284 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER. 
October  13,  1893 
Chrysanthemum  Rust  (Uredo  chrysanthemi). 
This  fungus  first  appeared  in  this  country  during  the  year  1897, 
and  specimens  were  submitted  to  the  Editor  of  the  Journal  of 
Horticulture  on  August  26th,  reply  being  made  to  the  inquiry  on 
September  2nd  (page  231)  of  that  year.  It  seemed  to  correspond 
with  the  Mugwort  rust  (Trichobasis,  or  Uredo  Artemisiae),  and  was 
thus  referred  to.  Other  specimens  came  to  hand  during  September, 
and  a  reply  was  given  in  the  Journal  of  Horticulture  September 
23rd  (page  302),  the  fungus  still  being  referred  to  as  the  Mugwort 
rust.  It  was  there  said,  and  with  truth,  “  There  were  thousands  of 
spores — never  a  finer  harvest  seen — and  every  one  Avould  grow  under 
favouring  conditions,  such  as  the  tine  leaves  presented.  The  point  is 
to  prevent  the  spores  germinating ;  this  ought  to  have  been  done  a 
Tig.  50. — Chrysanthemum  Leaf-rust  Fungus  [Trichobasis 
(Uredo)  Chrysanthemi  with  final  stage  —  Puccinia 
Chrysanthemi,  and  other  Rusts.] 
Iteftrences. — A,  Part  of  affected  leaf  of  Chrysanthemum  (October  0th) ;  a,  small 
pustules  of  fungus;  b,  pustules  confluent  or  run  together.  B,  Trichobasis 
(Uredo)  Chrysanthemi  spores  ;  c,  usual  form  ;  d,  concatenate  type.  C,  summer 
spore  germinating  ;  e,  germinal  tube.  J>,  teleutospore  found  in  first  pustule 
examined.  E,  mature  teleutospore  =  Puccinia  Chrysanchemse.  F,  young 
leaf  of  Artemisia  vulgaris  (October  9th),  showing  :/,  small  pustules  ;  g,  pustules 
become  confluent  or  run  together.  G,  uredospores  =  Trichobasis  (Uredo) 
Artemisiae.  H,  teleutospore  —  Puccinia  Artemisiae.  7,  small  leaf  of  Carduus 
vulgaris ;  h,  pustules  of  root  fungus  ;  i,  pustules  confluent.  J ,  uredospores 
=  Trichobasis  (Uredo)  Ciclioracearum  or Heraclei.  K,  teleutospore  =  Puccinia 
Cichoracearum.  L,  Chrysanthemum  leaf  (August  26th) :  j,  small  pustules  ; 
t,  large  pustules  isolated ;  I,  clustered  pustules ;  m,  pustules  confluent. 
M,  uredospores  from  pustule  ;  n,  spores  with  transparent  spot  in  centre ; 
o,  spores  with  two  spots  ;  p,  spore  on  peduncle  ;  r,  miniature  teleutospore,  the 
uredospore  =  Trichobasis  (Uredo)  Chrysanthemi.  N,  part  leaf  of  Chrys¬ 
anthemum,  showing  spots  on  upper  surface,  and  corresponding  to  pustules  on 
the  under  side.  All  the  leaves  or  parts  natural  size,  and  all  the  fungi  enlarged 
260  diameters.— (From  Journal  of  Horticulture,  October  21st,  1897.) 
month  ago  by  dusting  the  under  sides  of  the  leaves  with  a  10  per  cent, 
sulphate  of  copper  preparation  in  powder,  such  as  anti-blight  or 
fostite.”  A  solution  of  sulphide  of  potassium,  1  oz.  to  3  gallons  of 
water,  was  also  suggested  as  a  preventive  and  remedy. 
From  that  date  (September  23rd,  1897)  I  commenced  investiga¬ 
tions  with  a  view  to  the  identity  of  the  species  of  rust  fungus 
found  on  Chrysanthemum  leaves,  and  the  outcome  thereof  appeared 
in  the  Journal  of  Horticulture ,  October  21st,  1897  (pages  380  and  381), 
and  the  illustration  there  and  now  given  (fig.  50)  is  the  first  that 
appeared  of  Chrysanthemum  leaf  rust.  The  leaf  there  shown  was  one 
of  the  first  attacked  by  the  fungus  in  this  country.  It  came  from 
Berkshire,  but  since  then  I  have  learned  that  the  parasite  appeared  on 
some  cuttings  in  the  spring  of  1897  ;  the  cuttings  were  destroyed. 
Still  the  fungus  presented  itself  on  up-grown  plants  in  August.  The 
fungus  was  referred  to  in  the  “Gardeners’  Chronicle”  as  Uredo 
Hieracii ;  also  by  Dr.  Halsted  in  “  American  Gardening  ”  as  probably 
Puccinia  tanaceti. 
For  the  reason  that  the  leaf-rust  fungus  does  not  accord  with 
any  British  species  the  parasite  was  provisionally  named  Uredo 
chrysanthemi,  and  specimens  from  Italy,  as  well  as  various  par's 
of  this  country,  tend  to  warrant  the  deduction  of  its  being  an 
entirely  new  species.  An  article  on  the  parasite  from  Mr.  Briscoe- 
Ironside  appeared  in  the  Journal  of  Horticulture,  November  4th, 
1897,  page  437,  and  a  reply  thereto  on  page  455.  Other  references  to 
the  fungus  will  be  found  in  the  issues  of  December  2nd,  page  532,  and 
December  9th,  1897,  page  557.  In  1898  the  fungus  was  mentioned 
on  February  3rd,  page  114;  February  10th,  page  136;  February  17th, 
page  151;  March  3rd,  page  188;  March  17th,  page  250;  June  2nd, 
page  473,  and  also  in  recent  numbers  of  this  Journal.  Thus  the 
matter  has  been  kept  constantly  before  the  Editor,  and  it  was  stated 
on  page  268,  October  6th,  1898,  that  the  fungus  had  “  taken  a 
permanent  hold.” 
The  fungus  attacks  the  Chrysanthemum  in  all  its  stages  of  growth, 
and  may  be  found  on  cuttings  in  the  spring  and  early  summer,  and 
very  abundantly  from  the  middle  of  August  to  the  end  of  the  season.  The 
cuttings  are  probably  attacked  by  spores  from  the  plants  infested  in 
the  previous  year,  but  the  enemy  must  have  come  from  somewhere 
when  it  first  made  its  appearance  in  this  country.  This  was  presumably 
in  the  winter  of  1896  or  the  spring  of  1897,  the  young  plants  containing 
the  mycoplasma  of  the  fungus  when  introduced  from  America.  That 
appears  the  only  feasible  way  in  which  the  parasite  could  find  its  way 
to  this  country  and  to  Italy.  But  neither  in  the  United  States,  Great 
Britain,  nor  Italy,  was  the  fungus  known  before  1897.  This  appears 
analogous  to  the  case  of  the  Potato  disease,  which  made  such  general 
appearance  in  1844,  and  subsequently  at  intervals  as  to  be  regarded  as 
quite  new. 
Whether  the  climatic  conditions  have  been  peculiarly  favourable 
to  the  development  of  the  Chrysanthemum  fungus,  or  the  Chrys¬ 
anthemum  has  been  so  changed  in  constitution  by  in-and-in-breeding, 
and  so  forced  into  unnatural  development  by  high  cultivation,  are 
matters  that  require  the  serious  consideration  of  growers,  as  there 
must  be  some  cause  for  the  sudden  and  widespread  prevalence  of  the 
rust. 
I  think  the  forcing  treatment  may  have  something  to  do  with  the 
murrain,  as  some  plants  I  have  are  practically  disease  proof  through 
being  grown  as  “  hard  as  nails”  in  a  poor  and  stony  soil,  though  the 
cuttings  were  from  the  same  plants  as  some  others  now  badly  infested 
with  rust,  these  plants  being  grown  in  rich  soil,  well  fed,  and  rela¬ 
tively  luxuriant.  A  pinch  of  salt  now  and  again  seems  to  strengthen 
the  leafage  of  Chrysanthemums  wonderfully,  and  renders  the  plants 
more  disease  resistant. 
In  the  next  illustration  given  (fig.  51)  are  shown  the  most  of  what 
I  have  found  of  leaf  rust,  though  I  have  examined  scores  of  specimens. 
The  fungus  in  every  instance  appears  to  originate  in  the  tissue  of  the 
leaf.  Attack  is,  for  the  most  part,  confined  to  the  under  side,  but 
occasionally  pustules  appear  on  the  upper  surface  of  the  leaf.  Such 
leaf  ( A )  generally  has  the  tissues  destroyed  and  browned  or  blackened 
(a),  but  the  pustules  on  the  lower  surface  do  not  give  evidence  of 
their  presence  by  more  than  a  light  colour  on  the  top  side  ( [b ).  The 
light  colour  afterwards  turning  first  yellowish,  then  brown,  is  due  to 
the  abstraction  of  substances  from  the  leaf  by  the  mycelium  of  the 
fungus,  which  does  not  extend  much  beyond  the  area  of  the  pustules. 
The  pustules  appear  more  or  less  scattered  on  the  under  side  of 
the  leaf  (_B),  and  in  bad  cases  run  together  (c).  They  are  at  first  very 
minute,  and  noticeable  only  by  their  paler  colour  to  the  general  leaf 
surface.  As  the  mycelial  hyphse  develop  in  the  tissues  the  pustule 
becomes  raised  and  paler  in  colour,  the  epidermis  overlying  being 
almost  white.  One  such  pustule  is  shown  at  C,  and  enlarged  six 
diameters  at  d. 
Having  developed  a  densely  matted  mycelium  there  spring  from 
this  oval  bodies,  which  raise  the  pustule  inconsiderably,  and  by  sheer 
