Fern leaves are called fronds. The leaves of Pteris are compound. Each segment of a compound leaf is called a leaf or pinna. Each leaf has one rachis. The leaves are arranged in pairs on either side of the rachis. Each leaflet is narrow, long, sessile, obtuse and the edges are smooth. Tidal pinnae are the longest. On the underside of the leaf there are tiny sporangia along the edges. The sporangia together form the sorus (spore leaf). Each sorus is covered by a false indusium. The leaves bearing the sorus are called sporophylls. Many psorai joined together to form Sinosaurus. Young leaves of ferns are called croziers. When the leaves are young, the coils are curled like a dog’s tail. This condition is called sarcinate vernation. Leaves are green and produce food through the process of photosynthesis.