MYCOTAXON Volume 107, pp. 307–313 January–March 2009 The genus Diatrype (Ascomycota, Diatrypaceae) in Arkansas and Texas (USA) Larissa N. Vasilyeva 1 & Steven L. Stephenson 2 1 vasilyeva@ibss.dvo.ru Institute of Biology and Soil Science Far East Branch of the Russian Academy of Sciences Vladivostok 690022, Russia 2 slsteph@uark.edu Department of Biological Sciences University of Arkansas, Fayetteville, AR 72701, USA Abstract — Seven species of the genus Diatrype are recorded as occurring in Arkansas and Texas (USA). Two of these (Diatrype caryae and D. ilicina) are described and illustrated as new to science. Key words — Sordariomycetes, south central United States, systematics Introduction Species of Diatrype are common inhabitants of dead branches of deciduous trees throughout the world. ese fungi produce perithecia imbedded in discoid or widely effused stromata that are erumpent from the bark. e young stromata are sometimes covered with a layer of sterile tissue that eventually peels off to expose a fertile surface studded with papillate or stellate ostioles. Members of the genus Diatrype do not cause diseases of their host plants and mostly participate in the decomposition of coarse woody debris. However, despite their saprotrophic way of life, many species of Diatrype are restricted to certain genera of host plants. Following the distribution of their host plants, some species of Diatrype occur over wide areas of the northern hemisphere. Prominent examples are D. bullata (Hoffm. : Fr.) Fr. on Salix spp. (willow) or D. undulata (Pers. : Fr.) Fr. on Betula spp. (birch). Among the more interesting are D. virescens (Schwein.) Ravenel on Fagus grandifolia Ehrh. (American beech) in North America and D. disciformis (Hoffm. : Fr.) Fr. on Fagus sylvatica L. (European beech) in Europe. e latter has been reported to be rare in North America, but the