Some  seeds  appear  to  have  only  an  occasional  chance
of  germinating  in  a  state  of  nature;  for  they  must  either
be  scalded,  or  scorched,  or  very  hard  frozen  before  they
can  sprout  at  all,  and  even  then  they  cannot  prosper  unless
they  have  a  clear  field,  with  no  other  plants  to  interfere
with  them.  This  is  the  case  with  the  seeds  of  the  black
locust-tree,  which  are  easily  carried  by  the  wind,  and  are
so  very  hard  that  they  may  lie  exposed  for  years  without
being  any  the  worse  for  it,  it  is  true,  but  also  without
being  able  to  germinate.  If  they  were  less  long-lived,
they  would  probably  die  before  their  opportunity  came.
But  if,  when  a  clearing  is  made  in  the  forest,  the  trees
should  be  fired  and  the  ground  burned  bare,  as  it  is  some-
times, then  comes  their  long-waited-for  opportunity,  and
up  they  spring  in  numbers  wherever  the  fire  has  passed.
The  seeds  of  a  certain  species  of  cedar  could  not  be  got
to  grow  at  all  at  the  Cape  until  they  had  been  thoroughly
boiled.  Such  very  hard-coated  seeds  are  well  protected
against  injury,  but  in  a  state  of  nature  they  must  be
dependent  upon  fires,  frost,  or  perhaps  on  being  swal-
lowed, for  the  opportunity  of  growing.
Other  seeds,  again,  though  they  require  no  special
preparation  of  themselves  or  the  soil,  are  quite  unable  to
germinate  unless  they  get  rain  immediately  after  they  have
fallen,  and  that,  too,  continued  for  some  little  time.
