Published online by Cambridge University Press: 12 April 2016
As yet there have been few detailed analyses of Wolf-Rayet (WR) emission line spectra. Such analyses must certainly take account of line transfer in a spherically extended, expanding medium, a problem not yet completely addressed in the complexity of WR envelopes. However, visual examination of optical spectra suggests real differences in line strengths among the Balmer and Pickering series lines in WN stars. If hydrogen is present, the Balmer lines will be stronger than the adjacent Pickering lines of ionized helium; if hydrogen is weak or absent, then there will be a smooth transition in intensities along the Pickering series with no additional contribution from the Balmer lines at alternatively blending wavelengths (Underhill 1967).