Dichotomous Venation

Photo Courtesy of Northern Arizona University Image Courtesy of Martin Cocks

The literal definition of dichotomous is "to cut in half." It therefor follows that Dichotomous venation is a splitting in half that results in two branches rather than one. There are two tyes of dichotomous venation: open and closed.

Open Dichotomous System

• no dominant bundles
• divide into two equal veins continuously
• most commonly found in the Ginkgo
• also found in pteridophytes, gymnosperms, and two dicots

Modified Open Dichotomous System

• midvein is the dominant bundle
• branching units are dichotomous
• found in many ferns

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