Recognized by its distinct conidiophores terminated by a swollen vesicle bearing flask-shaped phialides. The phialides may be borne directly on the vesicleor on intervening metulae. Some species may form masses of thick-walled cells called "hülle cells". The spores come in several colours, depending upon the species, and are produced in long chains from the ends of the phialides. Commonly isolated from soil, plant debris, and house dust; sometimes pathogenic to man.