Lichenomphalia umbellifera

Lichenomphalia umbellifera, also known as the lichen agaric or the green-pea mushroom lichen, is a species of basidiolichen in the family Hygrophoraceae. L. umbellifera forms a symbiotic relationship with unicellular algae in the genus Coccomyxa. It is regarded as nonpoisonous.

The mushroom is white to yellowish-tan and hygrophanous, and occurs throughout most of the year on damp soil and rotting wood. It can be found in the Northern Hemisphere, particularly in the region of the Arctic. In the Pacific Northwest, it is common and can be found northward from Santa Cruz. Its cap grows up to 3cm wide. Its stalk is 1–3cm tall and 1–3mm wide. The spores are white or yellowish.

Taxonomy
The species was first described by Carl Linnaeus in 1753 as Agaricus umbelliferus. It was transferred to Lichenomphalia in 2002.

L. umbellifera has a wide geographic range and displays a considerable amount of phenotypic plasticity, but phylogenetic research has confirmed that these populations represent a single species. Two related taxa have been described in the genus Lichenomphalia, but are yet unnamed.

Similar species
Similar species include Chromosera cyanophylla, Chrysomphalina aurantiaca, Chrysomphalina chrysophylla, Contumyces rosellus, and Rickenella fibula.