[2] Geoglossum species are distinguished from the related genus Trichoglossum by the lack of setae on the spore bearing surface.

Identification of species is based on the gross morphology of the ascocarp, color and septation of the ascospores, and shape and ornamentation of the paraphyses.

Persoon expanded the genus in several subsequent publications[4][5][6][7][8] and the name was sanctioned by Elias Magnus Fries in his 1821 Systema Mycologicum I.

[9] Several mycologists have treated the genus extensively since Persoon's first work, including George Edward Massee,[10] Elias Judah Durand,[11] Curtis Gates Lloyd,[12] Fred Jay Seaver,[13] and Edwin Butterworth Mains.

[14] Synonyms of Geoglossum include Frigyes Ákos Hazslinszky's Cibalocoryne and Corynetes (both published in 1881), Pier Andrea Saccardo's 1884 Microglossum, and Otto Kuntze's 1891 Thuemenidium.

[1] In 1908, Durand circumscribed Gloeoglossum to contain Geoglossum species with paraphyses in a continuous gelatinous layer on the stipe (including G. affine, G. difforme, and G. glutinosum),[11] but the genus is not considered to have independent taxonomic significance.

[16][17] The fruit bodies of Geoglossum species are usually club-shaped, with a surface that is dry to sticky or gelatinous (particular in wet weather), and brown to black.

There are paraphyses mixed with the asci, and in some species these occur on the stipes scattered or grouped together so as to form small tufts or scales.