146  SEEDS  TRANSPORTED  BY  MARINE  CURRENTS. 
eonfect.  Dose,  the  size  of  a  shellbark,  three  times  a  day. — 
American  Journal  of  Med.  Set.,  January,  1858. 
ON  THE  VITALITY  OF  SEEDS  TRANSPORTED  BY  MARINE 
CURRENTS. 
By  M.  C.  Martins. 
Botanists,  struck  by  the  facts  establishing  the  transport  of 
seeds  by  marine  currents,  have  thought  that  the  latter  must  have 
played  a  great  part  in  the  diffusion  of  the  disjoined  species  of 
plants  which  form  isolated  colonies  upon  islands  or  continents 
separated  by  vast  extents  of  sea.  Geologists,  surprised  at  the 
uniformity  of  the  vegetation  of  the  great  archipelagos  scattered 
in  the  ancient  seas,  were  still  more  disposed  to  consider  marine 
currents  as  the  principal  agents  in  the  dissemination  of  seeds 
upon  the  surface  of  the  globe.  These  a  priori  conclusions  have 
never  been  directly  verified  by  experiment :  it  has  never  been 
tried  (1)  whether  many  seeds  are  sufficiently  light  to  float  upon 
salt-water  ;  and  (2)  whether  these  seeds,  after  floating  for  a  long 
time  at  the  surface  of  the  sea,  still  retain  their  germinative  fac- 
ulty. 
To  settle  this  question  experimentally,  the  author  selected 
some  fresh  seeds,  of  which  the  germination  never  fails,  taking 
them  from  the  principal  families,  and  generally  preferring  those 
cf  large  size,  furnished  with  a  hard  and  thick  episperm,  or  those 
of  littoral  plants.  The  former  should  resist  the  action  of  salt- 
water, from  their  volume  and  the  impermeability  of  their  enve- 
lopes ;  the  other  should  have  more  chance  of  germinating  if  they 
fell  upon  a  sandy  shore. 
Of  98  species,  55  floated,  and  39  were  specifically  heavier  than 
the  water  of  the  Mediterranean,  the  density  of  which  off  Cette 
is  1.0258.  Four  seeds  had  a  specific  gravity  equal  to  that  of 
salt  water  :  these  are  Nelumbium  speciosum,  Datura  stramo- 
nium, Juglans  nigra,  and  GingTco  biloba.  Thus,  of  a  certain 
number  of  seeds  taken  by  chance,  we  may  say  that  two-thirds 
float. 
To  try  the  action  of  sea-water  upon  floating  seeds,  the  author 
endeavored  to  place  them  in  the  same  physical  conditions  to 
which  they  would  be  subjected  when  floating  at  the  surface  of 
