﻿158 
  

  

  INTRODUCTION 
  TO 
  BOTANY 
  

  

  \\--e 
  

  

  l 
  

  

  '-hyp 
  

  

  The 
  internal 
  structure 
  of 
  seeds 
  differs 
  greatly 
  in 
  the 
  vari- 
  

   ous 
  kinds. 
  Some 
  contain 
  no 
  separate 
  parts 
  that 
  can 
  be 
  readily 
  

   made 
  out. 
  Many 
  kinds, 
  however, 
  consist 
  of 
  

  

  1. 
  An 
  embryo, 
  or 
  miniature 
  plant. 
  

  

  2. 
  Some 
  plant 
  food 
  stored 
  elsewhere 
  than 
  in 
  

   the 
  embryo. 
  This 
  is 
  usually 
  called 
  endosperm. 
  1 
  

  

  3. 
  A 
  seed 
  coat 
  or 
  coats. 
  

  

  Frequently 
  the 
  embryo 
  is 
  found 
  to 
  have 
  a 
  

   fairly 
  well-defined 
  set 
  of 
  organs: 
  the 
  hypocof;/L 
  

   or 
  little 
  stem 
  ; 
  the 
  cotyledons, 
  or 
  seed 
  leaves 
  ; 
  

   and 
  the 
  plumule, 
  or 
  seed 
  bud. 
  

  

  149. 
  Classification 
  according 
  to 
  number 
  

   of 
  cotyledons. 
  The 
  seeds 
  of 
  one 
  great 
  divi- 
  

   sion 
  of 
  seed 
  plants, 
  the 
  monocotyledons, 
  com- 
  

   prising 
  grasses, 
  sedges, 
  palms, 
  lilies, 
  and 
  

   many 
  other 
  groups, 
  have 
  one 
  cotyledon. 
  As 
  

   shown 
  in 
  figure 
  158, 
  

   B, 
  the 
  reserve 
  food 
  is 
  

   stored 
  mainly 
  outside 
  

   the 
  embryo. 
  

  

  The 
  seeds 
  of 
  the 
  

   other 
  and 
  still 
  larger 
  

   division, 
  the 
  dicotyle- 
  

   dons, 
  have 
  two 
  cotyle- 
  

   dons 
  (figs. 
  141 
  and 
  

   144). 
  The 
  plant 
  food 
  

   in 
  the 
  seeds 
  of 
  dicoty- 
  

   ledons 
  is 
  often 
  stored 
  

  

  in 
  the 
  embryo 
  itself 
  (figs. 
  140 
  and 
  141), 
  

  

  as 
  in 
  the 
  chestnut, 
  hazel, 
  beech, 
  oak, 
  

  

  pea, 
  bean, 
  squash, 
  and 
  sunflower; 
  or 
  

  

  often 
  between 
  or 
  around 
  the 
  cotyledons 
  of 
  the 
  embryo, 
  as 
  

  

  in 
  the 
  buckwheat, 
  four-o'clock, 
  castor 
  bean, 
  honey 
  locust, 
  and 
  

  

  morning-glory 
  (fig. 
  144). 
  

  

  1 
  Reserve 
  food 
  that 
  was 
  formed 
  outside 
  of 
  the 
  embryo 
  sac 
  is 
  called 
  

   perisperm. 
  

  

  FIG. 
  140. 
  Length- 
  

   wise 
  section 
  of 
  

   squash 
  seed 
  

  

  hi, 
  hilum, 
  or 
  scar, 
  

   marking 
  place 
  of 
  

   attachment 
  to 
  the 
  

   ovary 
  ; 
  hyp, 
  hypo- 
  

   cotyl; 
  p, 
  plumule 
  ; 
  

   c, 
  cotyledon 
  ; 
  e 
  (in- 
  

   nermost 
  layer 
  next 
  

   to 
  cotyledon), 
  en- 
  

   dosperm 
  ; 
  t, 
  testa. 
  

   Two 
  and 
  one-half 
  

   times 
  natural 
  size 
  

  

  Fin. 
  141. 
  A 
  common 
  bean 
  

  

  split 
  open, 
  after 
  soaking 
  

  

  in 
  water 
  

  

  //, 
  hyporotyl, 
  lying 
  on 
  one 
  of 
  

   the 
  cotyledons; 
  fj, 
  groove 
  in 
  

   Ilic 
  other 
  cotyledon, 
  where 
  

   the 
  hypociityl 
  lay 
  : 
  /', 
  plumule 
  

  

  