And delayed meiosis lead to an alternation of generations with both haploid and diploid generations both prominent in the life cycle. This permitted the new plants to exploid a lot of nitches, particularly dry areas on land. Please study the figures in your text on the life cycle of the moss and fern to see how alternation of generations works in some modern plants. Here is a picture of a modern day plant, Psilotum . We think that this relative of the mosses and ferns might be very similar to the ancestors of all mosses, ferns, and many plants which are now extinct.
Gymnosperms are cone bearing plants like pines, fir, and cycads .
They don't have flowers but do have seeds, unlike mosses and ferns. Seeds are embryonic plants protected in a hard case so that they can be dispersed over long distances. Gymmnosperms were better adapted to dry land than mosses and ferns, which require wet conditions during at least part of their life cycle. So, gymnosperms discarded most of the haploid generation of the life cycle which became reduced to just the haploid sperm, eggs and a few other haploid cells to help the sperm and egg function. Look here to see a drawing, from a fossil, of Archaeosperma arnoldi , dating from from about 374 million years ago.