Diseases  of  Plants. 
263 
to  the  determination  of  the  fungus  were  present.  The  tubers 
were  planted  and  kept  under  constant  observation,  but  no 
further  development  of  the  disease  showed  itself.  They  are 
still  under  observation. 
From  Lancashire  some  tubers  were  received  covered  with 
the  conidial  growth  of  the  fungus  Nectria  solani  R.  & Bert. 
The  fuiigus  in  this  stage  is  called  Fusarium  solani  Sacc. ; 
it  causes  a wet  rot  of  potatoes  placed  in  pits.  When  filling 
the  pits,  care  should  be  taken  that  no  injured  potato  is  placed 
amongst  the  healthy  ones,  for  this  fungus  quickly  spreads  to 
neighbouring  healthy  tubers.  The  darkness,  moisture,  and 
temperature  of  the  pit  supply  conditions  very  favourable  to 
the  growth  of  the  fungus.  Indeed,  damaged  tubers  of  potatoes 
or  other  roots  should  be  carefully  excluded  from  the  place  of 
storage,  as  they  offer  suitable  conditions  to  various  fungi  and 
bacteria. 
Another  potato  was  sent  for  examination.  It  was  a case 
of  the  well-known  disease  called  potato  scab.  There  are 
different  opinions  on  the  cause  of  this  disease,  some  attributing 
it  to  a fungus,  Sorosporium  scabies  Fisch.  de  W.,  of  the  smut 
group,  others  to  the  presence  of  bacteria.  On  very  careful 
obseiwation  I found  plenty  of  bacteria  living  on  the  contents 
of  the  cells  (see  Fig.  1,  L and  M,  page  262).  No  other  fungus 
was  observed.  It  is  recommended  to  powder  the  potatoes 
with  flowers  of  sulphur  if  they  are  thus  attacked.  The  disease 
Explanation  of  Fig.  1. — Parasitic  Fungi  (see  page  262). 
A,  B.  Cercospora  hetirola  Sacc.,  on  mangel  wurzel.  A.  Fragment  of 
mangel  leaf  with  large  round  patches  of  the  fungus.  B.  Filaments  bearing  long, 
many-celled  spores  ; magnified  1.50  times  (see  page  261). 
A,  C — E.  /"rowycr.?  Pers.,  on  mangel  wurzel.  A,  Mangel  leaf  showing 
the  small,  dark  spots  of  the  fungus.  C,  The  fungus  bursting  through  the  skin 
of  the  leaf ; magnified  75  times.  D,  A uredospore,  and  E,  a teleutospore; 
both  magnified  120  times  (see  page  261). 
F — K.  Pseu(h>pezi:a  Trifulii  Fuckel,  on  clovers  and  lucerne.  F,  Leaf  of 
red  clover  spotted  with  the  fungus.  G,  Portion  of  the  leaf,  somewhat  enlarged. 
H,  Two  sacs  (asci)  .showing  the  contained  spores  ; magnified  250  times. 
K,  Four  spores;  magnified  350  times  (see  page  26(i). 
L.  jr.  Scab  disease  of  potato,  e.  Cells  of  the  potato  containing 
the  bacteria  ; magnified  1.50  times.  M,  Bacteria;  magnified  750  times  (see 
above). 
N— E.  Erijsiphe  MartU  Lev.,  on  clover.  N,  Leaf  of  red  clover  showing 
the  light-coloured  patches  which  have  been  attacked  by  the  fungus,  o.  Fruit 
of  the  fungus,  and  P,  section  of  a fruit  ; both  magnified  75  times.  Q.  Two  asci 
containing  spores,  and  H,  separate  spores ; both  magnified  250  times  (see 
page  260). 
s — u.  Botrytis  clnerea  Pers.,  on  cedar,  s.  Piece  of  cedar  branch  with 
several  tufts  of  leaves  killed  by  the  fungus.  T.  Single  leaf  with  the  lower 
portion  killed,  u.  Fruit-heads  of  the  fungus;  magnified  100  times:  and  below, 
sej)aratc  spores;  magnified  300  times  (see  page  266). 
w — Y.  Perotwitpora  parasitica  Pers.,  on  wallflower,  w.  Pods  of  wall- 
flower attacked  by  the  fungus,  x.  Fruiting  head  of  the  fungus;  magnified 
160  times.  Y,  Separate  spores;  magnified  320  times  (see  page  269). 
