What motivates Nick and Marta's visit to Mrs. Starch's house?

The motivation for Nick and Marta's visit to Mrs. Starch's house stems from their curiosity about her collection. This curiosity drives their desire to explore her home and discover more about the unique items she possesses. The context suggests that there is an element of intrigue surrounding Mrs. Starch and her belongings, which piques the interest of the characters. Their visit is not influenced by academic obligations, competitive bets, or specific gardening-related interests, but rather by a personal inclination to learn more about her collection, making their sense of curiosity the key driver for this visit.