  Single pulse data on radio pulsar polarization are traditionally presented in
the form of two-dimentional greyscale patterns with the pulse longitude and
polarization angle (PA) on the horizontal and vertical axis, respectively. Such
diagrams reveal several enigmatic polarization effects: 1) bifurcations and
loops of PA curve under central pulse components, 2) vertical spread of flux at
all PA values, 3) exchange of power content between PA tracks of two orthogonal
polarization modes (OPMs), and 4) peripherically-flat PA swings that span more
than 180 degrees. It is shown that all these phenomena result from passage of
observed polarization state near the pure-V pole of Poincare sphere. Much of
their complexity results from cartographic transformation from Poincare sphere
to the longitude-PA plane. An odd number of near-pole passage produces apparent
replacement of OPMs power in the profile wings, although the same amount of
flux keeps staying in each modal patch on the Poincare sphere. The fitting of
pulsar PA curves should therefore allow for transitions between the primary
(strong) and secondary (weak) PA track. The Stokes-space (or Poincare-sphere)
representation of pulsar polarization data contains crucial polarization
information and needs to accompany the traditional viewing if the published
figures are to be fully useful for interpretation.
