Echinodontium ballouii

The fungi's fruiting bodies are irregularly-shaped shelf-like formations. Their diameters can span 5-50 centimeters, and they can grow up to 20 centimeters tall.[1] They are brown in color,[3] and the body is tough and woody. They are commonly seen with “teeth” or “spines” protruding from the cap's underside. As a polypore, the fungus's spores are released from an underside covered in small pores, which is lighter in color. These pores are conchate or bell-shaped and release the fungus's basidiospores.[4] The fungus's spores measure between 5-7 µm long and 2-3 µm tall. As a polypore, Echinodontium ballouii is perennial, releasing spores once a year and forming a new layered hymenium directly on top of that of last year.

Echinodontium ballouii is a hemi-biotrophic wood decomposer, feeding off of only a single species of tree: the Chamaecyparis thyoides Atlantic white cedar. The fungus forms complex mycelial networks inside the tree's trunk, slowly digesting cellulose and lignin, and emerging as fruiting bodies in order to reproduce. They are often found relatively high up on trees, below branching points.[5]

Because this fungus only inhabits Chamaecyparis thyoides, its habitat is limited to this tree's ecological environment: swampy, coniferous forests within 150 miles of the Eastern coast of the United States.[2][6] The production of fruiting bodies can take up to forty years, which means that the fungus is typically found on old growth trees.[7]

The fungus's limited host species results in a very confined geographical distribution. Only about twenty visibly occupied trees have been documented to date, each in the East coast of the United States, with the first sighted in New Jersey.[8]

The small number of recorded Echinodontium ballouii has resulted in its classification as endangered.[9] This is in part due to the formerly high demand for the fungi's host body, the Atlantic white cedar, for shipbuilding lumber, especially due to its coastal proximity. Today, demand for lumber still puts this important decomposer at risk. The fungus is named for William Hosea Ballou, one of its earliest discoverers. He mistakenly claimed that “there [was] no fungus more beautiful – or more deadly”[10] to the Atlantic white cedar. In reality, the suffering trees that Ballou witnessed were likely due to logging development and changing hydrology. The fungus was generally thought to be extinct after no additional sightings occurred for the majority of the 20th century.[11] However, it was rediscovered in the early 2000s by mycologists Larry Millman and Bill Neill.[5]