124 
Pedigree  Seed  Corn. 
than  would  either  of  the  species  alone.  The  same  may  hold 
good  of  mixed  varieties  or  mixed  races  of  any  one  'species 
when  compared  with  seed  of  a pure  race,  unless  the  latter 
has  been  bred  with  special  reference  to  the  average  external 
conditions  of  the  locality. 
There  is,  however,  a great  difference  between  (i.)  a 
“ designed  ” mixture  of  varieties  and  (ii.)  the  aggregate  which 
results  from  either  (a)  natural  selection  in  a district  where 
“ pure  races  ” have  not  been  introduced  (e.g.,  Scotch  Common 
Barley)  or  (b)  the  aggregate  resulting  from  indiscriminate 
mixtures  of  pure  races. 
A good  deal  of  the  seed  corn  used  in  some  parts  of 
England  is  of  the  latter  class,  and  this  state  of  things  comes 
about  more  particularly  in  districts  where  one  “ type  ” of 
barley  is  found  to  be  generally  suitable,  but  where  this  type 
is  represented  by  a number  of  distinct  races  which,  possess- 
ing different  racial  characters  affecting  prolificacy,  yet  closely 
resemble  each  other  in  appearance,  sometimes  when  seen  as 
plants,  and  even  more  frequently  when  seen  only  as  grain. 
For  instance,  the  barley  grown  in  Yorkshire  is  nearly  all  of 
the  “ wide  ear  ” type,  but  this  type  is  represented  by  at  least 
half  a dozen  well  known  races,  some  (Goldthorpe  for  one) 
known  to  be  pure  races  raised  from  single  self-fertilised 
plants,  others  (like  Standwell)  resulting  from  cross  fertilisa- 
tion in  the  first  instance.  There  is  very  little  doubt  that  a 
considerable  proportion  of  the  seed  barley  used  in  Yorkshire 
is  a mixture  of  these  different  though  externally  similar 
races. 
Chevallier  and  Archer  barley  again  are  frequently  found 
mixed,  although  in  this  case  there  is  a distinct  structural 
difference  in  the  seed  (to  say  nothing  of  the  generally  obvious 
difference  in  the  straw)  which  entitles  the  two  sorts  to  be 
classed  as  distinct  “varieties.”  This  particular  mixture  is 
not  likely  to  give  good  results  in  most  seasons.  Archer  has 
about  a week  longer  growung  period  than  Chevallier,  and  even 
ripening  is  of  great  importance  with  barley. 
Effects  of  Natural  Selection. 
It  is  interesting  to  consider  what  happens  when  mixtures 
of  different  races  are  sown,  and  seed  taken  in  successive  years 
from  the  previous  crops. 
It  is  evident  that  the  character  of  the  resulting  aggregate 
after  some  years  depends  mainly  on  such  natural  selection 
as  goes  on  in  the  field.  The  effects  of  natural  selection  on 
the  racial  character  of  our  cereals  is  worthy  of  more  attention 
than  it  has  hitherto  received.  It  is  not,  of  course,  possible 
here  to  go  into  the  subject  exhaustively,  but  merely  to  indicate 
