Monica Gagliano has pioneered experiments in which she demonstrates that plants “know” what other plants are growing in their environs, even in the absence of chemical cues. Variant #3 Confound the worms with a false chemical gradient suggesting that the food source is on the left, while the real food source is on the right. Variant #4 Place a separate Petri dish with food on the right of the dish containing the target worms, another dish on the left with no food.