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ORIGIN  OP  VARIETIES  IN  PLANTS.  33 
ORIGIN  OF  VARIETIES  IN  PLANTS. 
According  to  the  Gardeners'  Chronicle,  quoting  from  Les 
Mondes,  "M.  Decaisne,  the  very  able  Professor  of  Cultivation, 
in  the  Garden  of  Plants,  Paris,  has  lately  brought  under  the 
notice  of  the  Academy  of  Sciences  some  very  interesting  re- 
marks upon  the  varieties  of  cultivated  plants  in  general,  and  of 
Pears  in  particular."  Decaisne  remarks ; — "The  almost  un- 
limited and  ever  increasing  number  of  varieties  in  fruit-trees, 
vegetables,  and  all  useful  plants  is  a  fact  to  which  science  has 
at  present  given  too  little  attention.  .  .  .  These  new  forms, 
what  are  they  ?  Can  they  be,  as  has  been  recently  asserted, 
true  species  which  have  remained  unknown  up  to  the  time  when 
they  were  first  subjected  to  cultivation  ;  or  are  they  merely 
modifications  of  ancient  known  species,  assuming  various  appear- 
ances according  to  climate  or  situation  ?  It  may  appear  strange 
that  such  a  question  should  be  brought  before  the  Academy,  so 
natural  does  it  seem  for  a  species  to  be  subject  to  change."  .  . 
Botanists  in  the  present  day  may  be  divided  into  two  schools. 
The  more  ancient,  which  may  be  called  the  Linnaean,  admits 
the  changeableness  of  species ;  within  certain  limits,  no 
doubt,  though  it  is  not  always  easy  to  define  them.  Hence  those 
large  polymorphous  species,  sometimes  vaguely  defined,  but  gen- 
erally easy  to  characterize  by  a  short  descriptive  phrase.  The 
other  school,  which  belongs  especially  to  our  own  time,  and 
which  may  be  designated  as  the  school  of  immutability,  denies 
most  positively  any  tendency  to  variation  in  the  vegetable  king- 
dom. According  to  it,  the  forms  of  species  never  alter  in  the 
slightest  degree ;  and  when  two  plants  of  the  same  genus  pres- 
ent any  palpable  difference,  however  slight  it  may  be,  these  two 
plants  form  two  species,  radically  distinct  from  the  beginning 
of  things.  According  to  M.  Jordan,  of  Lyons,  a  very  eloquent 
advocate  of  the  modern  school,  all  the  races  and  all  the  varieties 
admitted  by  the  ancients  become  so  many  species.  In  his  eyes, 
all  our  races  and  all  our  varieties  of  fruit-trees,  of  Pears 
amongst  others,  are  distinct,  unchangeable  species,  always  pre- 
serving their  own  characteristics  from  generation  to  generation. 
Hence  it  follows  that  these  trees  did  not  proceed,  as  is  common- 
ly believed,  from  a  single  or  even  from  a  few   specific  types, 
3 
