public void addBranch(Tree t) {
		if (t == null) {
			branches.add(null);
			return;
		}
		if (s == null) {
			this.s = t.s;
		}
		if (this.begin < 0) {
			this.begin = t.begin;
		}
		if (this.end < t.end) {
			this.end = t.end;
		}
		this.node = s.substring(begin, end);
		branches.add(t);
		t.parent = this;
	}