In the life cycle of a plant or alga undergoing alternation of generations, a haploid cell produced in the sporophyte by meiosis. Can divide by mitosis to develop into a multicellular haploid individual, the gametophyte, without fusing with another cell.

Spore

Explanation:

In the process of sexual reproduction, specialized haploid cells from two organisms, which can be called the (+) and (−) mating types, come together to produce a diploid zygote. The zygote after then will go through meiosis to produce four haploid cells termed spores. The spore, houses a new genetic combination from two parents with its capability to be dormant for varying time range.

Plants possesses a life cycle that switches between a multicellular haploid organism and a multicellular diploid organism. Take the ferns for example, both the haploid and diploid plant phases are free-living. The diploid plant is known as a sporophyte due to its ability to form haploid spores by meiosis. The spores grow into a multicellular, haploid plants termed gametophytes since they can have gametes. The gametes of two individuals will come together to produce a diploid zygote that is the sporophyte. The attached image 1 explains more on this.

Fungi, take for instance black bread mold (Rhizopus nigricans), possess haploid-dominant life cycles. The haploid multicellular stage give rise to specialized haploid cells by mitosis that come together to produce a diploid zygote. The zygote pass through meiosis to form haploid spores. Each spore will lead to a multicellular haploid organism by mitosis. The attached image 2 explains more on this.