The reproductive structure that grows into the haploid generation of a plant is the spore.

Here's why:

* Alternation of Generations: Plants exhibit an alternation of generations, meaning they have both a haploid (n) and diploid (2n) phase in their life cycle.

* Sporophyte: The diploid generation is called the sporophyte, which produces spores through meiosis.

* Spore Formation: Spores are haploid cells that can develop into a new individual without fusing with another cell.

* Gametophyte: The spore germinates and develops into the haploid generation, known as the gametophyte.

* Gametes: The gametophyte produces gametes (sperm and egg) through mitosis.

* Fertilization: The fusion of gametes creates a diploid zygote, marking the beginning of a new sporophyte generation.

Let me know if you'd like more details on any of these stages!