In the history of the plant world, the transition from the Carboniferous to the Permian has attracted much attention. Coexisting with the Cordaitales in the Late Paleozoic and persisting into the Mesozoic are the Voltziales, often called the transition conifers. They exhibit the reduction series and changes in symmetry of a cordaianthus-like fertile dwarf shoot (see Chap. 13) that lead to the ovuliferous scale of extant conifers. Florin (1939, 1944, 1945, 1950a, b) made an intensive study of the Voltziales. He compared the fertile dwarf shoot of Cordaianthus with the ovuliferous scale of modern conifers, and cited several intermediate stages within the Voltziales (Florin 1951). However, the Voltziales do not fill the many gaps between the cordaites and conifers (Stewart 1983).
KeywordsSecondary Xylem Primary Axis Seed Cone Resin Duct Secondary Shoot
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