Count Alexandre Henri Gabriel de Cassini (1781-1832) was a famous French botanist and naturalist, who specialised in the sunflower family (Asteraceae) (then Compositae).

He was the youngest of five children of Jean-Dominique Comte de Cassini (1748-1845), who had succeeded his father as the director of the Paris Observatory, famous for completing the map of France. He was also the grandnephew of famous Italian-French astronomer, Giovanni Domenico Cassini, discoverer of Jupiter's Red Spot and the Cassini division in the Saturn ring

The genus Cassinia was named in his honor by the botanist Robert Brown(1773-1858)

His auctorial abbreviation in botany is Cass.

He has named many flowering plants and new genera in the sunflower family (Asteraceae), many of them from North America. He published 65 papers and 11 reviews in the [Nouveau] Bulletin des Sciences par la Société Philomatique de Paris between 1812 and 1821.

In 1825, A. Cassini placed the North American taxa of Prenanthes in the new genus Nabalus , now considered a subgenus of Prenanthes (family Asteraceae, tribe Lactuceae).

In 1828 he named Dugaldia hoopesii for the Scottish naturalist Dugald Stewart (1753-1828).

Some genera (originally) named by him :

• Brachyscome (1816)
• Carphephorus
• Dracopis Cassini (Coneflower)
• Emilia Cassini (Tasselflower)
• Eurybia (Cassini) S.F. Gray
• Euthamia (Nuttall) Cassini 1825 (Flat-topped Goldenrod)
• Facelis Cassini
• Guizotia Cassini (Niger-seed)
• Helianthus pauciflorus Nuttall ssp. pauciflorus, (Stiff Sunflower), also reported as by H.laetiflorus var. rigidus and H. rigidus (Cassini) Desf.
• Heterotheca Cassini (Camphorweed, Golden-aster)
• Ixeris (Cassini) Cassini
• Ligularia Cassini
• Pallenis Cassini
• Pluchea Cassini (Marsh-Fleabane)
• Sclerolepis Cassini (Sclerolepis)
• Youngia Cassini (Youngia)

Reference

• Cassini, A. H. G. 1813: Cassini, Henri. 1813. Observations sur le style et le stigmate des synanthérées. Journal de Physique, de Chemie, d'Histoire Naturelle et des Arts 76: 97--128, 181--201, 249-75.
• King, Robert M., Paul C. Janaske, & David B. Lellinger (compilers). 1995. Cassini on Compositae II. Monographs in Systematic Botany from the Missouri Botanical Garden 54: [i]-xii, 1-190.