Polypodiopsida or Polypodiophyta) Ferns are ancient, flowerless, green plants with roots, stems, and leaves that are often called fronds:
Fronds
The leaves of ferns, which can be divided into segments called pinnae and pinnules. When young, fern fronds are tightly coiled into a spiral called a "koru" in Māori. The shape, size, texture, and complexity of fern leaves vary by species. Some ferns have two types of fronds: fertile fronds with sporangia and sterile fronds without sporangia.
Reproduction
Ferns reproduce sexually by tiny spores that grow on the underside of their leaves, or sometimes vegetatively. Water is usually necessary for reproduction, as sperm from one prothallus must swim to an egg on another prothallus to fertilize it. The fertilized egg then takes root and grows into a new fern.
Habitat
Ferns can be found in many different habitats, including tropical rainforests, bogs, marshes, ponds, fields, pastures, and on tree trunks and branches. Some ferns, like those in the desert, have adapted to survive in drier conditions by developing small fronds with waxy coverings, scales, or shading hairs to retain water. Other ferns, like those with dead-looking dry fronds, can turn green and begin photosynthesis when it rains.
Growth form
Ferns can be categorized by their growth form, such as tufted, creeping, climbing, perching, and tree ferns.