The dark brown spores are borne in simple or branched chains from the tips of simple dark conidiophores and are divided into several cells by transverse and vertical walls. New spores are produced by the extrusion of wall material through a pore at the tip of the previous spore. Commonly isolated from decaying plant materials; also causing plant diseases. Spores of Alternaria species are dispersed by air currents and are usually a major component of outdoor air. Holomorphs: Clathrospora, Leptosphaeria, Pleospora, Pyrenophora. Refs: Ellis 1971, 1976; Joly 1964