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Wednesday, October 14, 2015

The Roots of Paleobotany: Brongniart and Fossil Plants

French botanist Adolphe-Théodore Brongniart is known as the Father of Paleobotany. Active in many branches of botany, Brongniart is most-remembered for his pioneering work on the relationship between extinct and living plants. In 1822, he published a paper on the classification and distribution of fossil plants, which he subsequently followed-up with his masterpiece Histoire des vegetaux fossiles ("History of fossil plants") in 1828. This work was instrumental in the development of the field of paleobotany.

In 1828, Brongniart, son of the geologist Alexandre Brongniart (who worked with Georges Cuvier on geological studies in France), first published an introduction to his history of fossil plants, entitled Prodrome d'une histoire des végétaux fossiles. He then followed the introduction with his two-volume magnum opus, Histoire des végétaux fossiles.

Brongniart, Alexandre. Histoire des végétaux fossiles. (1828-37). http://biodiversitylibrary.org/page/40155235. Digitized by: Smithsonian Libraries.

Within Histoire, 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, Alexandre. Histoire des végétaux fossiles. (1828-37). http://biodiversitylibrary.org/page/40155265. Digitized by: Smithsonian Libraries.

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.

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