AGERATUM, or MAUDLIN, in botany, a genus of the syngenesia polygamia æqualis class. The receptacle is naked; the pappus has five arista or auns; the calix is oblong; and the stylus a little longer than the flower. There are three species of the ageratum, viz. the conyzoides, the ciliare, and the altissimum, all natives of America.