Dear Jeff,
CP stands for Carnivorous Plant. This is the same acronym that is the
name of this mailing list: "cp@opus.hpl.hp.com".
Aldrovanda is an aquatic CP. Some have described it as an underwater
Venus fly-trap. It has an active, snapping trap mechanism like Dionaea,
and grows in long strands like many common pond weeds such as Anacharis.
-- Rick