﻿SEEDS 
  AND 
  SEEDLINGS 
  161 
  

  

  of 
  seeds 
  apparently 
  serve, 
  in 
  some 
  cases, 
  as 
  aids 
  in 
  their 
  dis- 
  

   persal 
  and 
  in 
  others 
  as 
  means 
  of 
  preventing 
  the 
  seed 
  from 
  

   being 
  eaten 
  by 
  animals. 
  

  

  152. 
  Conditions 
  for 
  germination. 
  A 
  sound, 
  live 
  seed 
  will 
  

   germinate, 
  or 
  sprout, 
  when 
  suitable 
  conditions 
  are 
  present. 
  

   The 
  requisites 
  for 
  germination 
  are 
  

  

  1. 
  Proper 
  temperature. 
  

  

  2. 
  Enough 
  moisture. 
  

  

  3. 
  Air 
  or 
  oxygen. 
  1 
  

  

  4. 
  Seed 
  coats 
  permeable 
  to 
  air 
  and 
  moisture. 
  

  

  The 
  temperature 
  most 
  favorable 
  to 
  germination 
  varies 
  with 
  

   the 
  kind 
  of 
  seed 
  ; 
  for 
  any 
  given 
  kind 
  there 
  seems 
  to 
  be 
  a 
  

   lowest 
  limit, 
  a 
  most 
  favorable 
  (optimum) 
  temperature, 
  and 
  a 
  

   highest 
  limit. 
  

  

  Wheat 
  and 
  barley, 
  for 
  example, 
  will 
  sprout 
  at 
  temperatures 
  

   but 
  little 
  above 
  the 
  freezing 
  point, 
  though 
  they 
  succeed 
  best 
  at 
  

   about 
  84 
  F. 
  Muskmelons 
  and 
  cucumbers 
  sprout 
  at 
  60 
  F. 
  but 
  

   begin 
  much 
  more 
  promptly 
  at 
  temperatures 
  of 
  93 
  and 
  upward. 
  

  

  Most 
  farmers 
  have 
  learned 
  by 
  experience 
  that 
  the 
  temper- 
  

   ature 
  requirements 
  are 
  not 
  the 
  same 
  for 
  all 
  kinds 
  of 
  seeds. 
  All 
  

   know, 
  for 
  example, 
  that 
  if 
  corn 
  is 
  planted 
  before 
  the 
  ground 
  is 
  

   warm 
  enough, 
  it 
  will 
  decay 
  and 
  have 
  to 
  be 
  replanted, 
  but 
  that 
  

   peas 
  can 
  be 
  sown 
  very 
  soon 
  after 
  the 
  frost 
  is 
  out 
  of 
  the 
  ground. 
  

  

  There 
  is 
  moisture 
  enough 
  in 
  a 
  few 
  kinds 
  of 
  seeds, 
  like 
  those 
  

   of 
  the 
  willow 
  and 
  the 
  poplar, 
  to 
  allow 
  them 
  to 
  begin 
  to 
  ger- 
  

   minate 
  as 
  soon 
  as 
  they 
  are 
  ripe 
  ; 
  but 
  most 
  seeds 
  need 
  to 
  be 
  

   supplied 
  with 
  moisture 
  from 
  without. 
  Too 
  little 
  moisture 
  

   causes 
  them 
  to 
  germinate 
  very 
  slowly, 
  as 
  is 
  often 
  noticed 
  

   during 
  spring 
  droughts, 
  while 
  immersing 
  them 
  in 
  water 
  causes 
  

   many 
  kinds 
  to 
  rot 
  because 
  the 
  air 
  supply 
  is 
  not 
  sufficient. 
  

  

  The 
  germination 
  of 
  seeds 
  planted 
  too 
  deep 
  in 
  clay 
  soils 
  is 
  

   very 
  likely 
  to 
  be 
  hindered 
  by 
  lack 
  of 
  air. 
  In 
  warm, 
  open 
  

   soils 
  there 
  is 
  usually 
  air 
  enough 
  ; 
  the 
  danger 
  here 
  is 
  that 
  the 
  

   seeds 
  may 
  dry 
  up 
  because 
  of 
  too 
  shallow 
  planting. 
  

  

  1 
  Some 
  seeds 
  begin 
  to 
  gei'uiinate 
  without 
  air, 
  but 
  soon 
  die 
  unless 
  it 
  is 
  

   supplied 
  to 
  them. 
  

  

  