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  2 
  

  

  AMERICAN 
  HOMES 
  AND 
  GARDENS 
  

  

  November, 
  1907 
  

  

  often 
  noticeable 
  that 
  the 
  plumule 
  is 
  somewhat 
  more 
  ad- 
  

   vanced 
  in 
  growth 
  than 
  the 
  radicle. 
  This 
  advance, 
  however, 
  

   is 
  deceptive; 
  for 
  when 
  we 
  come 
  to 
  examine 
  the 
  next 
  important 
  

   stage 
  in 
  the 
  birth 
  of 
  the 
  wheat 
  (Fig. 
  7) 
  we 
  invariably 
  find 
  

   that 
  whereas 
  the 
  young 
  shoot 
  has 
  made 
  little 
  growth, 
  the 
  

   young 
  root 
  has 
  extended 
  in 
  a 
  surprisingly 
  rapid 
  manner 
  

   Moreover, 
  we 
  notice 
  that 
  the 
  tips 
  of 
  two 
  more 
  roots 
  have 
  

   made 
  their 
  appearance 
  — 
  the 
  first 
  pair 
  of 
  adventitious 
  roots 
  

   they 
  are 
  called; 
  and 
  we 
  begin 
  to 
  realize, 
  perhaps 
  for 
  the 
  first 
  

   time, 
  that 
  the 
  birth 
  of 
  the 
  wheat 
  is 
  a 
  complex 
  matter, 
  and 
  

   that 
  we 
  have 
  as 
  yet 
  by 
  no 
  means 
  seen 
  the 
  end 
  of 
  it. 
  

  

  For 
  the 
  moment, 
  however, 
  the 
  reader 
  will 
  do 
  well 
  to 
  pay 
  

   exclusive 
  attention 
  to 
  the 
  primary 
  root 
  which 
  has 
  become 
  so 
  

   suddenly 
  elongated. 
  The 
  very 
  fact 
  of 
  its 
  rapid 
  growth 
  seems 
  

   to 
  indicate 
  its 
  im- 
  

   portance. 
  Indeed, 
  

   upon 
  it 
  devolves 
  the 
  

   duty 
  of 
  obtaining 
  

   the 
  increasing 
  sup- 
  

   ply 
  of 
  moisture 
  de- 
  

   m 
  a 
  n 
  d 
  e 
  d 
  by 
  the 
  

   germinating 
  em- 
  

   bryo. 
  It 
  must 
  pro- 
  

   cure, 
  moreover, 
  cer- 
  

   tain 
  chemicals 
  in 
  

   solution 
  which 
  are 
  

   requisite 
  for 
  build- 
  

   ing 
  up 
  the 
  living 
  

   cell 
  tissue 
  of 
  the 
  

   plant 
  which 
  is 
  to 
  be. 
  

  

  So 
  the 
  primary 
  

   root 
  goes 
  down- 
  

   ward 
  into 
  the 
  soil; 
  

   and 
  at 
  a 
  very 
  

   early 
  age 
  it 
  de- 
  

   velops 
  root 
  hairs 
  — 
  

   delicate 
  white 
  fila- 
  

   ments 
  which 
  spread 
  

   out 
  at 
  right 
  angles 
  

   to 
  the 
  root. 
  They 
  

   assist 
  it 
  in 
  its 
  search 
  

   for 
  moisture; 
  also, 
  

   by 
  their 
  passage 
  

   among 
  the 
  minute 
  

   particles 
  of 
  soil, 
  

   they 
  probably 
  add 
  

   materially 
  to 
  the 
  

   holding 
  power 
  of 
  

   the 
  root 
  — 
  an 
  im- 
  

   portant 
  function 
  in 
  

   view 
  of 
  wind, 
  or 
  

   heavy 
  rain, 
  which 
  might 
  at 
  any 
  moment 
  strain 
  the 
  anchorage 
  

   of 
  the 
  germinating 
  seed. 
  

  

  The 
  most 
  interesting 
  part 
  of 
  this 
  tiny 
  root, 
  however, 
  is 
  

   its 
  tip, 
  or 
  growing 
  point. 
  This 
  is 
  semi-liquid 
  and 
  transpar- 
  

   ent; 
  yet 
  it 
  exhibits 
  an 
  exquisite 
  sensitiveness 
  which 
  enables 
  it 
  

   to 
  avoid 
  destruction 
  and 
  threatened 
  injury, 
  and 
  to 
  feel 
  its 
  

   way 
  between 
  the 
  particles 
  of 
  soil. 
  One 
  is 
  tempted 
  to 
  endow 
  

   it 
  in 
  imagination 
  with 
  a 
  species 
  of 
  intelligence. 
  "A 
  radicle," 
  

   wrote 
  Darwin, 
  "may 
  be 
  compared 
  with 
  a 
  burrowing 
  animal, 
  

   such 
  as 
  a 
  mole, 
  which 
  wishes 
  to 
  penetrate 
  perpendicularly 
  

   down 
  into 
  the 
  ground. 
  By 
  continually 
  moving 
  its 
  head 
  from 
  

   side 
  to 
  side, 
  or 
  circumnutating, 
  he 
  will 
  feel 
  any 
  stone 
  or 
  

   other 
  obstacle, 
  as 
  well 
  as 
  any 
  difference 
  in 
  the 
  hardness 
  of 
  

   the 
  soil, 
  and 
  he 
  will 
  turn 
  from 
  that 
  side; 
  if 
  the 
  earth 
  is 
  

   damper 
  on 
  one 
  than 
  on 
  the 
  other 
  side, 
  he 
  will 
  turn 
  thither- 
  

   ward 
  as 
  a 
  better 
  hunting 
  ground. 
  Nevertheless, 
  after 
  each 
  

   interruption, 
  guided 
  by 
  the 
  sense 
  of 
  gravity, 
  he 
  will 
  be 
  able 
  

   to 
  recover 
  his 
  downward 
  course, 
  and 
  to 
  burrow 
  to 
  a 
  greater 
  

   depth." 
  

  

  10 
  

  

  11 
  

  

  10 
  — 
  The 
  Beginning 
  of 
  the 
  First 
  Leaf 
  

  

  12 
  — 
  The 
  Expansion 
  of 
  the 
  First 
  Leaf 
  and 
  the 
  

  

  Furthermore, 
  the 
  root 
  tip 
  appears 
  to 
  be 
  gifted 
  with 
  a 
  cer- 
  

   tain 
  power 
  of 
  selection 
  — 
  some 
  of 
  the 
  chemicals 
  dissolved 
  in 
  

   the 
  fluid 
  which 
  surrounds 
  it 
  being 
  absorbed, 
  and 
  others 
  being 
  

   rejected. 
  Thus, 
  if 
  we 
  plant 
  a 
  pea 
  and 
  a 
  grain 
  of 
  wheat 
  in 
  

   the 
  same 
  soil, 
  the 
  root 
  tip 
  of 
  the 
  former 
  will 
  hunt 
  about 
  for 
  

   and 
  take 
  up 
  whatever 
  calcareous 
  substances 
  the 
  water 
  of 
  the 
  

   soil 
  contains. 
  But 
  the 
  root 
  tip 
  of 
  the 
  wheat 
  will 
  reject 
  these, 
  

   and 
  obtain 
  for 
  itself 
  all 
  the 
  silex, 
  or 
  flinty 
  matter, 
  afforded 
  

   by 
  the 
  soil; 
  and 
  it 
  is 
  the 
  deposition 
  of 
  this 
  silex 
  in 
  the 
  stem 
  

   which 
  gives 
  to 
  all 
  grasses 
  so 
  much 
  firmness, 
  enabling 
  them 
  

   to 
  withstand 
  wind 
  pressure, 
  and 
  to 
  raise 
  their 
  flowerheads 
  to 
  

   the 
  sunlight, 
  high 
  above 
  the 
  surrounding 
  herbage. 
  There 
  

   is 
  enough 
  silex 
  in 
  a 
  wheat 
  straw 
  to 
  make 
  a 
  bead 
  of 
  glass, 
  

   when 
  melted 
  with 
  potash 
  with 
  the 
  aid 
  of 
  a 
  blowpipe. 
  The 
  

  

  pea, 
  on 
  the 
  other 
  

   hand, 
  being 
  one 
  of 
  

   those 
  plants 
  which 
  

   clamber 
  over 
  and 
  

   support 
  themselves 
  

   upon 
  other 
  vegeta- 
  

   tion, 
  does 
  not 
  re- 
  

   quire 
  silex 
  for 
  

   strengthening 
  i 
  t 
  s 
  

   stems. 
  

  

  We 
  may 
  form 
  a 
  

   mind 
  picture, 
  then, 
  

   of 
  the 
  primary 
  root 
  

   t 
  i 
  p 
  of 
  the 
  baby 
  

   wheat 
  plant 
  work- 
  

   ing 
  its 
  way 
  among 
  

   the 
  particles 
  of 
  soil, 
  

   generally 
  with 
  a 
  

   downward 
  ten- 
  

   dency, 
  but 
  turning 
  

   aside 
  from 
  obstacles 
  

   in 
  its 
  path, 
  and 
  

   moving 
  hither 
  and 
  

   thither 
  in 
  its 
  search 
  

   for 
  moisture 
  and 
  

   such 
  chemical 
  sub- 
  

   stances 
  as 
  it 
  may 
  

   need. 
  Moreover, 
  the 
  

   primary 
  root 
  tip 
  is 
  

   not 
  left 
  long 
  to 
  

   labor 
  alone. 
  We 
  

   have 
  already 
  seen 
  

   (Fig. 
  7) 
  the 
  forma- 
  

   tion 
  of 
  two 
  adven- 
  

   titious 
  root 
  sheaths; 
  

   and 
  from 
  these 
  

   shortly 
  issue 
  and 
  

   pass 
  downward 
  into 
  the 
  soil 
  the 
  first 
  pair 
  of 
  adventitious 
  

   roots, 
  which 
  soon 
  produce 
  root 
  hairs 
  and 
  exhibit 
  all 
  the 
  char- 
  

   acteristics 
  which 
  we 
  have 
  observed 
  in 
  the 
  case 
  of 
  the 
  primary 
  

   root. 
  The 
  condition 
  of 
  the 
  grain 
  at 
  this 
  stage 
  is 
  shown 
  at 
  

   Fig. 
  8. 
  

  

  In 
  examining 
  this 
  photograph 
  the 
  reader 
  will 
  observe 
  that 
  

   the 
  plumule 
  has 
  made 
  comparatively 
  little 
  progress. 
  But, 
  as 
  

   the 
  three 
  roots 
  continue 
  to 
  work 
  their 
  way 
  into 
  the 
  soil, 
  the 
  

   tiny 
  plant 
  begins 
  to 
  feel 
  its 
  power 
  — 
  if 
  we 
  may 
  so 
  express 
  it 
  — 
  

   and 
  the 
  pale 
  yellow 
  plumule 
  grows 
  more 
  rapidly 
  upward 
  in 
  

   the 
  direction 
  of 
  the 
  free 
  air 
  and 
  light. 
  The 
  plumule 
  is 
  not, 
  in 
  

   itself, 
  a 
  leaf; 
  it 
  is 
  a 
  sheath 
  which 
  enfolds 
  and 
  protects 
  the 
  

   delicate 
  first 
  green 
  leaf 
  of 
  the 
  wheat 
  which 
  we 
  shall 
  event- 
  

   ually 
  see 
  produced. 
  Even 
  now 
  this 
  leaf, 
  complete 
  in 
  every 
  

   detail, 
  lies 
  packed 
  within 
  the 
  plumule; 
  but 
  the 
  status 
  of 
  the 
  

   plant 
  is 
  not 
  yet 
  sufficiently 
  assured 
  to 
  warrant 
  its 
  produc- 
  

   tion. 
  So 
  the 
  plumule 
  moves 
  upward, 
  while 
  the 
  three 
  roots 
  

   continue 
  to 
  burrow 
  more 
  deeply 
  into 
  the 
  soil. 
  

  

  And 
  now 
  we 
  note 
  the 
  commencement 
  of 
  yet 
  another 
  

  

  12 
  

  

  1 
  I 
  — 
  The 
  Growth 
  of 
  the 
  First 
  Leaf 
  : 
  no 
  Expansion 
  

   Development 
  of 
  the 
  Sixth 
  Adventitious 
  Root 
  

  

  