Antoine Jérôme Balard met John Stuart Mill while Mill was studying at the Montpellier Faculty of Sciences in the Winter of 1820. 
In Mill's journal of the period  he writes of visiting Balard at his home, being shown his herbarium and receiving from him a selection of his plants from the Montpellier area, in addition to other accounts of the two embarking on daytrips around the city of Montpellier and to the sea to look for coastal plants. In a later letter to Auguste Comte, Mill describes Balard as his first real friend. A ‘friend of my own choice as opposed to those given to me by family ties’. 
A portion of John Stuart Mill's Herbarium, believed to be in the vicinity of 4000 specimens, is housed at the National Herbarium of Victoria (MEL) and within the Mill Herbarium are contained these Balard collections, mainly from the area of Montpellier.