Retzia was placed by Thunberg (1794) near Datura and by Linnaeus f. (1781) near Convolvulus in the Pentandria Monogynia. The latter was followed by several authors, a.o. Schreber (1789), Willdenow (1797), Persoon (1805), Roemer & Schultes (1819), and Sprengel (1825). Jussieu (1789) placed it in the Convolvulaceae (as Convolvuli) and was again followed by various authors. Giseke (1792) placed it in the Campanulaceae (as Campanaceae) together with Convolvulus and Campanula. Bartling (1830) founded the Retziaceae which he composed of Retzia and Lonchostoma; the latter genus was moved to the Bruniaceae by Bentham & Hooker (1876). Bartling placed the Retziaceae near the Convolvulaceae, a view shared by G. Don (1838). Endlicher (1839, 1841) maintained the Retziaceae and placed it in the order of the Tubiflorae near the Solanaceae. Spach (1840) placed Retzia with doubt in the Solanaceae. Lindley (1846) gave it a more certain place in this family after Sessea. Dunal (1852) who studied the subject more thoroughly reduced Bartling’s Retziaceae in rank and made it a subtribe (as Retzieae) of the tribe Solaneae in the Solanaceae, while excluding two species added by Sprengel (1825) which are at present placed in Prismatocarpus (Campan.). Bentham & Hooker (1876) followed Dunal in placing Retzia in the Solanaceae, but they separated it from Lonchostoma (see above). In the Genera Platarum it appears between Metternichia and Fabiana in the Cestreae (as Cestrineae).