Plant life cycles follow alternation of generations, which means part of their life cycles are spent in a haploid state and the other part in a diploid state. The haploid for is called the gametophyte, and the diploid part is called the sporophyte. The acorn is an indehiscent dry fruit, enclosing the seed, but not splitting open at maturity. The acorn encloses the sporophyte, and the acorn is hard and dry at the seed’s maturity. The sporophyte, or seed, in this photo is found inside of the acorn, the fruit.