There is some way to access the Kew gardens monocot database. Alas, I don't know it but someone here probably does. Failing that, Jay's site is probably your best bet. With all the renaming and new discoveries, nothing will ever be truly complete of course. Here is a link that might be useful: Jay's site

That is not enough to go on. It would be best to show an entire front. And if that is the entire frond, it is not dryopteris.

Thanks Steve for all that information

Thanks a lot. I searched the aster with the complete name on he internet and found some interesting things, mostly japanese stuff about native Asters on lime stone soil. But with some luck a friend of mine can translate it for me. And egged on by your answers I dug out some books back from university, and in one I found the following (by an German author who refers to International rules for naming stuff) under the species you have the subspecies (ssp.) the variety (varietas or var.) and finally the form (f.). And just out of curiosity I will try to digg out why or how so many different strains of a species evolve or whether it is typical for certain types/genera of plants. Well, thanks a lot, cheers, Lin ps: and I got the cultivar Asran or Ashran and in a very detailed nursery cataloge it was rated as a real spreader which can hold its own and and is likely to take over a border in he long run. I noticed the runners/rhizomes (ca. 3 inches) when I transplanted some after their first season.