Aseptemfcri5oT}        Plant  Morphology  and  Taxonomy.  41  ] 
by  obedience  to  any  preformed  plan,  but,  except  for  the  influence  of  the  inertia 
of  the  heredity  of  the  particular  part,  follows  the  factors  potent  at  the 
moment. 
(3)  Functional  Domination. — In  metamorphosis  it  is  function  which  takes  the 
lead  and  structure  follows. 
(4)  Indeterminate  Anatomical  Plasticity. — In  all  anatomical  characters  (size, 
shape,  number,  position,  color,  and  cellular  texture)  plant- organs  are  not 
limited  by  anything  in  their  morphological  nature,  but  under  proper  influence 
may  be  led  to  wax  and  wane  indefinitely  in  any  of  these  respects. 
(5)  Metamorphosis  Along  lines  of  Least  Resistance. — When  through  a  change 
in  some  condition  of  the  environment,  the  necessity  arises  for  the  performance 
of  a  new  function,  it  will  be  assumed  by  the  part  which  happens  at  the  moment 
to  be  most  available  for  that  purpose,  regardless  of  its  morphological  nature. 
(6)  Metamorphosis  by  Transformation. — Since  all  parts  of  the  plant  actually 
are  organs,  new  organs  can  arise  only  by  the  transformation  of  previously 
existing  ones. 
(7)  Gradation  in  Morphological  Membership. — In  the  progressive  development 
of  metamorphoses,  difference  of  degree  passes  over  gradually  into  difference 
of  kind. 
TAXONOMY. 
It  will  not  be  possible  in  the  scope  of  this  paper  to  trace  the  his- 
tory of  taxonomy  with  the  same  detail  that  was  done  under  mor- 
phology. Nor  does  this  appear  to  be  necessary,  for,  as  pointed  out 
at  the  beginning  of  this  paper,  taxonomy  is  dependent  upon  mor- 
phology, and  therefore  the  history  of  the  latter  is  to  a  greater  or 
less  extent  the  history  of  the  former,  although  this  is  not  strictly 
true. 
The  older  systems  of  classification  were  called  artificial  because 
they  took  into  consideration  only  the  superficial  and  gross  charac- 
ters of  plants,  while  the  aim  of  the  so-called  natural  systems  has 
been  to  group  plants  according  to  their  essential  or  fundamental 
characters.  But  as  a  matter  of  fact  our  natural  systems  are  more 
or  less  artificial  or  conventional  because  of  our  imperfect  knowledge 
of  plants. 
Practically  speaking,  our  interest  in  taxonomic  work  dates  from 
the  time  of  Linnaeus,  who  was  an  all-round  naturalist,  and  in  his 
Systema  Naturae  ( 173 1 )  gave  a  classification  of  plants  and  animals  so 
far  as  they  were  known  to  him.  While  Linnaeus's  system  was  an 
artificial  one,  the  main  divisions  being  based  upon  the  characters  of 
the  stamens  and  pistils,  still  he  recognized  the  necessity  for  a  natural 
system  and  even  proposed  one,  although  he  did  not  follow  it  in  prac- 
tice.   To  him  we  are  also  greatly  indebted  for  the»  development  of 
