This is 3/4 of an ascospore of Passeriniella obiones; there is another light-colored cell at the top, just out of this image. The ascospore is about 30 µm long. P. obiones is a decomposer of the true stem of smooth-cordgrass ( Spartina alterniflora) shoots; it is not found on other portions of the shoots. How it colonizes the true stem, which is enwrapped by leaf sheaths during shoot life and most of the standing decay, is unknown. Hyphae of P. obiones can be seen in this TEM. P. obiones often produces purple-red pigments (anthraquinones) in the decaying stems, perhaps as a defense against other fungi or mycovorous animals. This reddening of the naked, decaying stems is easily seen in stems that have fallen and become part of the marsh wrack. See Newell & Porter, 2000, pp. 159-185, in Weinstein & Kreeger, Concepts and Controversies in Tidal Marsh Ecology, Kluwer.