Dichotomous venation in Ginkgo (detail)

Considered to be ancestral

This is a more detailed view of the vein pattern of one of the most ancient living trees in the world, (Ginkgo biloba). Each vein branches dichotomously into two others of equal size, and they in turn divide in the same way resulting in a dense venation pattern, all of the same size order. Veins are lacking anastomoses and end blindly in the mesophyll or approach the laminal margin.

Dichotomous venation is also typical of many pteridophytes. From an evolutionary perspective, such venation pattern is considered to be ancestral.