552  Relations  of  Plants  to  Distilled  Water.  {  ^lm£*mJ?' 
school  ('83,  '84,  '85,  '94,  '94a,  '94b,  '97),  Loeb  (  03),  and  others. 
The  writer  has  another  paper  ready  for  publication  in  which  is  given 
a  historical  treatment  of  the  subject  of  excretions  from  roots  and 
other  plant  parts,  so  the  discussion  of  certain  phases  of  the  plant 
work  is  reserved  for  that  publication. 
Upon  the  perfection  and  the  employment  of  conductivity  ap- 
paratus by  physical  chemists,  it  soon  began  to  be  used  also  by  the 
various  workers  in  the  fields  of  soil,  plant,  and  animal  investigations. 
In  this  connection  distilled  water  came  in  for  its  share  of  con- 
sideration. The  determination  of  the  purity  of  water  by  ascertain- 
ing its  electrical  conductivity  speedily  came  into  vogue,  and  it  should 
be  said  that  as  far  as  electrolytes  are  concerned  it  is  a  very  accurate 
and  excellent  method  and  has  deservedly  come  into  more  and  more 
general  use  for  this  purpose  in  the  fields  of  chemistry,  physics,  and 
biology. 
Koeppe  ('98)  for  instance,  determined  the  electrical  conductivity 
of  water  obtained  from  various  sources  and  compared  his  results 
with  those  of  other  workers.  He  believed  that  distilled  water  has  a 
deleterious  effect  which  is  partly  due  to  a  withdrawal  of  salts  neces- 
sary to  the  organism  and  partly  to  a  swelling  of  the  tissues.  He  was 
supported  in  his  views  by  Oldham  ('09),  while  Winckler  ('04), 
Kobert  ('05),  and  others  argued  in  favor  of  the  harmlessness  of 
distilled  water,  especially  in  medical  practice.  Peters  ('04)  used  the 
electrolytic  conductivity  method  in  his  work  on  Stentor  and  found 
that  there  was  an  exosmosis  of  electrolytes  when  the  organism  was 
placed  in  distilled  water,  and  he  therefore  concluded  that  the  in- 
jurious effects  noted  were  due  to  an  extraction  of  salts.  True  and 
Bartlett  ('12,  '15,  '15a)  considered,  for  certain  salts,  not  only  the 
excretion  but  also  the  absorption  of  electrolytes  under  balanced  and 
unbalanced  conditions  of  the  medium. 
In  a  recent  paper  in  which  a  historical  discussion  of  the  subject  is 
also  given,  True  ('14)  concludes  that  over  and  above  any  injurious 
effects  caused  by  deleterious  substances  in  the  distilled  water  there  is 
still  a  "residuum  of  harmful  action  due  to  no  known  type  of  impurity." 
Because  this  harmful  action  seems  to  be  most  marked  in  water  of 
least  conductivity  True  believes  that  the  withdrawal  of  electrolytes 
from  the  root  tissues  best  accounts  for  the  deleterious  action,  but 
that  this  withdrawal  is  "  not  due  to  the  aggregate  difference  in  osmotic 
pressure  between  the  cells  of  the  roots  and  the  external  medium." 
He  chose  lupine  seedlings  for  his  work  because  Frank  ('88) 
