 He published important systematic treatments of the families Brassicaceae (then known as Cruciferae) and Erythroxylaceae, and he is the authority for numerous species within these families.He was the author of a 1903 treatise on the genus "Cardamine" (family Brassicaceae), titled ""Monographie der Gattung Cardamine"".The genus "Ottoschulzia" (family Icacinaceae) was named in his honor by Ignatz Urban (1848-1931).