The  leaves  of  plants  impart  by  evaporation  during  the  growing  season
a  certain  amount  of  watery  vapor  to  the  air.  The  amount  of  this  evap-
oration differs,  not  only  in  the  different  kinds  of  plants,  but  it  also  de-
pends in  the  same  plants  upon  external  conditions — the  temperature  of
the  air,  the  intensity  of  light,  and  on  the  amount  of  moisture  in  the  air
and  in  the  soil.  The  greater  the  warmth  of  the  air,  the  more  intense
the  solar  light,  the  drier  the  air,  and  the  moister  the  soil,  by  so  much
more  will  plants  give  off"  moisture  from  their  leaves,  the  transpiration

*  So  far  as  known  to  us,  this  fungus  on  pine  plants  that  Lave  died  from  this  causo,
has  not  been  shown  by  the  microscope, — Ebcrmaijer.
