在悬停时替换文本不起作用(Jquery)

I'm unable to get one of my functions to work. My assumption is that there is a 'scope' issue due to the fact the function works when used in the same file it modifies. Anyway here is the function and fiddle. The function as the title suggests should replace text on hover and 'off-hover' put the original text back. The code snippet below works, but when used as I'm trying to(fiddle) it does not work. http://jsfiddle.net/s4q8bva6/3/

<!DOCTYPE html>
<html>
<head>
<script    src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>

</head>
<body>

<a href="#" class="open">01 - System Overview and System Manager</a>


<script>
$("a.open").hover(
    function() {
        var $this = $(this);
        $this.data('initialText', $this.text());
        $this.text("Click to return to previous page");
    },
    function() {
        var $this = $(this); // caching $(this)
        $this.text($this.data('initialText'));
    }
);        
</script>

</body>
</html>

EDITS:Update

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>PHP File Tree Demo</title>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
    <link href="styles/default/default.css" rel="stylesheet" type="text/css" media="screen" />

    <!-- Makes the file tree(s) expand/collapsae dynamically -->
    <script src="php_file_tree.js" type="text/javascript"></script>
    <script src="jquery-1.11.3.min.js"></script>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>


</head>

<body>

    <h1>File Tree </h1>     


    <h2>Browsing Training Videos...</h2>

    <?php

     //This links the user to http://example.com/?file=filename.ext
    //echo php_file_tree('Training/', "http://example.com/?file=[link]/");

    include("php_file_tree.php");
    // This links the user to http://example.com/?file=filename.ext and only shows image files
    $allowed_extensions = array("htm");
    echo php_file_tree("Training/", "http://URL/files/[link]", $allowed_extensions);
    echo "This is a TEST";
    // This displays a JavaScript alert stating which file the user clicked on
    //echo php_file_tree("demo/", "javascript:alert('You clicked on [link]');");            
    ?>

    <!-- This function collapses the li under an open li-->





    <!-- Togles all 'Other' Top Level il elements on click-->
    <script>
        $(document).ready(function () {
var col = 2
$(".pft-directory").click(function () {
    $(".pft-directory").toggle("fast");
    $(this).toggle("fast");
    if (col > 1) {
        $(".php-file-tree").css("columns", "1", "-webkit-columns", "1");
        col = 1;
    } else {
        $(".php-file-tree").css("columns", "2", "-webkit-columns", "2");
        col = 2;
    }

});
$(".open").hover(function () {
    var $this = $(this);
    $this.data('initial-text', $this.text());
    $this.text("Click to return to previous page");
},

function () {
    var $this = $(this); // caching $(this)
    $this.text($this.data('initial-text'));
});
});         
    </script>       

</body>

</html>