644 
Report  on  Wheat-Mildew. 
thus  dispensing,  for  a season  at  least,  with  the  assistance  of  the 
barberry  and  dropping  out  of  the  series  the  CEcidium  and  Sper- 
mogonia  stages  of  the  life  cycle.  It  is  true  that  De  Bary  did 
not  succeed  in  his  endeavours  to  produce  Uredo  in  wheat  directly 
from  mildew  ; but  this  is  merely  negative  evidence. 
The  following  Table  exhibits  side  by  side  (1)  the  normal 
and  complete  cycle  of  growth  of  Puccinia  graminis,  (2)  an  ab- 
normal or  incomplete  cycle,  and  (3)  a possible  abnormal  cycle  : — 
Puccinia  Graminis  in  its  successive  Stages  of  Growth. 
Seasons. 
Normal  or  Complete  Cycle. 
Abnormal  or  Incomplete 
Cycle. 
Hypothetical  Abnormal 
Cycle. 
Autumn 
Mildewed  straw,  black 
lines,  spots,  and  pat- 
ches, which  are 
(1)  Teleuto-Spores. 
(5)  Uredo-Spores 
(1)  Teleuto-Spores. 
Winter 
Of  Puccinia  Graminis ; 
continue  growth 
Spring 
these  remain  dormant 
until  the  spring,  when 
and  the  process  of 
reproduction,  if 
(2)  Promycelium-Spores 
growing  plants  of 
the  species  capable 
Promycelium- 
are  produced,  and  grow- 
of  acting  as  host- 
Spores 
ing  on  the  barberry 
plants  are  within 
which  it  is  thought 
produce 
their  reach  anl 
may  be  capable 
Summer 
(3)  (Eciiuum  Spores  and 
(4)  Spermogonia. 
The  former  (fertilised  by 
the  latter  ?)  germinate 
on  the  wheat  plant  and 
other  grasses,  and  de- 
velop mycelium  in  the 
cellular  tissue  of  the 
host-plant,  from  which 
spring 
(5)  Uredo-Spores. 
developing 
Uredo 
of  entering  the 
Wheat  Plant, 
and  there,  pro- 
ducing mycelium 
and  its 
(5)  Uredo. 
These  reproduce  the 
On  wheat  without 
without  passing 
parent  mycelium,  bear- 
passing  through 
through  the 
ing  Uredo-spores  gene- 
the  intermediate 
CEcidium  stage, 
ration  after  generation, 
stage  of  CEcidium 
and 
until  the  host-plant 
on  the  Barberry, 
finally 
Autumn 
approaches  maturity, 
when 
(1)  Teleuto-Spores 
and  as  the  crop 
ripens 
(1)  TELEUTO-SrORES 
(1)  Tei.euto-Spores 
are  formed,  and  the  cycle 
of  growth  is  completed. 
It  would  seem  then  that  in  one  way  at  least,  and  possibly  in 
two,  the  mildew-plant  can  propagate  its  species  without  the  aid 
of  the  barberry-tree.  If  it  can  do  this  for  one  season,  why  not 
