Found this one growing on damp soil just beside a swamp (you can see it on the 2nd photo in the background; also many Callitriche sp. growing on the spot). No flowers at the time, except the dense pinnatifid leaves. I'm out of ideas on this one. Photos were taken in August. Thanks!
yes... I found it out couple of days ago.... and it is endangered in Croatia Since there were no flowers and I've never seen that plant before I had no otehr choice but to take an iconographic handbook and go page by page:) Thanks anyway for your effort:)