588 
Economic  Botany. 
Am.  Jour.  Pharm. 
August,  1920 
enemies,  both  animal  and  vegetable,  and  to  investigate  the  condi- 
tions under  which  the  yield  of  the  desired  product  can  be  improved, 
whether  by  appropriate  modification  of  the  environment  or  by 
breeding.  As  the  nature  of  the  problems  becomes  more  clearly 
recognized  the  methods  of  cultivation,  selection  and  dealing  with 
the  raw  material  improve.  Breeding,  which  used  to  be  a  sort  of 
hit-and-miss  business,  is  now  becoming  more  and  more  an  exact 
science,  and  although,  owing  to  the  tangled  mass  of  factors  involved, 
immediate  success  in  a  particular  direction  cannot  always  be  pre- 
dicted, at  any  rate  we  do  not  know  how  to  attack  the  matter.  Thus 
it  is  that  in  the  more  direct  cases  it  is  now  possible  with  comparative 
certainty  and  rapidity  to  achieve  results  which  formerly  could  only 
be  secured  by  an  immense  waste  of  time,  material  and,  of  course, 
expense.  Intelligent  breeding  demands  a  wide  outlook  over  the 
many  aspects  presented  by  any  single  organism,  but  this  fact  is 
still  unappreciated  by  too  many  business  men.  To  give  but  one 
example,  one  often  hears  of  high  expectations  being  entertained 
that  races  of  rubber  trees  can  easily  be  produced  which  shall  give 
high  yields  of  caoutchouc,  shall  be  immune  to  the  attacks  of  disease, 
and,  in  short,  shall  possess  all  sorts  of  desirable  qualities  that,  un- 
fortunately, are  but  seldom  combined  in  a  single  individual.  Such 
expectations  are  entirely  unreasonable,  at  any  rate  for  so  long  as 
we  continue  to  remain  ignorant  of  the  physiological  significance  of 
latex  in  the  tree,  of  the  origin  and  significance  of  caoutchouc  forma- 
tion, as  well  as  of  the  other  substances  that  occur  along  with  it. 
Possibly  it  may  turn  out  that  there  exists  a  significant  connection 
between  the  caoutchouc  and  the  troublesome  resin  which  seems 
invariably  to  accompany  it  in  all  rubber  yielding  latices.  The 
destiny  of  the  oxygen  during  the  transformation  from  carbohy- 
drates to  rubber  is  in  itself  an  attractive,  and  perhaps  a  very  funda- 
mental, problem. 
The  matter  of  immunity  to  fungal  and  other  disease-producing 
Organisms  is  of  the  widest  possible  interest.  In  our  own  cultivated 
crops  the  problem  is  ever  arising.  Why  do  Victoria  plums  suffer 
so  badly  from  silver  leaf  (due  to  the  fungus  Stereum),  and  why  do 
certain  otherwise  desirable  varieties  of  potatoes  fall  victims  to  the 
attack  of  wart  disease  so  that  they  cannot  be  grown  at  all  in  districts 
where  the  disease  is  present?  It  is  plain  that  there  is  joint  work 
here  for  the  plant  physiologist  and  the  chemist.  There  will  have 
to  be  "many  knots  unravelled  by  the  road"  before  the  secrets  of 
