4l8  Modification  of  Color  in  Plants.       j  Amjuner'i£iarm' 
The  colored  areas  of  the  plant  are  generally  located  at  the  ter- 
minal portions  and  are  usually  located  in  the  tissues  in  the  periphery 
of  these  organs.  It  is  quite  likely  and  seems  very  reasonable  that  if 
the  proper  chemicals  were  supplied  the  plant  in  an  unaltered  form  or 
if  they  could  be  supplied  in  such  a  form  that  they  would  be  altered 
by  the  cell  distinct  color  changes"  would  ensue.  In  other  words  the 
same  change  would  be  attained  as  we  find  on  treating  the  pigment 
cells  upon  a  slide  with  reagents  or  substances  which  are  usually  pres- 
ent in  the  soil  and  water.  It  is  quite  possible  that  studies  on  the 
algae  would  yield  some  striking  and  variable  results  in  this  particu- 
lar. The  great  difficulty  would  be  in- noting  this  change  in  color, 
which,  however,  could  be  followed  by  the  device  which  I  have  made 
for  use  in  the  study  of  color  in  higher  plants.  Again,  before  taking 
up  flower  color  substances  this  work  might  be  developed  in  the  study 
of  color  in  root-like  organs,  in  the  raddish. 
In  my  own  experiments  I  think  the  mistake  that  was  made  was 
in  not  studying  more  extensively  the  distribution  of  colors  in  flowers 
than  I  did.  Subsequent  studies  show  that  the  pigment  is  distributed 
in  four  ways  in  the  flower  :  i.  The  pigments  are  usually  in  epidermal 
cells  as  in  the  rose  and  pansy.  2.  The  pigment  may  occur  in  sub- 
epidermal cells  in  addition  as  in  wild  hyacinth.  3.  It  may  occur  in 
the  mesophyl  layers  in  addition  as  in  Mertensia.  4.  It  may  occur  in 
the  conducting  tissues  surrounding  the  mestome  strands  in  the  flower 
as  in  blue  hyacinth.  From  this  study  of  the  distribution  of  flower 
color  substances  it  would  seem  that  if  the  study  was  made  of  those 
plants  in  which  the  pigment  in  the  flowers  was  in  the  immediate 
proximity  of  the  fibro-vascular  bundles  that  the  chemical  supplied 
the  plant  through  the  soil  might  be  more  or  less  unaltered  and  pro- 
duce communication  in  the  pigment  cells. 
Of  course,  there  are  a  number  of  other  features  that  are  funda- 
mentally important  and  that  should  be  ascertained  only  at  the  time 
of  formation  of  flower  coloring  process.  It  would  appear  that  these 
are  usually  formed  some  time  after  the  organs  of  the  flower  have 
been  formed.  However,  in  the  foliage  of  very  many  plants  that 
produce  flowers  there  are  indications  that  the  pigment  is  formed  in 
the  early  stages  of  organs  in  which  photosynthesis  takes  place,  as  in 
the  rose.  In  fact,  the  pigment  in  the  foliage  of  the  rose  as  well  as  in 
the  prickels  closely  correspond  to  the  pigment  of  the  flowers. 
