Giorgio Jan was an Italian taxonomist, zoologist, botanist, herpetologist, and writer. He is also known as Georg Jan or Georges Jan. He was the first director of the natural history museum at Milan.

Exsiccata is a work with "published, uniform, numbered set[s] of preserved specimens distributed with printed labels". Typically, exsiccatae refer to numbered collections of dried herbarium specimens or preserved biological samples published in several duplicate sets with a common theme or title, such as Lichenes Helvetici. Exsiccatae are regarded as scientific contributions of the editor(s) with characteristics from the library world and features from the herbarium world. Exsiccatae works represent a special method of scholarly communication. The text in the printed matters/published booklets is basically a list of labels (schedae) with information on each single numbered exsiccatal unit. Extensions of the concept occur.