GEOGRAPHICAL  RELATIONS  OF  LAURACEiE. 
357 
2.  They  are  distributed  over  the  five  continents,  having  their 
largest  number  in  America  (447  species)  and  Asia  (445  species) ; 
then  follows  Australia  with  56,  Africa  with  25,  and  Europe  with 
one  species. 
3.  The  Eastern  Hemisphere  possesses  60  species  more,  but  5 
genera  less  than  the  Western.  The  tribes  Litsseacese  (256  sp.) 
and  Perseacese  (149  sp.)  constitute  the  bulk  of  species  in  the 
Eastern,  and  the  tribes  Oreodaphnese  (246  sp.)  and  Cryptocaryeae 
(117  sp.)  in  the  Western  Hemisphere. 
4.  All  six  tribes  are  represented  in  America,  while  the  Oreo- 
daphnese  are  wanting  in  Asia  and  Australia,  and  the  Gyrocar- 
pese  in  Africa. 
5.  America  contains  absolutely  and  relatively  the  largest 
number  of  genera,  namely,  32,  of  which  23  are  peculiar  to 
herself. 
6.  The  Lauraceae  predominate  between  the  tropics,  rapidly 
decrease  in  number  towards  the  poles,  and  are  completely  ex- 
cluded from  the  colder  temperate,  high  alpine,  arctic  and  ant- 
arctic zones.  The  equatorial  zone  contains  538,  the  rest  of  the 
tropical  zone,  365,  the  northern  outer  tropical,  88,  and  the 
southern  tropical  zone,  85  species.  Excluding  the  equatorial 
zone,  the  Northern  Hemisphere  has  282,  and  the  Southern  256 
species. 
7.  The  majority  of  the  American  species  (406)  grow  on  the 
continent,  only  41  on  the  islands,  while  in  Asia  the  islands  pro- 
duce 310,  (of  which  only  24  are  not  tropical,)  and  the  continent 
only  135. 
8.  All  species  are  endemic,  growing  only  in  one  continent, 
and  mostly  in  one  of  its  floral  districts  only ;  the  same  is  the 
case  with  most  of  the  genera. 
9.  The  majority  of  the  Lauracese  appears  to  grow  in  hot,  low 
lands,  and  chiefly  in  moist  situations ;  next,  they  inhabit  drier 
hilly  parts,  the  lower  mountains  and  shady  mountainous  forests 
of  the  coasts. 
But  very  few  appear  to  reach  up  to  the  true  alpine  regions  ; 
only  under  the  tropics  some  grow  at  such  heights,  the  climatic 
conditions  of  which  approach  those  of  the  arctic-alpine  regions. 
10.  In  relation  to  the  history  of  the  organic  creation,  it  is  to 
