In  the  Saltwort  each  leaf  ends  in  a  stout  spine,
which  of  course  runs  into  the  nose  of  any  too  in-
quiring cow  or  donkey.  In  the  West  Indies,  Cactus
hedges  line  all  the  roads  in  the  plains,  and  rise  in  a
solid  wall  to  the  height  of  15  or  20  feet.  No  animal
on  earth  dare  attempt  to  pass  through  such  a  hedge,
and  the  task  of  cutting  one  down,  when  necessary,  is
extremely  difficult.  On  bare  dry  expanses,  like  the
Mexican  plain,  Cactuses  and  Agaves  run  wild  in  every
direction,  collecting  what  little  moisture  they  can  in


156  SAGACITY  AND  MORALITY  OF  PLANTS.
their  thick  stems  or  big  succulent  leaves,  and  defend-
ing it  against  all  herbivorous  enemies  by  their  for-
midable spines.  To  prevent  evaporation  they  are
covered  with  a  thick  and  very  firm  epidermis,  so  that
they  lose  very  little  of  their  moisture,  even  during
months  of  drought

"  What  these  great  desert  plants  do  on  a  large
scale,  our  little  English  Saltwort  does  on  a  much
smaller  scale.  It  has  the  same  strong  prickles,  the
same  thick,  juicy  leaves,  the  same  protective  epidermis,
and  the  same  general  aspect  of  growth  as  the  Cactuses
themselves.  If  one  were  to  enlarge  it  twenty -fold,
every  casual  observer  would  set  it  down  as  a  desert
species  at  once."

Perhaps  one  reason  for  the  succulence  of  such
maritime  plants  as  the  Saltwort  is  the  quantity  of
salt  entering  into  their  composition.  This  substance
is  remarkable  for  its  power  of  absorbing  moisture,
even  from  the  atmosphere,  and  it  must,  therefore,
be  a  gain  to  succulent  plants  to  grow  where  salt
abounds.  In  proof  of  this  we  have  the  fact  that
well-known  maritime  plants  have  settled  down  near
saltworks  inland,  as  in  Cheshire  and  Worcestershire.
