OBLIQUE  DIRECTION  OF  THE   LIGNEOUS  FIBRE. 
87 
the  coil.  Thus  viewed  the  bean-vine  turns  to  the  left,  the  hop- 
vine  to  the  right,  &c.  Linnaeus  and  others,  however,  have  adopted 
the  opposite,  or  subjective  view,  and  regard  the  bean  and  other 
leguminous  plants  as  turning  to  the  right,  as  they  appear  to  an 
observer  standing  before  the  coil. 
The  twist  of  the  fibre  may  be  discerned  in  splitting  the  wood, 
or  in  its  cracks  when  the  bark  is  stripped  off,  or  in  the  course  of 
the  fissures  made  by  lightning.  Very  often  the  bark  itself,  at  the 
angles  or  superficial  lines  of  the  trunk,  indicate  the  direction  of 
the  wood  within  very  distinctly.  We  make  a  few  extracts  from 
167  species  observed. 
No  manifest  twist  has  been  observed  in  the  species  of  Fagus, 
Juglans  and  Carya,  either  in  Europe  or  America,  nor  in  Ulmus, 
Ailanthus,  Fraxinusf  Acer  dasycarpum,  Grleditscliia  or  Pobinia, 
though  the  latter  exhibits  a  very  slight  twist  to  the  left.  The 
woody  fibre  twists  to  the  right  in  Pinus  strobus,  Ostrya  Virginica, 
the  Chesnut  of  Europe,  the  European  and  American  Salices, 
Populus  pyramidalis,  Cornus  Florida,  Liriodendron  (in  Indiana 
and  Illinois,  though  in  cultivated  specimens  the  twist  was  found 
to  be  the  other  way  ;  but  more  observations  are  required),  the 
Peach,  Plum,  and  Cherry  trees,  and  the  European  Cercis  siliquas- 
trum,  the  only  leguminous  tree  known  to  twist  to  the  right.  The 
twist  to  the  left  hand  is  the  more  common :  it  occurs  in  most 
Coniferce,  especially  in  Juniperus  Virginiana,  Taxodium  disti- 
chum,  Pinus  sylvestris,  (of  which  young  trees  twist,  however,  in 
the  opposite  direction),  Picea  excelsa,  &c,  Betula  Alnus,  Ostrya, 
vulgaris  and  Castanea  Americana  (both  in  opposite  direction  to 
the  nearly  allied  species  of  the  Old  World),  Quereus  robur,  Pop- 
ulus angulata,  Qatalpa,  JEsculus  hippocastanum,  the  Pear  tree, 
and  more  than  any  other,  the  Pomegranate,  also  most  Legumi- 
nous trees. 
Most  American  Oaks,  the  Sassafras,  Acer  nigrum,  the  Apple 
tree,  &c,  twist  about  as  often  to  the  right  as  to  the  left, 
The  cause  of  the  apparent  twisting  is  not  easily  ascertained. 
It  is  not  occasioned  by  an  actual  twisting  of  the  whole  stem,  but 
belongs  to  the  growth  of  the  successive  annual  layers.  Prof, 
Braun  connects  it  with  the  growth  of  the  wood-cells,  of  which) 
the  ends,  at  their  formation  are  horizontal  or  nearly  horizontal^ 
become  wedge-shaped  as  they  elongate,  and  if  these  wedges 
