Dry rot species of fungi cause brown rot decay, preferentially removing cellulose and hemicellulose from the timber leaving a brittle matrix of modified lignin. The term "dry rot" is somewhat misleading, as both species of fungi "Serpula lacrymans" and "Meruliporia incrassata" require an elevated moisture content to initiate an attack on timber (28–30%). Once established, the fungi can remain active in timber with a moisture content of more than 20%. At relative humidities below 86 percent, growth of "Serpula lacrymans" is inhibited, but it can stay dormant at relative humidities down to 76 percent. These relative humidities correspond to equilibrium moisture contents
Serpula (fungus) composing the family Serpulaceae. It is thought that the common ancestor was saprotrophic,and that ancestor to the latter two genera became mycorrhizal. Using molecular clock analysis, the split between "Austropaxillus" and "Serpula" has been estimated to have occurred about 34.9 mya, roughly coinciding with the separation of South America and Australia from Antarctica. The number of species is uncertain – the two species "S. lacrymans" and "S. himantioides" have been considered to be a single species, or the latter species has possibly five cryptic species within its complex. The members of the genus "Serpula" form flat brown fruit bodies that