October  13,  1898. 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER, 
285 
force  of  growth  they  break  through  the  epidermis,  causing  it  to  crack, 
shown  at  e.  Still  the  growth  from  beneath  forces  the  cuticle  farther 
off  the  pustule  (/),  and  the  ripe  spores  in  the  form  of  brown  dust 
drop  out  (g).  Ultimately  the  thin  skin  peels  off,  and  the  contents  of 
the  pustule  are  wholly  exposed  ( h ),  and  the  spores  liberated  in  such 
quantities  as  to  smother  the  leaves  below  with  dark  brown  dust  (*). 
A  portion  of  the  margin  of  a  pustule  with  the  spores  developing 
is  represented  at  D,  enlarged  260  diameters.  They  are  smooth  and 
glossy  when  young,  but  become  brown  when  mature.  They  are  attached 
by  a  short  stalk  to  the  prostrate  hyphae  (/),  and  when  mature  fall  away 
( E ).  These  Uredo,  or  summer  spores,  soon  become  more  or  less 
warted,  probably  a  provision  for  attaching  themselves  to  relatively 
smooth  leaf  surfaces.  They  tumble  out  of  the  pustule  in  little  heaps, 
and  appear  somewhat  concatenate  or  chained  ( [k ),  which  probably 
characterises  the  formation  in  the  large  pustules. 
The  spores  coming  in  contact  with  a  Chrysanthemum,  and  in 
But  how  long  will  the  Uredo  or  summer  spores  retain  vitality  ? 
Some  of  the  first  or  1897  harvest  are  shown  at  //,  and  one  of  these  has- 
pushed  a  germinal  tube  twelve  months  afterwards.  This,  shown  at  Jr 
indicates  that  the  spores  have  the  nature  of  resting  spores,  and  in  a 
greenhouse  would  retain  vitality,  so  as  to  infest  cuttings  or  plants- 
from  season  to  season. 
As  regards  preventive  or  remedial  measures,  badly  infested  leaves 
should  be  picked  off  and  burned,  also  any  plants  thoroughly  infested 
should  go  the  same  way,  in  order  to  prevent  the  spread  of  the  disease 
and  any  possibility  of  producing  teleutospores.  Cuttings  should  no-t 
be  taken  from  infested  plants  lest  they  should  contain  mycoplasma; 
but  stock  had  from  outdoor  plants,  which,  so  far  as  I  know,  do  not 
contract  the  disease.  To  prevent  attack  the  cuttings  should  be  dipped 
in  quarter  strength  Bordeaux  mixture — sulphate  of  copper,  11  lb.;  best 
chalk  lime,  l£lb.;  water  22  gallons.  Dissolve  the  sulphate  in  1  gallon 
of  cold  water.  Slake  the  lime  in  another  gallon  of  water,  and  when, 
Fig  51.— CHRYSANTHEMUM  LEAF  RUST  (UREDO  CHRYSANTHEMI). 
References.— A,  upper  side  of  leaf  ;  a,  pustules  destroying  tissues  ;  b,  light  coloured  spots  corresponding  to  pustules  ou  under  side  B,  under  side  of  leaf  ; 
c,  pustules  run  together  ;  cl,  enlarged  six  diameters.  C,  pustule  a  little  above  natural  size  ;  d,  the  same  enlarged  six  diameters  ;  e,  epidermis 
commencing  to  crack  ;  f  open  pustule  discharging  spores  ;  g,  h,  pustule  wide  open ;  i,  dust  or  spores.  L>,  section  of  portion  of  pustule,  showing 
uredospores  ;  j,  mycelial  hyphse.  JE,  discharged  spores  ;  Ic,  little  heap  of  spores,  showing  apparently  chained  formation.  F,  spores  germinating  ; 
l,  germinal  tube.  G,  concatenate  spores  growing  ;  m,  germ  tubes.  II,  spores  of  1897  after  twelve  months’  keeping.  I,  spore  of  1897  germinating 
twelve  months  afterwards.  D—I,  spores  enlarged  260  diameters. 
presence  of  moisture,  speedily  grow  ( F ),  each  pushing  a  germ  tube  (Z). 
Concatenate  spores  (G)  also  push  germinal  tubes  (m),  and  these  enter 
through  the  epidermis  into  the  tissues  of  the  leaf,  branch  and  push 
the  mycelial  hyphae  inter  and  intracellularly,  form  a  felted  mass,  and 
finally  produce  erect  hyphae  bearing  the  uredospores.  It  is  needless 
saying  that  the  fungus  abstracts  the  juices  of  the  plant,  or  so  much 
of  them  as  needs  for  its  growth  and  perfection,  thus  weakening  the 
Chrysanthemum  and  causing  the  collapse  of  the  foliage. 
Though  I  have  examined  many  specimens,  and  kept  an  eye  on  any 
semblance  of  a  teleutospore  or  final  stage,  I  have  not  succeeded  in 
finding  any,  except  the  one  shown  at  E,  fig.  50  (from  the  Journal  of 
Horticulture  for  October  21st,  1897,  page  381),  and  this  was  probably  an 
interpolation,  as  several  other  rusts  were  examined  at  the  same  time ; 
hence  the  winter  spore  may  be  suppressed,  as  the  Chrysanthemum 
being  grown  under  glass  does  not  necessarily  occasion  its  need  for  the 
continuance  of  the  species.  This,  and  the  fungus  living  a  latent 
symbiotic  life  as  a  mycoplasma  in  the  cells  of  a  cutting,  had  been 
foreseen,  hence  the  idea  of  Puccinia  of  necessity  falls  to  the  ground, 
and  the  Uredo  chrysanthemi  holds  sway. 
cool  pour  through  a  coarse  bag  into  the  sulphate  of  copper  solution 
slowly;  stir,  and  then  add  the  remainder  of  the  water.  For  preventing 
the  spread  of  the  disease  thorough  spray  with  sulphide  (not  sulphate) 
of  potassium  half  an  ounce  to  a  gallon  of  water,  or  1  oz.  permanganate 
of  potash  to  3  gallons  of  water.  The  plants  should  be  laid  on  their 
sides,  and  thoroughly  sprayed  on  the  under  side  of  the  leaves.  Mr. 
Briscoe-Ironside  mentioned  bisulphide  of  calcium  as  very  effective 
when  applied  with  a  sponge,  so  as  to  thoroughly  reach  the  spores  in 
the  pustules.  This  would  break  the  thin  epidermis  over  the  spores,  and 
thus  get  the  solution  in  contact  with  them,  and  effect  their  destruction 
when  in  a  comparatively  tender  state.  The  washing  in  that  way  with 
sulphide  of  potassium  or  permanganate  of  potash  would  be  even  more 
thorough. — G.  Abbey.  _ 
The  “  Chrysanthemum  rust  ”  would  appear  to  be  much  more 
prevalent  this  season  than  last,  and  has  at  last  aroused  the  Com¬ 
mittee  of  the  N.C.S.  to  hold  a  conference  on  the  subject,  which 
ought  to  be  the  means  of  unfolding  much  useful  information  for  the 
benefit  and  guidance  of  those  who  are  troubled  with  the  fungoi  l 
