258       CULTIVATION  OF  CINCHONA  PLANTS  UNDER  GLASS.  " 
ted  with  the  Cinchonce  in  their  native  woods,  some  beautiful 
treblj-scrobiculate  leaves  of  mj  plants,  and  we  agreed  that  in- 
spection demonstrated  the  improbability  of  a  theory  recently  ad- 
vanced as  regards  the  scrobiculation,  which  ascribes  its  origin  to 
an  inherited  defect  derived  from  the  attacks  of  insects.  The 
truth  being,  on  the  contrary  (as  I  have  often  observed),  that  in- 
sects are  not  found  to  attack  this  part  of  the  leaf  in  preference, 
but  are  much  more  addicted  to  some  other  portion  of  the  plant. 
The  additional  beauty  of  the  leaf  derived  from  the  scrobicules 
and  their  regularity  must  be  seen  to  be  appreciated,  presenting 
an  appearance  quite  unlike  that  of  an  accidental  monstrosity. 
As  to  the  light  to  be  thus  thrown  on  botanical  arrangement,  I 
may  mention  the  opportunity  afforded  of  raising  the  seeds  pro- 
ceeding from  the  same  bunch  of  capsules,  and  observing  thus,  as 
I  am  doing  at  the  present  moment,  the  amount  of  variation  to  be 
observed  in  the  children  of  one  parent  plant. 
The  very  difficulties  to  be  overcome  in  imitating,  as  far  as 
possible,  the  climate  and  soil  of  the  mountain  regions  of  the 
Andes,  present  many  subjects  of  not  unfruitful  consideration. 
The  influence  of  light  upon  vegetation  will  force  itself  upon 
the  attention  in  all  the  varied  aspects  of  the  question,  as,  indeed, 
presenting  some  of  the  most  formidable  difficulties  in  the  culti- 
vation of  plants  so  sensitive  as  these  are  to  the  deficiency  of 
stimulus  in  the  dreary  months  of  winter,  and  to  the  excess  both 
of  heat  and  light  in  our  summer  above  that  to  which  they  have 
been  accustomed.  The  effect  of  different  colored  rays,  of  polar- 
ized light,  of  a  greater  or  less  amount  of  actinism  necessarily 
comes  into  view. 
The  leaves  of  many  species  are  particularly  sensitive  to  light, 
and  turn  towards  the  rays  of  the  sun  in  a  manner  sufficiently  re- 
markable. In  some  kinds  the  structure  and  coloring  are  very 
beautiful,  and  would  quite  repay  cultivation,  with  this  object  in 
view.  They  are  frequently  covered  with  a  lustrous  epiderm,  as 
described  by  Dr.  Weddell,  in  reference  to  the  Qalisaya.  This 
epiderm  seems,  as  in  the  case  of  some  other  plants,  largely  com- 
posed of  wax  :  when  this  is  removed,  either  by  mechanical  injury 
or  by  chemical  solvents,  the  leaf  suffers,  and  the  oxidation  of 
the  juices  becomes  manifest.    It  is  not  easy  to  imagine  from 
