66  OBLIQUE  DIRECTION  OF  THE  LIGNEOUS  FIBRE. 
crucible,  and  calcined  at  a  red  heat.  After  the  mass  has  cooled, 
there  will  be  found  beneath  the  scoria  a  button  of  metal,  which, 
when  tested  with  the  blow-pipe  and  with  reagents,  will  not  afford 
evidence  of  the  presence  of  a  trace  of  any  foreign  metal,  and 
especially  of  arsenic. — Pharm.  Jour.,  Nov.,  1855,  from  Journal 
de  Pharmacie. 
ON  THE  OBLIQUE  DIRECTION  OF  THE  LIGNEOUS  FIBRE,  AND 
THE  TWIST  OF  THE  TRUNKS  OF  TREES  OCCASIONED 
THEREBY. 
Read  before  the  Academy  of  Sciences  at  Berlin,  and  published  in  its  Proceedings. 
This  twist  of  the  wood  of  many  trees  is  a  phenomenon  well 
known  to  wood-cutters,  shingle-makers,  carpenters,  and  others, 
but  almost  entirely  neglected  by  botanists.  The  distinguished 
geologist,  the  late  Leopold  von  Buch,  appears  to  have  first  di- 
rected the  attention  of  scientific  men  to  it ;  and  De  Candolle,  in 
his  Organographie  (1827)  was  the  first  botanist  who  spoke  of  it. 
Little  has  since  been  done  to  substantiate  or  elucidate  the  phe- 
nomenon. In  the  pamphlet  before  us  Prof.  Braun  gives  the  re- 
sult of  a  great  many  observations  made  by  himself  in  Germany, 
by  his  brother  in  France  and  Spain,  and  by  the  writer  of  this 
notice  in  the  Mississippi  Valley. 
Most  trees  show  this  obliquity  of  the  woody  fibre  more  or  less. 
In  certain  species  the  twist  is  almost  uniformly  in  the  same  di- 
rection :  in  others  both  directions  occur  with  about  equal  fre- 
quency ;  while  in  not  a  few  no  twist  is  distinctly  observable. 
Sometimes  the  same  direction  prevails  in  the  majority  of  the 
species  of  a  genus,  or  even  of  a  whole  family  :  in  other  cases  op- 
posite directions  occur  in  the  same  genus  or  family ;  and  it  is 
curious  to  remark  that  in  some  instances  nearly  allied  species  of 
Europe  and  America  twist  in  opposite  directions.  In  a  few  in- 
stances the  fibre  of  a  young  tree  is  twisted  in  one  direction  ; 
that  of  the  old  tree  in  the  opposite  direction. 
In  speaking  of  the  direction,  it  is  necessary  to  come  to  an  un- 
derstanding, first  of  all,  as  to  what  we  mean  by  right  or  left,  a 
distinction  attended  with  more  difficulty  than  would  appear  pos- 
sible. Prof.  Braun  follows  De  Candolle  and  others  in  viewing 
the  twist  or  coil  objectively ;  imagining  himself  in  the  centre  of 
