Studies in the genus Phoma. XIII. Concerning Phoma exigua var. exigua, a cosmopolitan, ubiquitous fungus on diseased and dead plant material.
P. exigua var. exigua is described and illustrated. An account is given of some of the perplexity surrounding the taxon, resulting from the application of numerous binomials to it. Its cultural characteristics and the anatomy of its pycnidial wall are documented. The distinctions between it and taxa with which it can be confused, including the other recognized varieties of P. exigua, are noted.