Septembers'}        Plant  Morphology  and  Taxonomy.  403 
While  the  seventeenth  century  is  marked  by  the  important  dis- 
covery made  by  Camerarius,  the  eighteenth  century  is  especially 
noted  for  the  establishment  of  the  doctrine  of  epigenesis.  In  1759 
Kasper  Friedrich  Wolff  showed  in  a  dissertation  on  the  Theory  of 
Generation,  that  instead  of  the  young  organism  being  preformed  in 
the  egg,  as  had  been  previously  maintained,  it  is  gradually  developed 
from  the  substances  contained  therein.  Wolff's  extensive  studies  on 
the  development  of  both  animals  and  plants  entitle  him  to  the  dis- 
tinction, given  him  by  Goebel,  of  being  the  founder  of  the  history  of 
development,  or,  in  other  words,  he  may  be  regarded  as  the  founder 
of  our  modern  ontogenetic  method  of  study.  To  Wolff  also 
belongs  the  credit  of  discovering  the  vegetative  point  {punctum 
vegetationis)  in  plants,  which  is  one  of  the  distinguishing  marks 
between  the  higher  plants  and  animals. 
In  the  early  part  of  the  nineteenth  century  De  Candolle  proposed 
a  natural  system  of  classification  of  plants,  and  by  many  this  is  con- 
sidered to  be  his  most  enduring  work.  While  this  may  be  true  it 
should  not  be  forgotten  that  his  system  was  based  upon  extensive 
morphologic  work,  and  his  doctrine  of  the  symmetry  of  plants 
embodied  a  series  of  morphological  observations  which  still  hold  true. 
De  Candolle  was  able  to  a  large  extent  to  free  himself  of  the  erro- 
neous teachings  of  the  past,  and  was  among  the  first,  as  pointed 
out  by  Darwin,  to  show  that  species  are  not  immutable  creations. 
In  spite  of  certain  inconsistencies  in  De  Candolle's  work,  Sachs  says 
that  to  him  "  belongs  the  merit  of  being  the  first  to  point  emphatic- 
ally to  the  distinction  between  morphological  and  physiological 
marks,  and  to  bring  clearly  to  light  the  discordance  between  mor- 
phological affinity  and  physiological  habit." 
Notwithstanding  the  far-reaching  importance  of  the  researches  of 
Wolff,  up  until  this  time  no  one  appears  to  have  appreciated  the 
necessity  of  a  study  of  the  successive  stages  of  development  of  the 
organs  of  plants  in  botanical  work,  it  being  the  custom  of  the  time 
to  devote  attention  to  mature  organs  only.  To  Robert  Brown 
(1825)  belongs  the  credit  of  developing  and  establishing  the  onto- 
genetic method  in  the  study  of  plants,  that  is,  the  study  of  the 
development  of  the  individual  beginning  with  the  germination  of 
the  seed  or  spore,  and  which  now  constitutes  one  of  the  most 
important  lines  of  investigation.  During  the  course  of  his  investi- 
gations on  the  organs  of  fructification  in  the  Cycads  and  Conifers  he 
