- 1959: West Germany (Grawitz, Quantz, Klappert, Oberste)
- 1961: West Germany (Hoppe, Schöll, Graßhoff, Grawitz)
- 1963: Great Britain (Metcalfe, Boulter, Campbell, Steane)
- 1965: Italy (Bianchi, Iraldo, Frinolli, Bello)
- 1967: West Germany (Müller, Röper, Krüsmann, Thiemann)
- 1970: United States (Ulan, Colglazier, Turner, James)
- 1973: United States (Bond, Schultz, Lutz, Jenkins)
- 1975: Poland (Hewelt, Pietrzyk, Gondek, Szlendak)
- 1977: United States (Jennings, Smith, Dale, Andrews)
- 1979: United States (Taylor, Kerr, Harris, McCoy)
- 1981: Soviet Union (Zolotaryev, Fedotov, Burakov, Markin)
- 1983: United States (Nix, Tabron, Babers, Wiley)
- 1985: Cuba (Martínez, Peñalver, Ramos, Hernández)
- 1987: United States (Pierre, Daniel, Patrick, Robinzine)
- 1989: Jamaica (O'Connor, Morris, Davis, Burnett)
- 1991: United States (Wilson, Cannon, Irvin, Luke)
- 1993: United States (Jones, Payne, Lyles, Turner)
- 1995: United States (Hayden, Byrd, Morris, Maybank)
- 1997: United States (Terry, Wheeler, Davis, Woodward)
- 1999: United States (Berrian, Couts, Brew, Davis)
- 2001: United States (White, Gerding, Couts, Pierce)
- 2003: Ukraine (Demchenko, Zyukov, Horbenko, Tverdostup)
- 2005: Poland (Wieruszewski, Dąbrowski, Kędzia, Klimczak)
- 2007: Poland (Bańka, Klimczak, Kędzia, Dąbrowski)
- 2009: Australia (Troode, Cole, Thomas, Wroe, Watkins, Burstow)
- 2011: Russia (Sigalovsky, Buryak, Vazhov, Kruglyakov)
- 2013: Russia (Dyldin, Buryak, Kashefrazov, Krasnov)
- 2015: Dominican Republic (J. Santos, Cuesta, Mercedes, L. Santos)
- 2017: Dominican Republic (J. Santos, L. Charles, A. Charles, L. Santos)
- 2019: Mexico (Vega, Jiménez, Ramírez, Mendoza)
- 2021: Turkey (Çanakçi, Ençü, Akçam, Nezir)
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Well, that’s interesting to know that Psilotum nudum are known as whisk ferns. Psilotum nudum is the commoner species of the two. While the P. flaccidum is a rare species and is found in the tropical islands. Both the species are usually epiphytic in habit and grow upon tree ferns. These species may also be terrestrial and grow in humus or in the crevices of the rocks.
View the detailed Guide of Psilotum nudum: Detailed Study Of Psilotum Nudum (Whisk Fern), Classification, Anatomy, Reproduction