By virtue of this symbiosis they produce hypogeous ascocarps, known as truffles.
Beatrice Belfiori, Claudia Riccioni, Francesco Paolocci, Andrea Rubini 2013, 'Mating Type Locus of Chinese Black Truffles Reveals Heterothallism and the Presenceof Cryptic Species within the T. indicum Species Complex', PLoS ONE10.1371/journal.pone.0082353. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
One of them was found underground, indicating a hypogeous fungus.
Maria Catarina Megumi Kasuya, Irene da Silva Coelho, Daniela Tiago da Silva Campos,Elza Fernandes de Araújo, Yutaka Tamai, Toshizumi Miyamoto 2010, 'Morphological and molecular characterization of Pisolithus in soil under eucalyptusplantations in Brazil', Revista Brasileira de Ciência do Solohttp://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832010000600013&lng=en&tlng=en. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)