Observation 10323: Dermatocarpon americanum Vain.

umbilicate lichen, on limestone, crowded in sheltered places
THALLUS: light gray due to pruina, covered with black dots flush with the surface (perithecia), strongly contorted, appearing to have many lobes; below tan to almost black, smooth, many holdfasts
MEDULLA: white, very tough, IKI/C+ blood-red

Keys in the literature always claim Dermatocarpon americanum is single-lobed with a single holdfast, but I find this virtually never to be the case. They often grow in dense contorted masses where it’s almost impossible to tell one specimen from its neighbor, with small to large holdfasts wherever the thallus touches the substrate. This seems to be by far the most common species of Dermatocarpon in the desert southwest.

If you can’t get your hands on Melzer’s reagent (a controlled substance), Lugol’s followed by bleach apparently accomplishes the same result1.

1 Lichen Flora of the Greater Sonoran Desert Region, Vol II, Nash et al., pg.88


10x magnification
10x magnification
10x magnification

Proposed Names

87% (1)
Used references: Nash’s Sonoran Flora
Based on chemical features: Medulla red in Melzer’s.

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= Observer’s choice
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Created: 2008-09-01 16:44:35 CDT (-0500)
Last modified: 2008-09-01 16:44:35 CDT (-0500)
Viewed: 21 times, last viewed: 2019-01-22 12:28:09 CST (-0600)