The genus was first published in 1871 by Louis and Charles Tulasne who had discovered that two species previously referred to Corticium or Thelephora possessed septatebasidia, similar to those found in the genus Tremella. Although it was unusual at that time to separate fungal genera on purely microscopic characters, Sebacina was erected for effused, Corticium-like fungi with tremelloid basidia. Subsequent authors added many additional species to the genus. Most, however, proved unrelated to Sebacina and were removed in 1957 by Ervin, who shuffled some species to Heterochaetella, Bourdotia and Exidiopsis. In 1961, Wells also transferred many species to the genus Exidiopsis. The type species, S. incrustans, has a variable morphology, which has led to it being assigned a number of names. Recent molecular research has shown that Sebacina is far more diverse than previously assumed, though this genetic diversity may not be reflected in morphological characters. The same research also shows that the genus splits into two groups, one clustered with the type species, the other clustered with a species sometimes referred to as "Sebacina vermifera". This latter species is distinct in forming thin, waxy fruit bodies and the group may not be part of Sebacina in the strict sense. Even in the strict sense, Sebacina is artificial, not being clearly distinct from related genera such as the coral-like Tremellodendron.
Description
Fruit bodies are typically cartilaginous or rubbery-gelatinous. In effused species, they are formed on the soil surface or in leaf litter, often encrusting fallen twigs and debris, sometimes encrusting the stem bases of living plants. In the type species, irregular or coral-like outgrowths may also be produced. In one species, bracket-like outgrowths are formed. In two other species, the fruit bodies are entirely coral- or net-like. Spores are white in mass.
Microscopic characters
Fruit bodies are composed ofhyphae lacking clamp connections in a gelatinous matrix. In one species the hyphal system is dimitic. The spore-bearing surface is initially covered in a layer of weakly branched hyphidia below which the basidia are formed. The basidia are tremelloid, giving rise to long, sinuous sterigmata or epibasidia on which the basidiospores are produced. These spores are typically ellipsoid to oblong, but in one species and in another.
Mycorrhizal associations
Sebacina species were assumed to be saprotrophic until DNA analysis of mycorrhizal roots showed that they were plant associates. They are now known to be ectomycorrhizal associates of forest trees as well as endomycorrhizal associates of orchids. They also form mycorrhizas with ericoid plants. Recent research has additionally revealed their presence on a range of non-mycorrhizal plant roots, suggesting they may be common root endophytes.
Species
For older names, the list is based on species retained in Sebacina by Wells.
