Hornwort confusion...

Hello all,
   I have just recently made the leap into raising live plants.  I now have 
about a dozen cuttings of "hornwort" (_Ceratophyllum_demersum_).  The *.aquaria 
plant FAQ described hornwort as a floating plant.  However, my cuttings--which 
I've had for ~1 week--are sending down some white shoots from their bases.  I'm 
assuming these are roots.  So, I'm wondering:  is hornwort indeed a floating 
plant?  Perhaps it is a floating plant that prefers to be anchored to 
something?!  Anyway, I have placed 7 of them onto a large piece of "lava rock" 
in my tank.  I figure they can anchor onto it if they care to.  Some of the 
others are still free-floating.  Some others are near a ledge that I have for 
the fire-bellied newts in my tank.
   I plan to get a few good books and also observe the plants' reactions to 
their relative placements.  In the meantime, can anyone tell me what is exactly 
going on with these pseudo-floating hornworts?