This function was taken over by seeds - dormant, protected, embryo sporophytes. Link to a discussion of the alternation of gametophyte and sporophyte generations in plant life cycles. The seed ferns , as these plants are called, were among the earliest gymnosperms. Although seed ferns are now extinct, some of their living descendants, the cycads , resemble them closely. Cycads reveal their ancient lineage by the fact that after the microspore reaches the ovule, it liberates a ciliated sperm which, swimming in moisture supplied by the parent sporophyte, reaches the egg.
Ginkgos are another group of gymnosperms that use motile sperm.
Conifers Conifers get their name from the cones in which the both microspores and megaspores develop. The male cones produce microspores that develop into pollen grains that are carried by the wind to the female cones. Here each germinates into a pollen tube which grows into the tissues of the female cone until it reaches the vicinity of the egg. Then the tube ruptures and a sperm nucleus fuses with the egg to form the zygote. After fertilization, the zygote develops into a tiny embryo sporophyte plant.