Hi Helga,
Great to hear that your L. mackliniae seeds are germinating. They need to be kept moist (not wet) and frost free but cool. Don't leave them dry in warm sunshine. If all goes well they should produce a small first leaf in a few weeks (the 'grass' you have are the cotyledons) and then after perhaps two more months you can begin feeding very weak general liquid feed every other watering. Keep them somewhere sheltered and in dappled shade and change to a very weak high potash feed (tomato feed) after mid summer.
Good luck with them.
Mel