Brongniart was an indefatigable investigator and a prolific writer of books and memoirs. As early as 1822 he published a paper on the classification and distribution of fossil plants. This was followed by several papers chiefly bearing upon the relation between extinct and existing forms - a line of research which culminated in the publication of the Histoire des végétaux fossiles, which has earned for him the title of "father of paleobotany." This classification arranged fossil plants with their nearest living allies; it formed the basis of much subsequent work in paleobotany. It is of especial botanical interest, because, in accordance with Robert Brown's discoveries of the fundamental difference between Gymnosperms and Angiosperms, the Cycadeae and Coniferae were placed in the new group the gymnosperms. In Brongniart's Histoire des végétaux fossiles attention was also directed to the succession of forms in the various geological periods, with the important result that in the Palaeozoic period the Pteridophyta are found to predominate; in the Mesozoic, the Gymnosperms; in the Cenozoic, the Angiosperms, a result subsequently more fully stated in his Tableau des genres de végétaux fossiles. But the Histoire itself was not completed; the publication of successive parts proceeded regularly from 1828 to 1837, when the first volume was completed, but after that only three parts of the second volume appeared. Apart from his more comprehensive works, his most important palaeontological contributions are perhaps his observations on the structure of the treelike lycopodiopsid, Sigillaria, an extinct plant related to the living club mosses, and his researches on fossil seeds, of which a full account was published posthumously in 1880.
Other pursuits
He was active in many branches of botany, including anatomy and the taxonomy of seed-producing plants. Among his achievements in this direction, the most notable is the treatise Sur la génération et le développement de l'embryon des Phanérogames, which is remarkable for the first account of any value of the development and structure of pollen, along with the confirmation of Giovanni Battista Amici's 1823 discovery of the pollen-tube, the confirmation of Robert Brown's views as to the structure of the unimpregnated ovule, showing how nearly Brongniart anticipated Amici's subsequent discovery of the entrance of the pollen-tube into the micropyle, fertilizing the female cell, which then develops into the embryo. Of his anatomical works, those of the greatest value are probably the "Recherches sur la structure et les fonctions des feuilles, and the Nouvelles recherches sur 1'épiderme, in which, among other important observations, the discovery of the cuticle is recorded; and, further, the Recherches sur l'organisation des tiges des Cycadées, giving the results of the first investigation of the anatomy of those plants. His systematic work is represented by a large number of papers and monographs, many of which relate to the flora of New Caledonia; and by his Énumération des genres de plantes cultivées au Muséum d'histoire naturelle de Paris, a catalogue of the plants in cultivation at the French National Museum of Natural History; it is a landmark in the history of classification in that it forms the starting-point of the classification system, modified successively by Alexander Braun, August W. Eichler and Adolf Engler, which was not superseded until the development of DNA research. In addition to his scientific and professorial labours, Brongniart held various important official posts in connection with the department of education, and interested himself greatly in agricultural and horticultural matters. With Jean Victoire Audouin and Jean-Baptiste Dumas, his future brothers-in-law, Brongniart founded the Annales des Sciences Naturelles, a peer-reviewed journal, in 1824. He also founded the Société Botanique de France in 1854, and was its first president.
