lxml bug with descendant::*/td or not?

Question

Hello

I'm use lxml to parsing big table and now have trouble:

>>> winvps[0].getnext().xpath("descendant::*")
118: [<Element td at 3a30180>,
 <Element a at 3a301b0>,
 <Element font at 3a301e0>,
 <Element b at 3a30210>,
 <Element td at 3a30240>,
 <Element td at 3a30270>,
 <Element font at 3a302a0>,
 <Element td at 3a302d0>,
 <Element td at 3a30300>]
>>> winvps[0].getnext().xpath("descendant::*/font")
119: [<Element font at 3a301e0>, <Element font at 3a302a0>]

But if I use xpath to find child td, I'm get nothing:

>>> winvps[0].getnext().xpath("descendant::*/td")
117: []

What is this?