Pteridophytes divided into four classes- Psilopsida, Lycopsida (club mosses), Sphenopsida (horse tails) and Pteropsida or Filicinae (ferns). Among all these four classes, only Lycopsida includes both homosporous and heterosporous forms. Homosporous pteridophytes produce only one type of spores e.g clubmoss, Salvia and puzzle grass. Heterosporous pteridophytes produce two types of spores one megaspore and other microspore. Example of heterosporous pteridophytes Selaginella, Salvinia, Marsilea and Azolla.