Flower

• considered to be a modified branch bearing modified leaves
• interpretation of anatomy
  • peduncle
    • the largely unmodified branch bearing the flower
    • may branch (to pedicels) with a flower on each pedicel;
      producing inflorescence
  • receptacle
    • thick stem-like structure bearing flower parts
    • considered to be a highly compressed modified stem
      with shortened internodes
  • sepals [taken together constitute calyx]
    • modified bracts, subtending modified branches of flower
    • spirally arranged
  • petals [taken together constitute corolla]
    • modified stems or leaves, depending on author
    • arranged spirally, continuing spiral of sepals
    • calyx and corolla together constitute perianth
  • stamens
    • highly modified leaves (or stems per some authors)
    • spirally arranged, continuing spiral of sepals and petals
    • filament may be leaf petiole
    • blade of leaf [microsporophyll] rolled,
      fused to enclose two microsporangia
    • microsporangia arranged along microsporophyll margin
  • pistils
    • one or more present
    • if multiple, spirally arranged continuing spiral of flower parts
    • stem, petiole and blade of megasporophyll rolled,
      fused enclosing one to many megasporangium
    • megasporangium on adaxil surface of megasporophyll
• megasporangium produces single megaspore, retained
  • megaspore divides 3 times, to 8-nuclei in single cell
  • cytokinesis separates 3 uni-nucleate cells at top end of gametophyte
  • cytokinesis separates 3 uni-nucleate cells at base of gametophyte
    base is technically attachment of gametophyte to megasporangium
    central basal cell enlarges as single egg
  • remaining 2 nuclei remain in bi-nucleate central large cell

Fruit

• interpretation of anatomy - from center outward
  • embryo, 2n F-1 sporophyte
    • plumule
    • epicotyl, and stem primordium
    • hypocotyl, and radicle (embryonic primary root) with root cap
    • 1 or 2 cotyledons, nutritive F-1 sporophyte tissue
    • embryo retained in megasporangium
  • endocarp, the vestiges of the megasporangium, 1n P-1 gametophyte
    • may be
      papery [apple, spanish peanut],
      hard [some beans],
      soft [peas],
      woody [peach, walnut]
    • embedded in female gametophyte
  • mesocarp, often enlarged 1n P-1 gametophyte
    often edible fruit
    • may include endosperm, 3n P-1 gametophyte
      fusion of pollen tube cell nucleus with 2 nuclei
      in central cell of female gametophyte
  • pericarp, vestiges of megasporophyll 2n P-1 sporophyte
    • may be
      reduced, soft [peach skin]
      thickened, soft [orange peel]
      thickened, fleshy [central portion of apple]
      thickened hard [walnut]
      woody [oak]
  • in Rosaceae [Rose family], receptacle grows over pericarp
    doubling radius of fruit [apple, rose hips]

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