Given a scientific passage and an answer, generate a question for the given answer.

Passage: Flowers are the reproductive organs of plants. Each pea plant flower has both male and female parts. The anther is part of the stamen, the male structure that produces male gametes (pollen). The stigma is part of the pistil, the female structure that produces female gametes and guides the pollen grains to them. The stigma receives the pollen grains and passes them to the ovary, which contains female gametes. Answer: stigma
What female flower structure, which is part of the pistil, receives the pollen grains and passes them to the ovary?