Of  the  plants  that  are  commonly  preserved  to
us,  the  ferns  seem  to  take  the  lowest  rank,  and
the  conifersB  the  highest,  the  Calamites,  SigiU
laruBy  and  Jjepidodendron  occupying  intermediate
positions.*  The  ferns  constituted  a  most  prolific
class,  occurring  in  vast  quantities  in  the  shales
which  overlie  the  coal-seams.  The  Sigillariae,
Lepidodendrons,  and  Calamites  appear  to  have
formed  the  greater  mass  of  coal ;  and  the  roots
of  the  former  especially  (StigmarisB)  penetrate  in

vast  quantities  the  under-clays  or  floors  of  the
coal-seams.  Coniferous  trees,  however,  formed
a  considerable  portion  of  the  mass  of  the  coal,

*  See  Sir  C.  LyeU,  '*  Elementary  Geology/'  5ih  edit.,  p.  899.
t  Dr.  J.  D.  Hooker  '<  On  the  Vegetation  of  the  Carboniferons
Period."    Mem.  Geol.  Survey,  vol.  ii.,  p.  S95.
46


THE   COAL-FIELDS   OF   GREAT  BRITAIN,


Pisr  1.
and  seem  to  have  grown  in  company  with  the
more  characteristic  plants  above  mentioned.  I
now  proceed  to  give  a  short  description  of  the
genera  which  have  been  most  prohfic  and  cha-
racteristic amongst
the  flora  of  this  an-
cient period.
Ferns.  —  These
form  a  very  large  pro-
portion of  the  Car-
boniferous flora ;  and,
with  the  exception  of
their  fructification,
which  has  ahnost
always  disappeared,
are  preserved  in  great
perfection.  They  are
represented  at  the
present  day  by  the
*,^v  *  .1    ui*^  arborescent  forms  of

Alethopteru  loncUtka.
Portion  of  frond  ;  two-thirds  rat.  size.    From  a    tho      TrOpiCS,      Wluch
apedmen  in  the  Natnral  Histoiy  Mnaeani,
Manchester.  flourish      iu      CcyloU,

the  islands  of  the  Pacific,  and  the  Indian  Archi-
pelago, where  they  are  so  abundant  as  to  equal
in  numbers  the  whole  of  the  phanerogamic  plants.
