2-Coloring of a Tree
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2-COLORING. Liquidambar styraciflua, Sweet gum, and Ginkgo biloba, Ginkgo.
800 block of Mayfield Avenue, looking north.
When considering a binary character evolving on a tree, the leaves of the tree can be assigned two colors, one corresponding to one state for the character, and one corresponding to the other state. If the two colors are exclusively located in different subtrees that correspond to distinct taxonomic groups, then the character can be said to have a fixed character difference between the two groups.