Fruiting structures (pycnidia) more or less round and ornamented, at least on the upper part, with stiff spines. The colourless to yellowish 1-celled spores (conidia) are borne from phialides produced along the length of elongated conidiophores lining the inner walls of the pycnidium. Some species of Phoma also have pycnidial spines, but differ in having simple phialides borne dirctly from the walls of the pycnidium. Isolated from soil and plant debris. Holomorphs: Acanthostigma, Herpotrichia. Ref: Dorenbosch 1970; Schneider 1979