^ptemUberPi9iT'}  Myricacece  of  Eastern  United  States.  393 
well  as  stone  cells  in  the  phloem;  (d)  the  uniformity  in  distribution 
of  the  tracheae.  It  resembles  the  aerial  stem  of  M.  Caroliniensis  in 
the  size  and  relative  number  of  tracheae  found  in  the  protoxylem.  It 
differs  from  both  parents  as  follows :  The  autumnal  wood  is  inter- 
mediate in  thickness  ;  the  pitted  tracheae  are  fewer  than  in  M.  cerifera, 
more  numerous  than  in  M.  Caroliniensis ;  the  mean  diameter  of  the 
tracheae  is  intermediate  between  that  of  both  parents.  The  primary 
medullar}*  rays  are  1-3,  rarely  1-4,  rows  of  cells  wide;  the  secondary, 
1-2  rows  in  width.  Other  stem  structures  common  to  both  parents 
are  likewise  seen  in  the  hybrid. 
Subterranean  Branch  (histology). — Compared  with  the  aerial 
stem  of  the  same  age,  it  shows  fewer  cork  layers  and  a  broader  cortex. 
The  cells  of  the  cortex  are  generally  larger,  less  angular,  and  contain 
more  starch  grains.  The  bast-fibres  of  the  phloem  are  about  twice  as 
numerous  and  in  larger  groups.  The  tracheae  are  fewer  and  generally 
broader,  while  the  woody  fibres  are  more  numerous  and  more  lignified. 
The  pith  is  narrower,  its  elements  smaller  and  more  lignified.  The 
primary  medullar}*  rays  are  broader  and  frequently  show  1-5,  less 
often  1-6,  rows  of  cells  in  width.  The  secondary  medullar}*  rays  vary 
in  width  .from  1-2  to  1-3  rows  of  cells.  Cortical  parenchyme,  phloem, 
and  tracheal  elements  with  a  gummy  lignin  content  are  more  frequent 
than  in  the  above-ground  stem.  Compared  with  the  rhizomes  of  its 
parents,  it  shows  intermediate  characters  in  respect  to  the  number 
and  mean  diameter  of  the  tracheae  and  woody  fibres. 
Leaves  (gross  structure) . — The  leaves  of  this  hybrid  show*  several 
striking  macroscopic  characters  which  are  intermediate  between  those 
of  its  parents.  For  instance,  they  vary  from  lanceolate-cuneate  to 
elliptic-obovate  in  shape,  many  of  them  being  a  mean  between  these 
two  forms.  In  duration  they  are  semi-evergreen,  and  usually  fall 
during  February  and  March,  by  which  time  they  have  often  assumed 
a  slight  copper}*  tint.  In  size  they  vary  from  25  to  58  mm.  in  length 
and  from  S  to  20  mm.  in  width.  They  have  numerous  orange- red  and 
golden-yellow  glandular  hairs  on  their  lower  surface,  with  merely  a 
few  of  each  of  these  on  their  upper  surface.  (M.  cerifera  leaves 
have  numerous  orange-red  and  golden-yellow  glandular  hairs  on  both 
surfaces,  while  the  leaves  of  M.  Caroliniensis  are  devoid  of  orange-red 
glandular  hairs,  have  numerous  golden-yellow*  glandular  hairs  on 
their  lower  surface,  and  a  mere  scattering  of  these  on  their  upper 
surface) .  Simple  hairs  are  found  on  both  surfaces  and  margin,  as  on 
the  leaves  of  M.  Caroliniensis,  but  relatively  fewer  in  number.  The 
