Abstract
Helicoön subglobosum sp. nov. from a decaying wood submerged in a freshwater stream at Juchi Town of Alishan area, Chiayi County, Taiwan, is described and illustrated with light and scanning electron micrographs. It differs from previously described species of Helicoön in having large subglobose conidia which are borne singly on very short conidiophores. The phylogenetic relationship of H. subglobosum and related taxa were sought by comparing the sequences of the ITS barcode and partial large subunit regions of the nuc rDNA. A synopsis of the 18 accepted species and a dichotomous key to the genus are given.