Seedless vascular plants are usually somewhat small. There, gametes are formed and flagellated sperm fertilize the egg . Horsetails are morphologically different from the club mosses, but are somewhat similar, biologically. Ferns have large leaves with branching vascular tissue. Both extinct and extant forms are abundant.
Spores grow into gametophytes which yield eggs and swimming sperm.
A new sporophyte grows from the fertilized zygote on the gametophyte. Included in this group are the conifers and cycads. The Coniferales dominates vast regions of northern hemisphere and is especially successful where the growing season is short due to latitude or altitude. This group includes the largest living organisms. There are about 750 living species of gymnosperms.