THE  JHAWAII AN 
FORESTER  a AGRICULTURIST 
Vol.  VI  MAY,  1909  No.  5 
PRINCIPLES  OF  PLANT  IMPROVEMENT . 
By  J.  W.  Gilmore,  President } College  of  HawaiL 
The  principles  of  plant  improvement  are  based  primarily  on 
the  theory  of  evolution.  The  theory  of  evolution  though  bit- 
terly  opposed  and  criticised  at  first,  is  now  practically  uni- 
versally accepted.  It  recognizes  that  instead  of  the  spon- 
taneous creation  of  individuals  and  groups  of  living  beings, 
these  are  the  result  of  constant  change  and  variation  in  accord- 
ance with  factors  of  environment  and  heredity.  That  such 
changes  and  variations  were  existant  among  individuals  and 
groups  of  living  beings  was  known  long  before  the  time  of 
those  writers  who  are  usually  credited  with  the  discovery  and 
propagation  of  the  theory.  But  not  until  about  the  time  of 
Lamarck  (1744-1829)  were  definite  scientific  reasons  ascribed 
to  the  changes  and  variations  that  were  commonly  observed, 
Lamarck  stated  that  in  most  instances,  specific  changes  and 
variations  in  different  forms  were  corelated  with  the  use  or 
non-use  of  the  organs  or  characters  of  the  being  involved.  In 
his  presentation  of  this  thesis  he  recognizes  two  laws  of 
nature,  namely  that  in  every  animal  that  has  not  finished  its 
term  of  development,  the  constant  and  systematic  use  of  anv 
organ  strengthens  and  develops  it  and  increases  its  size  propor- 
tionate to  the  length  of  time  it  has  been  employed.  On  the 
other  hand,  the  continued  lack  of  use  of  any  organ  gradually 
weakens  it  until  it  at  last  disappears.  The  second  law  was 
that  nature  preserves  everything  she  causes  the  individual  to 
acquire  or  lose  through  the  influences  of  the  environment  to- 
which  its  race  has  been  for  a long  time  exposed.  In  brief, 
Lamarck  explained  the  diverse  instances  of  certain  characters 
on  the  basis  of  the  use  or  non-use  which  was  made  of  these 
characters  or  organs  throughout  the  life  activity  of  the  in- 
dividual. Darwin,  on  the  other  hand,  based  his  researches  on 
the  theory  of  population  presented  bv  Maltheus.  This  author, 
in  his  work  on  population,  published  in  1798,  claimed  that 
population  increased  by  geometrical  ratio,  that  is  by  multi- 
plication, while  food  supply  on  which  populations  must  de- 
pend, increased  by  arithmetical  ratiov  that  is  by  addition. 
From  this  it  was  therefore  quite  evident  that  depletion  of 
population  by  pestilence  and  disease  are  brought  about  for 
