The haploid phase that produces gametes by mitosis is called the gametophyte. The gametophyte is the dominant generation in bryophytes (mosses, liverworts, and hornworts), whereas in vascular plants (ferns, gymnosperms, and angiosperms), the sporophyte is the dominant generation.

In bryophytes, the gametophyte is the leafy, photosynthetic plant that we see. The gametophyte produces gametes (eggs and sperm) by mitosis. The eggs are produced in archegonia, and the sperm are produced in antheridia. When a sperm fertilizes an egg, a zygote is formed. The zygote develops into a sporophyte, which is the asexual generation in bryophytes.

In vascular plants, the gametophyte is a small, often microscopic plant that is produced by the sporophyte. The gametophyte produces gametes by mitosis. The eggs are produced in archegonia, and the sperm are produced in antheridia. When a sperm fertilizes an egg, a zygote is formed. The zygote develops into a sporophyte, which is the dominant generation in vascular plants.

The gametophyte phase is an important part of the life cycle of plants. It is the phase during which gametes are produced, and it is therefore essential for sexual reproduction.