Build numbered couplets, tag examples under each result, print a worksheet and answer key.
Think of a specimen — real or made up — and answer the couplets as it would. The route is highlighted in the steps below, and the walk stops on a dead end or a loop, so you find those before a class does.
The same couplets drawn as branches, read left to right. The numbered steps above stay the key itself; this is the picture of it, with the route to every result written on the result.
Off by default: the numbered key prints exactly as before. The tree goes on its own page after the worksheet.
Uncheck to print just the reference key — e.g. to demonstrate what a dichotomous key is.