Ageratum
Ageratum (ȧ*jer"ȧ*tum or aj`ẽr*ā"tum) , proper noun
[New Latin, from Greek 'agh`raton a sort of plant; 'a priv. + gh`ras old age.]
(Botany) A genus of plants, one species of which (Ageratum Mexicanum) has lavender-blue flowers in dense clusters.