LISTEN & QUESTION: Zeepeduinen

The Zeepeduinen. Why is this area actually called that? What does soap have to do with it? Nothing at all. Zeepe comes from the Zeeland word sepelen, meaning seep. Groundwater seeps here from the dunes to the lower surroundings. There used to be many wet dune valleys, or dune lakes, but they have grown over time. Of four valleys, the top layer has been excavated, so that there is water in them again. There are marshy clearings with creeping willow, centaury, parnassia and field rush. You can now find natterjack toads, green frogs and newts. 

Question 4: Which beautiful white-yellow flower grows in the Sea Dunes? Take the 3rd letter of the answer.