Two-dimensional spectral classifications for O stars in the southern Milky Way

Spectral classifications in the two-dimensional system are given for 53 additional O stars in the southern hemisphere. A number of these stars are members of the interesting clusters NGC 3324, Trumpler 14/16, NGC 3603, and NGC 6334, which are discussed in particular. A 4-m H-alpha photograph of the remarkable nebulosities associated with NGC 6334 is reproduced.