A REVISION OF THE GENUS SCLEROCYSTIS (GLOMACEAE, GLOMALES)

The genus Sclerocystis was established by Berkeley and Broome in 1873 with their description of S. coremioides and since then 13 additional species have been described. Although some consider Sclerocystis allied to the genus Glomus, we conclude that the two genera are distinct based on spore ontogeny and sporocarp habit. In Sclerocystis, spores are arranged in a hemispherical layer, forming a "head" and a short stalk; no spores are formed at the sporocarp base. Sporocarpic species in Glomus exhibit several other spore arrangement patterns. The genus Sclerocystis is maintained with one species, S. coremioides. Sclerocystis coccogena, S. dussii, and S. alba are considered synonyms of S. coremioides. Five other Sclerocystis species are moved to the genus Glomus, G. clavisporum, G. liquidambaris, G. rubiforme, G. sinuosum, and G. taiwanense. The remaining five described species of Sclerocystis are considered synonymous with one of the latter species.