Freckled Tube Lichen

The lichen has a greenish-gray thallus measuring up to 8 cm (3 in) in diameter. The thallus comprises individual overlapping lobes that are 0.8–2.5 mm (0.03–0.10 in) wide, with slightly upturned edges on the marginal lobes. The thallus undersurface is dark brown to black and wrinkled, but becoming lighter-colored near the lobe tips. Apothecia (sexual fruiting bodies) are common on the thallus surface; they are on a small stalk (stipitate), have a brown disc and are 2.0–3.0 mm wide. The ascospores number 8 per ascus and measure 4.0–6.0 μm. Hypogymnia krogiae contains the secondary compounds atranorin, chloroatranorin, physodic acid, physodalic acid, and trace amounts of protocetraric acid. The expected results for standard chemical spot tests on the medulla are PD+ (red), K−, KC+ (pink), and C−. Hypogymnia krogiae reproduces by sexual means (via the apothecia) and does not have any soredia. It has a sorediate counterpart, Hypogymnia incurvoides, which is also found in North America. This pair is one of three such fertile/sorediate species pairs in the genus Hypogymnia.

Hypogymnia krogiae occurs in eastern North America from Tennessee and North Carolina, north to Quebec in Canada. It is a corticolous lichen, and grows on fir and spruce trees in both open and shaded forests.

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