Cetraria islandica.

Botanical name: 

Cetraria islandica Linn. Lichenes. Iceland Moss.

Iceland moss is found in the northern regions of both continents and on elevated mountains farther south. It serves as food to the people of Iceland and Lapland; the bitterness is first extracted with water, after which the plant is pounded up into meal for bread or boiled with milk.

Sturtevant's Edible Plants of the World, 1919, was edited by U. P. Hedrick.