treeness

A tree may, for the imagination, present forcibly one of its qualities at a time; it may be a green dome of shade on a hot day, a ladder of retreat for a man from the attentions of a mad bull, a peg on which an apple hangs, a screen for an assassin, a choir for birds; and its own business of spreading out its million pores to the air and propagating its kind, which comes nearest to being its “treeness,” may be what occupies the artist least and bores him most.

If factors that contribute to a tree-like pattern of the variance–covariance matrix dominate the evolutionary picture over those that tend to destroy it, one can expect treeness to be reasonably high. Only if this is true, reconstruction of the evolutionary process by tree analysis and a tree representation for descriptive purposes can be useful.

…such a tree can be built up incrementally by adding the shortest edge not yet explored, which also maintains treeness (acyclicity).