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  INTRODUCTION 
  TO 
  BOTANY 
  

  

  Phycocyanin 
  (seaweed 
  blue). 
  A 
  bluish 
  coloring 
  matter 
  found 
  within 
  

   certain 
  alg;c. 
  

  

  Phyllotaxy. 
  Leaf 
  arrangement. 
  

  

  Pinna 
  (a 
  feather) 
  ; 
  pi. 
  pinnae. 
  One 
  of 
  the 
  primary 
  divisions 
  of 
  a 
  pin- 
  

   nate 
  leaf, 
  as 
  in 
  ferns. 
  

  

  Pinnate. 
  Having 
  the 
  veins 
  or 
  the 
  divisions 
  of 
  the 
  leaf 
  arranged 
  in 
  

   rows 
  on 
  each 
  side 
  of 
  the 
  midrib, 
  as 
  in 
  black 
  locust 
  (Rohinln). 
  

  

  Pinnule 
  (a 
  little 
  feather). 
  One 
  of 
  the 
  divisions 
  of 
  a 
  pinna. 
  

  

  Pistil 
  (a 
  pestle). 
  A 
  simple 
  or 
  compound 
  carpel 
  in 
  spermatophytes. 
  

  

  Placenta; 
  pi. 
  placentae. 
  That 
  portion 
  of 
  the 
  ovary 
  which 
  bears 
  the 
  

   ovules. 
  

  

  Plerome 
  (that 
  which 
  fills). 
  A 
  name 
  given 
  to 
  that 
  part 
  of 
  the 
  men- 
  

   stein, 
  near 
  the 
  growing 
  points 
  of 
  the 
  plant 
  axis, 
  which 
  forms 
  a 
  central 
  

   shaft 
  or 
  cylinder 
  and 
  develops 
  into 
  the 
  axial 
  tissues. 
  

  

  Plumule 
  (a 
  little 
  feather). 
  The 
  terminal 
  bud 
  of 
  the 
  embryo 
  above 
  

   the 
  cotyledons. 
  

  

  Pod. 
  A 
  dry, 
  several-seeded, 
  dehiscent 
  fruit. 
  

  

  Pollen. 
  The 
  spores 
  developed 
  in 
  the 
  anther. 
  

  

  Pollen 
  tube. 
  The 
  structure 
  that 
  develops 
  from 
  the, 
  wall 
  of 
  the 
  micro- 
  

   spore 
  of 
  spermatophytes 
  and 
  carries 
  male 
  cells 
  to 
  the 
  egg. 
  

  

  Pollination. 
  The 
  transfer 
  of 
  pollen 
  to 
  the 
  stigma. 
  

  

  Polypetalous 
  (many 
  petals). 
  Applied 
  to 
  flowers 
  that 
  have 
  their 
  petals 
  

   free 
  from 
  one 
  another. 
  

  

  Prosenchyma. 
  Tissue 
  composed 
  of 
  elongated 
  cells, 
  with 
  tapering 
  ends 
  

   which 
  overlap. 
  

  

  Prothallium 
  (a 
  forerunning 
  shoot) 
  ; 
  pi. 
  prothallia. 
  The 
  small, 
  usually 
  

   short-lived 
  plant 
  which 
  develops 
  from 
  the 
  spore 
  and 
  bears 
  the 
  sex 
  organs. 
  

  

  Protonema 
  (that 
  which 
  is 
  first 
  sent 
  out) 
  ; 
  pi. 
  protonemata. 
  In 
  mosses, 
  

   the 
  filamentous 
  growth 
  which 
  is 
  produced 
  by 
  the 
  spores, 
  and 
  from 
  which 
  

   the 
  leafy 
  moss 
  plant 
  is 
  developed. 
  

  

  Protoplasm 
  (that 
  which 
  is 
  first 
  formed). 
  The 
  living 
  matter 
  of 
  cells. 
  

  

  Pubescent. 
  Downy, 
  with 
  fine 
  hairs. 
  

  

  Pyrenoid 
  (kernel 
  formed). 
  Minute 
  colorless 
  bodies 
  embedded 
  in 
  the 
  

   chlorophyll 
  structures 
  of 
  some 
  lower 
  plants. 
  

  

  Receptacle. 
  That 
  portion 
  of 
  an 
  axis 
  or 
  pedicel 
  (usually 
  broadened) 
  

   which 
  forms 
  a 
  common 
  support 
  for 
  a 
  cluster 
  of 
  organs, 
  either 
  sex 
  organs 
  

   or 
  sporophylls. 
  

  

  Respiration. 
  The 
  series 
  of 
  processes 
  by 
  which 
  plants 
  obtain 
  energy 
  

   through 
  breaking 
  down 
  of 
  protoplasm 
  or 
  food. 
  Usually 
  oxygen 
  is 
  used 
  

   and 
  carbon 
  dioxide 
  is 
  formed 
  as 
  a 
  result 
  of 
  the 
  process. 
  

  

  Reticulated 
  (net-like). 
  Having 
  a 
  net-like 
  appearance. 
  

  

  Rhizoid. 
  Rootrlike 
  ; 
  a 
  name 
  applied 
  to 
  the 
  rootrlike 
  hairs 
  found 
  in, 
  

   bryophytes 
  and 
  pteridophytes. 
  

  

  