Source : Webster's Revised Unabridged Dictionary (1913)

Populin \Pop"u*lin\, n. [L. populus poplar: cf. F. populine.]
   (Chem.)
   A glycoside, related to salicin, found in the bark of certain
   species of the poplar ({Populus}), and extracted as a sweet
   white crystalline substance.

Source : WordNet®

Populus
     n : a genus of trees of the family Salicaceae that is found in
         the northern hemisphere; poplars [syn: {genus Populus}]