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Indicators  in  Nature. 
Am.  Jour.  Phai-m. 
April,  1901. 
red  cyclamen,  varieties  of  Bumaldce,  hibiscus,  Tephrosia  (devil's 
shoestring),  and  leaves  from  four  varieties  of  coleus.  With  the 
exception  of  hibiscus,  scarlet  sage  and  coleus,  the  extracts  from 
these  were  colorless  or  nearly  so. 
The  purple  or  violet  flowers  were  phlox,  petunia,  coriopsis,  ver- 
bena, sweet  peas,  "Jimson  weed,"  maypop,  or  passion  flower, 
Specularia  perfoliata  and  Rue  ilia  ciliosa. 
The  lilac  flower  was  Salvia  urtica,  the  blue  ones  were  Ageratum, 
Runella  vulgaris  and  blue  larkspur,  the  yellow  one  was  nasturtium, 
and  the  black  material,  a  cow-pea  bean. 
The  colors  from  some  of  these  flowers  passed  through  several 
stages  on  the  way  from  acidity  to  alkalinity.  The  most  noteworthy 
are : 
Specularia  pet foliata:  Magenta,  blue,  green. 
Ruellia  ciliata:  Rose,  lilac,  green. 
Salvia  tittica:  Claret,  peacock-blue,  green. 
"Jimson  weed:"  Magenta,  purple,  green. 
Maypop  or  passion  flower:  Magenta,  blue,  green-blue,  olive-green. 
Blue  larkspur:  Magenta,  purple,  blue,  peacock-blue,  green. 
Purple  petunia :  Magenta,  purple,  blue,  green. 
California  poppy:  Magenta,  purple,  violet,  peacock-blue,  green. 
Red  coleus  :  Red,  claret,  violet,  green. 
Red  and  yellow  coleus:  Rose,  brown-red,  orange-red,  yellow- 
green,  olive-green. 
Light  red,  dark  red  and  green  coleus:  Cherry,  violet,  brown, 
green-brown,  dirty  green. 
Red  and  deep  red  coleus :  Magenta,  purple,  blue,  green. 
Most  of  the  colors  above  given  were  very  bright  and  beautiful, 
and,  as  a  rule,  fairly  sensitive. 
The  coloring  matters  of  the  following  flowers  in  this  group  are 
especially  sensitive :  "  Jimson  weed,"  maypop,  Salvia  urtica,  black 
cow-pea  (bean),  Ruellia  ciliata. 
Class  V. — This  group  includes  substances  giving  colors  with  acid 
and  alkali  that  do  not  come  into  the  classes  already  described. 
The  colors  are  those  produced  by  ammonia.  The  color,  when 
acid,  is  given  first,  then  the  stages  it  passes  through  to  alkaline. 
Bougainvtllea  spectabilis  (mauve):  Purple,  colorless. 
Gloxinia  hybnda  (pink) :  Pink,  purple,  brownish-red. 
Gloxinia  kybrida  (purple) :  Magenta,  purple,  olive-green. 
