,  C.  E.,  470,  473 
Rice,  Mabel  A.,  250,  252,  256 
Richards,  B.  L.,   110,   121 
Richards,  H.  M.,  13,  15,  34 
Richter,  Andreas,  62,  63,  68 
Rinderknecht,  H.,  87,  89 
Rippel,  K.,  23,  34,  219,  235 
Rittenberg,  S.  C,  171,  208 
Rixford,  E.  E.,  365,  368,  393 
Robbins,  W.  J.,  21,  22,  25,  26,  27,  28, 

34,  156,  157,  164 
Roberg,  Max,   10,   11,   13,   15,  24,  34 
Roberts,  L.,  390,  393 
Rodenheiser,    H.   A.,   260,   267,   274, 

277,  321,  336 
Rohrman,  E.,  25,  36 
Rolfe,  F.  W.,  341,  363 
Rolfe,  R.  T.,  341,  363 
Rose,  C.  S.,  289,  296 
Rosen,  H.  R.,  215,  235 
Rosenbaum,  J.,  245,  256 
Rosendahl,  R.  O.,  308,  315 
Rotini,  O.  T.,  66,  61 
Ruben,  S.,  19,  32,  436,  439 
Ruggles,  A.  G.,  173,  209 
Rumbold,  Caroline  T.,  452,  457 
Russell,  E.  J.,  429,  432,  440 

Sabouraud,    A.,    366,    367,    380,    382, 

383,  384,  393 
Saccardo,  420 
Salmon,  E.  S.,  252,  256,  260,  262,  263, 

277,  483,  489,  403,  415 
Salvin,  S.  B.,  168,  208 
Sampson,  K.,  305,  316 
Sando,  C.  E.,  245,  256 
Sanford,  G.  B.,  281,  286,  296 
Sansome,  E.  R.,  139,  146,  150 
Sarkar,  S.  N.,  46,  51 
Sass,  J.  E.,  328,  329 
Satoh,  S.,  289,  296 
Saunders,  D.  H.,  4,  15,  19,  25,  33 
Savastano,  G.,  285,  291,  296 
Savulescu,  T.,  268,  277 
Sawyer,  W.  H.,  113,  121,  184,  208, 

444,  457 
Scales,  F.  M.,  435,  440 
Schade,  A.  L.,  4,  19,  20,  22,  34 
Schaffnit,  E.,  160,  161,  164 
Schatz,  Albert,  87,  94 


Scheffer,   T.  C,   112,    116,    117,    121, 

162,  164 
Scherfel,  A.,  461,  473 
Scheuer,  Z.,  8,  9 
Schleisinger,  H.,  350,  363 
Schloesing,  T.,  429,  440 
Schmitt,  C.  G.,  328,  329,  331 
Schmitz,  H.,  47,  52,  281,  291 
Schneiderhahn,  F.  J.,  169,  208 
Schneider-Orelli,  Otto,  104,  121 
Schober,  R.,  24,  34 
Schopfer,  W.  H.,  26,  28,  34 
Schopmeyer,  H.,  289,  296 
Schreiber,  F.,  260,  277 
Schroeter,  G.,  361,  363 
Schroter,  J.,  257,  275,  277 
Schwann,  Theodor,  54,  68 
Schweinitz,  L.  D.  de,  189,  206 
Seaver,  F.  J.,  404,  405,  415 
Seward,    A.   C,   477,   479,   480,   485, 
487,  489 

Sevmour,  A.  B.,  412,  415,  444,  457 

Shapovalov,  M.,  99,  118,  120 

Sharp,  D.  G.,  141,  142,  150 

Shear,  C.  L.,  321,  338 

Sherman,  H.  C,  159,  164 

Sherrick,  J.  L.,  341,  362 

Sherwood,  E.,  155,  165 

Shibasaki,  Y.,  260,  268,  278 

Shoup,  C.  S.,  19,  23,  36,  64,  68 

Shrewsburg,  J.  F.  D.,  377,  393 

Shumwav,  C.  P.,  267,  278 

Sideris,  C.  P.,  159,  165 

Siebenauger,  H.,  73,  89 

Siggers,  P.  V.,  102,  120 

Simonart,  P.,  75,  93 

Sing-Fang,  F.,  28,  33 

Smart,  R.  F.,  225,  285 

Smedley-McLean,  Ida,  80,  94 

Smith,  C.  E.,  368,  391 

Smith,  D.  T.,  365,  391 

Smith,  E.  F.,  417,  428 

Smith,   Elizabeth   C,    125,    138,    143 
150,  218,  235,  397,  398,  415 

Smith,  F.  B.,  431,  432,  433,  440 

Smith,  F.  F.,  175,  208 

Smith,  G.,  76,  87,  88,  91,  93,  94 

Smith,  H.  S.,  450,  457 

Smith,  J.  Henderson,  45,  52,  226,  235 

Smith,  P.  E.,  216,  217,  234 

Smith,  R.  E.,  237,  256,  264,  265 

Snell,  E.  S.,  28,  36 


500 


AUTHOR  INDEX 


Sparrow,  F.  K.,  460,  461,  462,  466, 

470,  473 
Spaulding,  P.,  214,  225,  235 
Speare,  A.  T.,  444,  445,  450,  457 
Speg^azzini,  C,  454,  457 
Stacey,  M.,  88,  91 
Stager,  R.,  260,  277,  356,  363 
Stahl,  E.,  307,  316 
Stakman,  E.   C,    169,    170,   208,   260, 

262,    265,   271,   274,   277,   278,   327, 

329,  330,  331,  332,  338 
Stanier,  R.  Y.,  471,  473 
Stanton,  T.  R.,  260,  276 
Stcenbock,  H.,  81,  82,  91,  93 
Steinberg,  R.  A.,  4,  10,  11,  13,  14,  15, 

16,  18,  21,  22,  35,  83,  94 
Steiner,  J.  A.,  260,  278 
Stephanov,  K.  M.,  172,  209 
Stern,  K.  G.,   11,  35 
Stevens,  F.  L„  144,  146,  150 
Stevens,  N.  E.,  Ill,  122 
Stevenson,  J.  A.,  401,  414 
Stirrup,   M."  459,  473 
Stock,  F.,  218,  223,  235 
Stoll,  A.,  359,  363 
Stone,  R.  W.,  86,  92 
Strassber^er,  L.,  361,  363 
Strong,  F.  M.,  80,  94 
Studhalter,  R.  A.,  173,  209 
Sutherland,    G.    K.,    460,    468,    469, 

470,  473 
Swabev,  Alarjorie,  260,  277 
Sweet,'  H.  R.,  99,  111,  122 
Sweetman,  H.  L.,  448,  450,  457 

Takahashi,  R.,  432,  440 
Talice,  R.  V.,  377,  387,  392 
Talley,  P.  J.,  7,  35 
Tamiva,  H.,  20,  35,  65,  68 
Tate,' P.,  364,  385,  386,  389,  390,  393 
Tatum,  E.  L.,  70,  83,  94,  325,  338 
Tauber,  H.,  28,  52 
Tausson,  W.  O.,  21,  35 
Taylor,  C.  B.,  286,  295 
Ternetz,  C,  24,  35 
Thatcher,  F.  S.,  247,  256 
Thaxter,  R.,  444,  457,  466,  473 
Thavsen,  A.  C,  50,  52 
Thelen,  H.,  70,  90 
Thenard,  Louis  Jacques,   54,  68 
Thimann,  K.  V.,*  290,  295 
Thorn,  Charles,  71,  74,  91,  92,   398, 
415 


Thomas,  A.  C,  159,  164 
Thompson,  A  I.  R.,  359,  363 
Timofeeva,  A.  G.,  73,  90 
Tisdale,  W.   H.,  240,  256,  260,  266, 

279,  406,  415 
Tiukow,  D.,  71,  73,  79,  90,  91 
Tochinai,  Y.,  18,  35 
Todd,  R.  A.,  369,  393 
Togashi,  K.,  260,  268,  278 
Ton:,  C.  J.  du,  376,  394 
Toursel,  D.,  30,  33 
Truog,  E.,  438,  440 
Tsaugi,  H.,  223,  226,  230,  235 
Tschesnokow,  W.,  72,  92 
Tulasne,  Al.  R.,  356,  363 
Tyler,  L.  J.,  264,  278 

Ukkelbergr,  H.  G.,  172,  209 
Uphof,  J.  C.  Th.,  453,  454,  457 
Uppal,  B.  N.,  230,  235 

Valleau,  W.  D.,  246,  256,  264,  275 
Yerujskv,  D.,  388,  394 
Yigneaud,  V.  du,  289,  296 
Yolkonskv,  A  I.,  4,  36 

Waksman,  S.  A.,   16,  36,  38,  52,  76, 

87,  94,  280,  296,  429,  430,  431,  432, 

433,  434,  435,  436,  439,  440,  441 
Walker,    J.    C,    110,    122,    223,    235, 

245,  255 
Walker,  Leva  B.,  203,  205,  209 
Ward,  G.  E.,  15,  16,  32,  80,  92,  94 
Ward,    H.    Alarshall,    169,   209,   236, 

256,  262,  278 
Ward,  J.  L.,  87,  89 
Wassiljew,  G.,  15,  36 
Waterhouse,   W.   L.,   240,   244,   256, 

260,  266,  269,  271,  278 
Waterman,  H.  I.,  16,  31 
Watson,  J.  R.,  449,  457 
Wptterson,  A.,  15,  36 
Webb,  R.  W.,  155,  158,  165,  229,  235 
Weber,  N.  A.,  453,  454,  457 
Weetman,  L.  M.,  215,  235 
Wehmer,  C,  3,  13,  36,  70,  71,  72,  75, 

76,  94 
Wehmever,  L.  E.,  405,  415 
Weidcnhagen,  R.,   38,   52,  63,  67 
Weimer,  J.   L.,    18,   36,  48,   51,    102. 

122,  187,  192,  209,  224.  235,  260,  275 
Weindlin?,    R.,    280,    281,    284,    287, 

296 


AUTHOR  INDEX 


501 


Weiss,  F.  E.,  480,  487,  489 
Weiss,  Freeman,  175,  208 
Wellman,  F.  L.,  110,  122,  223,  235 
Wells,  P.  A.,  78,  92 
Welsford,  E.  J.,  238,  240,  254 
Wenck,  P.  R.,  19,  22,  36,  80,  93 
Werkenthin,  F.  C,  430,  433,  441 
Werkman,  C.  H.,  39,  52 
Weston,  W.  H.,  Jr.,  168,  180,  209 
Wev,  H.  G.  van  der,  131,  135,  150 
Wheeler,  W.  M.,  454,  457 
Whetzel,  H.  H.,  417,  422,  428 
Whiffen,  Alma  J.,  436,  441 
Whitaker,  T.  W.,  423,  428 
White,  Mollie  G.,  77,  94 
W7hitford,  A.  C,  485,  486,  489 
Wieland,  G.  R.,  485,  489 
Wilcox,  M.  S.,  321,  322,  338 
Wilcoxon,  Frank,  212,  234 
Wildiers,  E.,  24,  36,  288,  296 
WTilhelm,  P.,  260,  278 
Wilkins,  W.  H.,  88,  94,  95 
Willaman,  J.  J.,  48,  51,  77,  92,  94 
Williams,  R.  J.,  4,  15,  19,  25,  27,  28, 

33,  36,  66,  68,  289,  296 
Wilson,  G.  W.,  436,  440 
Wingard,  S.  A.,  423,  428 
Winge,  O.,  469,  472 
Wise,  Fred,  388,  394 
Wober,  A.,  145,  149 
Wolf,  D.  E.,  28,  32 


Wolf,  Frederick  A.,  108,  111,  113, 
122,  126,  128,  150,  170,  173,  176, 
209,  264,  265,  278,  292,  296,  321, 
338 

Wolf,  Fred  T.,  19,  23,  36,  64,  68, 
176,  209,  264,  265,  278,  432,  441 

Wolf,  Jack,  388,  394 

Wolff,  L.  K.,  11,  14,  36 

Wolpert,  S.,  155,  156,  157,  158,  162, 
165 

Worley,  C.  L.,  12,  13,  36 

Wright,  Ernest,  452,  457 

Wright,  E.  P.,  460,  473 

A\ Yckoff,  R.  W.  G.,  146,  150 

Yao,  K.  F.,  377,  378,  393 
Yarwood,  C.  E.,  136,  150,  243,  256 
Young,  E.  L.,  470,  473 
Young,  H.  C,  4,  7,  22,  36 
Young,  H.  E.,  311,  316 
Young,  P.  A.,  243,  256 
Yuill,  J.  L.,  77,  95 

Zalewski,  A.,  200,  209 
Zebrowski,  George,  480,  489 
Zeller,  S.  M.,  47,  52,  281,  296,  461, 

473 
Ziegenspeck,  H.,  187,  209,  218,  235 
Zillig,  H.,  260,  278 
Zimmerman,  A.,  356,  363 
Zwetkoff,  E.   S.,  69,  73,  82,  86,  92, 

352,  362 


SUBJECT  INDEX 


Abies,  406 

firma,  303,  315 
Abortion,  358 
Absidia,  107,  431 

ramosa,  26 
Acacia,  407 

Acanthorhynchus  vaccinii,  143 
Acer,  403 

trilobatum,  482  * 
Acetaldehyde,  58,  59,  60,  62,  77, 
Acetic  acid,  49,  55,  56,  60,  71,  73, 

75,  268,  283 
Achlya,  4,  180 

ambisexnalis,  290 

bisexualis,  290 

Carolinian  a,  431 

conspicua,  4 

penetrans,  459 

prolifera,  18 

raceinosa,  18,  168 
Achorion,  381,  382 

gypsenm,  106,  385,  386,  389 

?miris,  389 

qninckeannm,  388 

schoenleinii,  366,  388,  389,  390, 
Acidity,  151 
Acmea,  469 

digitalis,  468 

jenestrata,  468 

I'nnatula,  468 

peltata,  468 

scabra,  468 

scutum,  468 
Aconitic  acid,  73,  163 
Acremonites  succineus,  486 
Acremonium,  444 
Acrovtyrex,  453 

disciger,  452 

/////J/',  452 
Acrostalagmus,  431 
Acrotheca,  372 


81 

74, 


394 


Actinomucor  repens,  453 
Actinomyces 

bovis,  373-375,  374,  392 

chromogenus,  161 

hominis,  375 

israeli,  375 

praecox,  286 

scabies,  286,  296 
Actinomvcetes,    280,    313,    365,    430, 

43  i 
Actinomycosis,  145,  366,  373-375 
Activated  hexoses,  59 
Active  acidity,   151 
Aecidhim  symphyti,  200 
Aegerita,  449 

webberi,  449,  450 
Aerobic  respiration,  56,  58 
Aesculus,  403 
Aestatic  fungi,  161 
Aethalium  septicnm,  104,  107 
Agar,  471 

Agaricaceae,  98,  286,  486 
Agaricites  Wardiamis,  486 
Agarics,  86,  408 
Agaricus,  454 

campestris,  58,  75#,  352 

terviitigina,  454 
Age  of  fossil  fungi,  477-478 
Agriolimax  agrestris,  176 
Agropyron,  335 
Agrostis  alba,  358 
Air  currents  in  spore  dispersal,  168- 

171 
Alanine,  22,  23,  64 
/3-Alanine,  25,  325 
/4/rtna  fistnlosa,  461,  472 
Albinism,  264 
Albugo,  211 

Candida,  181,  223,  230,  260,  268,  278 

Candida  macrospora,  268 

Candida  microspora,  268 


*  An  italic  numeral  indicates  that  the  page  contains  an  illustration  or  a 

table. 

502 


SUBJECT  INDEX 


503 


Albugo 

ipomoeae-panduranae,  260,  274 

tragopogonis,  260 
Alcohol,  20,  54,  55,  56,  58,  59,  60,  61, 
62,  63,  69,  72,  75,  77,  268,  280, 
283 
Alethopteris  aquilina,  481 
Aleuria 

re  panda,  190 

vesiculosa,  135,  190 
Aleurodiscus  poly  gonitis,  328 
Aleurospores,  381,  382 
Alewife,  463 

Aleyrodes  citri,  447,  456 
Algae,  468,  488 

blue-green,  429 

green,  429 
Alkaloids,  45,  350,  358,  359 
Allium  cepa,  165 
Allomyces 

arbuscula,  19,  22,  64,  399,  431 

cystogenus,  19,  64,  431 

javanicus,  19,  64,  84,  431 

kniepii,  26,  27,  34 

moniliformis,  19,  64,  84,  431 
Alnus  cordata,  451 
Altemaria,    104,    141,    170,    171,   373, 
431,  448,  452  . 

citri,  20 

maritima,  470 

solani,  175,  218,  223,  111 

tenuis,  23 
Althea,  401 

Alwisia  bombarda,  397 
Amanita,  343,  341 

caesarea,  340,  409 

chlorinosoma,  350 

citrina,  302,  350 

cremdata,  350 

mappa,  312,  350 

jnorrisii,  350 

muscaria,    85,    158,    302,    312,    342, 

344,  345,  347,  350,  351,  409 
pant  her  ina,  312,  342,  351 
phalloides,  340,  341,  342,  343,  344, 

345,  350,  362 
porphyria,  350 
radicata,  350 
rubescens,  302,  343 
spreta,  344 
strobiliformis,  350 

wm,  341,  342,  344,  345,  350 
wwa,  341,  342,  344,  350 


Amanita-toxin,  350 
Amanitin,  350 
Amanitopsis 
strangulata,  345 
vaginata,  201,  302 
volvata,  350 
Amber,  478,  479,  483,  484,  485,  486 
Ambrosia  beetles,  451 
Ambrosia  fungi,  451^52 
American    Phytopathological    Soci- 
ety, 421 
Amidase,  48 
Amino  acids,  22,  83,   289,   325,   331, 

390,  436 
Ammonia,  21,  22,  23,  283,  390,  436, 

437 
Ammonification,  436 
Ammonium  chloride,  282,  288 
Ammonium  tartrate,  282 
A?nphisphaeria  posidoniae,  466,  469 
Amphisphaeriaceae,  484 
Amyelon  radicans,  482,  487,  489 
Amvgdalase,  40 
Amvgdalin,  49 

Amylase,  38,  42,  45,  46,  41,  159 
Anaerobic  respiration,  56-62 
Anellaria,  176 
Angiosperms,  477 
Angstrom  unit,  123 
Anisochytridiales,  462 
Anisolpidiaceae,  461 
Anisolpidium  ectocarpii,  461,  472 
Annulus,  343,  344,  347 
Anopheles,  444 
Antagonism,  279,  280-287 
Anthostromella  destruens,  143 
Anthracene  pigments,  390 
Anthracnose,  108,  109,  179 

bean,  179,  221,  410 

clover,  410 

cotton,  179,  239,  410 

pepper,  239 

watermelon,  410 
Anthracomyces 

cannallensis,  487 

rochei,  487 
Anthrax,  354,  418 
Antibiotic,  279,  427 
Antigens,  423-424 
Antisera,  350 
Ants,  168,  174,  175,  452-454 

leaf-cutting,  451 


504 


SUBJECT  INDEX 


Aphanomyces,  180,  437 

camptostylus,  4 
Aphids,  175,  443 
Aphis,  walnut,  450 

woolly,  173 
Aphis  spiraecola,  450 
Apium  graveolens,  247 
Aplanes,  180 
Apodachlya  brachynema,  4,  19,  20, 

22  ' 
Apple,  48,  54,  103,  143,  163,  170,  225, 

231,  239,  283,  402,  443,  450 
Apple  bitter-rot,  179 
Apple  blotch,  411 
Apple  canker,  173,  174,  411 
Apple-leaf  spot,  411 
Apple  scab,  111,  221 
Apple  sucker,  450 
Appressorium,  238-241,  245,  249,  250, 

253 
Apricot,  246 
Aquatic  fungi,  167-168 
Arabinose,  18,  19,  65,  75,  79,  390 
Arachnids,  172 
Arachnopeziza  cmrata,  190 
Arbuscules,  299,  303 
Arbutus,  trailing,  304 
Archimvcetes,  458 
Arcvria,  397 

Arg'inine,  22.  23,  41,  64,  83 
Armadillidiwn  vulgare,  176 
Arv?illaria,  107 

mellea,  44,  47,  51,  52,  138,  155,  156, 
151,  158,  162,  200-201,  230, 
304,  315,  339 

mucida,  409 

shii-take,  353 
Arsenic,  49,  50,  88 
Arthrospores,  380,  381 
Artichoke,  313  . 
Aschersonia,  444,  449 

aleyrodis,  447,  449 

goldia/ia,  449 
Ascobolus,  291 

crouani,  190 

Je  mid  at  its,  135 

magnificus,  135 

stercorarins,  135,  190 
Ascochyta,  4 

fagopyrmu,  224 

graminis,  281 

pisi,  178,  410 


Ascomycetes,  186-193,  227,  302,  303, 
318,  321-325,  365,  402-405,  431, 
444,   451,   458,   459,   460,   466- 
468,  481-485 
Ascophyllum  nodosum,  469 
Ascospora 

beijerinckii,   192 
ruborwn,  192 
Ascotricha,  191 
Asparaginase,  46,  41 
Asparagine,  22,  23,  64 
Aspartic  acid,  22,  23,  25,  41,  64 
Aspen,  397 

Aspergillaceae,  436,  483 
Aspergillic  acid,  87 
Aspergillosis,  379 

Aspergillus,  3,  50,  86,  107,  268,  373, 
388,  431,  435,  444,  470 
chmamomeus,  74 
clavatus,  72,  87,  89,  126,  121,  128, 

129,  289,  296 
effusus,  78 
elegans,  79 

fischeri,  19,  22,  36,  80,  91,  93 
flavus,  14,  21,  33,  49,  77,  78,  87,  92, 

95,  282 
flavus-oryzae,  77,  94 
juvtarkus,  15,  16 
juviigatus,  87,  93,  379 
glaums,  11,  84,  91,  291,  430 
itacouicus,  73 
vielleus,  141 
nidulans,  79 

niger,  2,  4,  5,  6,  11,  13,  14,  15,  16, 
17,  18,  21,  22,  23,  24,  29,  31,  32, 
33,  34,  35,  36,  45,  50,  51,  58, 
70,  72,  74,  75,  77,  79,  80,  81, 
82,  83,  88,  89,  90,  91,  92,  93, 
94,  106,  108,  121,  143,  155,  229, 
280,  281,  283,  289,  290,  296, 
432,  433,  438,  440 
ochraceus,  71 
oryzae,   11,  20,  31,  35,  49,  65,  78, 

81,  82,  155,  159 
parasiticus,  72,  78,  450 
sydotvii,  80,  82,  88,  94 
tamarii,  77-78 
terreus,  16,  146,  149 
terricola,  155,  436 
uvibrosus,  291 
versicolor,  21,  32 
z-iolaceus-fuscus,  71 
virescens,  88 


SUBJECT  INDEX 


505 


Aspergillus  wentii,  78,  79 
Associative     effects     among     fungi, 
279-296 
antagonism,  280-287 
causes,  282-285 

evidence  from  cultures,  280-282 
evidence   from   growth   in   host 

tissues,  285-286 
evidence  in  soils,  286-287 
general  considerations,  292-293 
stimulation,    by    associative    inter- 
action, 287-292 
of    reproductive    activity,    289- 

290 
of    vegetative    activity,    288-289 
svnergetic  reactions,  290-292 
Aster  yellows,  172 
Asterina,  483 

Astreptonema  longispora,  466,  472 
Athlete's  foot,  380 
Atropin,  351 
Atta 

cephalotes,  453,  457 
sexdens,  453 
Aurantin,  84 
Auroglaucin,  84 
Autodigestion,  50,  202 
Auxins^O,  288,  308 
Avena 

barbata,  272 
sativa,  215 
Canadian,  272 
Markton,  272 
Navarro,  272 
Victoria,  272 
Aversion,  282,  284 
Azalea,  175 
Azotobacter  chroococcum,  24 

Bacillus  anthracis,  87 

Bacteria,  280,  281.  292,  398,  429,  430, 

434,  448,  458,  470,  471,  477 
Badhamia,  397,  398 

panicea,  211 

utricularia,  211 
Balanus,  469 

glandidosa,  468 
Baltic  amber,  478 
Banana,  412 
Barberry,    166,    169,    245,    266,    271, 

334,   376,   419 
Barber's  itch,  380 
Barium,  3 


Barley,   145,  262,  263,  269,  303,  355, 
359,  360,  361 

scab,  359-361 

stripe,  410 
Barnacles,  468 
Basidiobolus  ranarum,   22,    174,   185, 

207,  208 
Basidiomycetes,    194-205,    302,    318, 
325-335,  405-410,  431,  436,  458, 
485-486 
Basisporiwn  gallarum,  291 
Beans,    109,   221,   224,   239,   242,   243, 

402,  410 
Beauveria,  444 

bassicma,  445,  446-441,  449 

globtdifera,  445,  449 
Beech,  173,  305,  307 
Beer,  54 
Bees,  168,  173,  443 

bumblebees,  175 

carpenter,   175 

honev,  174,  175 
Beetles,"  168,  172,  443,  445,  466 

ambrosia,  451 

and  fungi,  451^52 

bark,  451 

Colorado  potato,  174 

engraver,  451 

flea,  174,  449 

longicorn,  173 

May,  173,  445 

scarabeid,  174 
Beets,  172,  179,  313 

curly  top,  172 

leaf  spot,  410 

sugar,  179 
Begonia,  241 

Beinesia  gossipiperda,  172 
Benzol,  427 
Berberis,  246 

vulgaris,  240,  256 
Beryllium,  16 
,  Betida  alba,  302 
Bicarbonates,  283 
Biocatalysts,  11 
Biochemistry,  69-95 

amino  acids,  83 

citric  acid,  71-74 

ethyl  acetate,  77 

ethyl  alcohol,  77 

fats,  79-81 

fumaric  acid,  75 

gluconic  acid,  74-75 


506 


SUBJECT  INDEX 


Biochemistry,  glycerol,  77-78 

implications,  88-89 

kojic  acid,  78 

lactic  acid,  76-77 

malic  acid,  76 

mannitol,  79 

organic  acids,  70-79 

other  metabolic  products,  86-88 

oxalic  acid,  70—71 

pigments,  83-86 

polysaccharides,  79 

sterols  and  vitamins,  81-82 

succinic  acid,  76 
Biological    control    of    insects,    442, 

448-450 
"Bios,"  24,  25,  288,  289 
Biotic   factors   in   geographic   distri- 
bution, 396 
Biotin,  25,  26,  28,  288,  289 
Birds,  176 

Bitter-rot  of  apple,  239 
Black  root-rot  of  tobacco,  105,  109, 

161,  246 
Black-shank  of  tobacco,  178 
Black  spot  of  roses,  248 
Blackberry,  250,  253 
"Black-feliow's  bread,"  352 
Blakeslea  trispora,  166,  401 
Blastocladiales,  444 
Blast ocladiella  variabilis,   26,    27,    34 
Blastomyces  dennatitidis,  369 
Blastomycosis,  366,  368,  369 
B  let  ill  a/ 312 

hyacintbia,  310 
Blissus  leucopterus,  445,  449 
Blister  rust,  285,  420 
Blodgettia  confervoides,  470 
Blue  grass,  258 
Blue  stain,  162,  174,  372,  443 
Bodinia,  384 
Boletaceae,  409 
Boletes,  86 
Boletol,  86 
Boletus,  341,  349 

bad  ins,  303 

cbrysemeron,  302 

cyanescens,  302 

edulis,  82,  352 

elegans,  303 

felleus,  201 

fiavidus,  312 

gramdatus,  303 

lurid  its,  86,  348,  351 


Boletus 

luteus,  302,  303 

viineato-olivaceus ,  343,  348 

sat  anus,  86,  343,  348,  351 

scaber,  302,  352 

strobilaceus,  86 

variegatus,  303 

viscidus,  312 
Bordeaux  mixture,  243,  401,  420,  449 
Boron,  10 
Bostrychus,  485 
Botrychium,   299 

Botryosphaeria  ribis,  264,  265,  278 
Botrytis,    15,  48,    106,    143,    182,   216, 
243,  268,  291,  431,  437 

anthopila,  443 

bassiana,  445 

cinerea,  4,  18,  25,  29,  45,  48,  104, 
128,  149,  151,  155,  226,  227, 
229,  231,  235,  237,  238,  240, 
242-244,  247,  254-256,  264,  265, 
270,  273,  275,  281,  283 

sporoidewn,  435 

vulgaris,  224,  242 
Brachysporhnn  trifolii,  264,  273 
Brassica,  241 
Brevilegnia  diclina,  431 
"Bridging  host,"  262,  263 
Bromatia,  452,  453 
Brome  grasses,  262 
Brovnis,  335 

conmiutatus,  262 

hordeaceus,  262 

racemosus,  262 
Brown  rot,  of  peaches,  115,  173,  246 

of  stone  fruits,  443 
Brown  spot  of  pines,  179 
Brown  rot  of  woods,  44 
Bryophyta,  299 
Bryopsis  pluvwsa,  461,  462 
Bryozonns,   137 
Buckwheat,  224,  242 
Budding,  211,  212 
Bucrs,  443 

Burmanniaceae,  298 
Butterflies,  cabbage,  444 
Butyric  acid,  49,  55,  283 
Buxbaumia,  299 
Byssocblainys  fulva,  94 

Cabbage,  242,  398 
blackleg,  173,  410,  443 
club  root,  160,  161 


SUBJECT  INDEX 


501 


Cabbage,   maggot,  173 

yellows,  109,  110 
Cadophora,  452 

americana,  372,  393 
Caenomyces  sapotae,  487 
Caeoma  nit  ens,  174 
Caesium,  3 

Calcium,  3,  4-5,  7,  10,  438 
Calcium  carbonate,  10,  11,  70,  71,  75, 

76,  478 
Calcium  oxalate,  71 
Calhtna  vulgaris,  304 
Caloscypha  fid  gens,  190 
Calvatia  gigantea,  166 
Cambrian  period,  477,  481 
Camellia,  205 
Camembert  cheese,  49 
Canada  balsam,  479 
Candida,  89,  377-379 

albicans,  318 

tropic  alls,  378 
Cannizzaro  reaction,  59,  77 
Cantharelhis 

ci bar ins,  82,  352 

clavatus,  82 

floccosus,  303,  315 
Capnodiaceae,  254 
Capric  acid,  20,  49 
Caproic  acid,  49 
Carbohvdrases,  50 

Carbon'  dioxide,   53,   54,   55,   59,   60, 
61,   62,   69,    116-117,   210,   231, 
435,  436,  459 
rCarbon  monoxide,  65 
Carbon  requirements,  17-21,  213 
Carboniferous  period,  477,  483,  485, 

486,  487 
Carboxylase,  57,  59,  217,  218 
Carboxvpolypeptidase,  41 
Cardinal    temperatures,    96,    97-103, 

221,  222,  223,  224,  225,  226 
Carlic  acid,  88,  163 
Carlosic  acid,  88,  163 
Carnation-bud  rot,  173,  377 
Carolic  acid,  88,  163 
Carolinic  acid,  88 
Carotene,  82,  84,  182 
Carotinoid  pigment,  134 
Carrionia,  372 
Carrots,  *03,  313 
Caryophyllia  smithii,  459 
Casein,  390 
Cassava,  401 


Castagnea  chordariaeformis,  469 
Castanea 

dentata,  404 

mollisima,  404 

vesca,  302 
Castor  bean,  242 
Catalase,  12,  40,  41,  45,  46,  41 
Catalysts,  37-38,  61 
Catechol,  44 
Catenophora  pruni,  211 
Catenularia,   171 
Caterpillars,  444 
Cats,  366,  376 
Cattle,  176,  366,  367,  374 
Cattleya,  303,  310 
Cecidomvid,   174 
Cedar,  170,  404 
Celery  blight,  410 
Cellobiose,  19,  65 
Cellulase,  40,  45,  46,  41,  292 
Cellulose,  19,  44,  50,  435,  436,  437,  460 
Cellulose  acetate,  479 
Cenangiaceae,  484 
Cenangites  piri,  484 
Cenangium,  484 
Cenozoic  era,  478 
Cephalosporium,  171,   178,  444 

acremonium,  243 

lecanii,  446^41 
Cephalothecium,  170,  431 

roseum,    104,    127,    223,    225,    226, 
229,  287,  294,  436 
Ceramium 

diaphanunu  461 

rubrum,  461,  466 
Ceratostomella,  137 

ampullacea,  188,  193 

coerulea,  99 

fimbriata,   191 

ips,  99,  452 

piceaperda,  452 

pilifera,  99,  443,  452 

pint,  452 

phirianmdata,  99,  452 

pseudotsugae,  452 

uhni,  174,  177,  404,  443,  452 
Cercospora,  4 

beticola,  179,  250,  256,  410,  411 

daizu,  410 

per  sonata,  170,  173 

salinia,  470 
Cercosporella  rubi,  253 
Cercosporites,  482 


508 


SUBJECT  INDEX 


Cereals,  354,  386 

Cert  hi, i  familiar  is  americana,  176 
Ceuthospora  limit  at  a,  143 
Chaetocladhem,  240 

brefeldii,  26 
Chaetomella,  143 
Chaetomiaceae,  484 
Chaetomites  intricatus,  4S4 
Chaetomhtm,  50,   146,   191,  373,  484 

cocblioideSj  148 

kunzeanum,  435 
Chaetosphaerites  bilycbnis,  4S 2,  484 
Cbamaecy  parts  thyoides,  405 
Charcot."  283 
Chemotherapy,  427 
Chemotropism,  241,  242,  243 
Cherries,  54,  246,  411 
Chestnut  blight.    111,    170,    177,  404, 

420,  445 
Chili,  401 

Chinch  bug.  445,  449 
Chi-square  test,  213 
Chiti/i,  253,  4"1 
Chlaniydospores,  329,  330,  380,  381, 

J  82 
Chloroform,   214 
Chlorospleuiuni     aeruginosum,      85, 

190,  452 
Choanephora  cucurbit  arum,  26,  401 
Choline,  350,  361 
Chondrus  cr is  pits,  469 
Chromaphis  juglandicola,  450 
Chromium,   16 

Chromoblastomvcosis,   370-3 "2 
Chromosome  maps,  323 
Chrvsogenin,  284 
Chrysophlyctis  endobiotictmi,  145 
Chymotrypsin,  41 
Chytridiaceae,  286 
Chytridiales,  180,  460,  462 
Cbytridium 

alarhtm,  461,  472 

codicola,  461 

polysiphoniae,  461,  462 
Chytrids,  456,  460,  461,  462,  466,  481 
Cicada,  445 

Cicadula  sex not.it a,  172 
Cicirmobolus  cesatii,  285 
Ciliaria  scutellata,  135,  190 
Citric  acid,  13,   15,   19,  20,  69,  71-74, 

75,  76,  79,  88,  214,  280 
Citrinin,  B3-84 


Citromyces 

glaber,  71 

pfefferiammi,  71 
Citromycetin,  83-84 
Citrus, '20,  49,  77,  163,  282,  285,  291, 
292,  402,  449 

melanose,  269,  402,  449 

scab,  269,  411 
Cladobotryum,  444 
Cladochvtriaceae,  481 
Cladospites 

bipartitus,  486 

fasciculatus,  486 

oligocaemcum,  486 
Cladosporhtm,    141,     170,    171,    388, 
431,  448 

algarum,  470 

carpophihtm,  411 

fulvum,    219,    220,    235,    291,    388, 
410 

herb  arum,  283,  435 

myrmecophilum,  452 
Clamp  connections,  325,  328 
Clasterosporium,  76,  78 
Clavacin,  87 
Clavaria 

cormculatus,  158 

rugosa,  158 

turbinata,  485 
Clavariaceae,  485 
Clavatin,  87 
Claviceps 

paspali,  174,  355,  358,  362 

purpurea,   174,  260,   354,   356,  351 \ 
358,  362,  363,  443 
Claviformin,  88 
Cleomis  punctiventris,  445 
Climatic   factors   in  geographic   dis- 
tribution, 396 
Clitocybe 

dealbata  var.  sudorifica,  346,  362 

ill  ltd  ens,    137,    340,    342,    345,    3f1 
409 

laccata,  158 

vi  or  Infer  a,  346 

nebulosus,  346 

sudorifica,  346,  362 
Clonostachys  araucariae,  453 
Clostridium 

pastorianum,  24 

septique,  87 
Clover,  402,  450 

anthracnose,  410 


SUBJECT  INDEX 


509 


Clover-blossom   blight,  443 

Club  root  of  crucifers,  160,  161,  398 

Clupea  harengus,  462,  471 

Coal,  485 

"Coal  balls,"  478,  479,  487 

Coal  Measures,  480,  483,  487 

Cobalt,  16 

Cocarboxylase,  41 

Cocci,  pyogenic,  284 

Coccidioidal  granuloma,  367 

Coccidioides,  370 

immitis,  361,  368,  391,  437 
Coccobacteria  septic  a,  257,  273 
Coccomyces,  49,  252 
Coccospora  agricola,  434 
Codiwn  mucronatum,  461,  473 
Coelomyces  stegomyiae,  444,  456 
Coenzymes,  41^2,  57,  61 
Coffee,  138 
Coffee  rust,   177 
Coleoptera,  173,  174 
Coleosporiaceae,  485 
Coleosporium,  333,  408,  485 

campanulae,  199 

petasitidis,  199 
Colletotrichum,  4,  216,  238,  243,  437 

circinam,  242,  245 

falcatum,  175 

gloeosporioides,  143,  239,  255,  291 

gossypii,  159,  229,  410 

lagenarium,  99,  145,  150,  178,  223, 
410 

lindemtithianum,  99,  109,  178,  179, 
224,  238,  239,  255,  260,  273, 
275,  276,  281,  410 

lint,  35 

nigrum,  243,  281 

phomoides,  145,  149 
Collybia 

albuminosa,  454 

cirrhata,  138 

dryophila,  172,  201 

longipes,  138 

radicata,  158,  409 

tuber  osa,  138 

velutipes,  26,  33,  102,  328,  339,  352 
Colon-tvphoid  organisms,  284 
Colorimetric   method   of  pH   meas- 
urement,  154-155 
Columbium,   16 
Comatrichia,  398 

nigra,  397 
Compositae,  298 


Conifers,  269,  308,  397,  398,  405,  410, 

437,  443,  478 
Coniophora   cerebella,   44,   100,    102, 

155 
Coniothyrium,  144 
Conjugate  nuclear  division,  318 
Copper,  10,  11,  13,  14,  15 
Coprinus,  176,  202 

atramentarius,   158,  200,  339 

comatus,    166,    200,   228,   230,    339, 
351,  352 

ephemerus,  329 

fimetarius,  328 

lagopus,    174,    206,    328,    330,    337, 
338,  450,  455 

micaceus,   158,  228,  230,  339 

plicatilis,  111 

rostrupianus,  328,  338 
Coprophilous    fungi,    176,    177,    182, 

191,  203,  321,  399,  404 
Coral  fungi,  339 
Corals,  459 
Cordyceps,  444,  445 
Corkv  tissue,  247 
Corn;  240,  303,  360,  399,  405 

borer,  445,  450 

ear  rot,  410 

smut,  231 
Cornell  University,  420 
Cornus  sanguined,  403 
Cornutine,  358 
Corticium 

chrysocreas,  102 

coeruleum,  138 

effuscatum,  102 

vagum,   110,   121,  273 
Cortinarius 

bivelus,  302 

calisteus,  303 

collimtus,  302 

multiformis,  302 

proteus,  302 

violaceus,  158,  302 
Cory  his  avellana,  302 
Cosmic  rays,  123,  124 
Cotton,  49,   108,   239,  242,  401,  403, 

410,  412 
Cotton  blue,  248 
Cottonwood,  397,  398 
Cottony  cushion  scale,  447 
Covered  smuts,  272 
Cowpea,  401 
Cozymase,  41 


510 


SUBJECT  INDEX 


Crab,  mole,  464 

mud,  464 

pea,  464 
Crabapple,  411 
Cranberry,  143,  184,  304,  444 
Craterium,  398 
Creeper,  brown,  176 
Cretaceous  period,  477,  485,  486 
Cribraria,  397 
Cricket,  443,  444 

tree,  174 
Cronartium,  333,  406,  408 

asclepiadeum,  199 

ribicola,    169,    174,    176,    177,    207, 
208,    214,    223,    225,    235,    285, 
334,  408,  420 
Crop  rotation,  427 
Crossing-over  percentages,  323 
Crown  rust  of  oats,  170,  215 
Crucifcrs,  398 
Crustacea,  137,  4^4 
Cryptococcus 

fagi,  173,  206 

histolyticus,  368-369 
Cryptovieriopsis  mesozoica,  484 
Ctenoviyces  serratus,  385 
Cucumber,  242 
Cucurbitaria  laburni,  192 
Culex,  444 
Cultivation  of  fungi,  352-353 

bv  insects,  451-454 
Cunoniaceae,  298 
Cupulifereae,  306 
Curculio,  sugar-beet,  445 
Curlv  top  of  beets,  172 
Cuticle,  236,  237,  239,  244,  246,  252 
Cutworms,  445 
Cvanide,  65,  66 
Cyatbus 

'olla,  228,  230 

pallidas,  205 

stercorals,  205 

stricttus,  228 
Cycad,  483 

Cylindrocladium  scopariwn,  2 1 8,  223 
Cyviadotbea  trifolii,  232 
Cvmbidium,  310 
Cvnodontin,  85 
Cvpripedium,  303 
Cystine,  4,  22,  41,  64 
Cystopas  Candidas,  223 
Cystoseira  osvnmdacea,  469 
Cvtase,  40 


Cytochrome,  12,  58,  63 
Cyttaria 

dartvmii,  352 

gunnii,  352 

harioti,  352 

bookeri,  352 
Czapek-Dox  solution,  79,  83,  85,  88 
Czapek's  solution,  3,  229 

Daedal ea,  202,  410 

ambigua,  102 

confragosa,  41,  SI,  155,  151 

flavida,  46 

quercina,  102 

anicolor,  102 
Dahlia,  401 
Daldinia,  191 
Darluca  fihmi,  285 
Djsyscypha 

ellisiana,  404,  415 

virginea,  190 
"Death  angel,"  341 
Debaryomyces 

hormnis,  369 

iieofon/nms,  369 
Decapods,  464 
Dehvdrogenase,  58,  59,  63 
Dematiaceae,  371,  436,  486 
Dematium,  373,  431 

pullulans,  81,  143,  211,  452 
Dendroctomis,  174,  451 
Depazites 

picta,  482 

rabenborsti,  486 
Dermatitis  verrucosa,  371 
Derviatomycetes,  366 
Dennatomycosis,    145,    366,    379-390 
Dermatophytes,  106,  366 
Deuterium  oxide,  221 
Deuteromycetes,  410-412,  486-487 
"Devil's  cigar,"  190 
Devonian  period,  477,  483 
Dewberries,  253 
Dextrin,  19,  64,  386 
Dextrose,  18,  19,  20,  213,  331 
Dhobie  itch,  379-380 
Diacbea,  398 

leucopoda,  217 
Diantbus,  241 
Diaportbe,  137 

citri,  269,  282,  291,  402,  449 

perniciosa,  284,  294 
Diastase,  38,  40,  48,  49,  292 


SUBJECT  INDEX 


511 


Diatrype,  191 

discifor?}iis,  189 
Die ary otic  mycelium,  328,  329 
Dicranophora  fulva,  26 
Dictydiaethalhim  plumbeum,  217 
Dictyophora  phalloides,  138 
Dictyuchus,  4,  168,  180 
Diderma,   398 

Didymella  conchae,  468,  469 
Didymhim,  398 

squamidosum,  211 
Didymosphaeria 

fucicola,  469 

pelvetiana,  469 
Didymosphaerites  bethelii,  485 
Diketoadipic  acid,  74 
Dilsea  edidis,  469 
Dimethylpvruvic  acid,  163 
Dinosaur,  485,  488 
Diplocarpon,  252 

ear  liana,  190 

rosae,  190,  232,  238,  239,  249,  253, 
254 
Diplodia,  143 

natalemis,  20,  22,  99,  116,  291,  452 

tubericola,  18,  29 

zeae,  170,  178,  243,  285,  410 
Diplodina  laminariana,  470 
Diploidization,  333,  450,  451 
Diplosis,  173 
Diptera,  174 

Direct  penetration,  237-248 
Disaccharides,   386,  436 
Discomyces,  375,  403,  404 
Discomycetes,  135,  176,  186,  189-190 
Dissemination  of  spores,   166-209 
Dissociation,  259 
Dogs,  366,  367,  376 
Domestic  animals,  360,  366,  367 
Dominant  characters,  317,  335 
Dormancy,  214,  216 
Dothideaceae,  484 
Dothideales,  466 
Dothidella 

laminariae,  469 

pelvetiae,  469 
Dothidites,  484 
Dothiorella,  4 
Douglas  fir,  452 
Down  mildew,  252,  268,  400 

of  grapes,  420 

of  tobacco,  111,  177,  401,  427 
"Drop-excretion  mechanism,"   194 


Dryobates  pubescens  medianus,   176 
Dulcitol,  78 

Dutch    elm    disease,    174,    177,    404, 
443 

Earth,  age  of,  475,  476 

Earthworms,  137 

Eccrinales,  466 

Eccrinid,  465 

Eccrinopsis  hydropilorum,  466 

Echinodontium  tinctorium,  41,  52 

Ecology,  279 

Ectoascus,  192 

Ectocarpus,  460 

v  lite  hell ae,  461 

silicnlosiis,  461 
Ectoparasites,  253-254 
Ectosymbiosis,  451,  454 
Ectotrichophyton,  384 

jelinetim,  384 

mentagrophytes,  384 
Ectotrophic    mvcorrhiza,    299,    300, 

309 
Edaphic   factors   in  geographic   dis- 
tribution, 396 
Edible  fungi,  339-363 
Eel  grass,  460,  470 
Eidamia 

catemdata,  11 

viridescens,  11 
"Einfach  Alykorrhiza,"  299 
Elaphoviyces  gramdafiis,   303,   307 
Electrometric   measurement   of  pH. 

154-155 
Elegans,  section  of  Fusarium,  264 
Elephantiasis,  443 
Elm,  404,  452 
Elyimis,  335 

canadensis,  358 
Enierita  talpoida,  464 
Emmer,  250 

Vernal,  271,  335 
Empitsa  lecanii,  445,  456 
Emulsin,  40,  42,  45,  46,  41,  48 
Endemism,  396,  400-401,  402-408 
Endoascus,  192 
Endocarditis,  375 
Endoconidiophora 

coerulescens,  452 

moniliformis,  452 
Endo  derm  ophy  ton,  383,  384 

concentricnm,  384 
Endo?nyces  v emails,  80 


512 


SUBJECT  INDEX 


Endomvcetaceae,  370 

Endomycetales,  80 

Endophyllum   euphorbiae-sylvaticae, 

199 
Endosvmbiosis,  454 
Endothia    parasitica,    111,    122,    170, 
173,    176,    177,    187,   189,    193, 
207,   404,   420,  443 
Endotrophic    mvcorrhiza,    299,    301, 

304,  309 
Enteridiitm  olivaceum,  211 
Enterobryus,  464,  465 

compressus,  466 
Enteromorpha  minima,  469 
Entoloma,  345 
livid  urn,  343,  348 
rhodopoliunu  312 
sinuatwn,  348 
F.ntomogenous  fungi,  444-448 
Entomophthora,  185,  448 
chromaphidis,  450 
fresenii,  450 
grylii,  444 
lecanii,  445 
muscae,  184,  444 
pseudococci,  444 

sphaerosperma,  113,  184,  208,  444, 
450 
Entomophthorales,  185,  444 
Entyloma 
linariae,  197 
lobeliae,  197 
nienispcrmi,  197 
Enutotrichophvton,  5<9-/ 
Enzymes,    37-52,    55,    159,    237,   238, 
283,  285,  389,  416 
chemical  properties,  39-41 
classification,  39 
coenzymes,  41-42 
general  considerations,  50 
in  decay  of  fruits  and  vegetables, 

48  ' 
influence  of  reaction,  temperature, 

and  time,  42 
methods  for  detection,  43 

of  wood-destroving  fungi,  43-48 
other  activities,  49-50 
production  hv  fungi,  43 
specificity,  42 
Eocene  period,  478,  483,  487 
Epicoccwn  marhimum,  470 
Ipicridnceae,  298 
Epidermis,  252 


Epidermophvtid,  387 
Epidermophyton,  381,  383,  384 

floccosiim,  384 
Epigaea  repens,  304,  314 
Kpipactis,  310 
Epitrix  cucumeris,  174 
Eremascaceae  Imperfectae,  377 
Erepsin,  40,  46,  41 
Ereptase,  48 
Ergobasine,  359 
Ergometrine,  359 
Ergosterol,  80,  81 
Ergostetrine,  359 
Ergot,  354-359,  443 
Ergotinic  acid,  358 
Ergotinine,  358,  359 
Ergotism,  354-359 
Ergotocin,  359 
Ergotoxin,  359 
Ericaceae,  298,  301,  304 
Ervsiphaceae,    1,    186-187,    211,    232, 

253,  285,  483 
Erysiphe,  186 

dehor  ace  arum,  402 

communis,  244,  260 

communis  tritici,  262 

graminis,    175,   244,   252,   262,   277, 
402 

graminis  hordei,  260,  276 

graminis  tritici,  221,  260,  276 

horridula,  260,  273 

polygoni,  219,  233,  241,  402 

t  auric  a,  253 

tortilis,  402 
Erysiphites 

metilli,  483 

protogalus,  483 
Essential  elements,  10 
Esterase,  40 
Ethyl  acetate,  77,  231 
Ethyl  alcohol,  77 
Ethvl  mercury  chloride,  427 
Ethyl  mercury  phosphate,  427 
Euachorion,  384 
Eucalyptus,  231 
Eucharis,  243,  244 
Eufavotrichophvton,  384 
Eumicrosporum,  384 
Euphorbia,  200 
Euphorbiaceae,  298,  407 
Eurotium 

amstelodami,  291 

herbariorum,  270,  273 


SUBJECT  INDEX 


513 


Eiirychasma,  461 

dicksonii,  460,  471 
Eutetix  tenella,  111 
Exosmosis,  238 
Exotics,  404 

Facultative  anaerobes,  56 
Fagns  sylvatica,  302 
Fats  and  oils,  21,  62,  67,  79-81 
Faviformes,  384 
Favotrichophyton,  384 
ochraceum,  384 
violaceum,  384 
Favus,  366,  380,  382,  388 
Feathers,  367,  379,  385,  389 
Federal  Plant  Quarantine  Law,  420 
Fenn  respirometer,  64,  65 
Fermentation,  43,  53,  54,  55,  58-62, 

69,  418 
Fern  allies,  477 
Ferns,  406,  477,  486 
Fertilization,  317 
Festuca,  335 
Feteretia,  266 
Filters,  Berkefeld,  291 

Chamberland,  289 

porcelain,  283 
Fire  blight  of  pears  and  apples,  443 
Firs,  406 

Douglas,  452 

white,  452 
First-division  segregation,  326 
Fish,  137,  462 

ganoid,  485 
Fistidina  hepatica,  352 
Flagellates,  137 
Flavacin,  87 
Flavoglaucin,  84 
Flavone,  84 
Flax,  77,  403,  411,  412 

stem  break,  410 
Fleas,  172 

Flexuous  hvphae,  333 
Flies,  168,  172,  183,  184,  443,  450 

carrion,  202 

house,  444 

muscid,   174 

sarcophagid,    174 
Florideae,  459 
Flounder,  463 
Fluorescence,   388-389 
Fly  agaric,  344,  350 
Folic  acid,  325 


Eomes 

annosus,  101,  102,  114,  138 
applanams,  166,  410 
cryptarum,  101 
ever  bar  tit,  102 
foment  arias,  51,  166,  208 
fraxineus,  41,  52 
igniarius,  41,  52,  102 
marmoratus,  102 
nigrolineatus,  102 
officinalis,  102 
pint,  44,  138,  269,  410 
pinicola,  16,  45,  41,  52,  102 
rimosus,  102 
rosens,  155 
subroseus,  102 
Fonsecaea,  372 

Food  value  of  fleshy  fungi,  351-353 
Foraminifera,  481 
Forestry,  311-312 
Formic  acid,  20 
Fossil  fungi,  474-489 
age,  477-478 
classification,  479-487 
Myxomycetes,  480 
Phycomycetes,  480-481 
Ascomycetes,  481-485 
Basidiomycetes,  485-486 
Deuteromycetes    (Fungi   imper- 
fecti),  486-487 
fossil  mycorrhizae,  487 
geological  time,  474-477 
implications,  488 
nature,  478-479 
preparation,  for  study,  479 
"Fox  fire,"  137 
Frogs,  174,  185 
Froghopper,  sugar-cane,  445 
Fructose,  42,  74,  75,  390 
7-Fructose,  59 
Fucus  vesiculosus,  469 
Fuligo,  398 

septica,  211,  230 
Fulvic  acid,  163 
Fumago  vagans,  74,  76 
Fumarase,  40 

Fumaric  acid,  19,  71,  73,  75,  76,  163 
Fumigatin,  87 
Fungi  Imperfecti,  286,  379,  431,  460, 

468-470,  486-487 
Fungicides,    162,    163,   243,  401,  420, 

427 
Fimgites  jenensis,  487 


514 


SUBJECT  INDEX 


Fungus-insect  interrelationships,  442- 
'  457 

biological  control  of  insects,  448- 
450 

fungi   cultivated   bv   insects,   451- 
454 
ants,  452-454 
beetles,  451-452 

fungi  occurring  on  or  within  in- 
sects, 444-448 

implications,  455 

insects  as  vectors  of  plant-patho- 
genic fungi,  442-443 

insects    in    relation    to    reproduc- 
tion of  fungi,  450-451 
Fusariuvi,    107,    109,    143,    159,    178, 
229,    265,    268,    284,    292,    355, 
359,   361,  431,  435,  437 

acuminatum,  18 

angustum,  453 

argillaceum,  144 

aurantiacum,  161 

avenacearum,  161,  360 

avenaceum,  28,  34 

bull at i in 7,  155 

cepae,  144 

chromophythoron,  165 

coeruleum,  99,  144,  281 

conglutinans,  109,  110 

cubense,  412 

culmorum,  161,      281,      286,      294, 
296 

discolor  var.  sulphur  eum,  99,  114, 
118,  119,  127,  128,  148 

equiseti,  161,  453 

eumartii,  99,  118,  143,  144 

gramin  ace  arum,  61 

gramineum,  80,  360,  361 

herb  arum,  161 

lini,  18,  35,  77,  82,  92,  94,  260,  281, 
412 

lycopersici,  155,  156,  412 

moniliforme,  264,  275,  291,  452 

im'itzii,  436 

nival  e,  160,  161 

niveuni,  27,  28,  412 

oxysporum,  4,  5,  7,  15,  29,  99,  118, 
412,  453 

polymorphum,   161 

putrefaciens,  104 

radicicola,  29,  99,  104,  118,  437 

roseum,  452 

solani,  283 

trichothecioides,  99,  437 


Fusarium 

zashifectimi,  412 

viride,  452 
Fuseaux,  3<S7,  382 
Fusicladiinn 

dendriticum,  227 

pirimim,  227,  291 

saliciperdum,  177 

tremidae,  238 

"Gabelmykorrhiza,"  299,  303 
Galactinia  badia,  190 
Galactocarolose,  79 
Galactose,  18,  19,  21,  42,  45,  65,  75, 

79 
Gal  era  ten  era,  329 
Gallic  acid,  44,  163 
Gallium,   16 
Gamma  rays,  123,  124 
Gaimnarus  locusta,  466 
Gangrene,  354,  358,  359 
Ganodervia 
applanation,  44,  51,  101,  102 
lucid  inn,  82,  103 
Garlic,  50,  88 
Gastroidea  elata,  304,  315 
Gastrointestinal      tract,      effect      of 

fungi,  343 
Gastromvcetes,     194,    202-205,    312, 

406,  410 
Ge  aster 

finibriatus,  303 
fornicatus,  303 
Geasterites  florissantensis,  486 
Geese,  176 
Gelatin,  389,  430 
Genetics,  317-338 
Dominance  and  lethal  factors,  335 
homothallism    and    heterothallism, 
319-335 
in  Phvcomycetes,  319-321 
in  Ascomycetes,  321-325 
in  Basidiomvcetes,  325-335 
in  Ustilaginales,  329-333 
in  Uredinales,  333-335 
resume,  336 

sexual  and  asexual  stages,  317-318 
Geographical   distribution   of  fungi, 
96,  102,  395-415 
Mvxomycetes,  397-399 
Phvcomvcetes,  399-402 
endemic  species  artificially  dis- 
persed, 400-401 
influence  of  latitude,  401-402 


SUBJECT  INDEX 


515 


Geographical   distribution  of  fungi, 
Ascomycetes,  402-405 
exotics,  404 

powdery  mildews,  403 
Pyrenomycetes    and     Discomy- 

cetes,  403-404 
species     with     erratic     distribu- 
tion, 404-405 
Basidiomycetes,  405-410 
smuts,  405-406 
rusts,  406-407 

endemism  in,  407-408 
septobasidium,  408-409 
other  Basidiomycetes,  409-410 
Deuteromycetes,  410-412 
seed-borne,  410-411 
nursery  stock,  411 
soil-borne,  411-412 
implications,  412-414 
Geolegnia 
inflata,  431 
septisporangia,  431 
Geological  time,  474-477,  416 
Geraniaceae,  298 
Germ  theory  of  disease,  418 
Germination  of  spores,  210-235 
carbon  dioxide,  231 
germination  types,  210-212 
hereditary  factors  and,  214-218 
light,  231-232 

methods  of  testing,  212-213 
nutrition,  232 
oxygen,  230-231 
reaction,  229-230 
resume,  232-233 
temperature,  221-229 
water  relations,  218-221 
Giant  colonies,  383 
Gibberella 
saubinettii,   66,   67,    105,    119,    120, 

178,  355,  359-361 
zeae,  355,  359-361 
Gilchristia  dermatitidis,  369 
Gills,  attachment  of,  344 
Gliocladhnn    fimbriatum,    284,    287, 

294 
Gloeosporhim,  216,  237,  243,  292,  437 
album,  104 
aridwn,  211 

jructigemnn,  25,  99,  104,  239 
herb  arum,  104 
limetticolum,  143 
minus,  143 


Gloeosporhim. 

musarum,  99 

piper atum,  281 
Glomerella,  48,  193,  325 

cingidata,  18,  32,  99,  104,  144,  146, 
150,  213,  234 

gossypii,  24,  99,  108,  178,  179,  427 

rujomaculans,    48,    111,    143,    179, 
223,  225,  226,  229 
Gluconic  acid,  16,  74-75,  76,  88 
Glucose,  18,  19,  42,  49,  65,  74,  79,  80, 

81,  389,  390 
7-Glucose,  59 
Glucose  diphosphate,  61 
Glucose  monophosphate.  61 
Glucosidase,  40 
Glucosides,  45 

Glutamic  acid,  22,  23,  41,  64,  83 
Glutaric  acid,  290 
Glutathione,  41,  63,  86 
Glyceric  aldehyde,  60,  61 
Glycerol,   18,   19,  21,  59,  60,  61,  74, 

77-78,  79,  80 
Glycine,  22,  23,  65 
Glycogen,  67,   192,  202,  205,  220 
Glycolase,  40,  57,  59 
Glycolic  acid,  71,  163 
Glycuronic  acid,  163 
Glyoxalic  acid,  71 
Gnomoma,  137 

rubi,  193 

ulmea,  232 
Goats,  176 

Gomphidius  gracilis,  302 
Gomphinaria,  372 
Gonatobotrytis  primigennis,  486 
Gooseberries,  54 
Gramineae,  403 
Graminiaceae,  298 
Grapefruit,  269 
Grapes,  53,  143,  239,  400 

mildew,  177,  420 
Graphium 

rigidum,  452 

idmi,  28,  414 
Grass,    85,    252,   258,   262,    305,    357, 
358,  398,  483 

blue,   258 

brome,  262 

kangaroo,  216 
Grasshoppers,    443 
Grill etia  sphaerospermii,  481,  489 
Growth,  measurement  of,  12,  13,  96, 
97,  155-157 


516 


SUBJECT  INDEX 


Growth-inhibiting    substances,    280, 

289 
Growth-stimulating  substances,  280, 

289,  308 
Grubyella,  384 
G nine ol,  44,  45 
Guignardia,  143 

alaskana,  466,  469 

chondri,  469 

irritans,  469 

ulvae,  466,  469 
Guinea  pig,  387,  388 
Gums,  50 

Gvmnoascaceae,    385 
Gymnoconia,   333 

interstitialis,  250,  252,  256 
Gynmogongrus  norvegicus,  470 
Gvmnosperms,  477 
Gymnosporangiwn,  333,  407,  408 

clavipes,  218,  223 

juniperi-virginianae,  166,  169,  199, 
206,  223 

nidus-avis,  199,  208 
Gyvmoteliinn  myricatum,  200 
Gyromitra 

esculenta,  352 

gigas,  352 

Hadromase,  44 

Hair,  367,  379,  389,  390 

Halidrys  dioica,  469 

Haltica,  449 

Hamamelis  virginiana,  403 

Haptotropism,  243 

Harden   theory  of  fermentation,  58 

Hardwoods,  398,  410,  452 

"Hartig-net,"  299,  302,  309 

Hashish,  343 

Hatch  Act,  420 

Haustoria,  244,  252-253 

Heartwood  rots,  251,  410 

Heavy  metals,  10,  11 

Heavy  water,  221 

Hebeloma 

crustultforme,  345 

fastibile,  347 
Hegari,  266 
Helicoma,  482 
Helium,  476 
Helminthosporin,  85 
Heluunthosporium,  141,  170 

avenue,  85 


Helminthosporhmi 

catenariinn,  85 

cynodontis,  85 

euchlaenae,  85 

geniculatum,  77,  78,  79,  431 

grarmneum,  85,  243,  260,  273,  410 

ravenelii,  85 

sativum,    146,    148,    161,    260,    264, 
273,  281,  286,  287,  294,  296 

tritici-rulgaris,  85 
Helotium  scutula,  190 
Helvetia 

crispa,  158,  190 

elastic  a,  190 

epihippium,  190 

esculenta,  82,  343,  351 
Helvellic  acid,  351 
Hematin,  41 
Hemicellulase,  46,  41 
Hemicellulose,  50 
Hemileia  vastatrix,  169,  177,  209 
Hemiptera,   173,   174 
Hemisphaeriaceae,  254 
Hemitrichia,  179 

clavata,  217 
Hemlock,  432-433 
Hemolysis,  343,  350,  351,  358 
Hemophilus  influenzae,  86 
Hemp  seed,  430 
Hepaticae,  298 
Hereditary  factors  and  germination, 

214^218 
Hermaphroditism,  319 
Herpes,  380 
Herring,  sea,  462,  463 
Hertzian  rays,  123,  124 
Heteroauxin,  82 
Heterocaryosis,  265,  266 
Heteroecism,  419 

Heterothallism,  284,  289,  290,  319-335 
7-Hexoses,  59 

Hexose    phosphate    theory    of    fer- 
mentation, 58,  61 
Hibiscus,  401 

High  temperatures,  108-109 
Hirneola  poly  trie  ha,  353 
Histidine,  40 
Histoplasma     capsulation,     369-370, 

391,  392,  393 
Histoplasmosis,  366,  369-370 
"Holy  fire,"  354 
Homothallism,  319-335 


SUBJECT  INDEX 


511 


Honey  agaric,  339 
"Honey  dew,"  357 
Hooves,  367,  379 
Hordeum 

ardaemiensis,  263 

commutatas,  263 

europaeiim,  262 

hordeacens,  263 

mtemiptus,  263 

racemosus,  263 

sativum^  274 

secalimis,  263 

vulgare,  262 
Hormischim  pithy  ophilum,  453 
Hormodendron    cladosporioides,    23 
Hormodendrwn,  452 

pedrosoi,  371,  372,  392,  393 
Hormones,  280,  288,  290 
Hornbeam,  306 
Horns,  367,  379,  386,  389 
Horses,  176,  366,  374,  376,  406 
Host  penetration,  236-256 

bv  ectoparasites,  252-253 

direct,  237-248 

haustoria    and    their    significance, 
252-253 

implications,  254 

stomatal,  248-251 

wound,  251-252 
Hwnaria  gram  data,  177 
Humidity,  215,  218 
Humus,  '50,  305,  430,  434,  435 
Hvalospora,  408 
Hybridization,     263,     266-267,     272, 

317,  334,  427 
Hydathodes,  236 
Hydnaceae,  486 
Hydnites  argillae,  486 
Hydnam 

jerrugineum,  85 

imbricatum,  82 

ochraceitm,  102 

pidcherrimum,  103 

repandwn,  302 
Hydroergotinine,   359 
Hydrofluoric  acid,  479 
Hydrogen  acceptor,  58 
Hydrogen  peroxide,  283 
Hydrogen-ion    concentration,     151- 

164 
Hydroids,  137 
Hydroquinone,  44 


Hydroxyl  ions,  151,  154 
Hygrophorus 

bresadolae,  302 

conicus,  342,  348,  350 

lucorum,  302 
Hylurgopinus,  451 
Hymenomycetes,   125,  137,  176,  195, 
7^/199,200-202,  285,  302,  312, 
325,  327,  405 
Hymenoptera,   174 
Hyperparasite,  240,  280,  285,  286 
Hyphal  anastomosis,  385 
Hyphal  fusions,  265 
Hyphochytriaceae,  462 
Hypholoma 

fascicidare,  158,  328,  409 

incertum,  82 
Hyphomycetes,  373,  435,  445 
Hyphopodia,   254 
Hypochnaceae,  485 
Hypochnus 

centrifugus,  281,  294 

cyanescem,  302 

sasakii,  281,  294 
Hypochiiites,  485 
Hypocreaceae,  484 
Hypocrella,  444,  447 
Hypoderma,  431 

lam'mariae,  469 
Hypodermataceae,  232 
Hypomyces,  285 

ipomoeae,  266,  274,  323,  337,  453 

ipomoeae  alba,  325 

ipomoeae  purple,  325 

ipomoeae  r  eve  eta,  325 

ipomoeae  revoliita,  325 

lactifluorum,  187 
Hypoxylon 

coccineum,   189 

fuscztm,  136,  131,  187 
Hysteriaceae,  483 
Hysteriales,  466 
Hysterites 

ancinitis,  483 

cordiatis,  483 

lcerya  purchasi,  447 

Ichthyophomis  hoferi,  462,  463,  471, 
472 

Ichthy osporidhun  hoferi,  463 

Identification  of  poisonous  mush- 
rooms, 343-349 


518 


SUBJECT  INDEX 


Ids,  388 

Immunity,  423,  424 

Impurities  in  C.P.  reagents,  10,  11 

Incubation,  236 

Indicators,  151,  155 

Infection,  236 

and  temperature,  96,  109-111 
"Infection  hypha,"  238,  239,  245 
Infrared  ravs,  123,  124 
Inhibitors  of  respiration,  65-66 
Ink  cap,  common,  339 

glistening,   339 
Inoculation,  236 
Inocybe 

decipiens,  351,  362 

geophylhh  409 

infelix,  342,  347 

bifida,  342,  346,  347,  351 
/-Inositol,  25,  26,  28,  288,  289 
Insect  diseases,  442 
Insects,    137,    168,    172-175,  236,   251, 

442^57,  484,  485 
Intercellular  parasites,  252 
Intoxication  from  eating  fungi,  343 
Intracellular  parasites,  252 
Inulase,  40,  46,  41,  390 
Inulin,  19,  78 

Invertase,  40,  42,  48,  292,  390 
Iodine,  79 
Ionization,   152 
Ipomoea,  325 
Ips,  174,  451 
Iron,  3,   10,   11,  13,   14,  16,  289,  438, 

478,  481 
Irpex  mollis,  102 
lsaria,  444,  445 

farinosa,  445 
Isoachlya,  4 

eccentrica,  431 

monilijera,  4 
Isoboletol,  86 
Isoelectric  point,  156,  157 
Itaconic  acid,  73,  163 
I  thy  phallus  coralloides,   174 

Jack  bean,  41 

"Jack-in-the-box"     dehiscence,     191, 

192 
Jack-o'-lantern,  345 
Jelly  fish,   137 
Jelly  fungi,  84 
Jungermanniaceae,  298 


Juniperus 

communis,  405 

virginiana,  405 
Jurassic  period,  <\11 ',  481 

Kabatiella 

caidivora,  410 

nigricans,  2 1 1 
Kalotermes  minor,  175 
Keithia 

chamaecy parissi,  405 

juniperi,  405 

tetraspora,  405 

thujina,  405 

tsugae,  405 
Keratin,  366,  379,  389,  390 
Kerion,  380,  384 
Ketosuccinic  acid,  71 
Khapli  emmer,  250 
"Knollenmykorrhiza,"  299,  303 
Koch's  rules,  419 
Kojic  acid,  78,  163 
Kroepoek  of  tobacco,  172 

Laboulbeniales,  444 

Labvrinthula    macrocystis,    460,    470 

Labvrinthulales,  460 

Laccaria  laccata,  409 

Laccase,  46,  41,  86 

Lachnea 

scutellata,  135 

set  os  a,  190 

st  ere  or  ea,  177 
Lac  tar  ins,  285,  346 

blennius,  158,  302 

coryli,  302 

deliciosus,  352,  409 

helms,  312 

necator,  302 

rufus,  302 

snbdulcis,  302 

torminosits,  302,  343,  346,  351 
Lactase,  40,  46,  41,  390 
Lactic  acid,  20,  55,  56,  16,  81,  248, 

268,  280,  283 
Lactobacillus 

acidophilus,  16 

bidgaricus,  16 
Lactophenol,  248 
Lactose,  18,  19,  21,  74,  390 
Laestadites  nathorstii,  484 
Lagenidium  rabenhorstii,  181 


SUBJECT  INDEX 


519 


Laminaria,  469 

digitata,  469 

saccharina,  469 
Laviproderma  violaceum,  211 
Larch,  300,  303,  452 
Larix,  303 

decidna,  302 
Lasiosphaeria  pezizula,  452 
Lasius 

fuliginosus,  452,  453 

innbratus,  453 
Late  blight  of  potato,  111,  177,  221, 

419 
Latitude    and    geographic    distribu- 
tion, 401-402,  407,  408,  409 
Lauraceae,  298 
Lead,  476 

Leaf  rust  of  wheat,  170 
Leather,   389 
Leathery  fungi,  176 
hecanidion  atratum,  188,  192,  206 
Lecaminn  viride,  446-441 
Lecanosticta,  216 
Lecithinase,  40 
Leguminosae,  298,  402,  407 
Lenticels,  236,  246 
Lentimis,  409 

atticolus,  453 

cartilaginens,  454 

lepidens,  101,  103,  126,  148,  200 
Lenzites,  202 

berkeleyi,  102 

betulina,  101,  410 

saepiaria,  26,  41,  52,  99,   103,  155, 
151,  158,  229 

tigrimis,  99 

trabea,  101,  103 
Lenzithes  gastaldii,  486 
Leocarpus,  398 
Leotia  chlorocephala,  158 
Lepidodendron,  481,  483,  485 

aculeatiim,  481 
Lepidoderma  tigrinwn,  211 
Lepidoptera,  173 
Lepiota 

cepaestipes,  228,  230 

cygnea,  409 

morgcmi,  343,  345 

naucma,  344 

procera,  339,  345,  352,  409 
Leptinotarsa  decemlineata,  174 
Leptolegnia,  4,  180 

subterranea,  431 


Leptomitus  lactens,  4,  19,  20,  22 
Leptosphaeria 

acuta,  192,  207 

chondri,  469 

coniothyriwn,  174 

herpotrichoides,  281-282 
Leptosphaerites  lemomii,  485 
Leptostrovia  camelliae,  205,  206 
Leptostylus  macidata,  173 
Lethal  factors,  335 
Lettuce,  237 
Leucine,  22,  23 
Leveilhda  tanrica,  253 
Levulose,  18,  19,  42,  65 
Lice,  172 

Lichens,  297,  390,  466 
Light,  210,  231-232,  308,  470 
Lignin,  43,  44,  50 
Ligninase,  46,  41 
Lilac,  203 
Liliaceae,  298 
Lilies,  237 

Lima-bean-pod  spot,  443 
Lime,  143,  398 
Limpets,  468 
Lineolic  acid,  80 
Linospora,  137 

gleditsiae,   193,  232 
Lipase,  40,  41,  46,  41,  48,  50 
Lithopythhnn  ganglitf orme ,  460 
Litrophilic  fungi,  160-161 
Littorina,  469 

planacis,  468 
Liverworts,  298 
Lolhtm 

perenne,  305,  316,  358 

temulentwn,  305,  316 
"Long  roots,"  301 
Long-cycled  rusts,  407 
Longleaf  pine,  258 
Loose  smuts,  272 
Lophoderminm  pinastr'i,  26,  405 
Lophophyton,  384 
Low  temperatures,  103-108,  227 
Lucif erase,  40,  138 
Luciferin,  138 

Luminescence,  137-138,  329,  345 
"Lumpy  jaw,"  374 
Lupine,  402 
Luteic  acid,  79 
Lycogala 

epidendritm,  82 

fzisco-fiavum,  398 


520 


SUBJECT  INDEX 


Lycoperdaceae,  486 
Lycoperdales,  1,  410 
Lycopodium,  299 

Lyghwdeihiron  oldhaniimn,  481 
Lysine,  23,  41 
Lysis,  335 

Alacroconidia,  381 
Macrophoma  gymnogongri,  470 
Alacrosporkes 

ropaloides,  486 

subtrichellus,  486 
Macrosporiinn,  4,  15,  431 

commune,  24 

laminarium,  470 

sarcinaeforme,  7 

tomato,   144,  245,  246,  256 
Madreporia,  459 

Magnesium,  3,  4,  7,  10,  213,  438,  478 
Magnusia 

brachytrichia,  99,  111 

nitida,  99,  111 
Maireomyces  peyssonelia,  469 
.Maize,  285,  329,  331,  405 
.Malaria,  443 

Malassezia  oralis,  372-373,  318 
Malic  acid,  20,  71,  73,  75,  76,  79,  163 
.Malstenia,  384 

Maltase,  40,  42,  45,  46,  41,  292 
.Maltose,  19,  64,  74,  78,  220,  389,  390 
.Man  as  vector,  177 
.Manganese,  10,  11,  14 
Mannitol,   19,  21,  65,  79,  229 
Mannocarolose,  79 
c/-Mannonic  acid,  163 
Mannose,  18,  42,  79,  390 
.Mantle,  306,  309 
Marasmius,  409 

oreades,  82 
.Marattiaceae,  299 
Marchantia,  179 
Marchantiaceae,  298 
.Marine  fungi,  458-473 

historical  background,  459-460 

implications,  470 

Phycomycetes,  460-466 

Ascomvcetes,  466-468 

Fungi  Imperfecti,  468-470 

slime  molds,  470 
Marine  worms,  137 
Marssonia,  238,  243 
Massospora,  186 

ci  cad  in  j,  445,  457 


Mealy  bugs,  444,  450 

Medical  mycology,  364-394 
Actinomyces  bovis,  373-375 
Aspergillus  fwnigatus,  379 
Coccidioides  immitis,  367-368 
Cryptococcus  histolyticus,  368-369 
Histo plasma    capsulation,    369-370 
historical,  366-367 
implications,  390 
Malassezia  oralis,  372-373 
Monilia     (candida)    spp.,    377-379 
Phialophora  verrucosa,  370-372 
physiologic   activities,   389-390 
Sporotrichum  schenckii,   375-377 
Trichophytoneae     or     ringworm 
fungi,'  379-390 
classification,  382-385 
fluorescence,  388-389 
mycides,  387-388 
pleomorphism,  385-387 
relationship    with    other    fungi, 
385 

Mcgalospora,  212 

Megaspores,  384 

Megatrichophyton,  384 
roseum,  384 

.Meiosis,  318,  328 

Melampsora,  333,  406,  408 
//'///',  215,  223,  234 

Melampsoraceae,  406 

Melampsorella,  333 

Melanconiaceae,  486 

Melanconis,  405 

Mclanconium,   143 

Melanose  of  citrus,  269,  402,  449 

Melanospora 
admorum,  291 

destruens,  26,  32,  66,  61,  291,  293 
pampeana,  291,  294 

Melanosporites  stefani,  484 

Mclibiose,  42 

Meliolaceae,  254 

Meliola  circintms,  254,  255 

Membranes,  collodion,  283 

Meningitis,   369,  375 

Merulius 
domesticus,  99 
lacrymans,   43,   44,    100,    102,    155, 

232 
sclerotiorum,  99 
silvestris,  99,  100,  102 
tremellosus,  102 

Mesanthrophilic  ftmgi,  161 


SUBJECT  INDEX 


521 


Mesozoic  period,  477 
Metarrhizium  anisopliae,  445,  450 
Metasphaeria  asparagi,  192 
Methane,  435 
Methylarsine,  50 
Methvlglucosides,  42 
Methylglyoxal,  57,  59,  60,  62 
Mice,  367 

Microbial   composition   of  soils,  429 
Microcera,  444,  446-441 

coccophila,  447 
Microides,  384 
Alicrosporid,  387 
Microsporum,  381,  382,  383,  388 

audouini,    385,   386,   388,   389,   390 

jelineum,  389 

julvum,  289,  384 

gypseum,  384 

lanosum,  385,  387,  390 
Microstroma  jaglandis,  211 
Microthyriaceae,  254,  483 
Microthy rites  dy sod His,  483 
Microtrichophvton,  384 
Middle  lamella,  48 
Milesia,  333,  406,  408 

vogesiaca,  406 
Milo,  266 

Mineral  nutrition  of  fungi,  2-16 
Miocene  period,  478,  481,  483,  484, 

485,  486 
Mitella,  469 

polymerus,  468 
Mites,  172,  173 
Moisture,  210,  220 
Molasses,  74,  82 
"Mold  starch,"  79 
Mollisia  cinerea,  190 
Molluscs,  137,  459,  460,  468,  481 
Molybdenum,  16 
Monascoflavin,  84 
Monascorubrin,  84 
Monascus  purpureas,  84 
Monilia,  321,  377-379,  388,  431 

albicans,  378 

Candida,  451 

fructicola,  225,  226,  229 

frzictigena,  48,   104,   128,  223,  229, 
242 

viacedoniensis,  289 

metalondinensis,  289 
oregonensis,  48 

psilosis,  378 

sitophila,  86,  166,  242 


Moniliaceae,  436 
Moniliales,  411,  486 
Moniliasis,  378 

Moniliopsis  aderholdii,  160,  453 
Monilites  albida,  486 
Monoblepharidaceae,  464 
Monocaryotic    mycelium,    334 
Monochaetia,  264 
Aionochromator,  125,  140,  143 
Monosaccharides,  386,  436 
Monosporium  maritimum,  470 
Monosporous  cultures,  319 
Monotropa,  306 

hypopitys,  305,  314,  315 
Morchella 

conica,  136,  352 

crassipes,  136 

esculenta,  339,  340,  349,  531,  352 

gigas,  189 
Morel,  339,  349,  351,  352,  353 
Morenoella  quercina,  254,  255 
Morning  glory,  243 
Morphogenesis,  125-129 
Mortierella,   107 
Morns  rubra,  403 
Mosquitoes,  172,  442,  443,  444 
Mosses,  398 
Moth,  gvpsv,  174 
Mu  Erh,  353 
Mucedinaceae,  486 
Mucilago,  398 

spongiosa  var.  solida,  398 
Mucor,  13,  106,  107,  431,  433 

christianensis,  22 

dispersus,  141 

genevensis,  145,  146 

glomerula,  155 

griseocyanus,  22 

hiemalis,  84 

mucedo,  76,  78,  88,  91,  242,  283, 
399,  430 

parasiticus,  240,  241 

piriformis,  104 

racemosus,  18,  22,  77,  88,  289,  430, 
436,  453 

ramannianus,  26,  27,  28 

solani,  313 

sphaerospora,  22 

spinosus,  22 

stolonifer,  23,  71,  90,  282,  430 
Mucoraceae,  240,  286,  436,  481 
Mucorales,  399,  430,  431,  433,  436 
Mucorites  cambrensis,  481 


522 


SUBJECT  INDEX 


Muscardine  fungus,  445 
.Muscarine,  350 
.Muscarufin,  85 
Mushrooms,  176,  285 

edible,  339 
.Mussels,  487 
.Mutations,  259,  262,  264,  331,  385 

radiation  and,  139 
My  c aureola  dilseae,  469 
Mycelium  radicis  sylvestris  /3,  303 
Mycelium    radicis   sylvestris    7,    303 
Mycena 

pur  a,  158 

vulgare,  158 
Mycides,  377-388 
Mycobacterium  tuberculosis,  379 
Mycoderma,  373 

viui,  55 
.Mycodextran,  79 
.Mvcogalactan,  79 
Mycogone 

nigra,  434 

perjiiciosa,  285 

puccinioides,  435 
.Mycology   in   relation   to   plant   pa- 
thology, 416-428 

contributory     advances     in     bac- 
teriology, 418-419 

developments  in  terminology,  421- 
423 

early    concepts    of    plant    disease, 
'417-418 

fungi    as    antigens    and    plant    pa- 
thology, 423-424 

implications,  427-428 

present  trends,  424-427 

signposts    along    the    phvtopatho- 
logical  trail,  419-422 
Mycophenolic  acid,  88,  163 
Mvcorrhiza,  178,  409,  482,  487 
.Mvcorrhizae  and  •  mvcotrophv,  297- 
316 

function,  305-31 1 

fungi  involved,  302-305 

implications,  314 

importance  to  forestry,  311-312 

kinds,  299-302 

occurrence,  298-299 

tuberization,  312-314 
Mycosphaerella,  193 

ascophylli,  469 

pelvetiae,  468,  469 

rubina,  192 


Mycosphaerella  sentina,  192 
Mycosphaerellaceae,  484 
Alycotrophy,  297-316 
Myriangium,  444 

curtisii,  447 

duriaei,  447 

montagnei,  447 

thwaitesii,  447 
Myriapods,   137 
Myrmicine  ants,  452 
.Myrtaceae,  298 
.Myxomycetes,  39,  277,  218,  225,  397- 

399,  460,  480 
Myxomycetes  mangini,  480 


Nadsonia  julvescens,  145 
Nails,  367,  379 
"Native  bread,"  352 
Naucoria  semiorbicidatus,  329 
Nectarine,  411 
Nectria,  444 

aurantiicola,  447 

cinnabarina,  136,  173,  187 

coccinea,  26,  113,  173 

ditissima,  173 
Nematodes,  168,  178,  442,  443 
Nematospora 

gossypii,  26,  288 

phaseoli,  443 
Neoachorion,  384 

Neocosmospora  vasinfecta,   113,   114 
Neofabrea  malic orticis,  104 
Neomicrosporum,  384 
Neotrichophvton,  384 
Nervous    system,    effect    of   poison- 
ous fungi  on,  342,  343 
Neuroptera,  173 
Neurospora 

crassa,  83,   106,   108,  120,   146,   150, 

321,  323,  325,  337,  338 
sitophila,    137,    143,   264,    290,    321, 

322,  323,  326,  321,  337,  338 
tetrasperma,    216,    217,    234,    266, 

290,  321,  323,  324,  335,  337 
Nicotiana,  401 
Nicotinic  acid,  41 
Nidulariaceae,   205 
Nitrate  nitrogen,  21,  22,  429,  436 
Nitrification,  429,  436 
Nitrogen  fixation,  23,  24,  304 
Nitrogen    requirements,    21-24,    213, 
^308,  311 


SUBJECT  INDEX 


523 


Nocardia,  375 

"Nodular  organs,"  380,  381,  383 
Nucleoproteins,   140 
Nursery  stock,  410,  411 
"Nutrilites,"  289 

Nutrition,  1-36,  210,  232,  265,  282 
growth  factors,  24-28 
implications,  29-31 
mineral,  2-16 
calcium,  4-5 
concentration    and    proportion, 

5-10 
copper,  13-14 
difficulties,  10-13 
iron,  13 
manganese,  14 
other  elements,  16 
sulphur,  4 
zinc,  14-16 
organic  nutrients,  16-24 
carbon  requirements,  17-21 
nitrogen  requirements,  21-24 
Nyctomyces  entoxylinns,  487 

Oak,  98,  306 

Oats,  108,  258,  262,  272,  359 

Fulgum,  267 

Green  Mountain,  269 

Green  Russian,  269 

loose  smut,  267 

Red  Rustproof,  267,  269   , 

Ruakura,  269 

White  Tartar,  269 
Ocellus,  134,  135,  182 
Odontoglossum,  304,  309,  310 
Oecantlms  niveus,  174 
Oedocephalum  albidiim,  151 
Oidium,  431 
Oils,  45 
Okra,  401 
Oleic  acid,  80 

Oligocene  period,  478,  479,  484 
Olpidiopsis  andreei,  461 
Olpidiwn,  461 

brassicae,  181 

dicksonii,  460 
Omphalia  flavida,  137,  138 
Onion  smudge,  245 
Onions,   110,   175,  231,  241,  243,  245 
Onychomycosis,  366 
Oochytriceae,  481 
Oochytrhim  lepidodendri,  481 


Oomycetes,  231,  464 
Oospora,  375 

aurantia,  84 

citri-aiirantii,  20,  291 
Oosporin,  84 
Ophiobolus 

careciti,  193 

halimus,  466,  461,  469,  470 

herpotrichus,  161 

graminis,  22,  31,  158,  160,  161,  165, 
281,  286,  287,  292,  294,  296 

Icmrinariae ,  469 

miyabeamis,  289,  296 
Ophiodothella,  137 
Ophioglosswn,  299 
Ophionectria  cylmdrothecia,  405 
Ophrys,  310 

Oranges,  108,  143,  163,  225,  269 
Orbilia  xanthostigma,  190 
Orcadia 

ascophylli,  469 

pelvetiana,  469 
Orchidaceae,  298,  301,  308 
Orchids,  303,  304,  309,  310,  312 
Ornithine,  83 
Orthoptera,  173 
Oryza  sativa,  414 

Oryzaephilus  surinamensis ,  454,  456 
Osmotic  pressure,  5,  7,  29,  220,  247 
Ostracoblade  implexa,  460 
Ostracoda,  481 
Otidea  leporina,  190 
Ovularhes  barbouri,  486 
Ovulinia  azaleae,  175 
Oxalacetic  acid,  71,  74 
Oxalic  acid,  13,  15,  62,  69,  70-71,  75, 

79,  163,  237,  238,  268 
Oxaloacetate,  19 
Oxidase,  48,  50,  58,  63 
Oxidation-reduction    systems,    63-64 
Oxygen,  210,  230-231,  280 
Oxygenase,  46,  41 
Oxyphilic  fungi,  161 
Oyster  mushroom,  339 

"Pacemakers,"  98 
Falaeomyces 

bacilloides,  480 

gordoni,  487 

gracilis,  481 

ma  jus,  487 
Paleozoic  period,  481 
Palm,  405,  486 


524 


SUBJECT  INDEX 


Palmitic  acid,  80 
Panaeohts,   176 

campanulatus,  343 

papilionaceus,  343,  348 

retinitis,  540,  345 ',  348 
Pan  opens  herbstti,  464,  465 
Pantothenic  acid,  25,  26,  28,  66,  289, 

325 
Pantoyl-lactone,  325 
Panus 

incandescens,  111 

rndis,  103 

stipticus,    137,    138,   201,   329,   337, 
409 

torulosis,  158 
Papain,  41 
Papaw,  401 
Papulospora,  431 
Paraffin,  479 
Parasitella 

parasiticus,  240,  241 

siviplex,  26 
Parasol  mushroom,  339 
Paratrophic  fungi,  1,  30,  295 
Paratyphoid,  87 
Paronychia,  378 
Parsnip,  313 
Pasiphaea 

cristata,  464 

sivado,  464 
P  asp  alum,  358 

laeve,  355 
Passalus,  466 
Pathogen,  422,  437 
Pathogenicity,  261-263 
Patulin,  88 
Paxillus 

lateralis,  302 

pamioides,  101 

prunulus,  312 
Pea  crab,  464 

Peach,  246,  402,  407,  411,  453 
Peach-leaf  curl,  111 
Peanut,  401 

leaf  spot,  173 
Pears,  443 
Peas,  317,  402 

leaf  and  pod  blight,  410 
Peat,  310,  311 
Pectase,  40,  48 
Pectic  acid,  48 
Pectin,  48,  49,  50,  436,  460 
Pcctinase,  46,  41,  48,  238 


Pectinate  hyphae,  380,  381 
Pegomya  brassicae,  111 
Pehetia,  468 

canaliculata,  469 
Penatin,  87 

Penicillic  acid,  87,  88,  163 
Penicillin,  9,  86,  87,  171,  284 
Penicillites  cnrtipes,  483 
Pemcillium,    3,    13,    15,    17,    77,    107, 
145,    175,    268,    303,    388,    431, 
434,    435,    437,    444,    448,    453, 
470 

aurantio-brunnewn,  80 

auramio-rcirens,  76,  90 

aureum,  452 

brevicaule,  49,  88 

brevi-compactuvi,  90 

camemberti,  18 

cbarlesii,  79,  88,  90 

chrysogemnn,  74,  79,  84,  92,  284, 
294 

citrimnn,  72,  83,  87,  94 

claviforme,  88,  89 

cyclopium,  87,  88,  93,  155,  229 

daleae,  78 

digitatnm,  20,  77,  108,  111,  120, 
143,  163,  164,  223,  225,  226, 
229,  285 

divaricatum,  72,  452 

expamuvu   24,   45,   72,   79,   81,   91, 

104,  143,  433 
glaber,  74 
glabrum,  83 

glaucnm,  4,  13,  16,  18,  29,  31,  32, 
50,   55,  70,  72,  74,  81,  88,  90, 

105,  106,    127,    149,    151,    224, 
242,  281,  282,  283,  430 

globosum,  54 

griseo-iulvnm,  75,  93 

grisenm,  282 

italicmn,    108,    120,    143,    155,    159, 

163,   164,  229,  281,  285 
janthivellum,  81 
javanicwn,  16,  32,  80,  92,  94 
lilacimnn,  433 
luteum,  72,  79,  92 
votatum,  9,  86,  92,  284 
oxalicwn,  71 
patidum,  88 
phoenictmu  86 
puberidimu  88,  90,  93 
pnrpurogemim   yar.    rubriscleroti- 

um,  74 


SUBJECT  INDEX 


525 


PenicilHum 

roquefortii,  49 

rosenm,  452 

spimilosnm,  72,  87,  93 

stolonifertim,  20,  88 

variable,  155 

varians,  79 
Penwphora  gigantea,  102 
Pennsvlvanian  period,  477 
Pentosans,  44,  45 
Pentoses,  18,  45,  77 
Pepper,  237,  239 
Pepsin,  10,  41,  46,  41 
Peptase,  390 

Peptone,  64,  282,  386,  390 
Perisporiaceae,  483 
Perisporites,  843 

Permian  period,  477,  483,  484,  485 
Peronoplasmopara  cubensis,  222 
Peronospora,  182,  260 

calothecae,  244 

destruct'wr,  175 

parasitica,  223,  231,  267 

pygmaea,  218 

tabacina,    108,    111,    170,    177,    180, 
208,  240,  401,  414 

trifolionnn,  231 
Peronosporaceae,  1,  211,  214,  232,  481 
Peronosporales,  180,  222,  230,  399 
Peronosporites 

amiquarhis,  481,  482 

gracilis,  481 

miocaemcus,  481 

palmi,  480 

siculus,  481 
Peroxidase,  12,  40,  46,  41 
Pertusaria,  212 
Pestalozzia,  143 

funerea,  259,  260,  264,  265,  273 

guepini,  260,  261,  265,  275 
Pestalozzites  sabalana,  486 
Petersenia  andreei,  461,  462 
Petrification,  478 
Petrosphaeria  japonica,  484 
Peyssonelia  squamaria,  469 
Peziza,  189 

acetabulum,   190 

aurantia,  190 

re  pan  da,  190 

epispartia,  454 
Pezizaceae,  484 
Pezizkes  candidus,  484 
Pfeffer's  solution,  3,  7,  310 


pH,  42,    151-164,   210,  226,   229-230, 

265,  282,  286,  310 
Phacidiaceae,  483 
Phacidites,  483 
Phalaenopsis,  304,   310 
Phallales,  1,  174,  410 
Phallin,  350 
Phalloidin,  350 
Pharcidia  pehetiae,  469 
Phaseolus  vulgaris,  277 
Phellomyces  dubius,  487 
Phenol,  248 
Phenolase,  40 
Phenolic  compounds,  45 
Phialophora  verrucosa,  370-372,  311, 

393 
Phlebia 

merismoides,  102 

strigosa-zonata,  103 
Phloroglucinol,  44 
Phoenicin,  86 
Pholiota 

adiposa,  155,  151 

autiimnalis,  342,  346,  350,  362 
Phoma,  4,  292 

apiicola,  7 

betae,  23,  24,  161 

linga?n,  178,  247,  410,  443 

oleracea,  173 

radicis,  24 

radicis  andromedae,  304 

radicis  ericae,  304 

radicis  oxy cocci,  304 

radicis  tetralicis,  304 

radicis  vaccinii,  304 
Ph  om op sis 

citri,  20,  99,  116,  143,  163 

vexam,  178 
Phosphate,  61 
Phosphorus,  3,  4,  8,  10,  213,  308,  311, 

438 
Photosynthesis,  56 
Phototropism,  129-137,  138,  182 
Phragmidium,  333,  408 

disciflorum,  407 

potentillae,  214 

ritbi,  220 
Phragmothyrites  eocemca,  483 
Phycomyces,  27,  106 

blakesleeamis,  26,  27,  84,  146,  319, 
336 

blakesleeamis  arbuscuhis,  319 

blakesleeamis  gracilis,  319 


526 


SUBJECT  INDEX 


Phycomyces 

blakesleeamis  mucoroides,  319 
blakesleeamis  palleiis,  319 
Ion  gi  pes,  134 

linens,  17,  26,  27,  129,  130,  134 
Phycomvcetes,      167-168,       180-186, 
210-211,  214,  236,  240,  289,  302, 
319-321,  368,  399-402,  431,  436, 
458-459,  460-466,  478,  480-481 
Phy  corny  cites  frodinghamii,  480,  481 
Phyllachorella  oceanica,  469 
Phyllactinia 
corylea,  253,  403 
guttata,  260 
Phyllosticta 
antirrhini,  218 
solharia,  216,  223,  233,  411 
Phymatotrichum,  437 

omnivonim,  7,  8,   19,  33,  35,  411, 
412 
Physalospora  malorum,  192 
Physarnm,  398 

cinereum,  217,  398 
serpula,  230 
strcnninipes,  211 
Physcia,  390 

Physiologic   specialization  and  vari- 
ation, 257-278 
definition  of  terms,  257-259 
differences     in     artificial     culture, 

263-264 
fungi    having    physiological    spe- 
cialization, 259-261 
hybridization,  266-267 
importance,  271-272 
influence    of    environmental    fac- 
tors, 269-271 
morphological  differences  between 
physiological   species,   267-268 
pathogenicity  tests,  261-263 
physico-chemical  differences 

among  specialized  races,  268- 
269 
sectoring,  264-266 
Physoderma 
maydis,  181 
zeae-maydis,  240,  400 
Phytomonas  citri,  292 
Phytopathology,  421 
Phytophthora,  143,  178,  211,  268,  303, 
310,  437 
boebmeriae,  26 
cactornm,  26 


Phytophthora 
cambivora,  26 
capsici,  26 
cinnamomi,  26 
citrophthora,  282,  291 
colocasiae,  230 
cryptogea,  26 
drechsleri,  26 
fagopyri,  27 
infestans,   113,   120,   177,   182,  222, 

223,  230,  231,  233,  400 
nicotianae,  178 
palmivora,  26,  230 
parasitica,  16,  45,  230,  282,  287 
parasitica  var.  rhei,  260,  268 
parasitica  var.  mcotianae,  401 
terrestris,  99,  116 
Pice  a  abies,  312 
Pigments,  83-86,  159,  390 
Pigs,  374 

Pilaira  anomala,  26 
Pilens,  342 

Pilo bolus,  84,  129,  131,  133,  176,  182, 
185,  194,  399 
kleinii,  132,  182 
longipes,  182 
"Pilz-atropin,"  351 
Pineapple,  225 

Pines,   300,   301,   303,   307,  309,   311, 
312,  404,  405,  452 
brown-spot  disease,  179 
five-needle,  420 
longleaf,  259 
Scots,  312 
white,  420 
Pink  bakery  mold,  321 
Pinnotheres,  464 
Pinus,  307 
austriaca,  303 
caribaea,  311 
montana,  303 
strobus,  311 
sylvestris,  303 
Piswn  sativum,  241 
Pityrosporhim  ovale,  372-373,  393 
Plant  lice,  450 

Plant  pathology,  416-428,  442-443 
Plantaginaceae,  298 
Plasmodiophora   brassicae,   160,    161, 

223,  398 
Plasmodiophorales,  398 


SUBJECT  INDEX 


521 


Plasmolysis,  244 
Plasniopara,  211 

viticola,    177,    214,    223,    230,    400, 
420 
Plenodomus  meliloti,  282 
Pleolpidiwn  marinum,  461,  462 
Pleomorphism,  50,  257,  385-387 
Pleospora,  260 

herbarwn,  192 

scirpicola,  192 
Pleosporaceae,  484 
Pleosporites  shirianus,  485 
Pleurage 

anserina,   320,   321,   322,    323,    336, 
337 

curvicola,  209 
Pleurotus 

facifer,  138 

gardneri,  138 

igneus,  138 

incandescens,  138 

noctilucens,  138 

olearius,  138 

ostreatus,  44,  51,  707,  103,  755,  755, 
757,  158,  752,  201,  339,  557,  352 

phosphor  eus,  138 

provietheus,  138 
Pliocene  period,  478 
Plotvrightia 

morbosct,  260 

ribesia,  192 
Plums,  225,  246,  284,  407 

cervimis,  201 

termitus,  454 
Pew  pratensis,  358 
Podonectria,  444,  447 

coccicolct,  449 
Podosphaera 

biuncinata,  403 

leucotricha,  187 
Poicyponz 

anserma,  338 

curvicola,  187 

curvula,  136,  7£#,  7£P,  191 

fivnseda,  187 

minuta,  189 
Poisonous    and    edible    fungi,    176, 
339-363 

ergot  and  ergotism,   354-359 
ergotism  in  livestock,  357-358 
historical,  354-357 
toxicology,  358-359 


Poisonous    and    edible    fungi,    food 
value    of    flesh v    fungi,    351— 
353 
artificial    cultivation    of    fleshy 
fungi,  352-353 
implications,  361 
poisonous  fleshy  fungi,  339-351 
classification     bv     toxic     effect, 

342-343 
identification        of       poisonous 

mushrooms,  343-349 
toxicologv,  350-351 
toxicity   of   Gibberella   saubinettii 
(G.  zeae)  and  Fusarium  spp., 
359-361 
Polygyra  thyroideus,  203,  209 
Polyporaceae,  98,  102,  114,  286,  410, 

486 
Polypores,  176,  408 
Polyporites 
foliatzis,  486 
bovmianii,  485 
broivnii,  485,  486 
Polyporus,  478 

abietinus,  26,  41,  51,  102,  114,  410 

adustus,  26,  44,  755 

betidinus,  41,  52 

cinnabarimis,  127 

conchifer,  410 

farloivii,  121 

fumosiis,  101 

hlrsutus,  103 

hispidus,  SI 

hicidus,  41,  52 

mylittae,  352 

ostreiformis,  46 

pargamenus,  410 

radiatus,  102 

rob'mophilus,  102 

sanguineus,  114 

schweinitzii,  44,  102,  410 

sinuosus,  102 

squamosus,   46,   57,    125,    148,    166, 

200,  201 
sulphur  eus,  43,  51,  102,  138 
texanus,  410 

vaporarius  spumarius,  99 
vaporarius  succinea,  485 
versicolor,  99,  102,  410 
volvatus,  47,  52 
zonalis,  46 
Polysaccharides,  79,  386 


528 


SUBJECT  INDEX 


Polysiphonia,  461 

fi  brill  osa,  461 
Polyspora  lini,  211-212,  260,  410,  411 
Polystictus,  202 

adustus,  101,  288 

hirsutus,  46 

leoninus,  46 

sanguineus,  46 

versicolor,  44,  45,  46,  51,  52,  101, 
112,    116,    117,    121,    155,    156, 
151,  158,  162 
Poly  stigma  rubra  in,  238 
Povwbolus  pseudoharengus,  463 
Populus,  174 

tremella,  302 
Porta 

cocos,  353 

in  eras  sat  a,  102 

subacida,  102 

vaporaria,  101 

xantha,  102 
Poronia  leporina,  404 
Porthetria  dispar,  174 
Posadasia,  370 
Posidonia  Oceania,  466,  46P 
Potassium,  3,  4,  8,  10,  311,  438 
Potassium  hydroxide,  389 
Potassium  iodide,  379 
Potato,   110,   145,   161,  231,  240,  245, 
303,  313,  400,  412,  437 

powdery  scab,  399 
Potato  scab,  161,  286 
Potato  wart,  399 
Powdery  mildews,  176,  186,  203,  252, 

253,  262,  268,  403 
Powdery  scab  of  potato,  399 
Prasiola  borealis,  466,  469 
Pre-Cambrian  period,  476,  477 
Predisposing    factors    in    infection, 

422 
Preissia,  298 
Proline,  83 

Propionic  acid,  20,  283 
Prosopis  juli  flora,  410 
Prosthecium,  405 
Protease,  48 

Proteolytic  enzymes,  389 
Protocatechuic  acid,  245 
Protocoronospora  nigricans,  211 
Protomycetaceae,  483 
Protonnycites  protogenes,  483 
Protopectin,  48 


Protopectinase,  48 
Protoparce  Carolina,  174-175 
Protozoa,  280,  292,  429,  443,  448,  454 
Prunus,  49 
P  sal  I  iota 

arvensis,  352,  409 

campestris,  82,  126,  166,  196,  191, 
200,  201,  339,  341,  345,  351, 
352,  353 

silv  i  col  a,  409 
Psathyrella  disseminata,  200 
Psendococcus  calceolariae,  445 
Pseudomonas  aeruginosa,  86 
Pseudomycorrhiza,  301,  302 
Pseud  opeziza  ribis,  227 
Pseudoplectania  nigrella,  190 
Pseudopleuronectes  americanus,  463 
Pseudopolyporus     carbonicus,     486, 

488 
Pseudotsuga  taxifolia,  404 
Psendovalsa,  405 
Psyllia  mali,  450 
Pteridiuni 

aquiliniwn,  299 

latiusculum,  406 
Pteridophyta,  299 
Pteridosperms,  477 
Ptychoverpa  bohemica,  136 
Puberulic  acid,  88,  163 
Puccinia,  407,  40,?,  485 

adoxae,  244 

annularis,  199 

anomala,  260,  215 

antirrhini,  223 

arachidis,  177,  408 

asparagi,  177,  214,  408 

calystegia,  200 

chrysanthemi,  177,  408 

clem  at  id  is,  200 

coronata,  200,  218,  219,  222,  223, 
230,  231,  234,  275.  333 

coronata  alopecuri,  258 

coronata  avenae,  172,  215,  258, 
260,  269,  276 

coronata  calamagrostis,  258 

coronata  festneae,  258 

coronata  lolii,  258 

coronata  melicae,  258 

coronifera,  82,  223 

coronifera  avenae,  274 

dispersa,  139,  223,  258,  262,  278 

dispersa  agropyri,  258 


SUBJECT  INDEX 


529 


Puccinia 

dispersa  brovii,  258 

dispersa  secalis,  258 

dispersa  tritici,  258 

fraxinata,  200 

glechoviatis,  199 

ghimarum,  177,  215,  219,  235,  258, 

260,  408 
ghimarum  agropyri,  258 
ghimarum  elyvti,  258 
glwnarum  hordei,  258 
ghimarum  secalis,  258 
glwnarmn  tritici,  258,  272,  278 
graviinis,    199,   200,   218,   220,   225, 
224,    229,    239,    245,    247,    256, 
257,    258,    267,    276,    277,    278, 
333,  336,  337,  338,  451 
graviinis  agrostidis,  258,  266 
graviinis    avenae,    258,    219,    231, 

260,  269,  272,  274,  334 
graviinis  phlei-pratensis,   177,  215, 

258 
gramims  poae,  258 
graviinis  secalis,  111,  258,  260,  274 
graviinis  tritici,  143,  148,  169,  172, 
174,    177,    215,    219,    231,    250, 
251,    253,    254,    258,    260,    264, 
266,    267,    269,    270,    271,    275, 
276,  278,  334 
grossulariae,  200 
helianthi,  174,  214,  333,  451 
hieraciata,  200 
impatientis,  200 

malvacearuvi,  177,  199,  223,  408 
menthae,  214 
peridermiospora,  214 
phlei-pratensis,  223 
poarum,  200 
pringsheimiana,  333 
pidvernlenta,  200 
rhavini,  138 
rubigo-vera,  223,  276 
rubigo-vera  secalis,  408 
rubigo-vera  tritici,  173,  250,  408 
ruelliae,  214 
simplex,  269,  275 

sorghi,  179,  214,  225,  250,  250,  277 
sydowiana,  214 
triticina,    172,    216,   225.    269,    275, 

276 
urticata,  200 
ivindsoriae,  214 


Pucciniaceae,  407,  485 
Pucciniastrum,  333,  406,  -/0£ 
Succinites 
cretaceous,  485 
cretaceum,  485 
lanceolatus,  485 
Whitfordi,  485 
Puffballs,  202,  339,  352 
Pulvis  parturiens,  356 
Pure  cultures,  280 
Pustularia  catinus,  190 
Pycniospores,  333 
'  Pyrausta  nubilalis,  445,  456 
Pyrenomycetes,    135,     186,    190-193, 

285,  403,  404,  460 
Pyridoxine,  25,  26,  28,  289 
Pyrirnidine,  27,  28 
Pyrogallic  acid,  230 
Pyrogallol,  44 
Pyrolaceae,  298 

Pyronema  confluens,  45,  190,  287 
Pyrus  coronaria,  411 
Pyruvate,  19,  20 
Pyruvic  acid,  59,  60,  62,  81,  163 
Pyruvic    acid    theory    of    fermenta- 
tion, 58,  59 
Pythiaceae,  460,  481 
Pythiacystis  citrophthora,  99,  116 
Pythiomorpha  gonapodioides,  27,  28 
Pythites  dysodilis,  481 
Pythium,  107,  155,  178,  299,  303,  437 

arrhenomanes,  26 

butler'i,  27 

de   baryanum,    160,  181,  245,  246, 
255 

marinnm,  466 

polycladon,  26,  27 

Quadripolar  sexuality,  328 
Quarantine,  420,  427 
Quaternary  period,  478,  483,  484,  485 
Quercus,  403 

cnspidata,  353 

robitr,  302 

varibilis,  353  . 

Quinol,  45 
Quotient,  respiratory,  62 

Rabbits,  176,  376,  404 
Radiation,  123-150,  265,  270 
effect,  of  X-rays,  145 
on  sporulation,  144 


530 


SUBJECT  INDEX 


Radiation,  implications,    147 
induction  of  saltations,  145-146 
inhibitory  effects,  138-143 
luminescence,  137-138 
mode  of  action,  147 
morphogenic  reactions,  125-129 
phototropism,   129-137 
stimulatory  effects,  143-144 
Radiculites  retictdatus,  487,  489 
Radioactive  carbon,  19 
Radioactivity,  476 
Radish,  398' 
Raffinase,  40,  46,  41 
Raffinose,  42 
Ramigenic  acid,  88 
Ramularites  oblongisporus,  486 
Ranunculaceae,  298 
Ranunculus  ficariae,  313 
"Raquette  cells,"  380,  381 
Rats,  367 

Raulin's  solution,  2,  79 
Ravenelia,  408 
cassiaecola,  407 
epiphylla,  407 
opaca,  407 
Ravenelin,  85 

Reaction  of  substrate,  151-164,  229- 
230,  280 
alkaline  fungicides,  162-163 
H+     concentration,    meaning    of, 
152 
measurement  of,  153 
implications,  163 
pH,  and  enzymatic  activity,  159 
and  growth,  155-157 
and  media,  157-158 
and  pigmentation,  159 
and  plant  disease,  159-161 
measurement  of,  154-155 
of  fungus  tissues,  158-159 
significance  of,  153-154 
Recent  Glacial  period,  478 
Recessive  characters,  317 
Reductases,  50 
Relative  humidity,  215,  218 
Rennetase,  46,  41 
Rennin,  40 
Resins,  45 
Resorcinol,  44,  45 
Respiration,  53-68,  83 
aerobic,  mechanism,  58 
anaerobic  mechanism,  58-62 


Respiration,  historical,  53-55 
implications,  66,  61 
inhibition,  65-66 

interrelations   of  aerobic   and  an- 
aerobic, 57-58 
respiratory  quotient,  62-63,  117 
respiratory  systems,  63-64 
respirometer  techniques,  64-65 
stimulation,  66 
tvpes,  56-62 
Respiratory  enzymes,  11 
Respiratory  pigments,  58 
Reticularia  ly  coper  don,  211 
Reticulotermes  hesperus,  175 
Rhamnus,  215 
Rhinotrichum,  431,  444 
Rhizidiomycetaceae,  461,  462 
Rhiziua  inflate,  190 
Rhizoctoma,   4,    107,    109,    178,    303, 
310,  437 
lanuginosa,  304,  309 
minor oides,  304 
repens,  303-304 
solani,  45,  99,  103,  116,  155,  161,  260, 

273,  276,  287,  296,  437 
rciolacea,  161 
Rhizomorpha  sigillariae,  485 
Rhizomorphites 
intertextus,  487 
polymorphic,  487 
Rhizophy ctis  rosea,  34 
Rhizophydium 
codicola,  461 
dicksonii,  460 
polysiphoniae,  461,  472 
Rhizopogon 
luteolus,  312 
roseolus,  312 
Rhizopus,   16,  48,  86,   106,   107,   268, 
280,  373,  431 
arrhizus,  76,  77,  224 
artocarpi,  224 
chinensis,  16,  102,  224 
delemar,  224 
elegans,  16 
japonicus,  16 
microsporia,  224 

nigricans,  4,  5,  14,  33,  45,  50,  75, 
77,  80,  82,  90,  104,  143,  156, 
157,  223,  224,  225,  226,  229, 
242,  255,  260,  281,  283,  399, 
433,  453 


SUBJECT  INDEX 


$31 


Rhizopus 

nodosus,  224 

oryzae,  32,  75-77,  224 

reflexus,  224 

suinus,  27-28,  141 

tritici,  18,  48,  51,  75-77,  224 
Rhodopaxilhis  nudus,  302 
Rhopobota  vaccmimia,  184,  444 
Rhytisnia 

acerinum,  190,  232 

salicinum,  189 
Rhytismites,  483 
Ribes 

americanwn,  22$ 

nigrum,  214,  22$ 

rotundijolium,  214 
Riboflavin,  25,  26,  41,  82,  290,  325 
Rice,  49,  281,  405 

Richards'  solution,  3,  $,  156,  157,  283 
Rickets,  82 

Ringworm,  366,  379-390 
Ripe  rot  of  grapes,  239 
Rocks,  474 

sedimentary,  475 
Rodents,  168^  176,  202,  251,  367 
Root,  mycorrhizal,  306,  309 
Roquefort  cheese,  49 
Rosaceae,  298,  403,  407 
Rosellinia  necatrix,  26 
Rosellinites 

Beyschlagii,  484 

congestus,  484 

congregants,  482 

schusteri,  481 
Roses,  238,  239,  244,  376,  407 

black  spot,  248 
Rotifer,  463 

Rozella  marinum,  461,  462 
Rozites  gonglyophora,  452 
Rubidium,  3 
Rubroglaucin,  84 
Russula,  285 

cyanoxantha,  302 

emetica,  201,  302,  343,  34$,  346,  351 

laricina,  302 

lepida,  302 

nigricans,  302 

rhodoxantha,  302 

rubra,  302 
Rusts,    84,    168,    169,    170,    176,    177, 
199-200,    214,    252,    263,    264, 
268,   271,    285,    327,   405,'  406- 
408,  417,  418,  419,  451 


Rusts,  blister,  285,  420 

Ruta,  231 

Rutaceae,  298 

Rye,  258,  262,  3$1,  358,  359 

Sabouraud's  media,  380 
Sabouraudia,  384 
Sabouraudites,  384 

aster oides,  386 

felmeus,  387,  392 

granidosus,  386 

gypseus,  386 

lactic olor,  386 

radiolatus,  390 

ruber,  390 
Sabulina  octona,  \16 
Sac  char  omyces,  431 

cerevisiae,  28,  60,  63,  77,  140,  145, 
268,   282,  288 

rosaceus,  282 
Saccharomycetaceae,  369 
Sake,  49 
Salamander,  174 
Salep,  310 
Salicaceae,  403 
Saltations,  145-146,  259,  385 
Sambiicus  nigra,  307 
Sanitary    measures    in    disease    pre- 
vention, 427 
Sapindaceae,  298 
Saprolegnia,  180,  181 

ferax,  19,  431,  459 

mixta,  4 

monoica,  19 

parasitica,  22 

torulosa,  168 
Saprolegniaceae,  459,   460,  461,  463, 

464,  466,  480 
Saprolegniales,  167,  180 
Saprotrophic  fungi,  1,  30,  295 
Sapwood  rots,  251 
Sarcoscypha 

coronaria,  190 

minuscula,  404 

protracta,  189,  190 
Sargassum,  469 
Scab,  of  barley,  360-361 

of  citrus,  269,  411,  449 

of  potatoes,  161,  286 

of  stone  fruits,  411 
Scale  insects,  408,  443,  445,  447,  448, 
449 


532 


SUBJECT  INDEX 


Schizomycetes,  373 
Schizoneura  lanigera,  173 
Schizophyllum,  202 

commune,  26,  101,  103,  105,  106, 
155,  156,  157,  158,  162,  328 
Scleroderma 
aurantiinn,  312 
vulgar e,  302 
Sclerospora,  211 

grcnninicola,    178,    214,    225,    226, 

230,  235 
graininis,  180 
philippinensis,  180 
Sclerotica,   4,   5,  48,    109,   243,    377, 
437 
cmerai,  26,  29,  48,  52,  104 
fructicola,   173,  190,  213,  234,  285, 

402,  443 
jructigena,  218,  231 
libertianci,   20,    189,   237,   238,   239, 

254 
sclerotiorum,  247 
trifoliorum,  143,  190 
Sclerotites  brandonianus,  482,  487 
Sclerotium,  178,  437 
bataticola,  18 
del  phi  ii  ii,  26,  27 
err zae-sativae,  2  8 1 
ro/fj/i,   26,   27,    111,  237,  238,   255, 
287 
Scolytidae,  451 
Scolytus,  451 

nrultistriatus,  174,  452 
scolytus,  174,  452 
-centralis,  457 
Scopulariopsis,  431 
Seaweed,  471 
Secale  luxurious,  356 
Secalintoxin,  359 
Second-division      segregation,      321, 

322,  323,  526 
Secotimn  acuminatum,  82 
Sectoring,  264-266,  272,  385 
Sedimentary  rocks,  475 
Seed  treatment,  427 
Seed-borne  fungi,  178,  410-411 
Selection,  427 
Semisolid  media,  418 
Sepedonium,  370,  431 
Septobasidium,  408,  448 
curtisii,  409 
pseudopedicellatwn,  409 


Septobasidium  rhobarbarinum,  409 
Septoria,  260 
apii,  178,  410 

lycopersici,     175,     410,     411, 
443 
Sequoia,  487 
Serica  sericea,  174 
Set  aria  italic  a,  233 
Seventeen-year  locust,  445 
Sex  linkage,  336 
Shag^gv  mane,  339 
Sheep;  176,  367,  374 
Sbii-take,  353 
Short-cvcled  rusts,  407 
"Short  roots,"  301 
"Shot  hole,"  49 
Sid  a  spin  os  a,  166 
Silk,  389 

Silk-worm  larva,  445,  449 
Sirex 

cyaneus,  175 
gigas,  175 
"Sky-hook,"  171 
Slime  molds,  280,  470,  480 
Slugs,  168,  176 
Smut  grass,  85 

Smuts,    108,    110,    176,    197-199,    214, 
216,    224,    252,    263,    264,    268, 
271,    305,    327,    329-333,    335, 
405-406,  418 
corn,  231 
covered,  272 
flag,  405 
kernel,  266 
loose,  272 
stinking,  405 
Smvrithurus,   173 
Snails,  168,  176 
Sodium  albuminate  agar,  430 
Sodium  bicarbonate,   163 
Sodium  caseinate  agar,  430 
Sodium  sulphite,  60,  78 
Sodium  tetraborate,   163 
Soil    fungi,    178,    286-287,    410-412, 
429-441 
biochemical  activities,  434-437 
decomposition       of       carbohy- 
drates, 435-436 
decomposition  of  proteins,  436- 
437 
implications,  437-438 
soil-borne  pathogens,  437 


SUBJECT  INDEX 


Soil   fungi,  taxonomic  studies,   429- 
434 
kinds  of  fungi  isolated,  430-432 
methods,  429-430 
number    of    fungi    in    soils    and 
factors      influencing      preva- 
lence, 432-434,  434  ' 
Solarium 

dulcamara,  313 

magia,  313 

tuberosum,  313 
Sorbose,  18 
Sordaria,  176,  191,  431,  484 

fimicola,  26,  187 
Sordariaceae,  484 
Sorosporella,  448 

uvella,  445,  446-447,  457 
Sorosporium     reilianam,     260,     267, 

278,  337 
Sow  bugs,  176 
Soya  sauce,  49 
Soybean,  237,  402 

fros^-eve  leaf  spot,  410 
Spawn,  353 

Spegazzinites    crucifor?uis,    482,    487 
Spermoedia  davits,  356 
Sphacelia,  355 

segetum,  356 
Sphacelic  acid,  358 
Sphaceloma  faivcetti,  269,  291,  411, 

449 
Sphacelotheca 

cruenta,  267,  278 

sorghi,  260,  266,  267,  276,  278 
Sphacelotoxin,  359 
Sphaerella  chondri,  469 
Sphaeria 

ellipsocarpa,  192 

inquinana,  192 

lanada,  192 

lemaneae,  192 

scirpi,  192 
Sphaeriaceae,  484 
Sphaeriales,  466 
Sphaerioidaceae,  486 
Sphaerites,  481 

suessi,  484 
Sphaero bolus,  202,  204,  205 

ionxensis,  209 

stellatus,  203,  209 
Sphaeronema,  430 

fimbriatum,  18 


Sphaeropsis,  5 

malorum,  22,  29,  104,  242 
Sphaerostilbe,  444,  449 
aurantiicola,  446-447 ',  449,  456 
coccophila,  447 
■flammea,  447 
Sphaerotheca 
humuli,  260,  278 
lanestris,  403 
mors-uvae,  186,  7## 
pamwsa,  403 
pannosa  var.  re^ae,  113 
Sphaerulina  trifolii,  26,  27 
Sphagnum,  310 
Sphenophorus  obscurus,  175 
S pic  aria,  171,  444,  445 
anomala,  452 
fariuosa,  447 
javanica,  446-441 
Spiculisporic  acid,  163 
Spinulosin,  85 
Spiral  hyphae,  380,  5S/,  383 
Spiralia,  5#-/ 
Sponges,  137 

spicules,  481 
Spongospora  subterranea,  399 
Spontaneous    generation,    417,    418, 

422 
Sporangioles,  299 
Spore  dissemination,  166-209 
distribution  of  spores,  167-179 
air  currents,  168-171 
animals  as  vectors,  175-177 
aquatic  fungi,  167-168 
insects  as  vectors,  172-175 
rate  of  fall  of  spores,  172 
seed-borne  fungi,  178 
soil-borne  fungi,  178 
spore  traps,  171-172 
terrestrial  fungi,  168 
the  human  agency,  177 
water,  179 
hygroscopic  mechanism  in  Myxo- 

mycetes,   179 
implications,  205 
spore    discharge   among   Ascomy- 

cetes,  186-193 
spore    discharge    among    Basidio- 

mvcetes,  194-205 
spore  expulsion  among  Phycomy- 

cetes,  180-186 
structural  adaptation,  179 
Spore  germination,  96,  210-235 


534 


SUBJECT  INDEX 


Spore  traps,  110,  111 
Sporobolus,  85 
Sporodinia  grandis,  319 
Sporormia 

bi  partis,  192 

iiitennedia,  189 
Sporotrichites  heterospemnis,    486 
Sporotrichum,  171,  388 

anthophihnn,  173 

beunnanni,  375,  376 

bombycinum,  435 

equi,  US 

globulijerum,  445 

griseolinn,  435 

inarit'nnum,  470 

olivaceitm,  435 

potfe,  377 

roseohim,  435 

schenckii,  375-377,  37  tf 
Spruce,  300,  303,  305,  311,  312,  452 
Sprue,  379 
Squash,  401 
Squash  bugs,  173 
Squids,   137 
Squirrel,  ground,  367 
Stachybotrys,  431 

alternans,  435 
Staining  of  wood,  162,  174,  372,  443, 

452 
Staling  products,  242,  265,  282,  283 
Staphylococcus,  87,  373 

albus,  284 

aureus,  87,  284 
Starch,  19,  74,  390,  436,  460 

soluble,  65,  386 
State    agricultural    experiment    sta- 
tions, 420 
Stearic  acid,  80 
Stegites  poacitum,  483 
Stegomyia  scutellaris,  444,  456 
Stem  rust  of  cereals,  170,  266 
Stenwnitis,  398 

favogenita,  211 

ferrnginea,  211 

fuse  a,  397 
Steniphylium,  171 

codi'u  470 
Stereum,  202 

fasciatum,  102,  114 

frustulosum,  26,11,  98,  44,  100,  102 

fuscum,  103 

gausapatum,  102,  120,  155,  164 

hirsutuvu  100 


Stereinn 

lobatum,  114 

purpurewn,  44,  47,  52,  98,  iOO 

rameale,  102 

rugoswn,  100 

sanguine  olentum,  175 

spadiaceum,  100 
Sterigfnatocystis,  106 

Wgrtf,  29,  32,  33,  92,  151,  242 
Sterols,  25,  81-82 
Stictidiaceae,  483 
Stigmaria,  481 
Stig7tratea  pehetiae,  469 
Stilbaceae,  487 
Stilbites  coniventzi,  487 
Stinkhorns,  202 
Stinking  smut,  176,  405 
Stokes'  law,  172,  201 
Stomata,  236,  240,  246,  248-251 
Stomatoscope,  248 
Straw,  389 
Strawberry,  309 
Streptococcus,  87 

lactis,  76 

viridans,  284 
Streptothrix,  375 

Strobilomyces   strobilaceus,    86,    302 
Strobilomycol,  86 
Strontium,  3 
Stropharia 

depilata,  409 

psathyroides,  409 
Stypocaidon  scoparum,  469 
Stysamis,  431 
Succinic  acid,  19,  20,  61,  71,  73,  75, 

76,  78,  163 
Sucrase,  39,  40,  45  46,  41 
Sucrose,  18,  19,  42,  45,  61,  64,  74,  80, 

390,  430 
Sugar  beet,  229,  250 
Sugar  cane,  166,  174,  445 
Sugar-cane  borer,  175 
Sulfonamides,  284,  427 
Sulphur,  3,  4,  10,  438,  478 
"Sulphur  granules,"  375 
Surface  tension,  196-197 
Suscept,  422 
Sweet  potato,  224,  225 
Svchosis,  366 
Svlindein,  85 
Symbiosis,    279,    304,    305,    306,    313, 

466,  488 
Synchaeta  vwnopus,  463 


SUBJECT  INDEX 


535 


Synchaetophagus   balticus,   463,   471 
Synchytrium      endobioticum,      145, 

161,  240,  255,  400 
Synergism,  279,  290-292 
Syringospora 

albicans,  378 

psilosis,  378 
Svrups,  49 
Systremma  acicola,  179 

Tangerines,  450 
Tannase,  40,  46,  41 
Tannic  acid,  44 
Tannin,  45 
Taphrina,  211 

deformans,  136,  137,  150,  402 

mirabilis,  285 
Tarichium  nvella,  445 
Tartaric  acid,  79 
Teeth,  374 
Tegula,  469 

fwiebralis,  468 
T eleutosporites  milloti,  485 
Temperature,   96-122,    210,    221-229, 
265,    269,    270,    280,    282,    313, 
389,  470 

and  reproduction,  111-114 

cardinal,  97-103 

implications,  119 

influence,  on  infection,  109-111 

oxvgen  tension,  117 

resistance  to  low  and   high,    103- 
109 

zonation,  114 
Temperature    coefficients,    96,    114- 

117 
Terfezia  leonis,  303 
Terminal  clubs,  380 
Termites,  175,  451,  454 
Terpenes,  45 
Terrestric  acid,  163 
Tertiary  period,  477,  483,  485,  487 
77-Tetracosic  acid,  80 
Tetraplodon,  299 
Tetrapolar  sexuality,  328,  329 
Texas  cattle  fever,  443 
Texas  root-rot  fungus,  412 
Textiles,  49 
Thalassomyces 

batei,  464 

spizakovii,  464 
Thalassomycetineae,  464 
Thaimridhmt  elegans,  270 


Thelephora,  85 
Thelephoraceae,  98,  102,  114 
Thelephoric  acid,  85 
Thermal  death  point,  226-228 
Thermolabile     metabolic     products, 

283,  289 
Thermostable     metabolic     products, 

283,  289,  350 
Thiamin,  25,  26,  27,  28,  41,  66,  82, 

288,  289 
Thiazole,   27,   28 
Thielavia    basicola,    161,    255,    291, 

295,  402 
Thielaviopsis,  109,  178,  437 

basicola,    246,    264,    275,   402,   423, 

428 
paradoxa,  111,  225,  226,  229 
Thraustochytridium  proltferum,  461, 

462 
Thraustotheca,  461 
Thread  blight,  409 
Thrips,   175 
Thrush,  378 
Thuja  occidentalis,  405 
Tibicina  septendecem,  445 
Ticks,  172,  443 
Tiliaceae,  407 
Tilletia,  485 
asperifolia,  197 
foeta?is,  405 
hold,  197 
horrid  a.,  405 
lews,  197,  260,  267,  272,  274,  276, 

277,  330,  337 
tritici,  166,  178,  197,  198,  216,  260, 
267,    272,    274,    277,    330,    337, 
405 
Tilletiaceae,  197,  198,  211,  485 
Timothy,  256 
Tinea,  379,  384 
Titania,  405 
Titrable  acidity,  151 
Toadstools,   339 
Tobacco,    108,    242,    246,    303,    401- 

403,  427 
Tobacco  black-shank,   178 
Tobacco   downy  mildew,    111,    177, 

401 
Tobacco  kroepoek,   172 
Tobacco  root-rot,  105,  109,  161,  246 
Tolyposporiwn  biirswn,  216 
To?naspis  varia,  445 
Tomato,  242,  246,  412 


536 


SUBJECT  1XDEX 


Tomato-leaf  mold,  410 
Tomato-leaf  spot,  410,  443 
Tonsils,  374,  375 
Tor ula,  29,  82,  373 

cerevisiae,  55 

histolytica,  369 

rubra,  82 

saccharina,  29 
Toritlites  moniliformis,  486 
Torulosis,  366,  368-369 
Total  acidity,  151 
Toxicology,  350-351 
Toxins,   89,   237,  238,  250,  280,  282, 

284,  286 
Tradescantia,   241 
Trailia  ascophylli,  469 
Trametes,  410 

c  in  gnl  at  a,  46 

gibbosa,  101 

lactinea,  46 

pini,  51,  102 

radiciperda,  44 

serial  is,  101,  102,  127 
Transpiration,    307 
Tranzschelia  pruni-spinosae,  407 
Trehalase,   40 

Trematosphaerites  lignitum,  484 
Tremella  mesenterica,  82 
Triangle  system,  7,  9,  12 
Triassic  period,  477,  487 
Tributyrin,   390 
Trichaviphora  pezizoides,  397 
Trichia,   179 

botrytis,  211 

favoginea,  211 

lateritia,  211 

scabia,  211 
Trichocladhim  asperum,  435 
Trichoderma,  50,  107,  171,  175,  434, 
435,  437,  453 

flai'obrwinewn,   302 

koningii,  15,  433,  436 

lignoritm,    11,   287,   289,   296,   432, 
4r3  3 

viride,  88,  90 
Tricholoma 

albobrunneum,  312 

imbricatum,  312 

pessundatum,  312 

portentosum,   352 

subgambosum,  454 

terreus,   303 

vaccinium.  312 


Trichophytids,   387 
Trichophyton,  366,  SSI,  383 

acuminatum,  389,  390 

album,  389 

cerebriforme,   388 

crateriforme,  389 

denticulatum,  386 

discoides,  25,  34 

ectothrix,  5#2,  383,  384,  389 

endothrix,  3<?2,  383,  384,  389 

flavum,  389 

floccosnm,  389 

granulosum,  388,  389 

gypseum,    384,    385,    388,    389,    301 

interdigitale,  4,  15,  19,  25,  33,  388, 
389,  390,  392 

magnini,  390 

mentagrophytes,  140,  146,  149,  389 

neoendothrix,  383,  3#4 

polygomnn,  389 

radians,  386 

radiolatnm,  390 

sabouraudia,  384 

sulfur eum,  389 

tonsurans,  384,  389,  390,  394 

vinosum,  390 
Trichophytoneae,   365,   379-390,   5S-J 
Trichosporium,  372 

symbioticuvu  452,  457 
Trichothecium  roseum,   224-225 
Trimethylarsine,  88 
Tripalmitin,  62 
Triticum  vulgare,  215 
Tritisporin,  85 
Trout,  462 
Truffles,  306,  352 
Trypodendron  betnlae,  453 
Trypsin,  40,  41,  -M,  -*7 
Tryptophanase,  42,  82,  83 
Tryptophane,  40 
Tsuga  canadensis,  405 
Tuber,  303 

aestivum,  352 

melanospernium,  352 
Tuberculariaceae,  487 
Tuber rulina   maxrma,   285 
Tuberculosis,  368,  379 
Tuberization,  312-314 
Tungsten,   16 
Turnips,  103,  116,  398 
Typha,  485 
Typhoid,  87 


SUBJECT  INDEX 


531 


Typhula 

gramineum,   160,   161 

incamata,  158 
Tyrosinase,  40,  46,  41 
Tyrosine,  23,  41,  44,  45,  65 

U hints  americana,  410 

Ultraviolet,    123,  124,   139,    142,   143, 

146,  325,  388 
Ulva,  468 

californica,  466,  469 
Unci  mil  a 

aceris,  403 

flexitosa,  403 

geniculata,  403 

salicis,  403 
Uncimdites  baccarini,  482,  483 
United  States  Department  of  Agri- 
culture, 420 
University  of  Wisconsin,  420 
Uranium,  16,  476 
Urea,  55,  390 
Urease,  40,  41,  46,  41 
Uredinales,  1,  211,  318,  327,  333-335 
Uredinopsis,  406,  408 

adianti,  406 

investita,  406 

macrosperma,  406 

mayor'icma,  406 
Urmda 

crater h im,  190 

ge aster,  189,  190,  404 
Urocystis,  485 

anemones,  214 

cepulae,    110,    122,    178,    214,    216, 
223,  235 

occulta,  223,  229,  234 

tritici,  223,  234,  405,  415 
Uromyces,  333,  407,  408 

appendiculatus   phaseoli,    177,   408 

appendiculatus  vignae,   111,  408 

betae,  111,  408 

bidenticola,   174 

caryophyllinus,   177,  223,  241,  408 

frt/^e,  220,  241 

phaseoli,  242 

pw,  200 

poae,  200 

mfo///,  177,  223,  408 
Uromvcladium,  407 
Urophlyctites 

oliverianus,  481 

stigmariae,  480,  481 


Uropyxis,  407,  40«? 
Uschinskv's  solution,  3 
Ustilaginaceae,  197 
Ustilaginales,  211,  318,  329-333 
Ustilago,  170 

avenae,    108,    178,    220,    223,    234, 
260,  267,  272,  276 

Zw//tfta,  335,  337 

hordei,  219,  250,  267,  274,  330 

levis,  260,  267,  272,  276,  330 

longissima,  214 

medians,  267,  350 

7?7/</a,  145,  219 

striaeformis,  214,  223,  233 

tritici,  108,   145,  250,  275 

violacea,  260,  274,  278 

zeae,   143,   149,  231,  235,  264,  273, 
274,    277,    278,    285,    293,    329, 
330,    331,    332,    336,    337,    338, 
405 
Uterine  contraction,  356,  358,  359 

Vaccines,  423 
Vaccinium 

corymbosum,  304 

macrocarpon,   184,  304 

myrtillus,  304 

ovatum,  304 

oxy coccus,  304 

pennsylvanicum,  304 

vacillans,  304 

■vitisidaea,   304 
Valeric  acid,  283 
Valley  fever,  367,  437 
Van  Tiegrhem  cells,  212 
Vanda,  304,  310 
van't  Hoff's  rule,  98,  114 
Varianose,  79 
Variation,  257,  259 
Vectors  of  fungi,   172-179,  442,  443 
Velvet-stemmed  mushroom,  339 
Venturia    inaequalis,    170,    192,    218, 

219,   228,  402 
Vermicularia,  5 

circinans,  245 
Verpa  bohemica,  99,  136 
Verticillic  acid,  88 
Verticillium,  109,  178,  431,  444 

albo-atrum,  97,  99,  113,   117,  118, 
120 

candidum,  453 

cellulosae,  435 


538 


SUBJECT  INDEX 


Verticillhnn 

cinnamomeum,  449 

glaucum,  435 

heterocladiwn,  446-447 
Vesicle,  303 
Vetch,  403 
Vibrio  cholerae,  87 
Vicia  faba,  240 
Violaceae,  298 
Viridin,  88 
Viruses,  443,  448 

Vitamins,   81-82,   88,   266,   280,   288, 
325,  331,  379 

Vitamin  A,  82 

Vitamin  B  complex,  325 

Vitamin  B,,  25,  26,  27,  28,  41,  66, 
82,  288 

Vitamin  B4,  82 

Vitamin  D,  81 

Vitamin  H,  289 
Vol ut el Ha  jructi,  104 
Volva,  343,  344,  341 

Warburg  respirometer,  64,  66 

Wasps,  172,  173,  175,  443 

Wasting     disease     of    Zostera,     460, 

466 
Water,  211,  218-221 
"Water  molds,"  430,  431 
Watermelon,  401,  403,  410,  412 
Weather,  210 
Weevil,  454 

Wheat,   108,   145,   168,   169,  257,  267, 
270,  271,  303,  359,  405,  419 

Ceres,  271 

durum,  271 

flag  smut,  405 

Kanred,   334 

Marquillo,  269 

.Marquis,  269 

.Mindum,  241,  335 

rust,  239,  251 

stem  rust,  266 

Thatcher,   271 

vulgare,  2 "2 
White  ants,  454 
White  flies,  449,  450 
White-pine  blister  rust,  177 


White  rot  of  woods,  44 
Willow  scab,   177 
Wilting,  361 
Wine,  53,  54 

Wood-destroving      fungi,      98-103, 
436 
enzymes,  43^8 
Woodpeckers,  176 
Worm,  horn,  174 
Wort,  430 

Wound  penetration,  251-252 
MToJ7iowicia  graminis,  282 
Wuchereria  bancrofti,  442 

Xanthone,  84 

X-rays,  123,  124,  145,  146,  325,  335 

Xylaria 

hypoxylon,  138 

viicrttra,  452 

nigripes,  454 
Xyleborzis  dispar,  451 
Xylomites 

astertformis,  483 

polar  is,  487 

zamitae,  487 
Xylose,  18,  21,  79,  80 

Yeast,  27,  28,  43,  54,  55,  61,  62,  66, 
69,  76,  77,  82,  144,  147,  270, 
288,  289,  325,  365 

baker's,  268 

brewer's,  268 

Zignoella 

calospora,  469,  412 

enormis,  469 
Zinc,  3,  7,  10,  11,  14-16,  289 
Zonation,  114,  127-129 
Zootermopsis   angiisticollis,    175 
Zostera,  460 

marina,  466,  461,  469,  470,  473 
Zygorhynchus,  431 

'mblleri,  26,  145,  433 

vuilleminii,  432,  433 
Zvgosaccharomvces  acidifaciens,  290 
Zygote,  318 

Zymase,  40,  42,  57,  58,  390 
Zymonema  dermatitidis,  369