Each step in the key offers two characters: you have to look at the sheet and pick the one you see. Run the magnifier over it; the stem's cross-section and the leaf's edge aren't visible to the naked eye.
The donated herbarium has three unlabeled sheets and a determination key on the wall. The key doesn't ask what plant it is: it asks what you can see. Opposite or alternate leaves, square or round stem, toothed or smooth edge. You answer by looking, and at the end of the path is a name. For two of them.
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