Here,  all  the  species  of  two-thirds  or  more  of  the  mountain-genera
are  confined  to  that  group.  Only  in  a  relatively  small  number  of
cases  are  the  species  in  touch  with  the  regions  outside.  The
mystery  of  disconnection  that  is  so  evident  in  the  instance  of
the  peculiar  or  endemic  mountain-genera  of  the  Compositae  and
Lobeliaceae  and  other  orders  is  here  again  presented  to  us,  and


XXIII  THE  HAWAIIAN  MOUNTAIN-FLORA  271

once  more  in  the  upland  regions  4,000  to  10,000  feet  above  the  sea.
We  will  now  endeavour  to  discover  from  an  examination  of  the
present  distribution  of  the  isolated  mountain-genera  (those  non-
endemic  genera  possessing  only  peculiar  species)  along  what  tracks
they  arrived  at  the  Hawaiian  uplands,  tracks,  as  indicated  by  the
local  distribution  of  the  species,  that  have  been  more  or  less
abandoned  since.
