July  11,  1895. 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER. 
37 
Fig.  5. — Section  of  Potato  tissue  affected  with  curl  and  dry  or  wet 
rot  fungi. 
The  section  A  is  from  living  tissue  or  that  diseased,  yet  not  wholly 
destroyed  ;  but  B  is  from  dead  matter  from  the  same  plant.  Which  of 
these  fungi  is  the  cause  of  the  disease — that  is,  producing  the  collapse  of 
the  Potato  crops  in  Cheshire  and  other  parts  of  the  country  at  the  present 
time  1  Both  !  Nothing  of  the  kind.  The  presence  of  carrion  crows 
does  not  imply  that  they  killed  the  carcase  on  which  they  are  feeding, 
but  they  are  there  in  consequence  of  death  by  natural  causes  or  the 
injuries  inflicted  by  some  other  agent;  therefore,  we  must  look  closely, 
examine  carefully,  and  obtain  evidence  leading  to  a  correct  judgment. 
In  this  case  tte  disease  is  not  produced  by  curl  fungus,  for  it  is  in  the 
part  above  ground,  in  the  living  but  impaired  tissue,  while  the  dry  rot 
fungus  is  on  the  stem  and  wholly  below  ground,  and  present  in  all  its 
various  conditions.  The  plant,  however,  presents  all  the  symptoms  of 
curl  disease,  and  well  it  may,  as  it  is  also  attacked  by  the  fungus  pro¬ 
ducing  it,  yet  it  has  no  connection  whatever  with  dry  rot  fungus  to 
which  we  will  now  proceed  definitely. 
In  the  illustration  (fig.  6,  C)  is  shown  a  Potato  top,  half  natural  size, 
as  sketched  on  June  6th,  1895.  The  leaflets  curled  upwards,  the  whole 
haulm  being  more  or  less  discoloured.  On  the  stem  was  a  diseased 
patch  (.s),  encircling  it,  and,  cutting  off  the  supply  of  nutriment,  accounted 
for  the  cessation  of  the  growth,  curling,  drooping,  and  collapse  of  the 
haulm.  Taking  a  traverse  section  (i)  through  the  diseased  part,  and 
subjecting  it  to  a  power  of  five  diameters  (m),  certain  growths  appeared 
from  the  discoloured  part  externally,  the  jarownish  matter  being 
mainly  confined  to  the  vessels  (vascular  tissue)  surrounding  the  hollow 
part  (®).  On  further  examination,  and  a  power  of  260  diameters, 
the  section  of  stem  and  the  fungoid  growth  being  in  the  same 
sketch  as  the  Potato  top,  have  been  reduced  half,  showing  sufiicient 
for  all  practical  purposes,  that  enlargement  was  brought  to  bear  upon 
the  fungus  appearing  at  (w),  and  behold  it  was  Reinke’s  and  Berthold’s 
Verticillium  atro-album,  now  called  Diplocladium  solani,  syn.  D.  lyco- 
persici  (Zl).  Still  further  prying,  our  old  enemy  the  “dry  rot”  fungus, 
Fusarium  (Fusiporium  of  old  times)  solani,  syn.  F.  lycopersici  (Z^  came 
into  view,  and  lastly  in  the  most  decayed  part  of  the  tissue,  the  resting 
spores  or  “  fruits”  of  the  Fusarium,  this  term  being  manifestly  inappli¬ 
cable,  as  the  “  fruit  ”  only  should  give  the  generic  definition,  which  in 
this  case  is  Hypomyces  solani,  from  the  seed  or  spore  of  which  (F’) 
issues  the  germ  tube  entering  the  Potato  plant,  and  producing  dry  rot 
or  wet  rot,  according  to  time  of  year,  in  Potatoes  and  the  “  drooping  ” 
disease  in  Tomatoes.  The  resting  spores  or  fruits  (a?)  are  formed  of  a 
single  septa  or  cell  (as  common  in  some  Algae)  some  unknown  sexual 
union  taking  place,  at  least  in  some  cases,  for  the  resting  spores  are  of  two 
kinds,  the  mature  (y)  sometimes  only  producing  one  growth  (germinal  tube 
or  pro-mycelium)  (yf).  which  entering  a  Potato  or  Tomato  stem  below 
ground  gives  rise  to  the  Verticillium  or  Diplocladium  stage  (D)  about  fifteen 
days  in  warm  weather,  twenty-one  to  twenty-eight  or  thirty  in  cold 
weather  after  entering  the  Potato  plants,  always  when  the  mycelium 
has  become  firmly  seated  in  the  vascular  tissue  of  the  plant,  and  able, 
if  need  be,  to  ascend  the  stem  without  destroying  the  cellular  or 
epidermal  tissues,  or  at  any  rate  be  capable  of  forming  resting  spores  in 
the  attacked  part,  for  be  it  understood  that  the  fungus  has  not  matters 
all  its  own  way,  the  plant  resisting,  and  sometimes  is  able  to  throw  off 
the  enemy,  as  in  the  case  of  the  plant  figured,  which  we  will  allude  to 
presently.  But  sometimes  two  growths  issue  from  a  resting  spore  or 
fruit  (z),  the  one  (zP)  being  a  pro-mycelium  or  germ  tube,  septate,  and 
every  septa  capable  of  producing  a  new  cell  or  continuing  the  growth  if 
detached  ;  the  other  (zJ)  strikes  for  the  air  (understand  the  fruits 
always  germinate  in  the  soil,  in  moist  dead  tissue,  or  on  the  ground), 
and  produces  the  Diplocladium  stage,  the  conidia  of  which  are  septate, 
or  consist  of  two  conidium  or  spores,  and  these  are  scattered  by  the 
wind,  and  falling  on  a  suitable  nidus  germinate,  and  give  rise  to  their 
and  the  Fusarium  stage  (Z').  So  also  the  germinal  tube  entering  a 
Potato  or  a  Tomato  stem  below  ground  gives  rise  to  the  Diplocladium, 
which  is  followed  in  about  a  week  by  the  Fusarium  stage,  and  that  in 
turn  by  the  Hypomyces  or  resting  spores,  which  tide  the  fungus  over 
the  winter  or  indefinitely.  The  Fusarium  can  only  produce  Fusarium, 
and  its  resting  spore,  or  the  germinal  hyphre  from  it,  can  only  give  rise 
to  Diplocladium.  I  hope  I  have  made  the  life  history  of  dry  rot  fungus 
in  Potatoes  and  drooping  disease  in  Tomatoes  quite  clear. 
But  there  is  another  phase  of  the  subject  that  requires  careful 
consideration — namely,  the  dry  rot  from  planting  diseased  sets.  This  is 
a  common  cause  of  collapse  when  the  plants  are  a  few  inches  high,  as  in 
the  engraving.  If  the  sets  are  cut  through  before  planting  they  will  be 
found  to  contain  a  number  of  reddish  streaks,  especially  at  the  thread 
end,  where  the  woody  bundles  are  situated,  and  these  pass  through  the 
Potato  (which  is  simply  an  underground  stem  thickened  into  a  tuber), 
and  up  these  threads  the  mycelium  or  hyphte  makes  its  way.  If  the 
plant  has  sprouted  up  these  sprouts  the  hyphae  passes,  and  when  near 
the  surface  of  the  soil  breaks  through  the  cellular  tissue  and  pushes  out¬ 
growths,  first  the  Diplocladium  (D),  and  then  the  Fusarium  (-Z),  while 
within  the  vascular  system  the  “fruits”  (Z)  are  formed.  Should  the 
fungus  mycelium  destroy  the  cells  all  round  the  stem  it  is  all  over 
with  the  plant.  But  Nature  is  strong,  especially  in  the  struggle  for 
existence,  and  it  heals  over  the  wound  by  occlusion,  throws  on  the 
external  wall  a  coating  of  silica — a  flinty  barrier  that  no  fungal  growths 
can  penetrate.  It  puts  forth  a  root  (a)  into  the  soil,  forms  a  tuber  (J) 
out  of  a  shoot  or  stem,  and  repeats  it  at  c,  this  having  leaves  at  its  eye 
end.  Such  tubers  are  of  no  use  for  food  ;  they  are  everything  to  the 
plant — essential  to  its  perpetuation.  The  top  dies,  but  the  tubers  (&,  c) 
remain — the  fungus  is  foiled.  i 
Gardeners  take  advantage  of  this  in  the  case  of  drooping  disease  in 
Tomatoes  and  earth  up  the  plant,  for  it  pushes  roots  freely  from  the 
stem,  and  thus,  despite  the  fungus,  they  secure  a  good  crop  of  fruit  in 
some  cases,  but  not  always,  for  the  fungus  may  have  mycelia  in  the  stem 
above  the  point  of  first  attack,  and  then  it  breaks  out  here  and  there 
from  the  stem  and  sometimes  from  the  fruit,  being  given  all  kinds  of 
names,  such  as  blotch,  spot,  stripe,  and  rot.  The  spores  of  both  Diplo¬ 
cladium  and  Fusarium  are  spread  far  and  wide,  but  usually  do  not 
germinate  on  living  Potatoes  or  Tomatoes.  This  is  conditional  on  their 
being  perfectly  healthy  and  fortified  in  the  epidermal  cells  with  silica, 
lime,  magnesia,  and  iron  ;  but  they  will  grow  on  dead  or  decaying  tissue,, 
of  which  there  is  no  lack  on  both  Potatoes  and  Tomatoes,  and  once  in 
the  mycelium  will  grow  and  produce  the  Fusarium  stage  and  the  resting 
spores.  All  is  mistake  about  its  being  a  saprophyte,  but  it  leads  an 
endophytic  life,  hence  it  is  fostered  by  decaying  matter,  the  Diplo¬ 
cladium  being  followed  by  the  Fusarium,  and  that  by  the  resting  spores 
in  the  soil  or  on  any  decaying  vegetable  matter,  even  on  humus  and 
manure  or  even  very  rich  soil. 
The  soil,  therefore,  and  the  dead  plants  are  the  source  of  the  evil. 
Affected  plants  should  be  burned  —  haulm  of  Potatoes,  tops  of 
Tomatoes.  Then  disinfect  the  soil  by  dressings  of  quicklime,  using 
1  peck  per  rod  as  a  preventive  measure,  and  double  that  quantity  in 
case  of  attack  slightly,  and  four  times  in  bad  cases.  Dusting  quicklime 
(air-slaked)  on  plants  is  an  excellent  dressing  for  either  Potato  o? 
Tomato  crops,  for  that  will  make  an  end  of  any  dead  or  decaying  tissue, 
drying  it  up  and  hardening  the  epidermis  of  the  living  parts,  but  the 
thing  is  to  get  the  lime  into  the  soil  so  as  to  destroy  the  fungus,  and 
into  the  plant  so  as  to  enable  this  to  place  it  in  the  woody  fibre,  on  the 
cell  walls,  and  especially  on  the  epidermis.  The  lime  should  be  applied 
freshly  slaked — hot — in  March  for  Potatoes,  and  a  month  or  six  weeks 
before  use  for  compost  intended  for  Tomatoes,  one-tenth  not  being  too- 
much  for  rich  composts,  mixing  thoroughly.  Thorough  cleanliness 
should  be  practised  in  the  houses,  not  being  afraid  of  using  hot  lime- 
wash  in  Tomato  structures,  while  every  precaution  should  be  taken  to 
FIG.  6. —  DKY  EOT  FUNGUS  IN  POTATOES. 
C,  infested  Potato  top ;  s,  stem  girdled  by  fungus ;  t,  transverse  section  of  stem,  half 
natural  size;  u,  the  same  enlarged  five  diameters;  i;,  vascular  tissue ;  w,  point  of 
breaking  forth  of  fungal  outgrowths.  D,  Diplocladium  solani,  first  stage  of  fungus 
from  mycelial  hy  ph®.  E,  Fusarium  solani,  second  stage  of  fungus,  which  is  somewhat 
ousing  and  often  accompanied  with  bacteria,  F,  Hypomyces  solani,  final  or  resting 
stage  of  fungus;  x,  formation  of  resting  spore;  y,  mature;  yl,  single  growth 
from  resting  spore  ;  z,  resting  spore  pushing  two  growths  ;  ^2,  ordinary  pro¬ 
mycelium  ;  zZ,  pro-mycelium  producing  Diplocladium  solani.  Eecuperation  of 
Potato  plant  from  above  attacked  part ;  a,  root ;  &,  tubes  from  a  shoot ;  c,  tuber¬ 
like  shoot  with  growing  leaf  eye,  both  capable  of  resting  and  of  reproducing  or 
continuing  the  plant. 
plant  only  sound  sets  of  Potatoes,  treating  them  with  freshly  slaked 
lime  before  planting,  especially  cut  ones. 
In  the  case  of  the  drooping  disease  infesting  the  part  above  ground 
in  Tomatoes,  the  plants  should  be  pulled  up  and  burned,  removing  as 
much  of  the  root  portion  as  possible  from  the  soil,  and  use  quicklime 
freely  for  disinfecting  the  soil.  Stone  lime  is  much  better  than  chalk 
lime,  being  much  stronger,  it  being  essential  that  it  be  freshly  burned, 
enough  water  only  used  to  slake  it,  and  apply  while  hot  and  floury, — 
G.  Abbey. 
