What makes the Counting Pines particularly noteworthy, however, is the way they count. Being dimly aware that human beings had learned to tell the age of a tree by counting the rings, the original Counting Pines decided that this was why humans cut trees down. Overnight every Counting Pine readjusted its genetic code to produce, at about eye-level on its trunk, in pale letters, its precise age. Within a year they were felled almost into extinction by the ornamental house number plate industry, and only a very few survive in hard-to-reach areas.

— Reaper Man by Terry Pratchett (Discworld, #11)