THE  AMERICAN 
JOURNAL  OF  PHARMACY. 
SEPTEMBER,  1887. 
SOME  KEMAEKS  ON  GRAPE  CULTURE. 
By  Henry  Snyder  Mauger,  Ph.G. 
(From  an  Inaugural  Essay). 
It  is  well  known  that  in  some  localities  many  of  the  best  varieties 
do  not  succeed  solely  on  account  of  their  foliage  being  destroyed  more 
or  less  by  mildew,  and  the  criterion  of  a  useful  grape  depends  solely 
upon  its  freedom  from  mildew  on  the  leaves,  and  not  on  account  of 
the  flavor  or  other  good  qualities  of  the  fruit;  so  we  find  that  the 
most  popular  varieties  are  not  those  of  the  highest  merit  in  flavor,  but 
those  that  are  least  affected  with  mildew  on  the  foliage  and  fruit.  The 
most  prevalent  form  of  mildew  on  the  leaves  of  our  native  grapes  is 
known  as  Peronospora  viticola,  Berk.  This  is  always  found  on  the 
under  surface  of  the  leaf ;  it  commences  in  small  spots  of  a  brownish 
color  which  adhere  closely  to  the  leaf  ribs,  and  when  the  conditions 
are  favorable  it  spreads  rapidly  and  destroys  the  vitality  of  the  part 
attacked.  Its  presence  is  made  apparent  by  a  yellowish  tinge  which 
may  be  seen  on  the  upper  surface  of  the  foliage,  and  in  clear  weather 
these  spots  become  brown-colored,  afterwards  crisp  and  dry,  and  ulti- 
mately the  leaf  is  more  or  less  destroyed.  This  appearance  on  the 
foliage  is  sometimes  termed  sun-scald,  but  it  hardly  need  be  stated 
that  the  leaves  would  not  be  injured  b}r  the  sun  were  it  not  that  their 
vitality  is  impaired  by  mildew ;  yet  we  frequently  meet  with  cultiva- 
tors who  maintain  that  their  vines  are  free  from  mildew,  while  they 
admit  the  foliage  is  scalded  by  the  sun  and  drying  off. 
By  the  time  its  effects  are  thus  visible  the  mildew  is  not  so  easily 
discerned,  or  it  may  have  run  its  course  and  left  but  little  evidence  of 
its  presence  in  an  active  state,  and  this  may  be  the  reason  why  many 
grape-growers  show  so  little  knowledge  of  the  disease.    Hence  the 
2S 
