The structure on a plant that makes seeds and allows reproduction is the flower.

Here's a breakdown:

* Flowers are the reproductive organs of flowering plants.

* Inside the flower, you'll find the ovary which contains the ovules. These ovules are what develop into seeds.

* Pollen from the flower's anther is transferred to the flower's stigma (usually by insects or wind). This process is called pollination.

* Fertilization occurs when the pollen grain reaches the ovule, and the ovule develops into a seed.

* The seed contains a tiny plant embryo and stored food, ready to grow into a new plant when conditions are right.

So, while the flower is the main structure for reproduction, the ovary, ovules, and pollen are all crucial parts of the process.