  The transverse size of q q-bar fluctuations of the longitudinal photon is
reduced relative to the transverse size of q q-bar fluctuations of the
transverse photon. This implies R(W2, Q2) = 0.375 or, equivalently, FL/F2 =
0.27 at x<<0.1 and Q2 sufficiently large, while R(W2, Q2) = 0.5, if this effect
is not taken into account. Forthcoming experimental data from HERA will allow
to test this prediction.
