Gonidia, green cells leading an independent existence, being, in fact, unicellular Algae (q.v.). They are generally spherical, and have seldom a defined cellulose membrane. In addition to chlorophyll (q.v.) they sometimes contain phycocyan or other colouring matters. The term is especially applied to those algal cells belonging to various members of the sub-classes Cyanophycete and Chlorophycete, which, imprisoned by the hypha; of various fungi, constitute the symbiotic compound organism known as a lichen (q.v.).