Why do everone hate D. glanduligera?? you have a short memory Barry! (or
you're just so very sweet and forgiving!)
I haven't the foggiest about fertiling tubers. If you are mailing out
to Lowrie soon, I'd just ask him. course, he probably just uses bugs.
I have an idea about substrate. Utrics with dimorphic stolons probably
grow in shallow water. Certain stolons will "root" or burrow into the
substrate, which is close at hand (these be the bladderless ones?) "Root-
ed" stolons would probably last longer (in the wet soil) should the water
level drop. They would also anchor the plant and keep it from washing
downstream (into the rapids!) Most of all, they would anchor the tall
topheavy flower stalks. This may be why flowering requires substrate.
Other bladworts have floats, and big macrorhiza types can probably support
themselves, but delicate gibba and striata types especially need external
support.
MJC