Thus, the homologies between pollen bearing structures in Cordaites and the conifers are problematic. These homologies, or lack thereof, may present the greatest challenge to Florin's evolutionary interpretations. Sacci are thought to help make large conifer pollen grains buoyant in the air as most are wind pollinated and rely on long-distance pollen transport. Although this generalization is useful, there is substantial diversity among conifer pollen types. An example of saccate pollen.
Saccate pollen is a primitive character for conifers.
Cordaites, glossopterids, Caytonia, Callistophyton, and corystosperms all have this type of pollen. Ginkgo, peltasperms, and anthophytes lack saccate pollen. A variety of Mesozoic and Cenozoic conifers, including Pagiophyllum, Sequoia, and Metasequoia are available for you to study. Note the features you observed in modern foliage and cones. The Mesozoic is the hey-day of conifer diversity and ecological importance.