The Collaborative International Dictionary of English v.0.48:

Pellitory \Pel"li*to*ry\, n. [Sp. pelitre, fr. L. pyrethrum. See
   Bertram.] (Bot.)
   (a) A composite plant (Anacyclus Pyrethrum) of the
       Mediterranean region, having finely divided leaves and
       whitish flowers. The root is the officinal pellitory, and
       is used as an irritant and sialogogue. Called also
       bertram, and pellitory of Spain.
   (b) The feverfew (Chrysanthemum Parthenium); -- so called
       because it resembles the above.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pyrethrine \Pyr"eth*rine\, n. (Chem.)
   An alkaloid extracted from the root of the pellitory of Spain
   (Anacyclus pyrethrum).
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bertram \Ber"tram\, n. [Corrupted fr. L. pyrethrum, Gr. ? a hot
   spicy plant, fr. ? fire.] (Bot.)
   Pellitory of Spain (Anacyclus pyrethrum).
   [1913 Webster]

WordNet (r) 3.0 (2006):

Anacyclus pyrethrum
    n 1: a small Mediterranean plant containing a volatile oil once
         used to relieve toothache [syn: pellitory, pellitory-of-
         Spain, Anacyclus pyrethrum]