Trees

(with apologies to Joyce Kilmer)

I think that I shall never see
A graph as lovely as a tree.

A tree whose thick, strong root is prest
Against the lower bound at rest;

A tree that looks a little strange
While its data does self arrange;

A tree that may grow up or out
But never round and round about;

Upon whose path constraint is lain
To go forward or back again.

Graphs are made by fools like me,
But only math can make a tree.
~ Jean Bauer