This is an ascospore of Phaeosphaeria spartinicola, one of the principal species of ascomycetes that carry out the decay of standing-dead parts of smooth cordgrass (Spartina alterniflora), and thereby serve as major microbial secondary producers in saltmarshes. The golden-brown, 30-µm-long, 4- celled ascospore is shown at the base of its enclosing ascus, the structure that eventually propels the ascospores explosively out of the decaying leaf into the air (up to x1000 the length of the spore). The ascospore has a thin, transparent sheath that is likely to allow it to adhere at least semi-selectively to blades of smooth cordgrass. The asci are produced within dark brown ascomata (115 µm diam) just under the abaxial surfaces of cordgrass-leaf blades; average concentration of ascomata in decaying blades is about 1000 cm^-2 leaf surface. The total annual fungal production within dead marshgrass-shoot material is being measured at Sapelo Island, and now appears likely to be about 3 times the total bacterial production, on a m²-marsh basis. See Newell & Wasowski, 1995, Estuaries 18:241-249, and Newell & Porter, 2000, pp. 159-185, in Weinstein & Kreeger, Concepts and Controversies in Tidal Marsh Ecology, Kluwer.