  Density, temperature and magnetic field dependences on electron transport in
a quantum wire were studied. Decrease of carrier density gives a negative
conductance correction on the first plateau at low temperatures. The prominent
and mysterious "0.7 structure" is more clearly resolved at low densities. The
thermal behavior of the conductance follows the predictions of the
spin-incoherent transport. The 0.7 structure at a low density drops to $e^2/h$
in a smaller in-plane magnetic field. The features are qualitatively consistent
with the theoretical predictions and provide evidence for the existence of
Wigner Crystal in low density quantum wires.
