“He determined that if they cross-pollinate, they produce more seed and more vigorous seedlings,” said Margaret Falk, a horticulturalist and associate vice president at the New York Botanical Garden. The variation is evolution’s way of increasing cross-pollination, she said.

Now the Botanical Garden is replicating this work, and more of Darwin’s Down House experiments, in a stunning, multipart exhibition called “Darwin’s Garden: An Evolutionary Adventure.”