Franz Thonner

In the spring of 1896, he made his first trip to the African interior to explore the botany and people in the northern part of the Congo Basin.

He was a scientist of independent means who explored Europe and North Africa and in 1891, at age 28, privately published a key to the families of flowering plants of the world.

A second edition of his key appeared in 1917 and was based on Engler & Prantl's Die Natürlichen Pflanzenfamilien and Das Pflanzenreich.

Thonner's German plant key of 1891 was translated into English for the second time in 1981, and became more accessible to English-speaking botanists, rivalling that of John Hutchinson and Families of Angiosperms by Bertel Hansen & Knud Rahn[2] (1969).

Thonner also used back-up features ensuring correct choice of the family even when there is uncertainty about classifying botanical structures.