"Over het geslacht Nepenthes" (lit. "Concerning the genus Nepenthes") is a Dutch-language monograph by Pieter Willem Korthals on the tropical pitcher plants of the genus Nepenthes.[1] It was published in 1839 in Coenraad Jacob Temminck's Verhandelingen over de Natuurlijke Geschiedenis der Nederlandsche overzeesche bezittingen. It is generally regarded as the first monograph on Nepenthes.[2] [3]
Korthals recognised 9 species: N. ampullaria, N. bongso, N. boschiana, N. distillatoria, N. gracilis, N. gymnamphora, N. madagascariensis, N. phyllamphora (now known as N. mirabilis),[4] and N. rafflesiana. Three of these—N. bongso, N. boschiana, and N. gracilis—were described for the first time, and six were illustrated with hand-coloured lithographs.