\documentclass{ppex}
\nonstopmode
\usepackage [curve,frame]{xy}
\pagestyle{empty}
\setlength\textwidth{183.0pt}
\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage [curve,frame]{xy}
\[\begin{xy}
  0*[o]+{L};(50,20)*[o]+{R}="R"
        **\crv{} ?(.6)*@{+}*^+!UL{0}
   ,"R" **\crv{(30,30)} ?*@{+}*^+!DR{1}
   ,"R" **\crv{(20,30)&(30,40)} ?*@{+}*^+!DR{2}
   ,"R" **\crv{(10,-20)&(25,-20)&(40,20)}
     ?(.4)*@{+}*^+!DR{3}
   ,"R" **\crv{(0,-10)&(12,-20)&(28,25)&(40,20)}
     ?(.4)*@{+}*^+!DR{4}
 \end{xy}\]

\end{document}