Acarospora janae

The lichen thallus (body) consists of dispersed areoles (a small rounded area that is more or less polygonal or angular, and delimited by cracks) that are dark to light brown in color. The surface of the areoles often have fine grooves. The disc of the apothecium (a round, plate-like spore-producing part of the fruit body) has a rough texture and is either the same color as the thallus or darker. It sometimes has umbos and ridges, but these tend to disappear as the disc fully dilates. The hymenium (spore-bearing tissue) is about 100 μm thick and contains paraphyses that have a diameter of 2 μm. The asci (spore-bearing cells) are club-shaped, measure 60 by 20 μm, and contain roughly 100 ascospores. The spores are 3–4 by 2 μm.^[2]

Most specimens are epruinose (lacking a pale, powdery coating), although slight pruina has been observed in some collections. The species typically develops a single apothecium per areole, but in certain microhabitats an areole may temporarily produce several apothecia; these generally separate again as the areole divides into smaller units, each bearing one apothecium. The colour of the lower surface appears variable: it was described as white in the holotype, while an isotype (duplicate) is brown, and some eastern specimens have a darker, melanized lower surface that may reflect interaction with the substrate.^[3]

Acarospora janae grows on rock. It was described from sandstone at the type locality in New Mexico,^[2] and it has since been documented on a range of substrates including sandstone, granite, schist and gneiss, rhyolite and other igneous rocks, and locally on limestone or calcareous sandstone.^[3]

In addition to the original southwestern records (including New Mexico and Colorado), published records extend eastward across parts of the central and eastern United States; reported localities include Arkansas, Kansas, Georgia, Missouri, Oklahoma, Pennsylvania, North Carolina, and South Carolina. It has also been reported from Newfoundland in Canada.^[3]