A fern frond has 18 pinnae. Under each pinna there are 10 sori, and each sorus holds 25 sporangia.

Pteridophytes are the first land plants with xylem and phloem. The main plant body is the diploid sporophyte, with true roots, stems and leaves. Sporangia on sporophylls make spores by meiosis (in many ferns, 16 spore mother cells give 64 spores in a sporangium); some form strobili. A spore grows into a free-living prothallus with antheridia and archegonia, and fertilisation needs water. Classes: Psilopsida, Lycopsida, Sphenopsida, Pteropsida.