454  London  Botanic  Gardens.  {^m6£™**wL™' 
that  alpine  and  aquatic  plants  require  especial  conditions  for  their 
successful  cultivation,  and  such  conditions  are  accordingly  provided 
in  the  shape  of  rock  gardens,  water  tanks,  etc.  As  these  plants, 
however,  play  an  unimportant  part  in  medicine,  we  may  pass  them 
over. 
We  have,  so  far,  only  considered  plants  growing  out  of  doors,  but 
a  large  number  of  medicinal  plants  from  foreign  lands  would  perish 
under  ordinary  conditions  in  this  climate,  so  that  some  means  had 
to  be  found  by  which  the  conditions  of  their  habitats  could  be  repro- 
duced artificially,  and  this  was  attained  by  placing  them  in  plant- 
houses,  heated  if  necessary.  The  name  of  "  stoves  "  was  given  to 
houses  in  which  artificial  heat  was  employed,  as  stoves  were  used 
for  producing  the  necessary  temperature,  while  those  which  were 
not  heated  artificially  were  known  as  "greenhouses;"  and  these 
names  have  survived  to  the  present  day.  These  houses  were  origi- 
nally buildings  with  large  windows,  and  there  is  an  example  of  them 
on  an  elaborate  scale  in  the  orangery  at  Kew  (now  Museum  No.  Ill), 
built  in  1761  (see  Plate  V).  A  stove  was  erected  in  the  Chelsea 
Physic  Garden  as  early  as  1681.  We  learn  from  Evelyn's  "  Diary" 
that  its  author  went  to  see  the  keeper  of  the  "Apothecaries'  garden 
pf  simples  at  Chelsea"  on  August  7,  1865,  and  the  following  re- 
marks which  he  makes  in  this  connection  give  us  an  idea  of  the 
method  of  heating  adopted :  "  What  was  very  ingenious  was  the 
subterraneous  heat  conveyed  by  a  stove  under  the  conservatory,  all 
vaulted  with  brick,  so  as  he  has  the  doores  and  windowes  open  in 
the  hardest  frosts,  secluding  only  the  snow;"  it  is  also  interesting  to 
record  that  "  the  tree  bearing  jesuit's  bark  (Cinchona),  which  had 
done  such  wonders  in  quartan  agues  "  was  then  growing  in  the  col- 
lection at  Chelsea.  In  1760  we  hear  of  the  construction  at  Kew  of 
a  stove  warmed  by  pipes  containing  hot  air.  The  method  of  heat- 
ing by  hot  water  pipes  appears  to  have  been  introduced  by  the  Hor- 
ticultural Society  in  their  garden  at  Chiswick.  Experiments  were 
made  with  these  as  early  as  1822,  but  it  was  not  until  1838  that 
they  were  brought  to  a  satisfactory  conclusion.  The  system  of 
heating  by  hot  water  has  now  superseded  all  others. 
Improvements  in  methods  of  heating  were  accompanied  by  ad- 
vances in  other  directions,  one  of  the  chief  of  these  being  the  use  of 
iron  for  the  framework  of  glass  houses.  The  conservatory  in  the 
Regent's  Park  Gardens,  erected  in  1845,  was  the  first  iron  and  glass 
