Leaves of Fagopsis are one of the two most abundant fossils found at Florissant, so this tree was likely very common around the Eocene lake. We are able to reconstruct some remarkable details of this extinct genus from fossils showing attached organs such as leaves, flower heads, and fruits. It’s much more difficult to know what the entire tree might have looked like or what its size was because its fossil wood is unknown, but the reconstruction here makes some inferences based on modern relatives such as beeches and oaks. The fossils do show clearly that there were separate male and female flower heads, and those can be reconstructed in detail. We also know what the pollen looked like because it can be extracted from anthers in the male flowers and examined microscopically. The fruiting heads are preserved as fossils showing details of the different stages in their development.
This male flowering head produced the pollen on its protruding anthers. The pollen of Fagopsis is described as "tricoporate" because it has three colpi (grooves) with a pore in each.
This fossil shows a female flowering head covered with protruding pistils, attached to a twig bearing the leaves of Fagopsis. After it was pollinated from the male flowering head, it began maturing into a fruiting head.
A Funky Fruit
Later in the season, the female flowering head of Fagopsis matured into this fruiting head. Strings of clinging fruit wedges spiraled around the center axis of the fruiting head and unraveled as they shed into the wind. Each fruit wedge had three tiny nuts near the base. These features are not found in any modern plant, which shows that Fagopsis was an extinct genus in the Beech Family.
This illustration shows how the organs of Fagopsis changed through the seasons. The flowering heads developed from buds during the spring and early summer, with male flowers producing pollen. Once pollinated, the female flowers developed into fruiting heads during the late summer or autumn, and the strings of fruit wedges were dispersed in the wind. One study shows that the leaves remained on the tree for an entire year before they fell and covered the ground, or maybe landed in the lake to become fossilized!
For more information:
Manchester, S.R. and P.R. Crane, 1983. Attached leaves, inflorescences, and fruits of Fagopsis, an extinct genus of Fagaceous affinity from the Oligocene Florissant flora of Colorado, U.S.A. American Journal of Botany, vol. 70, p. 1147-1164.
Last updated: October 4, 2021