With his son, Hans, he authored works involving descriptions of new species of ascomycetes, rusts and smuts.
[2] Paul Sydow was a prolific author (or co-author) of new fungal species, having formally described 2331 in his career.
[4] Between 1880 and 1916 Sydow edited seven exsiccata series, among them Mycotheca Marchica (1880) with Friedrich Wilhelm Zopf as co-editor.
[5][6] With his son Hans Sydow he co-edited the first fascicles of the series Mycotheca Germanica (1903–1906).
[7] He also made contributions to volume 12 of Pier Andrea Saccardo's Sylloge fungorum omnium hucusque cognitorum, 1897,[4] as well as volume 11 of his Annales Mycologici.