The Collaborative International Dictionary of English v.0.48:

gum tree \gum" tree`\ n.
   Any tree that exudes a gum, such as:
   (a) The black gum (Nyssa multiflora), one of the largest
       trees of the Southern States, bearing a small blue fruit,
       the favorite food of the opossum. Most of the large trees
       become hollow.
   (b) A tree of the genus Eucalyptus; a eucalypt. See
       Eucalpytus.
   (c) The sweet gum tree of the United States (Liquidambar
       styraciflua), a large and beautiful tree with pointedly
       lobed leaves and woody burlike fruit. It exudes an
       aromatic terebinthine juice.
   (d) The sour gum tree.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pepperidge \Pep"per*idge\, n. [Cf. NL. berberis, E. barberry.]
   (Bot.)
   A North American tree (Nyssa multiflora) with very tough
   wood, handsome oval polished leaves, and very acid berries,
   -- the sour gum, or common tupelo. See Tupelo. [Written
   also piperidge and pipperidge.]
   [1913 Webster]

   Pepperidge bush (Bot.), the barberry.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tupelo \Tu"pe*lo\, n. [Tupelo, or tupebo, the native American
   Indian name.] (Bot.)
   A North American tree (Nyssa multiflora) of the Dogwood
   family, having brilliant, glossy foliage and acid red
   berries. The wood is crossgrained and very difficult to
   split. Called also black gum, sour gum, and pepperidge.
   [1913 Webster]

   Largo tupelo, or Tupelo gum (Bot.), an American tree
      (Nyssa uniflora) with softer wood than the tupelo.

   Sour tupelo (Bot.), the Ogeechee lime.
      [1913 Webster]