  The lightest gluonic meson is expected with J^{PC}=0^{++}, calculations in
full QCD point towards a mass of around 1 GeV. The interpretation of the scalar
meson spectrum is hindered as some states are rather broad. In a largely
model-independent analysis of pi+ pi- \to pi+ pi-, pi0 pi0 scattering in the
region 600-1800 MeV a unique solution for the isoscalar S-wave is obtained. The
resonances f_0(980), f_0(1500) and the broad f_0(600) or ``sigma'' are clearly
identified whereas f_0(1370) is not seen at the level B(f_0(1370)\to pi
pi)\gtrsim 10%. Arguments for the broad state to be a glueball are recalled. We
see no contradiction with the reported large B(sigma \to gamma gamma) and
propose some further experimental tests.
