Polarisation fraction associated to selected PGCC clumps. The first frame shows the relation p vs. intensity when both are measured at the clump centres. The second frame shows p as a functionof the estimated γ angle. The last frame shows the same for the p contrast (p at the clumpcentre divided by the average over radial distances 16–20′). The blue and red colours correspond to two clump samples (see text). The cyan and magenta lines show the corresponding median values calculated with a moving window with the width one tenth of the data range.