The Collaborative International Dictionary of English v.0.48:

Physostigmine \Phy`so*stig"mine\, n. (Chem.)
   An alkaloid found in the Calabar bean (the seed of
   Physostigma venenosum), and extracted as a white,
   tasteless, substance, amorphous or crystalline; -- formerly
   called eserine, with which it was regarded as identical.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Eserine \Es"er*ine\ (?; 104), n. [From native name of the
   Calabar bean: cf. F. ['e]s['e]rine.] (Chem.)
   An alkaloid found in the Calabar bean, and the seed of
   Physostigma venenosum; physostigmine. It is used in
   ophthalmic surgery for its effect in contracting the pupil.
   [1913 Webster]