acknowledgements

We wish to thank the directors and staff of the botanical gardens in Bayreuth, Berlin, Bochum, Düsseldorf, Bonn, Frankfurt, Halle, Hamburg, Kew, Leipzig, Mainz, Marburg, München, Münster, Strasbourg and other botanical collections like Essen Grugapark, Palmengarten Frankfurt/Main, Rombergpark Dortmund, Arboretum Günterstal, Arboretum Freiburg, Arboretum Trompenburg, Flora Köln for their kind support in collecting material for our investigations.
We are grateful to many of our colleagues, especially Armin Jagel for the informed advice, Sabine Adler for linguistic support, Hanno Boeddinghaus for support with the homepage construction, and Nicole Hille, Heike Diekmann, Sabine Adler, Meike Tetzlaf, Julia Obermann, Markus Streckenbach, Armin Jagel, Nina Minkley, Thorsten Marx, Michael Markowski, Veit Dörken for testing the identification key.