I9I 
known  to  possess  the  characteristics  desired.  In  like  manner, 
a more  rapid  progress  may  be  made  by  selecting  seeds  of  all 
characteristics  from  only  those  plants  that  manifest  the  spe- 
cific characteristics  desired.  As  a specific  instance  it  may  be 
mentioned  that  oftentimes  good  potato  tubers  are  borne  by 
plants  that  have  no  ability  to  reproduce  the  excellent  char- 
acteristics. It  would  be  much  better  to  select  tubers  for  seed 
from  a potato  plant  bearing  a large  number  of  medium  sized 
tubers  than  it  would  be  to  select  from  a plant  bearing  one  large 
tuber  and  a number  of  small  ones.  Or  in  other  words,  if  a 
large  tuber  from  a hill  of  many  small  ones  were  selected  for 
seed,  in  all  probability  the  resulting  plant  would  manifest  the 
characteristic  of  producing  small  tubers.  This  instance  offers 
one  of  the  reasons  why  it  is  often  claimed  that  potatoes  “run 
out”.  Numerous  other  instances  could  be  mentioned  in  the 
cases  of  corn,  wheat  and  especially  in  the  fruit  plants  where 
the  seeds  do  not  come  true. 
In  the  improvement  of  plants,  three  steps  are  essential.  In 
the  first  place,  variation  must  either  be  found  or  induced,  be- 
cause there  can  be  no  definite  improvement  until  variation 
along  the  line  of  the  desired  improvement  is  either  found  or 
induced.  Variation  may  be  induced:  First,  by  modifying  the 
environment.  The  environment  may  be  modified  through 
changes  in  soil,  climate,  food  supply,  space  and  cultivation. 
Which  of  these  agencies  shall  be  employed  will  depend  largely 
on  the  nature  of  the  plant  in  hand  and  the  nature  of  the  im- 
provement sought.  Of  the  factors  mentioned,  perhaps  climate, 
food  supply  and  cultivation  play  the  most  important  parts. 
It  not  infrequently  happens  that  plants  may  be  dwarfed  or 
modified  to  suit  cropping  conditions  by  changing  from  one 
climate  to  another.  Lateness  or  earliness  of  flowering  or 
ripening  fruit  may  be  brought  about  by  change  from  a warmer 
to  a colder  climate,  and  from  a colder  to  a warmer ' climate, 
respectively.  Food  supply  often  plays  an  important  part  in 
changing  the  size,  flavor  and  color  of  fruits,  or  the  foliage  and 
vigor  of  plants.  Cultivation  may  play  an  important  part  in 
changing  the  quality  of  a plant  or  its  products.  Space,  per- 
haps, plays  its  most  important  part  in  enabling  the  plant 
breeder  to  recognize  individuality.  Thus  it  has  been  impos- 
sible to  improve  the  grasses  and  other  forage  crops  grown  in 
close  community  till  they  were  separated  as  individuals. 
The  second  method  of  inducing  variation  is  by  cross- 
ing, thus,  changing  the  pollen  of  one  flower  to  the  pistil 
of  another,  and  vice-versa.  Crossing  is  generallv  resorted  to 
when  it  is  desired  to  combine  one  desirable  quality  of  one  in- 
dividual with  another  desirable  quality  of  another  individual. 
For  instance,  wheat  has  been  improved  by  this  method  when 
it  was  desired  to  blend  the  standing  quality  of  one  variety 
with  the  high  yielding  quality  of  another.  It  is  also  employed 
for  the  mere  purpose  of  producing  variation,  for  it  is  a well 
