The energy flow and particle flow distributions of planar three-jet events produced in e+e−→ hadrons at CM energies between 29.5 and 36.4 GeV have been interpreted in terms of the reactions e+e−→qg and compared with the distributions calculated from two different fragmentation schemes, one based on independent parton fragmentation, the other one on fragmentation along colour flux lines. The particle density at angles between the two highest energy jets is found to decrease more strongly with increasing transverse mass of the particles than the particle density at angles between any of these jets and the lowest energy jet. The high momentum particles within the two most energetic jets are emitted at larger angles with respect to the lowest energy jet than the average particles. These observations are well reproduced by fragmentation along colour flux lines, but not by independent parton fragmentation.