SummaryA species ofLeptosphaeriahere described asL. Opuntiaeis associated withHendersonia OpuntiaeEllis&Ev. on segments ofO. Lindheimerifrom Texas collected by Wolf and deposited in The New York Botanical Garden. A specimen labeled“Hendersonia OpuntiaeE.&E.”from Alabama in the Ellis Herbarium also shows numbers of ascocarps of the sameLeptosphaeria. The ascocarpic and pycnidial fruit bodies develop clypeate buffer tissue about the ostiolar region. Ascospores and conidia are brown and 3-septate. The association and similarities in morphology suggest that possibly these two forms belong to the same fungus. The connection would have to be proved by culture work.The perithecial cavity develops largely through the differential growth of the peripheral tissues as a wall while the cells at the center elongate vertically by adding intercalary cells so that one sees streamers of hyphae extending across the cavity and attached to the wall cells above and below. Ascogenous elements arise from the fertile tissue at the base and grow up between the disorganizing vertically growing space-making hyphae. These ascogenous elements do not arise from the lower ends of free swinging vertically downward growing hyphae as claimed forSporormia leporineby Arnold. Otherwise cavity formation in thisLeptosphaeriaand theSporormiaseems to be identical.The writer is indebted to Mr. Frank Paladino for the preparation of slides from herbarium material for this study.