Am.  Jour.  Pharin."! 
August,  1897.  / 
Official  Primus  Virginiana. 
much  starch.  At  this  time  the  bud  scales  were  open  far  enough  to 
disclose  the  leaves,  which  were,  however,  still  folded  closely  together. 
Bark  collected  in  May  contained  very  little  starch ;  in  some 
samples  none  appeared  to  be  present,  and  in  others  a  very  little 
could  be  made  out  by  the  use  of  dilute  iodine,  when  the  specimen 
was  heated.  Collections  of  August  5th  exhibited  no  starch  in  the 
cells  of  the  bark. 
The  seasons  of  maximum  amounts  of  starch  in  the  bark  are,  then, 
autumn  and  spring,  and  if  the  bark,  whether  powdered  or  whole, 
contains  much  starch  in  all  the  parenchymatous  cells,  we  are  sure 
the  collection  was  made  shortly  after  the  time  of  leaf-fall  in  autumn 
or  before  the  leaves  unfolded  in  the  spring.  A  test  based  upon  the 
presence  of  starch  cannot  exclude  the  spring  collection,  and  spring 
is  the  time  when  the  bark  is  least  valuable,  so  far  as  the  amount  of 
hydrocyanic  acid  which  it  may  yield  is  concerned. 
To  distinguish  between  the  collections  of  spring  and  autumn,  I 
have  found  the  following  color  test  for  tannin  applicable  to  those 
samples  of  Prunus  serotina  which  I  have  been  able  to  obtain.  The 
amount  of  tannin  in  barks  collected  in  spring  is  noticeably  greater 
than  that  found  in  .the  collections  of  the  autumn.  I  hesitate  to  sub- 
mit the  following  as  an  authentic  test,  because  I  have  not  made 
extended  tests  for  amounts  of  tannin  to  be  found  in  the  bark  of 
Prunus  serotina  throughout  the  year,  and  because  the  reasons  for  the 
periodicity  in  amount  and  the  phases  of  its  fluctuation  in  plants 
have  not,  so  far  as  I  am  aware,  been  fully  made  out.  It  seems  a 
matter  of  observation  that  when  great  activity  of  growth  is  going 
on,  tannin  appears  in  greater  amounts  than  usual.  This  observation 
seems  to  receive  support  in  the  case  of  Prunus  serotina,  as  a  much 
greater  amount  of  tannin  seems  present  in  the  bark  during  the  active 
growth  of  spring  than  in  the  autumn. 
The  following  test  shows  this  to  be  the  case : 
Upon  the  surface  of  distilled  water  in  a  watch-glass,  sprinkle  a 
little  of  the  powdered  drug,  which  will  spread,  forming  a  thin  film. 
Let  it  stand  ten  seconds,  and  then  drop  into  it  one  drop  of  a  1  per 
cent,  solution  of  ferric  chloride.  If  the  bark  was  collected  in  the 
spring,  a  cloudiness  will  appear  in  the  water  from  the  greenish  pre- 
cipitate, which  is  immediately  formed.  If  the  bark  was  collected  in 
autumn,  there  will  be  no  noticeable  precipitate  under  twenty  seconds. 
Powders  of  Nos.  20  and  50  exhibit  this  test  equally  well. 
