Don't forget H. lacustris and H. 'Pantanal wavy" :wink: . I'm sure there are dozens of others not mentioned...
I'm not positive, but I think they use "Nomaphila" as the
other genus name to avoid setting off alarms with "the powers that be." The LFS I get plants from works very closely with these "powers" and gets in many species of Hygros. AFAIK, only H. polysperma and its variations are illegal in the state AND illegal to import internationally no matter what state you're in. In fact, I think polysperma is banned from being sold anywhere, which is why it's almost impossible to find it on-line, even.
But no, there is no ban on
all hygros. Not by a long shot... Thank goodness

.
-Naomi