Plants of the Gila Wilderness

Leptogium milligranum has an brown upper surface that is covered in cylindrical dark isidia, and a lower surface that is smooth and brown, without a white tomentum. We did not find any apothecia on our specimen which was collected from the bark of a gray oak, Quercus grisea. The lichen was growing intermingled with the moss Syntrichia laevipila. The upper and lower cortices are both one cell thick. The photobiont (Nostoc) grows in chains dispersed through the medulla without a well-defined photobiont layer. Heterocysts (nitrogen fixation cells) are abundant.
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Leptogium milligranum, photo Russ Kleinman & Karen Blisard, Pinos Altos Range, Pinos Altos, March 26, 2020

Leptogium milligranum, closeup, photo Russ Kleinman & Karen Blisard, Pinos Altos Range, Pinos Altos, March 26, 2020

Leptogium milligranum, closeup with brown undersurface, photo Russ Kleinman & Karen Blisard, Pinos Altos Range, Pinos Altos, March 26, 2020

Leptogium milligranum, closeup, photo Russ Kleinman & Karen Blisard, Pinos Altos Range, Pinos Altos, March 26, 2020

Leptogium milligranum, photomicrograph of isidia, photo Russ Kleinman & Karen Blisard, Pinos Altos Range, Pinos Altos, March 26, 2020

Leptogium milligranum, photomicrograph of thallus cross section showing Nostoc in chains with abundant heterocysts and one cell thick upper and lower cortices, photo Russ Kleinman & Karen Blisard, Pinos Altos Range, Pinos Altos, March 26, 2020

Leptogium milligranum, photomicrograph of thallus cross section showing Nostoc in chains with abundant heterocysts and one cell thick upper and lower cortices, photo Russ Kleinman & Karen Blisard, Pinos Altos Range, Pinos Altos, March 26, 2020

Leptogium milligranum, photomicrograph of thallus cross section showing Nostoc in chains with abundant heterocysts and one cell thick upper and lower cortices, photo Russ Kleinman & Karen Blisard, Pinos Altos Range, Pinos Altos, March 26, 2020