640 
Report  on  Wheat-Mildew. 
ductive  organs,  which  burst  through  the  cuticle  and  appear 
in  red  or  black  patches,  disposed  in  rather  irregular  lines  on 
the  leaves,  straw,  or  chaff.  The  life-historj  of  this  fungus 
is  remarkable,  as  “it  has  no  less  than  five  kinds  of  repro- 
ductive forms  . . . CEcidium,  Spermogonia , Uredo,  PucciNIA, 
and  Promycelium  Of  these  five  forms  three  only,  CEciDIUM, 
Uredo,  and  PUCCINIA,  come  under  the  notice  of  the  ordinary 
observer  ; the  Qdcidium  of  Puccinia  graminis  being  the  rust 
which  is  so  conspicuous  on  the  leaves  of  the  common  barberry 
in  spring ; Uredo,  the  dark  orange-coloured  rust  found  on  the 
wheat,  &c.  ; and  Puccinia,  the  mildew.  The  wheat-rust  in 
question  must  not,  however,  be  confounded  with  the  spring- 
rust  which  has  been  so  common  during  the  last  two  seasons, 
1882,  1883.  This  rust  is  earlier  in  its  appearance,  and  of  a 
much  lighter  colour  than  the  Uredo  of  Puccinia  graminis.  It 
is  connected  with  another  form  of  mildew,  Puccinia  ruhigo  vera , 
which  is  not  often  injurious  to  corn-crops,  at  least  in  England. 
It  has  been  observed  that  years  in  which  rust  is  prevalent  are 
not  always  years  of  mildew  ; and  in  the  fen  districts,  which  suffer 
most  from  mildew,  the  prevalence  of  this  spring-rust  is  believed 
to  be  rather  beneficial  than  otherwise,  as  it  reduces  the  ex- 
cessive luxuriance,  which  is  the  usual  result  of  a mild  winter, 
and  which  is  popularly  supposed  to  make  the  wheat-crops  more 
liable  to  mildew.  On  stronger  soils,  and  where  the  growth  is 
less  luxuriant,  this  rust  is,  however,  much  dreaded  ; and  it  is 
said  that  the  yield  of  corn  is  always  much  diminished  by  an 
attack  of  it.  Mr.  Plowright  is  the  only  writer  on  this  subject 
whom  I have  met  with  who  has  pointed  out  that  this  common 
rust  is  not  connected  with  the  destructive  mildew  Puccinia 
graminis. 
To  return  to  the  last-named,  the  real  and  fatal  mildew  of  our 
experience.  As  this  is  the  only  form  in  which  the  spores  (called 
Teleuto-spores,  or  rest-spores)  are  capable  of  lying  dormant, 
and  retaining  their  vitality  for  more  than  a few  hours,  we  may 
regard  it  as  the  culminating  point  of  the  series,  the  final  de- 
velopment of  the  plant  and  the  completion  of  the  cycle  of 
growth. 
Starting  then  from  this  point,  that  is,  with  the  blackened 
straw  of  the  previous  year,  we  find  that  in  the  spring  the 
Teleuto-spores  are  quickened  into  life,  and  from  them  are  pro- 
duced another  kind  of  spores  ( Promycelium-spores ),  which  are 
said  to  be  unable  to  retain  life  and  bear  fruit  unless  they  can 
meet  with  a barberry-tree.  Having  settled  upon  a leaf  of  one 
of  these  shrubs,  the  spore  bores  into  the  interior  and  there  de- 
* Plowright. 
