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THE  EFFECT  OF  LIGHT  ON  THE 
GROWTH  OF  TREES. 
BY  S.  ARDEN. 
In  connection  with  the  cultivation  of  the  Para  rubber  tree  and 
— though  to  a less  extent — coconuts  and  other  tropical  products, 
there  is  perhaps  no  question  upon  which  opinions  are  divided  to 
such  an  extent  as  on  that  of  the  correct  distance  to  allow  between 
the  trees ; for  while  some  prefer  to  plant  the  Para  rubber  tree  for 
instance,  36'  x 36'  (about  33  trees  to  the  acre),  others  maintain  that 
planted  10'  x 10'  (435  trees  to  the  acre)  or  even  8'x  8'  which  gives 
680  to  the  acre  will  give  a larger  yield  per  acre,  although  prepared 
to  admit  that  the  yield  per  tree  will  be  considerably  less  when 
planted  so  closely. 
I have  recently  had  the  opportunity  of  seeing  some  20  acres  of  3 
year  old  trees  planted  6' x 6'  but  it  seems  impossible  to  believe, 
that  a practical  planter  who  plants  his  coffee  shrubs  12'  x 12' — the 
recognized  distance  on  soil  of  ordinary  fertility — would  attempt  to 
argue  that  a Para  rubber  tree,  which,  when  fully  developed  has  a 
spread  of  about  36  feet,  wo'dd  under  such  conditions  have  anything 
like  a fair  chance  to  develop. 
There  appears  in  the  current  number  of  the  “Indian  Forester” 
a review  of  a valuable  book  entitled  “ Economics  of  Forestry  ” 
written  recently  by  Professor  Fernow,  L.  L.  D.,  Director  of  New 
York  State  College  of  Forestry,  and  I have  made  a few  notes  hav- 
ing a direct  bearing  on  the  subject  trusting  that  they  will  prove 
interesting  to  those  readers  of  the  ‘Agricultural  Bulletin^  who  are 
interested  in  this  important  question,  and  who  may  not  have  an 
opportunity  of  studying  Dr.  Fernow’s  book. 
In  chapter  VI  Dr.  Fernow  deals  with  the  Natural  History  of  the 
forest,  and  after  observing  the  influence  of  temperature,  moisture, 
and  soil  conditions,  together  with  the  methods  adopted  by  nature 
for  the  transportation  of  the  seed,  on  the  natural  distribution  of  the 
various  species  which  form  the  particular  type  of  forest  met  with 
in  passing  from  the  Tropics  to  the  Northern  Latitudes,  and  from 
sea  level  to  the  highest  altitudes,  proceeds  to  show  that  “ not  only 
is  the  composition  of  the  forest  largely  a result  of  changes  in  light 
conditions,  but  the  actual  amount  of  production  is  a function  of  the 
light,  for  the  annual  production  of  wood  is  irp  direct  relation  with 
the  amount  of  foliage  which  the  tree  can  exhibit  to  the  influence  of 
light. 
This  is  a very  definite  statement,  emphasizing  a well  known 
scientific  fact  as  to  the  important  part  played  by  sunlight,  in  the 
elaboration  of  the  sap  which  is  destined  to  form  not  only  the 
wood  but  the  leaves,  fruit,  latices  and  other  parts  of  the  tree. 
The  whole  art  of  forestry  and  of  agriculture  also,  is  based  on 
the  laws  of  accretion. 
An  attempt  is  being  ma  le  in  the  United  States  after  the  manner 
of  the  German  Foresters  to  determine  the  volume  development  of 
