and are clamped, hyaline, and 1 to 3.5 µm wide. Similar species In Europe, Myxarium hyalinum (formerly considered synonymous with M. nucleatum) is very similar. Its fruit bodies tend to be more ochraceous or brownish with mineral inclusions less evident, except in older, coalesced specimens. Microscopically, it has slightly larger basidiospores, 9-16.5 x 4-6 µm. Myxarium populinum is known from poplar and willow in northern Europe, and lacks mineral inclusions visible with the naked eye. Myxarium cinnamomescens is another, similar northern species, also lacking mineral inclusions. Fruit bodies of Exidia thuretiana are similarly coloured, but are typically more opaque and often appear pleated. They do not (or very rarely) contain white, granular inclusions. Microscopically, E. thuretiana can easily be distinguished by its sessile (not stalked) basidia. Fruit bodies of several gelatinous Tremella species may also appear similar, but never contain granular inclusions. All can be distinguished microscopically by their non-allantoid spores. Habitat, distribution, and ecology Myxarium nucleatum is often found in association with old pyrenomycetes, but is presumed to be a wood-rotting species, typically found on dead attached or fallen branches. It was originally recorded on hawthorn, but is also known from many other broadleaf trees and shrubs, including beech, ash, sycamore, and ivy. Myxarium nucleatum typically fruits in autumn and winter. In its current, wide sense it is distributed in Europe, North, Central and South America, and New Zealand. In Europe, the fruit bodies can serve as host to the parasite Zygogloea gemellipara. This fungus has "auricularioid" basidia (more or less cylindrical basidia with lateral septa) and forms thin thread-like hyphae in the hymenium of its host. The hyphae of the parasite attach to the host hyphae through twisting, tendril-like haustorial cells. References Auriculariales Fungi of Central America Fungi of Europe Fungi of New Zealand Fungi of North America Fungi of South America Fungi described in 1833 Taxa named by Karl Friedrich Wilhelm Wallroth