Patricia E. Ryberg University of Kansas Ecology and Evolutionary Biology 2045 Haworth Hall Lawrence Kansas USA
Cycadeoidea (Bennettitales) is an extinct genus of seed plants that thrived in the Cretaceous (100 million years ago). This specimen was collected from the Black Hills of South Dakota. At the bottom of the picture is secondary xylem (wood) represented by the dark colored cells. At the top of the image is secondary phloem. Phloem is rarely preserved in the fossil record and the excellent preservation seen here is vital to studies on vascular tissue in fossil plants. (specimen from Yale University Peabody Museum of Natural History)
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