408  Plant  Morphology  and  Taxonomy.  {^eptembefS™' 
here  as  everywhere  else  in  science,  abstractions  of  this  kind  ;  and  they  are  not 
only  not  hurtful,  but  even  of  the  greatest  assistance  to  investigation,  if  the 
investigator  is  only  clearly  conscious  that  they  are  abstractions. 
It  is  thus  seen  that  Sachs  even  during  the  most  active  period  of 
his  life  not  only  admitted  the  propriety  of  separating  the  considera- 
tion of  function  from  the  study  of  morphology,  but  claimed  that 
there  was  an  advantage  in  so  doing.  As  a  basis  for  morphological 
investigation  Sachs  suggested  the  following  lines  of  study :  A  study 
of  the  development  of  parts,  that  is  the  development  of  members 
or  organs ;  their  mutual  positions ;  the  relative  time  of  their  forma- 
tion ;  and  their  earliest  stages.  From  the  modern  point  of  view  he 
has  left  out  the  most  important  factor  in  the  study  of  morphology, 
namely,  the  study  of  the  relation  of  the  form  and  function  of  organs. 
In  other  words  his  proposition  might  be  likened  to  an  equation  in 
chemistry  in  which  one  of  the  factors  is  left  out.  It  is  fortunate, 
however,  that  Sachs  later  changed  his  views  with  regard  to  this 
subject,  for,  as  pointed  out  by  Goebel,  the  teaching  of  such  abstrac- 
tions has  led  to  one-sidedness  and  incorrect  generalizations. 
TRUE  MORPHOLOGY  OR  ORGANOGRAPHY. 
According  to  the  morphology  of  to-day  the  structure  of  an  organ 
has  a  direct  relation  to  its  function,  or,  in  other  words,  structure  is 
modified  by  function,  and  the  two  can  not  be  separated  if  we  desire 
to  treat  the  subject  comprehensively. 
Herbert  Spencer  was  among  the  first  to  insist  upon  the  neces- 
sity of  the  study  of  function  in  connection  with  that  of  structure.  He 
says : — 
The  division  of  morphology  from  physiology  is  one  which  may  be  tolerably 
well  preserved,  so  long  as  we  do  not  carry  our  inquiries  beyond  the  empirical 
generalizations  in  their  respective  phenomena  ;  but  it  is  one  which  becomes  in 
great  measure  nominal,  when  the  phenomena  are  to  be  rationally  interpreted. 
It  would  be  possible,  after  analyzing  our  solar  system,  to  set  down  certain  general 
truths  respecting^the  sizes  and  distances  of  its  primary  and  secondary  members, 
omitting  all  mention  of  their  motions  ;  and  it  would  be  possible  to  set  down 
certain  other  general  truths  respecting  their  motions,  without  specifying  their 
dimensions  or  positions,  further  than  as  greater  or  less,  nearer  or  more  remote. 
But  on  seeking  to  account  for  these  general  truths,  arrived  at  by  induction,  we 
find  ourselves  obliged  to  consider  simultaneously  the  relative  sizes  and  places 
of  the  masses,  and  the  relative  amounts  and  directions  of  their  motions. 
Similarly  with  organisms.    Though  we  may   frame  sundry  comprehensive 
