Plants of the Gila Wilderness

Umbilicaria americana is quite an interesting lichen. It is an umbilicate, foliose lichen that is found growing on vertical rock faces on large boulders in moist canyons in the shade. The thallus is about 2-4 cm in diameter and roughly round, although the edges can be torn or eroded. The upper surface is smooth but pruinose-- covered in small whitish crystals that give it a frosted appearance. The lower surface is covered with fairly dense "rhizinomorphs". These are either branched or unbranched rhizine-like structures that are covered by brown to black granular multicellular asexual propagules called "thalloconidia". These granules fall off the rhizinomorphs as a dispersal mechanism for the fungus. U. americana is red in sodium hypochlorite. The ascomata of U. americana are apothecia, but they are produced infrequently. The photobiont is a unicellular green alga (Trebouxia-like). Dermatocarpon americanum looks similar to U. americana, but Dermatocarpon has obvious perithecia with black ostioles visible on the upper surface and its lower surface is brown and lacks rhizinomorphs.
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Umbilicaria americana, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, upper surface of thallus with obvious pruina, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, upper surface of thallus, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, photomicrograph of pruina on upper surface of thallus, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, bottom surface of thallus, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, photomicrograph of bottom surface of thallus with obvious rhizinomorphs, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, cut edge of thallus with green photobiont in cortex and rhizinomorphs on undersurface, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, photomicrograph of cross section of thallus with upper cortex on bottom left, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, photomicrograph of photobiont (Trebouxia-like), photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, photomicrograph of thalloconidia on rhizinomorph, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, photomicrograph of thalloconidia on rhizinomorph, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019

Umbilicaria americana, photomicrograph of red reaction in sodium hypochlorite, photo Russ Kleinman & Karen Blisard, Gila NF, McMillan Cmpgd trail, November 11, 2019