Unclumped log Ṁ/M vs. log Γ_e. The different symbols indicate stellar sub-classes following Sect. 4.1. The black solid line is a fit using the CAK wind theory (with α = 0.62 ± 0.08). The dotted line indicates a tentative fit of the Of and Of/WN stars with α = 0.53. The grey asterisks indicate the position of the stars with Y> 0.75 under the assumption of core He-burning. The grey triangles are stars from Mokiem et al. (2007) with upper limits. They are excluded from the fit.