548    Plant  Groups,  their  Constituents  and  Properties.  {Amx°™:Jm?m' 
Another  common  storage  material  is  fixed  oil,  secreted  chiefly  in 
the  fruit  and  seed.  While  rarely,  if  ever,  absent,  yet  it  is  very  gen- 
erally known  to  vary  very  considerably  in  amount  and  in  kind  ;  that 
there  are  grades  of  solid  and  liquid,  and  of  drying  and  non-drying 
fats  ;  that,  while  some  seeds  are  quite  oily,  yielding  the  fat  readily  on 
even  slight  pressure,  from  others  the  same  constituent  will  have  to 
be  extracted  by  solvents  in  order  to  prove  its  presence.  In  the  case 
of  lycopodium,  the  presence  of  a  large  amount  of  oil  was  noticed 
only  after  the  cell-walls  of  the  spores  were  torn  by  trituration  with 
sand  or  glass. 
Let  us  briefly  consider  a  few  groups  of  plants  and  their  relation 
to  others  with  regard  to  constituents  produced  by  them,  and  hence 
with  regard  to  their  medicinal  value. 
Among  the  Acotyledons  we  meet  with  the  extensive  class  of 
Fungi  yielding  the  drug  Ergota,  the  only  one  of  this  class  gener- 
ally recognized  by  pharmacopceial  authorities,  though  somewhat 
allied  fungi — like  the  cornsmut — possess  to  some  extent  analogous 
properties.  While  many  of  the  class  are  edible,  like  the  different 
mushrooms,  morel  and  truffle,  perhaps  the  largest  number  is  decid- 
edly poisonous,  probably  in  consequence  of  the  presence  of  one  or 
more  alkaloids.  These  compounds  are  known  only  to  a  limited 
extent,  including  those  present  in  ergot,  and  the  muscarine  of  fly- 
agaric. It  is  not  improbable  that  they  are  chemically  related  to  the 
ptomaines.  A  definite  compound  of  apparently  valuable  medicinal 
properties,  agaricin,  has  recently  attracted  attention.  It  is  not  posi- 
tively known  whether  it  exists  in  other  plants  than  the  white 
agaric,  which  is  also  characterized  by  resinous  compounds,  met  with 
only  to  a  limited  extent  in  this  class  of  plants. 
Of  greater  economic  value  are  the  algae,  more  especially  those 
growing  in  seawater.  Though  many  are  locally  used  as  food,  their 
real  nutritive  value  appears  to  be  insignificant.  The  so-called  Irish 
moss  has  retained  its  pharmacopceial  position  to  the  present  day. 
Algae,  possessing  anthelmintic  properties,  are  used  along  the  Medi- 
terranean, and  the  bladder-wrack,  some  years  ago,  acquired  much 
notoriety  as  a  remedy  in  obesity.  Since  iodine  is  present  in  the 
ash  of  marine  algae,  this  constituted  at  one  time  the  only  or  chief 
available  source  for  the  manufacture  of  this  element.  The  most 
important  organic  constituent  is  a  gelatinizing  carbohydrate,  which 
they  either  contain  or  else  readily  form  on  boiling,  and  upon  which 
