Jens,
While it can be a nuisance plant in some places it is an extremely "photogenic" alga. It has actually been 7 or 8 years since I last photographed it...
here, and
here.... but that was when I just a "beginner" at microscopy. The small piece used for these pictures was not in good condition so it was not possible to get a "net" pattern, thus the small details as shown here. It would be nice to find a larger clean sample in good condition.
Good luck in your search!
