The most conspicuous alteration of generation occurs in which division of the Plant Kingdom?
 

Pteridophytes are vascular plants that reproduce via spores rather than seeds, such as ferns, horsetails, and whisk ferns. They are important for ecosystem function, have been used for food, medicine, and ornamental purposes for thousands of years, and are considered primitive vascular plants.
The most noticeable alternation of generation occurs in Pteridophyta. This means that a diploid generation (the sporophyte, which produces spores) is followed by a haploid generation (the gametophyte or prothallus, which produces gametes). Pteridophytes differ from mosses and seed plants in that both generations are independent and free-living, though the sporophyte is generally much larger and more visible.