SUMMARY

With a view to an improved taxonomy of the genus Agrobadmiurn, 45 strains, including representatives of all nomen-species, were used to investigate the following features: base composition and compositional distribution of pure deoxyribonucleic acid (DNA) ; type of flagellation; 3-ketoglycoside formation; phytopathogenicity for tomato and Datura. It is proposed to limit the genus Agrobacterizlm to two, or possibly three, species: (1) Agrobmterium radiobader and its phytopathogenic variety A. radiobacter var. turnefmiens; ( 2) A. rhizogenes; and (3) possibly A.pseudo-tsugae. More work on the latter two species is required before they can definitely be accepted as separate species of this genus. The DNA of a11 the strains of the former two species has a T,,, value in the narrow range of 98*8°-95-10, corresponding with an average molar guanine + cytosine (GC) content of 5 9 + 6 2 * 8 ~ 0. The variance cr of the compositional distri-bution of the DNA molecules ranges between 0 and O- S 8 ~ 0 with an average of 0024 % (GC). The only available strain of A. pseudotsugae, wit