December  15,  1898/  JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER*  46$  " 
DISEASED  POTATOES. 
.  “  W.  P.’s  ”  specimens  were  remarkably  infested  by  pests.  One 
of  .the  tubers  bad  the  eye  end  shrunken,  blackened,  and  hollowed,  as 
shown  in  fig.  79,  A  at  a.  In  this  part  were  found  two  wire- 
worms  B,  or  larvae  of  the  click  beetle,  Elater  lineatus,  which  sufficed 
to  account  for  the  damage  there.  At  the  heel  end  of  the  Potato 
existed  an  excrescence  ( b ),  warted,  cracked,  scabbed,  and  decayed  ; 
the  colour,  to  a  great  extent,  brown,  but  in  the  depressions  black  and 
moist.  On  the  side  there  was  also  an  excrescence  (c),  similar  to  the 
other  at  the  heel. 
In  both  the  cracked  and  decaying  hollowed  parts  a  number  of 
minute  white  creatures,  about  inch  in  length,  were  browsing. 
They  belong  to  the  Thysanura,  or  “  spring-tails  but  thi3  form,  O, 
named  Lipura  fimetaria,  is  not  a  “jumper.”  The  animals  are  vege¬ 
tarians,  and  live  on  Carrots,  Parsnips,  and  other  fleshy  roots  ;  but  are 
probably  not  direct  causes  of  mischief,  as  they  are  chiefly  found  on 
parts  that  have  been  injured  or  partially  eaten  by  larger  pests. 
The  other  specimen  of  Potato,  D,  contained  several  protuberances 
on  various  parts  of  the  skin,  some  ( 'd )  beginning,  and  others  (e)  more 
advanced  in  development.  No  trace  of  animal  life  was  discovered  in 
the  cracks  of  the  excrescences,  which  were  black  and  moist,  the  warts 
being  brown  and  scabbed. 
Evidently  the  disease  was  not  the  ordinary  Potato  scab,  though 
somewhat  similar  at  the  commencement  of  the  infection,  but  instead 
of  eating  the  tuber  away,  the  infested  parts  swelled  out  somewhat 
after  the  manner  of  supertuberation,  yet  in  an  excrescent,  not  regular, 
way.  This  proceeded,  apparently  for  a  time,  then  the  tuber  turned 
black  where  attacked,  and  the  infection  spread  rapidly  until  the 
whole  or  greater  part  of  the  tuber  decayed  or  dried  up. 
On  examination  in  section,  E,  it  was  found  that  the  skin  (/)  was 
wholly  destroyed,  and  the  tissue  in  contact  blackened.  The  inner  part 
of  the  flesh  was  also  more  or  less  streaked  with  brown,  and  con¬ 
centrically  ( g ),  which  communicated  here  and  there  ( h )  with  the 
outside,  whence  the  causing  agent  unquestionably  commenced  and 
passed  from  into  the  tissues  of  the  tuber. 
Now  for  the  microscopic  examination.  A  bit  of  the  outer  surface 
of  the  tuber  A ,  from  the  part  b,  appeared  as  shown  at  F- — a  fungus, 
Oospora  scabies.  The  fertile  hypha  (i)  short,  sparingly  branched ; 
conidia  (./),  concatenate,  nearly  globose ;  sterile  hyphm  or  mycelium 
(/c)  interlaced,  and  from  which  spring  here  and  there  globose  bodies  ( l ), 
with  a  dense  wall,  and  the  centre  appearing  like  an  eye.  The  erect 
hypha  (to)  could  not  be  determined  with  certainty,  as  there  were  no 
conidia. 
Not  being  satisfied  that  the  Oospora  scabies  could  cause  the  swelling, 
whatever  it  may  have  to  do  with  scab,  a  section  through  the  browned 
internal  part  of  the  tissues,  shown  at  G,  revealed  something  extra¬ 
ordinary.  1,  There  existed  a  cavity  («),  which  corresponded  to  the  brown 
streak  in  E  g.  2,  The  Potato  cells  ( o )  alongside  were  dead,  only  the 
cell-walls  remaining  in  places  in  skeleton  form.  3,  In  two  of  the  living 
cells  were  amoeba-like  bodies  (p).  4,  An  advancing  spumous  body 
or  naked  mass  of  protoplasm  ( q ).  5,  Four  dark  brown  nearly  black 
cells  (r).  6,  Some  dead  or  empty  cells  adjoining  the  last  named  (s). 
7,  Living  cells  ( t ). 
Other  sections  gave  similar  results.  The  brown  part  in  E  had  been 
occupied  by  the  amoeba-like  body,  to  wit,  a  slime-fungus  or  member 
of  the  lowest  class  of  plants — Myxomycetes — and  its  action  had  caused 
the  abnormal  swelling  of  the  stem  of  the  host  plant  (a  Potato  tuber  is 
an  underground  stem),  similar  to  clubbing  in  Cabbages,  and  then 
invaded  them,  causing  the  blackness  and  ultimate  decay  of  the  tuber. 
The  parasite  unquestionably  is  akin  to  the  genus  Plasmodiophora,  but 
produces  a  dry,  not  a  wet  gangrene.  It  may  be  Pseudocommis 
vitis,  causing  browning  or  ‘‘ brunure”  in  Vine  shoots,  but  I  hardly 
consider  the  resemblance  sufficiently  clear.  Only  one  thing  is 
definite — namely,  its  malignity  in  the  Potato.  The  black  bodies  con¬ 
tained  round  bodies  or  spores,  are  each  (u)  filled  with  protoplasm,  and 
in  due  time,  in  the  presence  of  food,  there  emerge  from  each  in  amoeba 
like  form  (v),  the  so-called  zoospores,  which  coalesce  and  form  a 
plasmodium  (w\  and  creep  about  in  quest  of  food. 
Besides  the  bodies  already  mentioned  and  some  of  the  most 
important  shown  there  were  some  bacterial  (Bacillus  amylobacter) 
in  the  wet  parts,  and  the  mycelium  of  a  fungus  (Fusarium  solani), 
both  connected  with  the  “wet  rot”  of  Potatoes;  and  there  were 
also  root-worm  (77),  said  to  cause  China  Aster  sickness.  It  is 
Enchytroeus  minutus,  Tauber .  Likewise  an  eelworm  (7),  the  well- 
known  Tylenchus  obtusus,  and  a  mite  (7)  on  its  back,  which  is 
called  Bhizoglyphus  echinopus.  The  three  last  named  were  young 
larvae  ;  all  are  parasites,  and  such  a  number  points  to  a  sad  condition 
of  the  soil. 
In  1886  (according  to  my  notes)  I  planted  a  piece  of  ground  that 
had  been  neglected  for  many  years,  and  when  taken  in  hand  had  been 
crammed  full  of  animal  manure.  The  variety  of  Potato  was  School¬ 
master,  and  the  crop  went  wrong,  the  tubers  being  swollen,  scabby, 
black,  and  rotten.  What  few  tubers  were  sound  went  to  swell  the 
general  heap,  and  there  spoiled  more  than  half  the  lbt.  The  land  tvas 
given  a  good  dressing  of  best  chalk  lime,  freshly  burned,  slaked,  and 
spread  while  hot.  It  was  forked-in  and  left  for  the  winter.  By  force 
of  circumstances  it  was  again  planted  with  Potatoes,  without  manure, 
but  received  a  good  dressing  of  basic  slag;  nothing  else.  The  crop 
was  clean  and  heavy.  What  made  the  difference  ?  The  10  stones  of 
quicklime  per  rod,  or  the  1  stone  of  basic  slag  per  rod  sprinkled  in  the 
drills  before  covering  up  the  sets  ?  Perhaps  both  did  something  ;  but. 
I  suspect  the  lime  was  the  more  effective. 
Another  piece  of  land  that  had  grown  Potatoes  for  thirty  years- 
was  planted  with  Magnum  Bonum,  and  the  tubers  were  nearly,  but 
not  quite,  as  bad  as  the  Schoolmaster  in  places,  and  worst  where  not 
dressed  with  gas  lime.  We  had  gasworks,  and  the  lime  was  left 
exposed  until  it  approached  sulphate  of  lime  or  gypsum.  Five  stones 
of  that,  with  some  freshly  made,  per  rod  drove  out  the  enemy,  and. 
Fig.  79.— Diseased  Potatoes,1 
References.— A,  badly  affected  ;  a,  point  where  shrunken,  blackened,  and  hollowed  - 
b,  heel-end  scabbed  ;  c,  diseased  on  side  ;  JR,  wireworms  ;  C,  white  insect-like- 
creature,  natural  size,  and  magnified ;  D,  Potato  showing  early  stages  of 
disease  ;  d,  beginning  of  excrescences  ;  e,  protuberance  more  advanced  ;  E, 
section  through  part  of  diseased  Potato  ;  /,  skin  on  scales ;  g,  brown  tissue  r 
h,  points  of  communication  with  outside.  (All  preceding  two-thirds  natural 
size,  except  Lipura  timeteria  in  part).  F,  scab  fungus,  Oospora  scabies  ;  i,  fertile 
hypha ;  j,  conidia  or  spores ;  k,  prostrate  hypnie  or  mycelium  ;  1,  globose 
bodies,  with  thick  cell  walls  ;  m,  undetermined  hypha ;  O,  section  of  diseased 
tissue  ;  n,  cavity  ;  o,  dead  cells  of  Potato ;  p,  amieba-like  bodies ;  q,  naked 
protoplasm  ;  r,  black  cells  ;  s,  empty  cells,  adjoining  the  preceding  ;  t,  living 
cells ;  u,  resting  cell  (so-called  spores)  of  Pseudocommis  vitis ;  v,  naked 
protoplasm  (so-called  zoospore) ;  w,  plasmodium  ;  II,  root  worm,  Enchytraeus 
minutus  ;  T,  Tylenchus  obtusus  ;  J,  root  mite,  Rhizoglyphus  eehinopus  ;  O—J, 
enlarged  174  diameters,  except  u,  v,  and  w,  which  are  enlarged  700  times. 
we  had  a  crop  of  Magnum  Bonums  at  the  rate  of  25  tons  per  acre, 
clear),  sound,  and  not  coarse.  Did  this  show  the  virtue  of  sulphur  ? 
Or  was  it  lime  again  ? 
Some  American  mycologists  advise  dressings  of  sulphur  to  the 
soil,  2  to  3  cwt.  per  acre,  sprinkling  it  on  the  rows  before  closing  them, 
after  setting.  I  have  found  flowers  of  sulphur  rank  poison  to  some 
plants  when  the  soil  contained  a  large  amount  of  organic  matter. 
The  rubbing  of  Potato  sets  in  flowers  of  sulphur  before  planting  ,  is 
also  advised  by  English  and  American  specialists  for  preventing 
Potato  scab.  That  seems  a  feasible  means,  as  I  find  it  answers  well 
for  Lilium  bulbs  in  preventing  disease  (Botrytis  ga'anthina),  and  also 
Narcissus  and  Tulip  rot  (Penicillium  glaucum). 
Oospora  scabies  is  not  far  removed  from  them,  so  there  may  be 
something  in  it.  But  for  the  Potato  scab,  as  presented  in  the  speci¬ 
mens  submitted  to  the  Editor  by  “  W.  P.,”  there  is  no  cure  or  preven- 
