  A class of graphs G is chi-bounded if the chromatic number of the graphs in G
is bounded by some function of their clique number. We show that the class of
intersection graphs of simple x-monotone curves in the plane intersecting a
vertical line is chi-bounded. As a corollary we show that the class of
intersection graphs of rays in the plane is chi-bounded, and the class of
intersection graphs of unit segments in the plane is chi-bounded
