legend on every second data set

[oxy]

Hi friends,
how ca i put a legend on every second curve in a graph?

octave> plot(x1, y1, '*', x1, fit_y1, '-')
octave> hold on
octave> plot(x2, y2, '*', x2, fit_y2, '-')

Now a legend only for (x1, y1) and (x2, y2), and not the fitting curves.
Any tip?
Thanks in advance ...