﻿SEEDS 
  AND 
  SEEDLINGS 
  

  

  159 
  

  

  150. 
  Kinds 
  of 
  plant 
  food 
  found 
  in 
  seeds. 
  All 
  seeds 
  contain 
  

   some 
  protein 
  material, 
  though 
  frequently 
  it 
  is 
  present 
  only 
  in 
  

   small 
  quantities. 
  Carbohydrates 
  

   (in 
  the 
  form 
  of 
  starch, 
  sugar, 
  and 
  

   cellulose) 
  and 
  fats 
  or 
  oils 
  also 
  

   occur. 
  Many 
  other 
  substances, 
  

   such, 
  for 
  example, 
  as 
  the 
  poison- 
  

   ous 
  compounds 
  that 
  occur 
  in 
  the 
  

   seeds 
  of 
  larkspur 
  and 
  Jimson 
  

   weed, 
  and 
  in 
  the 
  castor 
  

   bean, 
  the 
  opium 
  poppy, 
  

   and 
  mix 
  voniica 
  (out 
  

   of 
  which 
  strychnia 
  is 
  

   made), 
  are 
  character- 
  

   istic 
  of 
  certain 
  seeds. 
  

  

  The 
  reserve 
  protein 
  

   is 
  indispensable, 
  since 
  

   it 
  is 
  the 
  basis 
  of 
  proto- 
  

   plasm, 
  without 
  which 
  

   life 
  cannot 
  exist 
  nor 
  

   growth 
  take 
  place. 
  

   Other 
  reserve 
  foods 
  

   serve 
  mainly 
  to 
  sup- 
  

   ply 
  building 
  material 
  

   for 
  the 
  plant 
  body 
  

   until 
  it 
  can 
  draw 
  raw 
  

   materials 
  freely 
  from 
  

   the 
  soil 
  and 
  the 
  air 
  

   and 
  carry 
  on 
  photo- 
  

   synthesis 
  for 
  itself. 
  

   For 
  this 
  purpose 
  the 
  

   rice 
  grain 
  supplies 
  

   mainly 
  starch 
  ; 
  the 
  

   Brazil 
  nut, 
  oil 
  ; 
  the 
  

   grain 
  of 
  Indian 
  corn, 
  

   coffee 
  seeds, 
  cellulose. 
  

  

  FIG. 
  142. 
  Two 
  stages 
  in 
  the 
  growth 
  of 
  the 
  

   bean 
  seedling 
  

  

  In 
  the 
  younger 
  stage 
  the 
  arch 
  of 
  the 
  hypocotyl 
  is 
  

   but 
  little 
  above 
  the 
  surface 
  ; 
  in 
  the 
  older 
  stage 
  the 
  

   cotyledons 
  have 
  separated, 
  the 
  first 
  internode 
  has 
  

   elongated 
  considerably, 
  and 
  the 
  first 
  pair 
  of 
  foli- 
  

   age 
  leaves 
  has 
  expanded, 
  cot, 
  cotyledon; 
  h, 
  hy- 
  

   pocotyl; 
  A 
  a, 
  hypocotyl 
  arch; 
  i, 
  internode 
  ; 
  I, 
  leaf 
  ; 
  

   r 
  v 
  taproot, 
  which 
  proceeded 
  from 
  the 
  tip 
  of 
  the 
  

   hypocotyl 
  ; 
  ?>, 
  branches 
  of 
  r^ 
  Natural 
  size 
  

  

  both 
  starch 
  and 
  oil; 
  and 
  date 
  seeds 
  or 
  

   Of 
  the 
  substances 
  mentioned 
  proteins, 
  

  

  