  We investigate the manifestation of the stripes in the in-plane resistivity
anisotropy in untwinned single crystals of La_{2-x}Sr_{x}CuO_{4} (x = 0.02 -
0.04) and YBa_{2}Cu_{3}O_{y} (y = 6.35 - 7.0). It is found that both systems
show strongly temperature-dependent in-plane anisotropy in the lightly
hole-doped region and that the anisotropy in YBa_{2}Cu_{3}O_{y} grows with
decreasing y below about 6.60 despite the decreasing orthorhombicity, which
gives most direct evidence that electrons self-organize into a macroscopically
anisotropic state. The transport is found to be easier along the direction of
the spin stripes already reported, demonstrating that the stripes are
intrinsically conducting in cuprates.
