This collection concerns his work with desmids, especially relating to his publications and including drafts and drawings; exchange and identification of specimens; the work and activities of fellow desmidologists; and personal affairs.

Correspondents include Pierre Bourrelly (1910–1995), Hannah Croasdale (1905–1999), Franz Eckert, Kurt Förster (1918–1983), Rolf Grönblad (1895–1962), Willi Krieger (1886–1954), John Walter Guerrier Lund (1912–2015), Gunnar Nygaard (1903–2003), William Randolph Taylor (1895–1990), Paul van Oye (1886–1969), Larry Alston Whitford (1902–1995) and Felix Woytkowski (1892–1966).