Serpula (fungus) are formed. The strand mycelium of "Serpula", which can be up to 8 mm thick, are invasive and can spread over non-nutritive surfaces to find new food sources, even spreading through pores in stone, brickwork, and cement. After its initial growth period, the fungus can produce the water it needs and can continue growth into dry timber, eventually degrading it to powder—hence the term "dry rot". "S. lacrymans" is the most serious cause of building timber decay in the UK and northern Europe. The "Dictionary of the Fungi" (10th edition, 2008), suggests that the genus contains two species. , the
Serpula lacrymans environments, the Himalayas, Northern California, the Czech Republic and east Asia. A recent study on the evolutionary origin and spread of this species using genetic markers (amplified fragment length polymorphisms, DNA sequences and microsatellites) on a worldwide sample of specimens suggested the existence of two main lineages, a nonaggressive lineage found in North America, and an aggressive lineage found on all continents, both in natural environments and buildings. "Serpula lacrymans" is considered to be the most damaging destroyer of indoor wood construction materials in temperate regions. In the United Kingdom alone, money spent by building owners rectifying damage caused by