The herbarium is named after its author, Giorgio Jan, professor of botany at the University of Parma and director of the Botanical Garden.

It consists of four herbaria: Flora Italiae superioris. Parma 1820 (36 centuria). Herbarium technico-georgicum. Parmae 1820 (2 centuria); Herbarium toxico-medicum. Parmae 1820 (1 centuria); Portable herbarium. Parmae 1820 (4 centuria).

The original herbarium consisted of 17,000 species and 98,000 specimens but was transferred to the Museo Civico in Milan.

The original, smaller portable herbarium remains at the Botanical Garden of Parma: a scientific herbarium with species names and collection data.