56  Notes  on  a  few  American  Drugs.  {^JS^'JjP^ 
cent,  of  volatile  oil.  Rauchfuss  (1796)  had  previously  obtained  3  per- 
cent, of  volatile  oil.  G.  W.  Grassmann  (1831)  noticed  for  the  first 
time  the  stearopten,  which  he  obtained  to  the  extent  of  nearly  seven-tenths 
per  cent,  of  the  weight  of  the  fresh  plant,  and  which  L.  A.  Buchner 
subsequently  (1857)  subjected  to  elementary  analysis,  and  found  to  be 
a  hydrate  of  a  terpene  agreeing  with  the  formula  5C10H16.3H2O. 
Willigk  also  examined  the  volatile  oil,  and  besides  the  stearopten., 
determined  it  to  consist  mostly  of  a  hydrocarbon  of  the  same  compo- 
sition as  turpentine.  Grassmann's  ledum-camphor  volatilizes  readily, 
its  vapor  producing  headache  and  vertigo. 
It  is  not  improbable  that  our  indigenous  species  may  contain  similar 
principles,  and,  aside  from  the  volatile  oil,  may  possess  the  tonic,-  some- 
what astringent  and  diuretic  properties  of  the  leaves  of  other  ericaceae. 
Dioscorea  villosa,  Lin. — This  is  the  only  representative  in  the 
United  States  of  the  nat.  ord.  Dioscoreaceae,  and  is  known  by  the  name 
of  wild  yam.  A  nu  mber  of  species  of  the  same  genus  occur  in  the  East 
and  West  Indies,  the  most  important  of  which  are  Dioscorea  alata, 
Lin.  ;  the  white  negro  yam,  D.  triphylla,  Lin,  ;  the  buck  yam,  D. 
trifida,  Lin.,  or  Indian  yam,  D.  bulbifera,  Lin.,  the  Ceylon  white  yam 
and  several  others  comprised  in  D,  sativa  of  Linnaeus.  They  are  gener- 
ally cultivated  in  tropical  countries  for  their  tubers,  which  attain  a  con- 
siderable size,  weighing  frequently  thirty  to  forty  pounds,  and,  though 
quite  acrid  in  their  fresh  state,  are  cooked  and  used  as  food.  They 
contain  starch  as  their  valuable  constituent,  which  appears  generally  to 
be  about  15  to  18  per  cent,  of  the  weight  of  the  fresh  tuber,  but  may 
occasionally  reach  24  per  cent.,  according  to  Sheir  (1847),  or  accord- 
ing to  Grouven  (1856)  fall  to  8  per  cent. 
The  rhizome  of  the  indigenous  species  has  a  very  different  appear- 
ance. 
The  wild  yam  occurs  throughout  the  United  States  from  New  Eng- 
land southward  to  Florida  and  westward  to  the  Mississippi,  and  is  quite 
common  in  the  southern  section.  It  grows  in  thickets  in  moist  locali- 
ties, its  slender  herbaceous  stems  running  over  bushes  and  attaining  a 
length  of  10  to  15  feet  and  more.  The  plant  is  dioecious,  the  greenish 
staminate  flowers  are  in  paniculate  hanging  bunches,  the  pistillate 
flowers  in  simple  drooping  racemes.  The  leaves  are  quite  variable, 
frequently  alternate,  but  sometimes  opposite  or  even  in  whorls  of  4  to 
6  ;  the  latter  appears  to  occur  oftener  in  the  South.    The  leaves  are 
