jquery click 隐藏显示的问题

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head><body>
<div id="tree">
<ul>
<li class="tree-1">
            <a href="#" >一级</a>
            <ul>
                <li class="aaa">
                    <a href="#">二级</a>
                    <ul>
                        <li>内容</li>
                        <li>内容</li>
                        <li>内容</li>
                        <li>内容</li>
                        <li>内容</li>
                    </ul>
                </li>
                <li class="aaa">
                    <a href="#">二级</a>
                    <ul >
                        <li>内容</li>
                        <li>内容</li>
                        <li>内容</li>
                        <li>内容</li>
                        <li>内容</li>
                    </ul>
                </li>
                <li class="aaa">
                    <a href="#">二级</a>
                    <ul >
                        <li>内容</li>
                        <li>内容</li>
                        <li>内容</li>
                        <li>内容</li>
                        <li>内容</li>
                    </ul>
                </li>
            </ul>
</li>
</ul>
</div>
<script type="text/javascript" src="jquery-1.7.2.js"></script>
<script type="text/javascript">
$(function(){
$(".aaa").click(function(e){
$("ul",this).slideToggle();
e.stopPropagation();
});
});
$(function(){
$(".tree-1").click(function(){
$(".tree-1 ul").slideToggle();
});
});
</script>
</body>
</html>冒泡了