Here's why:

* Sporophytes are the diploid generation of plants, meaning they have two sets of chromosomes. They produce spores through meiosis, a process that reduces the chromosome number by half.

* Gametophytes are the haploid generation, meaning they have only one set of chromosomes. They produce gametes (sperm and egg) through mitosis, which maintains the same number of chromosomes.

Therefore, spores are produced by the sporophyte generation and are haploid, marking the transition to the gametophyte generation.