A cryptogam is a plant (in the wide sense of the word) that reproduces by spores. "Cryptogamae" means hidden reproduction, referring to the fact that no seed is produced, thus cryptogams represent the non-seed bearing plants. Other names, such as "thallophytes", "lower plants", and "spore plants" are also occasionally used. As a group, Cryptogamae are the opposite of the Phanerogamae or Spermatophyta, the seed plants. The best known groups of cryptogams are algae, lichens, mosses and ferns.