Acknowledgements

Jan De Langhe is particularly grateful to the following people for their help (the abbreviations in this list refer to the abbreviations used in the picture names): 

Anthony Aiello, Folkert Aleva, Susyn Andrews, Clément Anthoine, Hugh Angus, Robin Ardito, James Armitage, Christelle Bacquet, Piotr Banaszczak, Bruce Bartholomew, Ben Baudts, Timothy Baxter, Richard Bellanger, Patrick Bellec (BELLEC), Clément Benoit, Dirk Benoit (PAVIA), Verena Berchtold, Dave Boufford, Charles Boulanger, Mona Bourell, Wolfgang Bopp, Jan Just Bos, Peter Brownless, Roman Businský, George Callen, Koen Camelbeke, Debbie Chubb, Tom Clark, Barry Clarke (BARCLA), Chris Clennett, Fran Clifton, Agustin Coello, Olivier Colin (OCOLIN), Allen Coombes, Christophe Crock, Dan Crowley, Helmut Dahlitz, Daniël De Belder, Diane De Belder, Robert De Belder, Michel Décalut, Antoon De Clercq (ADCN), Herlinde De Jaeck, Piet de Jong, Luc De Jonge (LDJ), Henk De Leeuw, Laurent De Lepeleere, Dirk De Meyere, Min Deng, Albert De Raedt (ADRA), Jean des Arbres, Philippe de Spoelberch, De Vrienden van de Plantentuin Gent, Eric Dewaele (EDWI), Malo Dormont, Catherine Ducatillion, Maurice Duhard, Raymond Durand, Peter Endress, Peter Enz, Hartmut Ern, Bruno Erny, Fiona Falcona, Aljos Farjon, Bernard Favier, Brigitte Fiebig, Richard Figlar, Mark Flanagan, Gert Fortgens, Maurice Foster (MFOST), Michael Frankis, Nicolas Freyre, Friederike Gallenmüller, Siegfried Gand, Martin Gardner, Francisco Garin, Stefan Giefer, Silvan Glauser, Paul Goetghebeur, Peter Gregory, John Grimshaw, François Hachette, Shaun Haddock (LABERG), Tom Hart Dyke, Larry Hatch, Michael Heathcoat Amory, Jean-Louis Hélardot, Didier Hermans (BUXHER), Vincent Herpailler, Hans Heybroek, Tony Hibbert, Elvira Hoerandl, Nigel Holman, Charles Howick, Tom Hudson, Stefanie Ickert-Bond, Eike Jablonski, Robert Jamieson, David Jewell, Owen Johnson, Douglas Justice, Alexandra Kehl, Tobias Kehrer, Lloyd Kenyon (KENYON), Tony Kirkham, Sabina Knees, Phillip Kodela, Henny Kolster, Jelena Kovačič – De Belder, Gregor Kozlowski, Horst Kraft, Anett Krämer, Matthias Krause, Rob Kruijt, Eric La Fountaine, Thierry Lamant, Neil Lancaster, Roy Lancaster (RLANC), Chris Lane (CLANEC), Christopher Lang, Herman Laporte, Isabel Larridon, Marianne Lauerer, Antoine le Hardÿ de Beaulieu, Raf Lenaerts (RAFLEN), Jie Li, Xi-wen Li, Marc Libert, Nick Lightfoot, Matt Lobdell, Cornelia Löhne, Pierre-Andre Loizeau, David Long, Dan Luscombe, Ben Lyte, James MacEwen, Christa Maes, Valéry Malécot, Rolf Marquardt, Andrew Marsh, Rosalyn Marshall, John Marston, Bruce Maslin, Michael Mauser, Hugh McAllister (HMCALL), Bob McCartney, Kevin McGinn, Jean Merret, Simon Momper, Peter Moore, David More, Jaime Morin, Daniel Murphy, Mike Nelhams, Henry Noltie, Mikinori Ogisu, Pamela Olshefski, Ralf Omlor, Joke Ossaer, Shaun Overstreet, Phill Parsons, Zofia Piecko, Ulrich Pietzarka, Donald Pigott, Mark Pitman, Jacky Pousse (POUSSE), István Rácz, Markus Radscheit, Abraham Rammeloo, Paul Reader, David Reid, Heribert Reif, Katja Rembold, Will Ritchie, Wolf-Achim Roland, Jens Rohwer, Nicolas Ruch, Keith Rushforth (KRUSH), Marie-Stéphanie Samain, Daniel Sanford, Deborah Schäfer, Marianne Schaller, Nico Schellevis, Peter A. Schmidt, Brian Schrire, Bernd Schulz, Jacques Sciboz, Charles Shine, Daan Smit, Doug Smith, Gijs Steur, Joeri Sergej Strijk, Wolfgang Stuppy, Michel Timacheff, Frédéric Tournay, Raymond Townsend, Louis et Michèle Tranchant, Philip Tregunna, Piers Trehane, Gemma Trier (GTS), Liesbeth Uijtewaal, Barry Unwin, Jan Van Bogaert, Filip Van den Bossche, Henk van der Werff, Kees en Lida van Gaal, Cor van Gelderen, Dick van Gelderen, James R.P. Van Hoey Smith, Jef Van Meulder (JVM), Kurt Van Nieuwenhuyse (KUVANI), Bruno Van Puijenbroek (BVPUIJ), Hans van Roon, Marian Vande Wiele, Vincent Vaxelaire, Patrick Vereecke, Jan Willem Vos, Freek Vrugtman, Eva Wallander, Neville Walsh, Laura Wester, Onno Wijnands, Charles Williams, Julian Williams, Robbert Willink, Johan Willm, Eric Windey (EW), George Witherwick, Bart Wursten, Bleddyn Wynn-Jones, Rolf Zumbrunn (RZM), Pieter Zwijnenburg Junior (PZJB).

and to the following institutions for their support and providing of herbarium specimens since 1982 (the abbreviations in this list refer to the abbreviations used in the picture names):

High resolution images identification keys