190 
X 
time  immemorial.  It  was  not  until  1691  that  Camerarius 
pointed  out  the  fact  that  in  order  for  a plant  to  produce  seeds 
or  fruit  it  was  necessary  for  pollen  of  one  flower  to  be  trans- 
mitted to  the  pistil  of  either  the  same  flower  or  that  of  another. 
He  pointed  out  that  the  essential  parts  of  a flower  in  the  pro- 
duction of  fruit  and  seeds,  were  the  stamens  and  pistils,  and 
experimental  evidence  that  the  transfer  of  pollen  was  neces- 
sary in  the  process  was  presented.  In  connection  with  dis- 
coveries of  this  kind,  however,  it  must  be  noted  that  knowl- 
edge of  this  nature  among  the  class  of  people  whom  it  might 
benefit,  travels  very  slowly.  It  is  a notable  fact  that  farmers 
are  very  conservative  and  oftentimes  do  not  have  the  means 
of  obtaining  the  information  that  is  available  to  other  classes 
of  people.  Moreover  they  are  slow  to  put  away  old  practices 
for  new,  until  profits  in  new  practices  have  been  demonstrated. 
For  these  reasons,  even  though  the  nature  of  pollination  was 
known,  yet  it  was  slow  to  find  application  to  the  practices  of 
plant  production. 
The  second  reason  for  the  tardiness  in  the  improvement  of 
plants  may  be  ascribed  to  the  difficulty  of  controlling  pollina- 
tion in  plants.  It  will  be  noted  in  this  connection  that  many 
plats  are  pollinated  solely  by  the  wind,  also  many  plants  are 
pollinated  by  insects,  and  a great  many  are  pollinated  by  both 
methods.  Very  few  plants  are  pollinated  solely  through  the 
agency  of  man.  By  reason  of  the  importance,  and  because  of 
the  difficulty  of  controlling  the  pollination  in  the  improve- 
ment of  plants,  slow  progress  has  been  made  in  improving 
strains,  either  in  yield  or  in  adaptation.  Until  methods  were 
devised  for  controlling  the  pollination  of  those  plants  coming 
under  the  first  two  causes  mentioned  above,  practically  no 
progress  was  made.  As  instances  of  this,  note  the  great  im- 
provement that  has  been  made  in  the  varieties  and  grades  of 
wheat,  while  on  the  other  hand,  improvement  in  cotton,  which 
plant  has  been  in  use  about  as  long  as  wheat,  was  nci 
made  in  any  marked  way  until  the  invention  of  the  cotton 
gin.  Pollination  of  wheat,  it  will  be  noted,  is  under  control, 
whereas  that  of  cotton  is  not.  Without  methods  for  con- 
trolling the  pollination,  we  have  no  way  of  knowing  the  nature 
or  parentage  of  the  pollen  by  which  a pistil  may  be  fertilized. 
Consequently,  oftentimes,  good  individuals  may  be  weakened 
in  their  progeny,  by  the  presence  of  pollen  from  weak  in- 
dividuals. 
In  the  third  instance,  until  only  recently  the  seed  has  been 
looked  upon  as  the  unit  for  propagation.  It  has  now  been 
demonstrated  with  almost  no  exceptions  that  instead  of  the 
seed,  the  plant  itself  constitutes  the  unit  for  purposes  of  propa- 
gation. It  is  well-nigh  impossible  to  improve  a strain  of  poul- 
try by  selecting  eggs,  whereas  on  the  other  hand,  it  is  quite 
possible  to  improve  the  strain  by  selecting  individuals  that  are 
