260       CULTIVATION  OF  CINCHONA  PLANTS  UNDER  GLASS. 
hospice  of  St.  Bernard,  a  similar  composition,  at  least  in  so  far 
as  nitric  acid  and  ammonia  being  present  in  greater  or  less 
quantities.  I  learn  from  Dr.  Anderson  that  some  species  of  cin- 
chona flourish  at  Darjeeling,  although  the  rainfall  averages 
127-30  inches  for  the  year,*  of  which  82  inches  fall  in  three 
months  of  the  summer.  But  then  the  character  of  the  soil  and 
slope  of  the  hills  is  such  that  the  rain-water,  after  having  bathed 
the  roots,  passes  away  immediately  from  them ;  for  Dr.  Ander- 
son, as  every  one  else,  finds  the  Cinchonse  to  be  most  impatient 
of  water  at  the  roots. 
This  is  difficult  to  imitate,  and  the  change  consequent  on  the 
scarcity  of  rain-water  to  that  derived  from  springs  has  (appar- 
ently) cost  me  the  health  of  some  valuable  plants.  Then,  again, 
as  the  leaves  can  form  chlorophyll  only  in  sunshine,  and  can 
only  then  derive  nourishment  from  the  air,  it  must  be  remem- 
bered that,  in  dark  and  gloomy  weather,  we  must  supply  less 
water  and  less  nonrishment  to  the  roots,  or  the  harmony  of  na- 
ture will  be  destroyed,  and  the  consequences  may  be  fatal.  From 
the  same  considerations  it  will  follow  that  too  much  artificial 
warmth  in  the  night  season  will  be  injurious ;  and,  indeed,  the 
plants  never  seem  to  thrive  better  than  when  a  considerable 
range  of  temperature  between  day  and  night  is  allowed  to  exist. 
I  have  found  great  practical  benefit  from  adopting  the  system  of 
double  glazing^  leaving  a  stratum  of  air  about  four  inches  in 
thickness  between  the  sheets  of  glass.  This  tends  greatly  to 
prevent  sudden  chills,  which  are  injurious,  and  also  to  retain  a 
larger  amount  of  moisture  in  the  air  surrounding  the  plants. 
This  is  much  required  and  best  secured  by  syringing  the  leaves 
with  tepid  water  twice  in  the  day,  avoiding  the  collection  of 
water  around  the  roots.  It  is  important  to  provide  well  for 
their  drainage  by  means  of  broken  bricks  or  tiles ;  and  I  find  an 
advantage  in  conducting  the  warm  water  of  the  return  pipes  be- 
low the  level  surface  of  the  ground,  so  as  to  secure  a  slight  and 
constant  elevation  of  the  temperature.  I  have  a  thermometer 
plunged  eighteen  inches  in  the  bed  of  earth  in  which  my  largest 
plants  grow,  and  I  have  not  noticed  this  below  50°  F.  in  winter. 
*JBeardmore,  "  Manual  of  Hydrology,"  p.  330. 
