Key Runner Game

A dichotomous key is how botanists name a plant they do not know: a chain of two-way questions, each answered from what you can see, until one name is left. Key Runner turns each question into a fork in a woodland path. A specimen's card shows its flower, a cut through its stem and its leaves, and the questions always come in the same order, so after a few runs the whole key is a route in your head with a question at each turn.

How to play

1. A specimen card drops in at the top: the plant's flower, a cut through its stem, and its leaves.
2. The path runs toward a fork with a question on its sign. The left branch is Yes and the right branch is No.
3. Pick a branch before you reach the fork. You can change your mind until then.
4. A right branch leads on to the next question, and the last one leads to the plant's family. Then the next specimen drops in, and the path speeds up.
5. A wrong branch costs a life. The runner stumbles, the right answer shows, and the run carries on along the right branch. 3 lost lives end the run.

On a keyboard, press the left arrow or Y for Yes and the right arrow or N for No. Escape or Space pauses. Sound starts off on a first visit.

Scoring

• A fork passed on the right branch scores 40 points.
• Reaching a plant's family scores 120 more.
• A wrong branch, or no pick at all, scores nothing for that fork.

Your five best scores are saved in this browser, with how many specimens each run reached. In practice no lives are lost, so the run goes on until you end it from the pause screen. Practice games are not saved.

The key

The questions come in this order. Are the flower parts in threes? If yes, is one petal a lip? Yes is the Orchid family, Orchidaceae, such as the early purple orchid, and no is the Lily family, Liliaceae, such as the tulip. If the parts are not in threes, does it have a banner, wings and a keel, the pea flower's upright petal, two side petals and a boat-shaped lower pair? Yes is the Pea family, Fabaceae, such as meadow vetchling and bird's-foot trefoil. If not, is the flower a composite head, a head of many small florets that looks like one flower? Yes is the Aster family, Asteraceae, such as the daisy and the dandelion. If not, is the stem square? Yes is the Mint family, Lamiaceae, such as red deadnettle and sage. If not, does it have four petals in a cross? Yes is the Mustard family, Brassicaceae, such as charlock and shepherd's purse. If not, are its flowers in umbrella clusters? Yes is the Carrot family, Apiaceae, such as wild carrot and cow parsley, and no leaves the Rose family, Rosaceae, such as the dog rose and the bramble.

A key like this works only for the plants it was written for. Bedstraws have square stems but are in the coffee family, and irises, daffodils and onions have their parts in threes but are not lilies. A field guide's key for your region asks more questions to tell them apart.

Remembering the key

The key is a route, and a route is what a memory palace is made of: the same turns, in the same order, every time. Give each fork a picture at its place on the path, a three-legged stool for the threes or a square post for the square stem, and the questions come back in order when you walk it.

Try our other free memory games.