Taxonomic studies of the genus Ageratum L. in India

Two species of the genus Ageratum L., viz., A. conyzoides and A. houstonianum are rather poorly distinguished morphologically. The former which has sparsely hairy involucre bracts and light blue heads is distributed throughout India. The latter is known to occur in Northern parts of the country and has densely hairy bracts and blue heads. Polygraph constructed on the basis of taximetric analyses of 16 quantitative characters, revealed significant similarities in most of the characters. They were also found similar in trichome types, the details of these have been discussed by the author (1979). On the basis of these studies it appears that two species which are not very clearly distinguishable, may better be merged together into one species and A. houstonianum may be treated as variety houstonianum of the species A. conyzoides .