a new xylaria species from iran

three species of the genus xylaria (xylariaceae) are presented based on collections from guilan province, iran. both morphological and molecular characteristics were used in order to identify these species. xylaria longissima sp. nov. is described and illustrated as a new xylaria species and x. cf. striata and x. xylarioides are reported as new records from iranian mycobiota. xylaria longissima and x. xylarioides were collected from wood of unknown dicotyledonous plants and x. cf. striata was collected from soil. differences between these species and other closely related taxa are discussed. the result of this study indicates that sequences of internal transcribed spacer (its) region have sufficient resolution to distinguish major species groups.