Xi  2  Plant  Morphology  and  Taxonomy.  K^S^^SSi' 
the  binomial  system  of  nomenclature.  In  Tournefort's  system 
(1693)  °f  classification  the  genera  were  considered  to  be  the  units, 
and  while  Linnaeus  at  first  agreed  with  this,  he  later  came  to  regard 
the  species  as  distinct  creations  and  therefore  the  units  in  systematic 
work. 
While  it  has  been  pointed  out  that  Linnaeus's  belief  in  the  immu- 
tability of  species  was  the  one  great  defect  of  his  teaching,  still, 
considering  the  fragmentary  knowledge  of  plants  and  the  more  or 
less  chaotic  condition  of  taxonomy  at  that  time,  it  is  doubtful  if  his 
work  would  have  been  any  more  accurate  than  it  was  had  he  not 
been  dominated  by  the  dogma  of  the  creation  of  distinct  species. 
But  of  course  it  should  not  be  forgotten  that  the  harm  which  lies  in 
erroneous  doctrines  or  teachings  is  the  influence  which  they  have 
on  subsequent  thought  and  work,  and  Linnaeus  being  such  a  high 
authority  it  is  no  doubt  due  largely  to  his  influence  that  the  belief 
in  the  fixity  of  species  prevailed  with  more  or  less  force  until  the 
appearance  of  Darwin's  Origin  of  Species,  in  1859. 
We  are  confirmed  in  this  latter  conclusion  by  the  fact  that  when 
Jean  Lamarck,  in  1809,,  clearly  showed  that  species  are  not  immu- 
table, his  views  were  opposed  by  nearly  all  of  the  highest  authorities 
and  were  practically  buried  for  fifty  years.  Lamarck  showed  that  the 
organism  was  modified  by  its  environment  and  that  the  existing 
complex  forms  were  derived  from  simpler  ones,  and  it  only  remained 
for  Darwin  to  supply  the  remaining  element  in  the  theory  of 
descent,  namely,  the  principle  of  natural  selection. 
Darwin's  views  were  backed  by  such  a  mass  of  empirical  data  and 
the  time  being  ripe  for  the  promulgation  of  his  doctrine  of  evolution, 
they  were,  not  long  in  gaining  a  following,  and,  as  is  now  well  known, 
marked  the  beginning  of  a  new  epoch  in  biological  science. 
As  pointed  out  by  De  Vries,  Darwin  recognized  two  possibilities 
with  regard  to  the  origin  of  species,  the  one  being  the  sudden  and 
spontaneous  production  of  new  forms  from  the  old  stock,  and  the 
other  being  "  the  gradual  accumulation  of  those  always  present  and 
ever  fluctuating  variations  which  are  indicated  by  the  common  asser- 
tion that  no  two  individuals  of  a  given  race  are  exactly  alike."  The 
view  founded  upon  the  supposition  that  individual  fluctuations  con- 
stitute the  chief  factor  in  organic  evolution  gained  the  ascendancy 
in  the  start,  this  view  being  accentuated  by  Darwin  himself  and 
supported  by  Wallace  as  the  exclusive  factor  because  there  was  more 
evidence  in  favor  of  it. 
