He was born in 1841, and died in 1916. It was said that few Belgian botanists came near the international reputation Cogniaux reached during his lifetime (1949). Before being hired by the state botanic garden, in 1872, he used to teach math and natural sciences in schools located in several small Belgian cities. Although he never graduated from any university and had no academic training in botany, he became a very saliant personality in the Belgian scientific world. In 1862, for instance, he collaborated in the foundation of the, soon-to-be famous, Société Royale de Botanique de Belgique. There, he mingled with the cream of the young Belgian botanists, and with Barthélémy Dumortier, the chairman of the new society. Dumortier, who was then regarded as the "Nestor" of Belgian botany, supported Cogniaux for a job at the botanic garden in 1872. That very same year he became "aide-naturaliste".
His work at the botanic garden focused on the herbaria: he created a Belgian Phanerogamic herbarium first, and then came up with a Cryptogamic equivalent. At the same time he was busy gathering dried material in the botanic garden’s collections to study the family Cucurbitaceae. Indeed, Eichler had asked Cogniaux (1872) to join the squadron of botanists that would go on with the job von Martius had begun in 1840: the famous Flora Brasiliensis. In 1879, Cogniaux was awarded the Prix quinquennal of the Société de Physique et d’Histoire naturelle de Genève for his contribution to the Prodromus A.-P. de Candolle had initiated some decades before. Here again, Cogniaux had concentrated on the Cucurbitaceae.In the botanic garden , he was one of Dumortier’s vassals and followed in his steps each and every time the old chairman of the board asked him, even during the infighting that occurred in the institution, before 1875. Although Cogniaux was once compared to the de Jussieus, Alphonse de Candolle and Bentham ( De Wildeman, 1919), thanks to his contribution to the Flora Brasiliensis he came first with 3118 pages!, the most part of his scientific work was done after he left the botanic garden, in 1880. It must be pointed out that Belgium had not bought the famous von Martius Herbarium, Cogniaux would never have succeed in his scientific studies. The aforesaid herbarium thus allowed the new born institution to find a place on the scientific forescene quite early in its life, as was planned by Dumortier when he battled for the acquisition of the herbarium and for the creation of the State botanic garden. Why Cogniaux resigned and left the botanic garden in 1880 remains unclear, but it seems that he had a disagreement with Director Fr. Crépin. He then came back to teaching in a small city in Wallonia and kept busy working on Orchidaceae, Melastomaceae and Cucurbitaceae, among others.
He has numerous plants named after him, including the orchid genus Neocogniauxia and Gurania cogniauxiana in the Cucurbitaceae.
by Dr. Denis Diagre