Background
Adolphe-Théodore Brongniart was born in Paris on January 14, 1801, the son of the geologist Alexandre Brongniart and Cécile Jeanne Coquebert de Montbret.
Adolphe-Théodore Brongniart was born in Paris on January 14, 1801, the son of the geologist Alexandre Brongniart and Cécile Jeanne Coquebert de Montbret.
Nothing in Brongniart’s life indicates the slightest hesitation in his pursuit of science. Between 1817 and 1828 he was able to attend to his studies and his initiation in science while carrying on original research. In 1818 he was registered for courses in medicine, but they constituted only a fraction of his occupations.
In 1920 Brongniart published his first report, on a new genus of crustacean. After this youthful attempt Brongniart hoped to reach the level of the great biological movements of his time: research on the primary divisions of the vegetable kingdom, anatomy and taxonomic anatomy (following the work of Mirbel and Candolle), and the theory of generalized plant sexuality. The progress already made in these fields, as well as that in geology and botanical geography (he had early acquired a knowledge of tropical flora), heralded a new science of which Brongniart was to be the architect: the comparative morphology of living and fossil plants.
In 1822 Brongniart published his first important memoir, on the classification and distribution of fossil plants. In it he conceived of paleobotany as a part of botany and gave it a theoretical value of prime importance for biology as well as for geology. Coming as he did after such scholars as Ernst Schlotheim and Kaspar von Sternberg, Brongniart was not entirely an innovator, but his study did show an assurance previously unknown.
The masterworks of 1828, the Prodrome and the Histoire des végétaux fossiles, mainly confirmed and extended his early ideas, giving them foundation and breadth of perspective. The Histoire, which he had hoped to continue in a second volume (only the first parts appeared in 1837), was a long, methodical, detailed, and precise study that clearly showed Brongniart’s two concerns: nomenclature and illustration. Its general principles and theoretical views were expressed in condensed form in the Prodrome, to striking effect. In it Brongniart recognized the existence of four successive periods of vegetation, each characterized geologically. Three were particularly well characterized: the first, extending to the end of the Carboniferous, by the vascular cryptogams; the third, covering the Jurassic and the Cretaceous, by ferns and the gymnosperms; the fourth, which was the Tertiary, by the dicotyledons.
At twenty-seven, Brongniart seemed to have reached the zenith of his creative power. The year before, he had passed his agrégation in medicine and had published a valuable memoir on the fertilization of phanerogams that followed up Amici’s early research. The improvements in the microscope (notably by Amici) finally made possible the direct study of fertilization, so Brongniart decided to repeat Vaucher’s investigation (which had been attempted by Brongniart’s great-uncle, Romain Coquebert, as early as 1794): to follow the process of fertilization all the way to the fusion of the male and female germ cells. Brongniart’s text confirmed and generalized the existence of the pollen tube; he also named the embryo sac and adopted the theory of epigenesis. But, most importantly, he confusedly provided a description of two fundamental discoveries: the existence of the tetrads, which appear during male sporogenesis, and the distinction between the fertilized egg and the seed. This work led to a new understanding of classification and of the alternation of generations.
In 1824 Brongniart and a few colleagues founded the Annales des sciences naturelles. He succeeded Desfontaines as professor of botany at the Muséum d’Histoire Naturelle in 1833, and the following year he was elected a member of the Académie des Sciences.
Until 1849 Brongniart extended his researches to the whole plant world, past and present, including taxonomy, anatomy, or biology. He was one of the first, after H. T. M. Witham’s work of 1833, to use thin sections in paleobotany (inaugurated by W. Nicol). His most notable use of thin sections was in his famous anatomical observations on the Sigillaria (1839), a genus in the class of plants proper to the Primary era and related to the lycopods.
In 1849 Brongniart’s article “Végétaux fossiles” appeared in d’Orbigny’s Dictionnaire universel d’histoire naturelle. This was the first attempt at a synthesis of paleobotany: the inventory of fossil genera as a whole and the place of these genera in natural classification.
After 1849 Brongniart’s activity turned more and more to the systematic study of living plants, particularly the Neo-Caledonian flora: Proteaceae, Eleocarpaceae, Saxifragaceae, Cunoniaceae, Myrtaceae, Pittosporaceae, Dilleniaceae, Umbelliferae, Epacridaceae, palms, conifers, and so on. His articles appeared in such journals as Annales des sciences naturelles, Annales du Muséum, Archives du Muséum, Comptes rendus de I’Académie des sciences, and Bulletin de la Société botanique de France. Yet he had not abandoned his interest in paleobotany. A quarter of a century after the Tableau des genres… fossiles, his pupil Grand’ Eury sent him some silicified seeds from Grand’ Croix, near St. Étienne. Brongniart went to work with enthusiasm and made a last great discovery: the pollen chamber in fossil cycads, a structure that he and Bernard Renault also found in a living cycad species from Mexico - Ceratozamia brongniart - in 1846.
Brongniart divided the vegetable kingdom into six classes: Agamae (thallophytes), cellular cryptogams (liverworts and mosses, i.e., Hepaticae and Muscae), vascular cryptogams, and three classes of phanerogams: gymnosperms, monocotyledonous angiosperms, and dicotyledonous angiosperms. This excellent classification clearly indicated modern views, but unfortunately, for unknown reasons, Brongniart did not follow it in his later publications. For the first time, gymnosperms were taken as a class and correctly placed among the phanerogams. After more than a century, the cotyledons were no longer the major criterion for classification.
Although Brongniart agreed with Cuvier’s theories of fixity of species and cycles in the history of the earth, he, like Candolle before him, accepted the law of organic improvement of plants, adding to it a fundamental geological dimension. The sequence went from the structural simplicity of the Carboniferous plant life, to the intermediary structure of the Jurassic gymnosperms, to the dicotyledons of the Tertiary and the modern flora. This work led to the biological chain formulated by Hofmeister in 1851. Brongniart noted both the phenomena of extinction, which affected the genera and even the classes of the Carboniferous flora, and the correspondence between changes in fauna and flora and changes in climate.
Within Histoire des végétaux fossiles, Brongniart asserted that the history of plants could be divided into four periods. Mirroring findings from the animal kingdom, Brongniart found that, with each successive period, the represented plants became more diverse and complex. The first period was dominated by cryptogams; the first conifers emerged in the second period and then cycads in the third. Finally, in the fourth period, flowering plants made their debut. Though there were sharp floral discontinuities during the transitions between these four periods, during each period there were gradual changes within the characteristic groups.
Brongniart’s work is important not only because of its impact on the field of paleobotany, but also because it further demonstrated the long, progressive history of life on Earth and the emergence of new, increasingly complex forms of life over time. His work also supported the theory that Earth’s climate changed over time, as Brongniart concluded that the fossil record indicated that northern Europe had once had a tropical climate. Furthermore, Brongniart suggested that there was a correlation between the profusion of plants and the emergence of terrestrial vertebrates. As plants increased and diversified, they locked up more and more carbon dioxide from the atmosphere and produced more and more oxygen, thus fueling the environment necessary to support first air-breathing reptiles and later mammals. His theories show striking similarities to modern theories about the evolution of Earth’s atmosphere.
From 1929, Brongniart was a corresponding member of the St Petersburg Academy of Sciences. In 1834 Brongniart became a member of the Académie des Sciences. In 1851, he was elected a foreign member of the Royal Swedish Academy of Sciences. He also founded the Société Botanique de France in 1854 and was its first president.
Adolphe-Théodore Brongniart was possessed with science, he was a skilled analyst and researcher.
Adolphe-Théodore Brongniart was married to Agathe Françoise Boitel. They had two sons.