AxoveXrP?9iT'}       Distribution  of  Tannin  Plants.  521 
quite  closely  to  that  of  these  species  of  trees.  So  far  as  known  it 
appears  that  the  tannin-bearing  Gymnosperms  are  practically  con- 
fined to  the  north  temperate  zone,  and  because  of  their  accessibility 
and  the  inroads  made  upon  them  in  order  to  meet  the  increasing 
demands  for  timber  it  is  probable  that  this  source  of  tannin  will  be 
one  of  the  first  to  be  exhausted. 
The  second  group  of  seed-plants,  the  Monocotyledons,  is  quite 
unimportant  from  the  standpoint  of  tannin,  although  it  contains 
many  hundreds  of  species  of  plants  which  are  well  known  and  widely 
distributed.  Here,  as  was  stated,  belong  the  grasses,  of  which  there 
are  more  than  3,500  varieties,  but  only  four  or  five  of  these  are 
known  to  contain  tannin.  In  the  one  order  which  contains  all  of 
the  tannin  plants  of  importance,  two  only  are  worthy  of  mention 
here.  These  are  the  palmetto  of  Florida  and  Areca  Catechu  of  India, 
which  is  one  of  the  commercial  sources  of  cutch.  There  are  35  other 
orders  in  this  group,  the  plants  of  which  are  widely  distributed,  but 
they  are  so  poor  in  tannin  that  from  the  commercial  standpoint 
at  least  they  cannot  be  regarded  strictly  as  tannin  plants. 
The  third  group  of  seed-plants,  the  Dicotyledons,  contains  by 
far  the  greater  number  of  tannin  plants.  In  some  of  the  natural 
orders  of  this  division  tannin  producing  families  are  practically 
wanting,  in  some  the  relative  number  of  tannin  families  is  variable, 
and  in  others  practically  every  family  contains  tannin  producing 
plants.  A  study  of  those  natural  orders  in  which  only  a  part  of  the 
families  contain  plants  rich  in  tannin  reveals  some  interesting  facts. 
Several  of  these  orders  are  widely  distributed  both  with  respect 
to  climatic  conditions  and  continental  location.  Representative 
species  which  contain  tannin  occur  in  various  situations  ranging 
from  the  tropics  to  areas  approaching  the  limits  of  vegetation  toward 
the  poles.  However,  when  the  locality  is  considered,  of  such  plants 
as  have  been  found  to  yield  tannin  in  percentages  sufficient  to  make 
them  commercially  promising,  it  becomes  evident  that  with  few 
exceptions  they  are  all  to  be  found  in  tropical  countries.  This  fact 
may  be  concretely  illustrated  by  citing  the  distribution  of  some  of 
the  more  important  tannin  plants  belonging  to  those  natural  orders 
in  which  there  is  great  variation  between  families  with  respect  to 
tannin  production.  For  example,  the  natural  order  Urticales  has 
three  tannin  producing  families  comprising  about  sixty  species  of 
plants  of  which  those  highest  in  tannin,  4  to  14  per  cent.,  are  a 
few  species  of  Ficus  growing  in  India  and  the  Philippines.    In  the 
