The production rates and the inclusive cross sections of the isovector meson π0 , the isoscalar mesons η and η′(958) , the strange meson K0S and the Λ baryon have been measured as functions of scaled energy in hadronic events, two-jet events and each jet of three-jet events from hadronic Z decays and compared to Monte Carlo models. The analysis is based on 3.7 million hadronic events collected with the ALEPH detector at LEP at a centre-of-mass energy of s√=91.2 GeV. The JETSET modelling of the gluon fragmentation into isoscalar mesons is found to be in agreement with the experimental results. HERWIG fails to describe the K0S spectra in gluon-enriched jets and the Λ spectra in quark jets.