There are two genetically different mates which are involved in Heterothallism. Blakeslee discovered it in 1903. He stated that only some species can perform sexual reproduction from just a single spore. There is no structural difference between thallic types. The difference is physiological and genetic type. An example of this type is rhizopus sexualis. Heterothallism is basically a device which prevents mating of closely related genetic similar organisms known as Inbreeding. It promotes mating of two genetically different organisms known as out breeding. It leads to variations and prepares the fungi to adapt to unfavorable circumstances. The offspring which are produced have variety of characteristics.