A.m.  Jour.  Pharm. 
June,  1894. 
Economic  Botany. 
287 
them.  Both  are  governed  by  the  same  general  principles.  In  hor-. 
ticulture,  however,  the  plant  is  more  often  subjected  to  artificial 
conditions,  for  example,  to  stove  heat,  root-pruning,  budding,  graft- 
ing, layering,  forcing,  and  so  on. 
The  proper  study  of  both  includes  in  its  scope  the  commercial 
history,  systematic  relationships,  life  histories,  structure,  physiology 
and  pathology  of  the  plants  cultivated. 
Of  these  physiology  takes  the  leading  rank  both  in  its  importance 
and  in  its  scope.  It  includes  not  only  the  study  of  plant  foods  and 
the  modes  of  their  assimilation,  respiration,  metabolism,  reproduc- 
tion, and  the  influence  of  various  external  agents  and  conditions,  as 
light,  heat,  soil,  drainage,  etc.,  on  plants  in  general,  but  the  study 
of  all  these  in  reference  to  each  particular  variety  or  species  under 
cultivation,  and  as  subject  to  more  or  less  artificial  conditions.  The 
kinds  of  soil  and  drainage  best  suited  to  the  plant,  the  best  manures 
to  employ,  the  proper  order  of  cropping  to  prevent  exhaustion  of 
the  soil,  these  are  things  also  which  are  not  to  be  neglected.  Of 
scarcely  less  importance  is  a  knowledge  of  the  facts  and  conditions 
of  plant  variation,  the  laws  and  methods  of  hybridization,  and  the 
modes  of  taking  advantage  of  these  for  the  improvement  of  plants 
in  any  desired  direction.  Nothing,  in  fact,  that  has  happened 
recently  has  so  stimulated  the  agricultural  arts  or  encouraged  so 
much  hope  for  future  progress  in  them,  as  the  revelations  of  the  last 
twenty-five  years  in  vegetable  physiology. 
The  pathology  of  cultivated  plants,  that  is  the  nature  of  the  bacterial 
and  fungous  diseases  to  which  they  are  liable,  and  that  of  the  insect 
pests  that  attack  them,  together  with  the  knowledge  we  are 
acquiring  slowly  but  surely  of  the  best  methods  of  dealing  with 
these  enemies,  is  of  scarcely  less  practical  importance.  It  is  a  sub- 
ject also  which  at  the  present  time  is  engaging  the  talents  of  many 
of  our  best  botanical  investigators. 
Forestry  is  a  comparatively  new,  though  none  the  less  thriving 
and  important  branch  of  economic  botany.  Besides  including  a 
knowledge  of  the  structure,  botanical  relationships,  physiology  and 
pathology  of  trees,  it  deals  with  such  subjects  as  the  best  modes  of 
planting,  caring  for  and  preserving  forest  growths,  of  re-foresting 
denuded  areas,  of  estimating  by  means  of  accurate  tests  the  relative 
values  of  different  timbers  for  constructive  and  other  purposes,  the 
rate  of  forest  growth,  the  age  attained  by  different  species  of  trees, 
