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.Thonner's analytical key to the families of flowering plants Despite the work's having been translated into English in 1895, it was largely ignored in that country. A second edition of his key appeared in 1917 and was based on Engler & Prantl's Die Natürlichen Pflanzenfamilien and Das Pflanzenreich.
