The Collaborative International Dictionary of English v.0.48:

Dewberry \Dew"ber`ry\, n. (Bot.)
   (a) The fruit of certain species of bramble (Rubus); in
       England, the fruit of Rubus c[ae]sius, which has a
       glaucous bloom; in America, that of Rubus canadensis
       and Rubus hispidus, species of low blackberries.
   (b) The plant which bears the fruit.
       [1913 Webster]

             Feed him with apricots and dewberries. --Shak.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Blackberry \Black"ber*ry\ (bl[a^]k"b[e^]r*r[y^]), n. [OE.
   blakberye, AS. bl[ae]cberie; bl[ae]c black + berie berry.]
   The fruit of several species of bramble (Rubus); also, the
   plant itself. Rubus fruticosus is the blackberry of
   England; Rubus villosus and Rubus Canadensis are the high
   blackberry and low blackberry of the United States. There are
   also other kinds.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Rubus canadensis
    n 1: North American dewberry [syn: American dewberry, Rubus
         canadensis]