Calopadia imshaugii

The thallus grows on bark (corticolous), typically 0.5–3 cm across and about 0.5–3 cm across and about 30–50 μm (micrometres) thick. It is continuous in the center but breaks into dispersed, irregular patches toward the edges. The surface is uneven and ranges from white to pale gray. The photobiont (the photosynthetic partner) is a green alga with chlorococcoid cells. The apothecia are rounded and sessile (sitting directly on the thallus), 0.4–0.8 mm in diameter. The disk is brown and coarsely white-pruinose (powdery), and the margin is conspicuous and pale gray to cream-colored. Microscopically, the excipulum is colorless (about 50–100 μm wide) and the hypothecium is brown (about 20–40 μm high); the apothecial base is dull brown. The hymenium is colorless and about 100–130 μm high, with paraphyses that are unbranched to slightly branched. The asci are about 90–100 × 20–30 μm and contain (1–)2(–3) ellipsoid, muriform ascospores per ascus. The spores measure about 50–80 × 15–23 μm. The species also forms campylidia (about 0.5–1 mm broad and 1–1.5 mm long) with a hood-shaped lobe that is dark gray with a paler apex and pruinose. The conidia are filiform with a clavate tip, 7–15-septate (divided by internal walls), and about 70–90 × 1.5–2 μm. All spot tests were negative.

Calopadia imshaugii is known from several collections in Florida, where it grows on the bark of small twigs of unidentified trees. In addition to the type locality in Collier County, collections were cited from the Homestead area in Miami-Dade County (near SW 388th Street, east of Old Dixie Highway).

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