de>: Color of the root symbol. The default is
      <code>"red"</code>.</p></li>
<li><p><code>bt.pch_root</code>: Symbol used for plotting the root.
      The default is <code>17</code> (filled triangle).</p></li>
<li><p><code>bt.pch_breakpoint</code>: Symbol used for plotting a
      breakpoint. The default is <code>5</code> (non-filled diamond).</p></li>
<li><p><code>bt.pch_basin</code>: Symbol used for plotting the leaf (i.e. a
      basin) of the barrier tree. The default is <code>19</code> (filled circ