var n3 = false;
image1       = new Image();  image1.src   = "images/tree3.gif";
image1on     = new Image();  image1on.src = "images/tree3a.gif";

image2       = new Image();  image2.src   = "images/tree4.gif";
image2on     = new Image();  image2on.src = "images/tree4a.gif";

image3       = new Image();  image3.src   = "images/tree2.gif";
image3on     = new Image();  image3on.src = "images/tree2a.gif";

image4       = new Image();  image4.src   = "images/tree5.gif";
image4on     = new Image();  image4on.src = "images/tree5a.gif";

image5       = new Image();  image5.src   = "images/tree6.gif";
image5on     = new Image();  image5on.src = "images/tree6a.gif";

function on3(name)
{    document[name].src = eval(name + "on.src");   }

function off3(name)
{    document[name].src = eval(name + ".src");     }

n3 = true;
function on(name)
{
   if (n3)
      on3(name);
}

function off(name)
{
   if (n3)
      off3(name);
}