Polymeridium submuriforme

{{Short description|Species of lichen}}

{{Use dmy dates|date=March 2023}}

{{Speciesbox

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| taxon = Polymeridium submuriforme

| authority = Aptroot (2013)

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Polymeridium submuriforme is a species of corticolous (bark-dwelling) lichen in the family Trypetheliaceae. It occurs in the Philippines. This {{lichengloss|ecorticate}} lichen is characterized by its pinkish-grey thallus, which does not fluoresce under ultraviolet light. P. submuriforme is similar to Polymeridium cinereonigricans but can be distinguished by its much smaller {{lichengloss|ascospores}} and {{lichengloss|inspersed}} {{lichengloss|hamathecium}}. The ascomata measure 0.3–0.6 mm in diameter, with a solitary, spherical {{lichengloss|centrum}} that is {{lichengloss|erumpent}}. As the ascomata age, the wall expands up to 0.2 mm sideways. The ostiole is apical, and the hamathecium is inspersed. The {{lichengloss|ascospores}} number 6–8 per ascus, iodine-negative, somewhat {{lichengloss|muriform}}, and measure 18–20 by 6–7.5 μm. These ascospores are not ornamented and are surrounded by a 1–2 μm wide gelatinous sheath. No chemical substances have been detected in this lichen. The type specimen was collected from Leyte on tree bark.