Issues with XML

[Andrew.Stubbs]

Apologies if I'm being completely stupid, which is the only conclusion I can come to but I'm having real trouble getting the XML traversal functions to return the values I expect, for example with the following xml:

var x:XML =
<a>
<b>
<c>
<d/>
<e/>
</c>
</b>
<f />
</a>

I would expect `trace("F: " + x..f);` to print "</f>, instead I get nothing.
Similarly, if I attempt to print each element with:
trace("A: " + x..a);
trace("B: " + x..b);
trace("C: " + x..c);
trace("D: " + x..d);
trace("E: " + x..e);
trace("F: " + x..f);
I would expect, from my understanding of the documentation, that each would print every occurrence of the named element, and its sub-elements, however I get:
A:
B: <b>
<c>
<d/>
<e/>
</c>
</b>
C: <c>
<d/>
<e/>
</c>
D:
E:
F:

i.e. B and C print what I expect, but I can't understand the reasons for the others failing.

Any clarification on my wrongdoings would be appreciated.