Is this an algae or higher plant?

[David Marshburn <marshbur at cs_unc.edu>]

I've had the following... thing... growing around in my tank, particularly
out of the H. difformis.  It looks to have a little more structure than an
algae, but I'm not sure.  It grows (usually) in a single long strand
extending out into the open areas of the tank.  When I pull it out, it's
embedded well into the stand of plants, however.  The strand has sort-of
nodules maybe every half-inch to inch along its length.  I thought these
nodules were tiny leaves at first.  I looked at them under a 10x loupe
tonight, though, and they looked like small bladders or some kind of more 
generic node.  There's a (rather poor) picture here:

http://www.cs.unc.edu/~marshbur/aquarium/2002-11-14/aquarium%20006.jpg
(sorry, the digital camera didn't want to focus that close-in, I think)

Any ideas what this might be?  I don't know that it looks particularly
horrible in the tank, rather strange and different.

thanks!
-David